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Occupational exposure to gaseous and particulate contaminants originating from additive manufacturing of liquid, powdered and filament plastic materials and related post-processes
Abstract
The aim of this study was to measure the concentrations of gaseous and particulate contaminants originated from additive manufacturing operations and post-processes in an occupational setting when plastics were used as feedstock materials. Secondary aims were to evaluate the concentration levels based on proposed exposure limits and target values and to propose means to reduce exposure to contaminants released in additive manufacturing processes. Volatile organic compounds were sampled with Tenax® TA adsorption tubes and analyzed with thermo desorption gas chromatography-mass spectrometry instrument. Carbonyl compounds were sampled with DNPH-Silica cartridges and analyzed with high-performance liquid chromatography device. Particles were measured with P-Trak instrument and indoor air quality was sampled with IAQ-Calc instrument. Dust mass concentrations were measured simultaneously with DustTrak DRX instrument and IOM-samplers. Particle concentrations were at highest (2070-81 890 #/cm³ mean) during manufacturing with methods where plastics were thermally processed. Total volatile organic compounds concentrations, in contrast, were low (113-317 µg/m³ mean) during manufacturing with such methods, and vat photopolymerization method. However, total volatile organic compounds concentrations of material jetting and multi jet fusion methods were higher (1114-2496 µg/m³ mean), perhaps because of material and binder spraying, where part of the spray can become aerosolized. Chemical treatment of manufactured objects was found to be a severe volatile organic compounds source as well. Formaldehyde was detected in low concentrations (3-40 µg/m³) in all methods except for material jetting method, in addition to several other carbonyl compounds. Notable dust concentrations (1.4-9.1 mg/m³) were detected only during post-processing of powder bed fusion and multi jet fusion manufactured objects. Indoor air quality parameters were not found to be notably impacted by manufacturing operations. Only low concentrations (below 2 ppm) of CO were detected during several manufacturing processes. All studied additive manufacturing operations emitted potentially harmful contaminants into their environments, which should be considered in occupational additive manufacturing and workplace design. According to the measured contaminant levels it is possible that adverse additive manufacturing related health effects may occur amongst exposed workers.
... The VOC emission concentration was measured in real indoor environments, expressed in units with the unit of mass emitted per volume (µg/m 3 ). For example, the TVOC values were 216.5-317.7 µg/m 3 for ABS filaments in a printing room and university laboratory [38,39]. The dominant VOCs species reported in the real indoor environment were sebacic acid, 3methylbut-2-enyl propyl ester, decane, styrene, 2-amino-2-oxo-acetic acid, N- [3,4-dimethyl], ethyl ester, and nonanal, and the concentration ranged from 3.0 to 23.0 µg/m 3 [38][39][40]. ...
... For example, the TVOC values were 216.5-317.7 µg/m 3 for ABS filaments in a printing room and university laboratory [38,39]. The dominant VOCs species reported in the real indoor environment were sebacic acid, 3methylbut-2-enyl propyl ester, decane, styrene, 2-amino-2-oxo-acetic acid, N- [3,4-dimethyl], ethyl ester, and nonanal, and the concentration ranged from 3.0 to 23.0 µg/m 3 [38][39][40]. These dominant species were mostly OVOCs, which may indicate that the emitted VOCs were being oxidized in the real indoor environment, where the concentration of oxidants (i.e., O 3 and OH) were likely significant under the light sources. ...
... In most of the chamber studies, the emission rate of VOCs was discussed in terms of the mass emitted per unit time (µg/min). Tables S1 and S2 summarize the emission rates of different VOC substances from ABS and PLA filaments [21,35,36,39,[41][42][43][44][45][46][47][48][49][50]. A total of 36 types of VOC, including hydrocarbons, ketones, aldehydes, alcohols, aliphatic hydrocarbons, carboxylic acids, esters, siloxanes, and other compounds, were identified from the emissions when ABS filaments were used as the printing material. ...
The utilization of 3D printing releases a multitude of harmful gas pollutants, posing potential health risks to operators. Materials extrusion (ME; also known as fused deposition modeling (FDM)), a widely adopted 3D printing technology, predominantly employs acrylonitrile–butadiene–styrene (ABS) and polylactic acid (PLA) as printing materials, with the respective market shares of these materials reaching approximately 75%. The extensive usage of ABS and PLA during the ME process leads to significant volatile organic compound (VOC) emissions, thereby deteriorating the quality of indoor air. Nevertheless, information regarding the emission characteristics of VOCs and their influencing factors, as well as the toxicological impacts of the printing processes, remains largely unknown. Herein, we thoroughly reviewed the emission characteristics of VOCs released during ME printing processes using ABS and PLA in various printing environments, such as chambers, laboratories, and workplaces, as well as their potential influencing factors under different environmental conditions. A total of 62 VOC substances were identified in chamber studies using ABS and PLA filaments; for example, styrene had an emission rate of 0.29–113.10 μg/min, and isopropyl alcohol had an emission rate of 3.55–56.53 μg/min. Emission rates vary depending on the composition of the filament’s raw materials, additives (such as dyes and stabilizers), printing conditions (temperature), the printer’s condition (whether it has closure), and other factors. Additionally, we reviewed the toxicological concerns associated with hazardous VOC species commonly detected during the ME printing process and estimated cancer and non-cancer risks for users after long-term inhalation exposure. Potential health hazards associated with inhalation exposure to benzene, formaldehyde, acetaldehyde, styrene, and other substances were identified, which were calculated based on concentrations measured in real indoor environments. This study provides valuable insights for future research on the development of ME printing technologies and offers suggestions to reduce VOC emissions to protect users.
... Individual sample constituents were identified by comparing the mass spectral patterns and retention times of peaks in the samples to the mass spectral patterns and retention times of a standard curve (acetone, isopropyl alcohol, hexane, benzene, toluene, ethylbenzene, xylenes, and methyl acrylate, ethyl acrylate, ethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, allyl methacrylate, glycidyl methacrylate, and hydroxypropyl methacrylate). Compounds in the standard curve were selected based on ingredient lists from Safety Data Sheets (SDS), prior characterization of vat resins (author's unpublished data), and available literature [5,[12][13][14][15][16][23][24][25][26]. Additionally, tentatively identified compounds were qualitatively identified from the remaining chromatographic peaks based on the mass spectral matches with mass spectral library software (Wiley Registry 8th Edition/NIST 2008 Mass Spectral Library, Wiley-Blackwell, New York, NY, USA) and a manual review by the analyst. ...
... This observation was consistent with Zhang et al. who reported that sub-micron size particle concentrations released during SLA printing were similar to the background [34]. In a series of studies, Väisänen et al. used a CNC to monitor emissions from several different VP machines and resins during printing [15,16]. In their studies, average particle concentrations during the operation of SLA and DLP printers were approximately 1200 to 3600 #/cm 3 . ...
... Though particle emission rates differed on a group-level basis in that study, for the specific SLA and DLP printers used in the current study, particle number concentrations were not significantly different [23]. Väisänen et al. reported that maximum particle number concentrations measured using a CNC instrument while printing with SLA and DLP printers were approximately 4000 to 13,500 #/cm 3 [15,16]; however, VP particle concentrations tend to be lower than fused filament fabrication (FFF). As heat is used to melt the polymer, particle concentrations can reach a maximum of 2 × 10 5 -1 × 10 6 #/cm 3 [3]. ...
Vat photopolymerization (VP), a type of additive manufacturing process that cures resin to build objects, can emit potentially hazardous particles and gases. We evaluated two VP technologies, stereolithography (SLA) and digital light processing (DLP), in three separate environmental chambers to understand task-based impacts on indoor air quality. Airborne particles, total volatile organic compounds (TVOCs), and/or specific volatile organic compounds (VOCs) were monitored during each task to evaluate their exposure potential. Regardless of duration, all tasks released particles and organic gases, though concentrations varied between SLA and DLP processes and among tasks. Maximum particle concentrations reached 1200 #/cm3 and some aerosols contained potentially hazardous elements such as barium, chromium, and manganese. TVOC concentrations were highest for the isopropyl alcohol (IPA) rinsing, soaking, and drying post-processing tasks (up to 36.8 mg/m3), lowest for the resin pouring pre-printing, printing, and resin recovery post-printing tasks (up to 0.1 mg/m3), and intermediate for the curing post-processing task (up to 3 mg/m3). Individual VOCs included, among others, the potential occupational carcinogen acetaldehyde and the immune sensitizer 2-hydroxypropyl methacrylate (pouring, printing, recovery, and curing tasks). Careful consideration of all tasks is important for the development of strategies to minimize indoor air pollution and exposure potential from VP processes.
... Thus far it is known that the VP and MJ machines both emit volatile organic compounds (VOCs) and ultrafine particles (UFPs), which are recognized as major occupational exposure agents of concern within the AM industry (Chan et al. 2020;MacCuspie et al. 2021;Petretta et al. 2019;Roth et al. 2019;Ryan and Hubbard 2016;Yi et al. 2016). These emission studies include our preliminary study (Väisänen et al. 2019), and research conducted by Yang and Li 2018;Stefaniak et al. 2019a;2019b;Zisook et al. 2020;Hayes et al. 2021. The accumulated data are still insufficient for comprehensive safety evaluation of these methods, and more exposure data are needed. ...
... Volatile organic compounds (VOCs), carbonyls, and UFPs were identified as the main emission products formed during AM with VP and MJ methods in our preliminary study, while no larger particles were produced in substantial quantities (Väisänen et al. 2019). These findings are supported by Ryan and Hubbard (2016), Yang and Li (2018), Stefaniak, Johnson, and Du Preez (2019a;, Zisook, Simmons, and Vater (2020), and Hayes et al. (2021). ...
... Few comparable investigations exist for the evaluation of carbonyls that originate from similar sources as VOCs, in addition to chemical interactions in the air (Barro et al. 2009). In comparison to our preliminary study, the measured concentrations were similar (Väisänen et al. 2019). Ryan and Hubbard (2016) and Zisook, Simmons, and Vater (2020) detected acetone and 2-butanone in <250 ppb-range during VP and MJ machine operations. ...
Photopolymer resins are applied at an increasing rate in additive manufacturing (AM) industry as vat photopolymerization (VP) and material jetting (MJ) methods gain more popularity. The aim of this study was to measure volatile organic compound (VOC), carbonyl compound, ultrafine particle (UFP), and particulate matter (PM10) air concentrations emitted in 3D printer operations. Individual chemicals were identified when multiple photopolymer resin feedstocks were used in various VP and MJ printers. The size distributions of UFPs, and indoor air parameters were also monitored. Finally, the VOC outgassing of the cured resin materials was determined over 84 days. The data demonstrated that 3D printer operators were exposed to low concentrations of airborne exposure agents as follows: average concentrations of VOCs were between 41 and 87 µg/m³, UFP number levels ranged between 0.19 and 3.62 × 10³ number/cm³; however, no impact was detected on air parameters or PM10 concentrations. A majority of the UFPs existed in the 10–45 nm size range. The identified compounds included hazardous species included sensitizing acrylates and carcinogenic formaldehyde. The outgassed products included similar compounds that were encountered during the AM processes, and post-processing solvents. Products heated to 37°C emitted 1.4‒2.9-fold more VOCs than at room temperature. Total emissions were reduced by 84‒96% after 28 days roughly from 3000–14000 to 100–1000 µg/m²/hr. In conclusion, resin printer operators are exposed to low concentrations of hazardous emissions, which might result in adverse health outcomes during prolonged exposure. Manufactured resin products are suggested to be stored for 4 weeks after their production to reduce potential consumer VOC hazards.
... The thermal processing of polymers is a known source of volatile organic compounds (VOCs). These compounds consist of a carbon skeleton and may carry bound functional groups [13][14][15][16][17][18][19]. The typical organic compounds emitted in a polymer decomposition process are short, usually 2 to 8 carbon atoms in length, and capable of attaching to airborne particles [2,7,20]. ...
... The VOC and UFP emission concentrations were measured during 3D printing of ASTM D638 type IV tensile test specimens. These pollutants were selected because they have been identified as the main emission products originating from material extrusion 3D printing [13][14][15][16][17][18][19][21][22][23][24]. The tensile test specimens with a calculated volume of 6.22 cm 3 were fabricated by applying 0/90-degree printing angle, 100% infill and feed rates, 0.2 mm layer thickness, and 0.4 mm path width. ...
... The compound concentrations were calculated as toluene equivalents. For additional details, please see the preliminary study [19]. ...
The alterations in volatile organic compound (VOC) and ultrafine particulate (UFP) matter emission profiles following thermal reprocessing of multiple materials were examined. Additionally, mechanical performance of the materials was studied. The VOCs were identified by collecting air samples with Tenax® TA tubes and analyzing them with a GC–MS system. UFP concentrations were monitored with a portable ultrafine particle counter. Total VOC emissions of all materials were reduced by 28–68% after 5 thermal cycles (TCs). However, slight accumulation of 1,4-dioxane was observed with poly(lactic acid) materials. UFP emissions were reduced by 45–88% for 3D printing grade materials over 5 TCs but increased by 62% in the case of a waste plastic material over 3 TCs. The mechanical performance of the materials was investigated by measuring their tensile strengths (TSs) and elastic moduli (EM) with an axial-torsion testing system. The reprocessed materials expressed fluctuations in their 3D printing qualities and mechanical performances. The mechanical performances were observed to reduce only slightly after 5 TCs, and the trend was observable only after the data was mass-normalized. The TSs of the samples were reduced by 10–24%, while the EM were reduced by 1–9% after 5 TCs. The TS and EM of one material were increased by 14 and 33%, respectively. In conclusion, recycled polymers are plausible 3D printing feedstock alternatives as they possess acceptable mechanical performance and low emittance according to this study. Furthermore, non-3D printing grade polymers may be applied in a 3D printer with caution.
... Toxicological studies [12]- [14] confirmed that the operators of SLS AM machines are exposed to particulate matter and ultrafine particles from powder handling, where the particles enter their lungs and bloodstream through respiration. According to Vä isä nen et al. [15], PBF technologies increase the risk of health hazards, especially during handling of materials and objects. Graff et al. [16] evaluated the occupational exposure to virgin and recycled metal powders during SLS AM process. ...
... To date, only a few studies [15], [16] have been conducted to investigate the association between occupational exposure the use of virgin and recycled powders in SLS processes. Hence, the objective of this study was to assess the occupational exposure (in terms of the total particulate concentration and respirable particulate concentration) during the pre-processing and post-processing activities of the SLS process, all of which involve powder handling. ...
... The pouring height was fixed at 0.25 m [20]. The pre-processing and post-processing activities conform with those of other studies [15], [21], [22] which involved investigating the occupational exposure during powder handling in other industrial sectors. The occupational exposure (in terms of the total particulate concentration and respirable particulate concentration) was monitored during the pre-processing and post-processing activities [23]. ...
Particulate matter and ultrafine particles are emitted during the pre-processing and post-processing activities of selective laser sintering (SLS) processes, which is major concern to operators exposed to the powders. This study aims to determine the occupational exposure (in terms of the total particle concentration and respirable particulate concentration) during the pre-processing and post-processing activities of SLS processes using virgin and recycled polyamide 12 (PA12) powders. Personal air sampling was performed for each activity according to the NIOSH 0500 and NIOSH 0600 methods. Based on the results, both powders were uniform spheres with a particle size of 40–60 μm. The total particulate concentration was most significant during the following pre-processing activities: 1) pouring powder into the mixing machine and 2) transferring the powder to the SLS AM machine. The total particulate concentration and respirable particulate concentration were slightly higher for the virgin powder for these activities. In conclusion, the virgin and recycled PA12 powders were both inhalable and respirable, which poses serious health hazards to the SLS AM operators. Hence, it is essential for operators to use suitable personal protective equipment (including respirators) and the working practices need to be improved by automating
... Exposure from printing polymeric materials has been assessed for ME (Du Preez, 2018;Stefaniak et al., 2019b,c) and MJ (Stefaniak et al., 2019b). Väisänen et al. (2019) evaluated exposure from different printing methods in industrial settings (ME, VP, PBF, and MJ) and similar research was done by Zisook et al. (2020). As the emission and personal exposure largely depend on differences in printing methods and related pre-and post-activities, as well as printing material, there is a need for further exposure measurements and development of appropriate measurement strategies for the specific printing methods. ...
... Knowledge of exposure from AM in industrial environments is relatively scarce with presently some data presented for ME printing (Du Preez, 2018;Stefaniak et al., 2019b,c;Väisänen et al., 2019;Zisook et al., 2020). For other printing methods even less has been published to date (Stefaniak et al., 2019b;Väisänen et al., 2019;Zisook et al., 2020). ...
... Knowledge of exposure from AM in industrial environments is relatively scarce with presently some data presented for ME printing (Du Preez, 2018;Stefaniak et al., 2019b,c;Väisänen et al., 2019;Zisook et al., 2020). For other printing methods even less has been published to date (Stefaniak et al., 2019b;Väisänen et al., 2019;Zisook et al., 2020). In the present study, Figure 2. Emissions of particles sized 10 nm to 1 µm during various AM tasks at A-PBF, measured by CPC 3007. ...
3D printing, a type of additive manufacturing (AM), is a rapidly expanding field. Some adverse health effects have been associated with exposure to printing emissions, which makes occupational exposure studies important. There is a lack of exposure studies, particularly from printing methods other than material extrusion (ME). The presented study aimed to evaluate measurement methods for exposure assessment in AM environments and to measure exposure and emissions from four different printing methods [powder bed fusion (PBF), material extrusion (ME), material jetting (MJ), and vat photopolymerization] in industry. Structured exposure diaries and volatile organic compound (VOC) sensors were used over a 5-day working week. Personal and stationary VOC samples and real-time particle measurements were taken for 1 day per facility. Personal inhalable and respirable dust samples were taken during PBF and MJ AM. The use of structured exposure diaries in combination with measurement data revealed that comparatively little time is spent on actual printing and the main exposure comes from post-processing tasks. VOC and particle instruments that log for a longer period are a useful tool as they facilitate the identification of work tasks with high emissions, highlight the importance of ventilation and give a more gathered view of variations in exposure. No alarming levels of VOCs or dust were detected during print nor post-processing in these facilities as adequate preventive measures were installed. As there are a few studies reporting negative health effects, it is still important to keep the exposure as low as reasonable.
... As a result, filament in the extruder nozzle continues to be heated though the machine is not printing. Particle number concentration and LDSA dose, as well as TVOC concentration, were found to increase when a FFF 3D printer malfunctioned compared with normal operation (Mendes et al. 2017;Stefaniak et al. 2019c;Väisänen et al. 2019). ...
... Four studies were identified on the emissions from MJ machines (Ryan and Hubbard 2016;Stefaniak et al. 2019b;Väisänen et al. 2019;Zisook et al. 2020). These studies reported measurements from five different workplaces, which included an office and industrial workplaces. ...
... MJ machine operators' PBZ exposures to VOCs at one facility included acetone (20 to 80 µg/m 3 ), ethanol (520 to 2020 µg/m 3 , REL = 1,900,000 µg/m 3 ), isopropyl alcohol (70 to 520 µg/m 3 ), naphtha (1530 to 1710 µg/m 3 , REL = 400,000 µg/m 3 ), and pentane (10 to 60 µg/ m 3 ) (Stefaniak et al. 2019b). Väisänen et al. (2019) characterized emissions and indoor air quality (IAQ) parameters during MJ printing and post-processing tasks using a transparent/clear liquid photopolymer resin (3D systems, VisiJet M2R-CL). Post-processing involved ultrasound treatment while submerging the manufactured part in a water container. ...
This comprehensive review introduces occupational (industrial) hygienists and toxicologists to the seven basic additive manufacturing (AM) process categories. Forty-six articles were identified that reported real-world measurements for all AM processes, except sheet lamination. Particles released from powder bed fusion (PBF), material jetting (MJ), material extrusion (ME), and directed energy deposition (DED) processes exhibited nanoscale to submicron scale; real-time particle number (mobility sizers, condensation nuclei counters, miniDiSC, electrical diffusion batteries) and surface area monitors (diffusion chargers) were generally sufficient for these processes. Binder jetting (BJ) machines released particles up to 8.5 µm; optical particle sizers (number) and laser scattering photometers (mass) were sufficient for this process. PBF and DED processes (powdered metallic feedstocks) released particles that contained respiratory irritants (chromium, molybdenum), central nervous system toxicants (manganese), and carcinogens (nickel). All process categories, except those that use metallic feedstocks, released organic gases, including (but not limited to), respiratory irritants (toluene, xylenes), asthmagens (methyl methacrylate, styrene), and carcinogens (benzene, formaldehyde, acetaldehyde). Real-time photoionization detectors for total volatile organics provided useful information for processes that utilize polymer feedstock materials. More research is needed to understand 1) facility-, machine-, and feedstock-related factors that influence emissions and exposures, 2) dermal exposure and biological burden, and 3) task-based exposures. Harmonized emissions monitoring and exposure assessment approaches are needed to facilitate inter-comparison of study results. Improved understanding of AM process emissions and exposures is needed for hygienists to ensure appropriate health and safety conditions for workers and for toxicologists to design experimental protocols that accurately mimic real-world exposure conditions.
ABBREVIATIONS ABS : acrylonitrile butadiene styrene; ACGIH® TLV® : American Conference of Governmental Industrial Hygienists Threshold Limit Value; ACH : air change per hour; AM : additive manufacturing; ASA : acrylonitrile styrene acrylate; AVP : acetone vapor polishing; BJ : binder jetting; CAM-LEM : computer-aided manufacturing of laminated engineering materials; CNF : carbon nanofiber; CNT : carbon nanotube; CP : co-polyester; CNC : condensation nuclei counter; CVP : chloroform vapor polishing; DED : directed energy deposition; DLP : digital light processing; EBM : electron beam melting; EELS : electron energy loss spectrometry; EDB : electrical diffusion batteries; EDX : energy dispersive x-ray analyzer; ER : emission rate; FDM™ : fused deposition modeling; FFF : fused filament fabrication; IAQ : indoor air quality; LSP : laser scattering photometer; LCD : liquid crystal display; LDSA : lung deposited particle surface area; LOD : limit of detection; LOM : laminated object manufacturing; LOQ : limit of quantitation; MCE : mixed cellulose ester filter; ME : material extrusion; MJ : material jetting; OEL : occupational exposure limit; OPS : optical particle sizer; PBF : powder bed fusion; PBZ : personal breathing zone; PC : polycarbonate; PEEK : poly ether ether ketone; PET : polyethylene terephthalate; PETG : Polyethylene terephthalate glycol; PID : photoionization detector; PLA : polylactic acid; PM1 : particulate matter with aerodynamic diameter less than 1 µm; PM2.5 : particulate matter with aerodynamic diameter less than 2.5 µm; PM10 : particulate matter with aerodynamic diameter less than 10 µm; PSL : plastic sheet lamination; PVA : polyvinyl alcohol; REL : recommended exposure limit; SDL : selective deposition lamination; SDS : safety data sheet; SEM : scanning electron microscopy; SL : sheet lamination; SLA : stereolithography; SLM : selective laser melting; SMPS : scanning mobility particle sizer; SVOC : semi-volatile organic compound; TEM : transmission electron microscopy; TGA : thermal gravimetric analysis; TPU : thermo polyurethane; UAM : ultrasonic additive manufacturing; UC : ultrasonic consolidation; TVOC : total volatile organic compounds; TWA : time-weighted average; VOC : volatile organic compound; VP : vat photopolymerization
... Air quality monitoring enhances awareness and support informed decision making towards better air quality. Research mostly focuses on high-end monitoring [5], [6], [14]- [19]. Some authors try to make low-cost monitoring feasible by integrating it with signal processing and analysis [17], [20]. ...
... [6] uses a membrane pump directly connected to a chamber through an extraction tube and an activated carbon vial on PLA and ABS to monitor VOCs. [14] uses absorption tubes, an air sampling pump, a thermo-desorption instrument, a chromatography system, and a mass spectrometer to analyse the VOC produced by diverse techniques for 3D printing in six different settings. [15] uses a scanning mobility particle sizer with a differential mobility analyser to measure particle size distribution to identify ultrafine particles (UFP) in a FDM 3D printing process with different materials. ...
Human exposure to poor air quality is a leading risk factor in the Global Burden of Disease (GBD) study, estimating 22,000 premature deaths related to indoor air pollution in 2019 in Europe. Diverse pollutants are found in manufacturing environments resulting from both combustion and non-combustion sources, including Particulate Matter and Volatile Organic Compound. Internet of Things (IoT) air quality monitoring can enhance awareness and support informed decision making towards better air quality. However, hardware sensors are not always capable of monitoring particular characteristics and behaviour of a pollutant, for instance, spatial limitations may impede deploying sensors close enough to the source of the pollutant. Virtual Sensors can extend hardware sensing options via signal processing and data integration. This paper presents an architecture for training and deploying virtual sensors. A virtual sensor is implemented using the architecture in the context of additive manufacturing to estimate the production of Volatile Organic Compounds (VOCs) of 3D printers and their transfer into the rest of the space. In the case study, the 3D printers are installed inside cabinets to limit the transfer of pollutants to the exterior. Several of these virtual sensors are deployed to monitor the VOCs produced by the 3D printers and the transfer rate out of the cabinets. The paper includes some early results and initial insights on the accuracy and usefulness of virtual sensors. Virtual Sensors can be cost-effective solutions when monitoring systems are escalated by reducing number of hardware sensors and complexity.
... Previous studies on emissions from polymer AM have shown that emissions are complex mixtures as can be expected from the combustion of polymer-based materials. Depending on technique and material, predominately ultrafine particles (<100 nm) are emitted in high concentrations, especially using material extrusion techniques (1)(2)(3). Isocyanic acid and volatile organic compounds (VOCs) are also emitted, including acetaldehyde, acetone, acrolein, formaldehyde, benzaldehyde, butadiene, iso-butanol, cyclohexanone, styrene, and ethylbenzene (3,4). ...
... The results presented herein showed that groups of organic compounds, e.g., acrylates, aliphatic hydrocarbons, aldehydes, and alcohols were present in emissions from feedstock and maintenance work. Techniques giving rise to the highest levels of VOC and compounds identified as dominating, e.g., methyl methacrylate (VP) and isobornyl acrylate (MJ), show a good correlation with a previous study of VOCs from various print techniques performed by Väisänen et al. (2). ...
Additive manufacturing (AM), or 3D printing, is a growing industry involving a wide range of different techniques and materials. The potential toxicological effects of emissions produced in the process, involving both ultrafine particles and volatile organic compounds (VOCs), are unclear, and there are concerns regarding possible health implications among AM operators.
The objective of this study was to screen the presence of respiratory health effects among people working with liquid, powdered, or filament plastic materials in AM.
Methods
In total, 18 subjects working with different additive manufacturing techniques and production of filament with polymer feedstock and 20 controls participated in the study. Study subjects filled out a questionnaire and underwent blood and urine sampling, spirometry, impulse oscillometry (IOS), exhaled NO test (FeNO), and collection of particles in exhaled air (PEx), and the exposure was assessed. Analysis of exhaled particles included lung surfactant components such as surfactant protein A (SP-A) and phosphatidylcholines. SP-A and albumin were determined using ELISA. Using reversed-phase liquid chromatography and targeted mass spectrometry, the relative abundance of 15 species of phosphatidylcholine (PC) was determined in exhaled particles. The results were evaluated by univariate and multivariate statistical analyses (principal component analysis).
Results
Exposure and emission measurements in AM settings revealed a large variation in particle and VOC concentrations as well as the composition of VOCs, depending on the AM technique and feedstock. Levels of FeNO, IOS, and spirometry parameters were within clinical reference values for all AM operators. There was a difference in the relative abundance of saturated, notably dipalmitoylphosphatidylcholine (PC16:0_16:0), and unsaturated lung surfactant lipids in exhaled particles between controls and AM operators.
Conclusion
There were no statistically significant differences between AM operators and controls for the different health examinations, which may be due to the low number of participants. However, the observed difference in the PC lipid profile in exhaled particles indicates a possible impact of the exposure and could be used as possible early biomarkers of adverse effects in the airways.
... Regarding particle emissions in polymer printing environments, a study by Väisänen et al. (2019) showed that particle concentrations were highest (2,070-81,890 particles/cm 3 ) during manufacturing with methods where plastics were thermally processed. Another study by Zisook et al. (2020) showed that submicron particles, predominantly nanoparticles, were produced during material extrusion printing using ABS at approximately 12,000 particles/cm 3 above background. ...
... Personal exposures were 380 to 6,470 μg/m 3 for acetone during AVP and 180 μg/m 3 for chloroform during CVP (Du Preez et al., 2018). Väisänen et al. (2019) showed that VOC concentrations, were low (113-317 μg/m 3 ) during manufacturing where plastics were thermally processed, and during vat photopolymerization. However, Zisook et al. (2020) showed that total VOC concentrations of MJ and multi jet fusion methods were higher (1,114-2,496 μg/m 3 ), probably due to material and binder spraying, where part of the spray can become aerosolized. ...
Additive manufacturing (AM) or industrial three-dimensional (3D) printing drives a new spectrum of design and production possibilities; pushing the boundaries both in the application by production of sophisticated products as well as the development of next-generation materials. AM technologies apply a diversity of feedstocks, including plastic, metallic, and ceramic particle powders with distinct size, shape, and surface chemistry. In addition, powders are often reused, which may change the particles’ physicochemical properties and by that alter their toxic potential. The AM production technology commonly relies on a laser or electron beam to selectively melt or sinter particle powders. Large energy input on feedstock powders generates several byproducts, including varying amounts of virgin microparticles, nanoparticles, spatter, and volatile chemicals that are emitted in the working environment; throughout the production and processing phases. The micro and nanoscale size may enable particles to interact with and to cross biological barriers, which could, in turn, give rise to unexpected adverse outcomes, including inflammation, oxidative stress, activation of signaling pathways, genotoxicity, and carcinogenicity. Another important aspect of AM-associated risks is emission/leakage of mono- and oligomers due to polymer breakdown and high temperature transformation of chemicals from polymeric particles, both during production, use, and in vivo, including in target cells. These chemicals are potential inducers of direct toxicity, genotoxicity, and endocrine disruption. Nevertheless, understanding whether AM particle powders and their byproducts may exert adverse effects in humans is largely lacking and urges comprehensive safety assessment across the entire AM lifecycle—spanning from virgin and reused to airborne particles. Therefore, this review will detail: 1) brief overview of the AM feedstock powders, impact of reuse on particle physicochemical properties, main exposure pathways and protective measures in AM industry, 2) role of particle biological identity and key toxicological endpoints in the particle safety assessment, and 3) next-generation toxicology approaches in nanosafety for safety assessment in AM. Altogether, the proposed testing approach will enable a deeper understanding of existing and emerging particle and chemical safety challenges and provide a strategy for the development of cutting-edge methodologies for hazard identification and risk assessment in the AM industry.
... The severity of these hazards varies between different AM techniques, operation parameters, and materials used (Roth et al., 2019;Stefaniak et al., 2021;Romanowski et al., 2023). Most of the studies have concentrated on MEX printers, especially desktop printers (Stephens et al., 2013;Viitanen et al., 2021;Dunn et al., 2020;Du Preez et al., 2018;Azimi et al., 2016;Wojtyła et al., 2020;Zhang et al., 2017;Stabile et al., 2017;Floyd et al., 2017;Mendes et al., 2017), but some studies on PBF (Graff et al., 2017;Kangas et al., 2023;Jensen, A.C.0., Harboe, H., Brostrøm, A., Jensen, K.A., Fonseca, A.S., 2020), directed energy deposition DED (Bau et al., 2020;Ding and Ng, 2021), binder jetting BJT (Kangas et al., 2023;Afshar-Mohajer et al., 2015) and VPP (Zisook et al., 2020;Väisänen et al., 2022;Väisänen et al., 2019) have been published as well. ...
... For a polyvinyl alcohol (PVA) filament, calculated particulate matter with diameter less than 2.5 µm (PM 2.5 ) mass concentration in an office reached approximately 1 mg/m 3 (Ding and Ng 2021). In a study that evaluated aerosol mass concentrations during the FFF 3DP with several different filaments (none of which was PC), dust mass levels ranged from 0.01 to 0.03 mg/m 3 (Chan et al. 2020;Ding and Ng 2021;Katz et al. 2020;Väisänen et al. 2019). A few studies reported aerosol mass concentrations during the FFF 3DP with PC filament with results ranging from approximately 1 to 4 mg/m 3 (Chýlek et al. 2019;McDonnell et al. 2016;Runström et al. 2022). ...
... These can all be entered with the help of software or the machine control unit and construct so-called input parameters. Figure 3 shows an extended cause and effect diagram of the FFF technology for obtaining correct dimensional accuracy (PD) and surface quality (CS) (Mosleh, Rezadoust, & Dariushi, 2021;Tsiolikas, Mikrou, Vakouftsi, Aslani, & Kechagias, 2019;Väisänen, Hyttinen, Ylönen, & Alonen, 2019). ...
Fused filament fabrication (FFF) is a popular additive manufacturing technique with the ability to produce products in industries such as automotive, aerospace, and medical due to the potential for material waste and the manufacturing of complex geometries with different materials. For high-strength parts, it is crucial to investigate and optimize printing parameters to make the printed parts as strong as possible. This work will focus on the experimental investigation of parameter optimization for the strength of carbon fiber reinforced PET-G (PETG+CF), which is carried out using Taguchi's method and the samples were produced according to the orthogonal matrix L16 and to study if influence by ANOVA (analysis of variance). It was possible to conclude that the best parameters for the tensile strength of PETG+CF with temperature of 250° C, part orientation at 60°, layer height of 0.30mm, 100% fill density and with triangle fill pattern.
... 2020). VOC concentrations measured previous studies in the additive manufacturing during the material jetting and multi jet fusion methods ranged from 1 to 2.5 mg/m 3 were determined to be lower than in this study results (Bravi et al. 2019;Väisänen et al. 2019). Sekar et al. (2022) carried out the characterization of VOCs in a lignite mine and the results present the total VOCs for 78 μg/m 3 , 57 μg/m 3 , and 2763 μg/ m 3 in blast-hole drilling, conveyor belt yard, and belt reconditioning plant, respectively. ...
Exposure to the high Volatile Organic Compounds (VOCs) concentration in the workplaces where solvents are used is an essential point for worker health. However, the VOCs in the indoor air of an adhesive tape production facilities that use large amounts of solvents and the health risk of the toxic compounds have not been sufficiently investigated to this date. VOCs samples were collected in the morning and afternoon times of day in the indoor air of workplaces of an adhesive tape production facility at 9 different points under two different central ventilation conditions. Carbon dioxide, humidity, temperature, flow rate and pressure values were measured continuously throughout the work time with an average recording period of 1 minute. The total VOCs value had a wide range from 0.1 to 138 mg/m³. BTEX (benzene, toluene, ethylbenzene, xylenes) contribution to total VOC accounted for between 40-60 % and the toluene, methylepentane and trichloroethane concentrations among the sampling points and campaigns dominated the total VOCs. The total hazard quotient (HQ) values for each measurement campaigns were higher than the acceptable limit of 1.0, while the lifetime cancer risk (LCR) values for benzene and carbon tetrachloride were lower than the acceptable limit of 1.0x10-6. This observational study suggests that the effective and efficient operation of the workplace ventilation systems and the feasibility of the designed ventilation systems are essential on the accumulation of toxic compounds in the air and must be well evaluated.
... These instruments combine photometric measurements of the particle cloud and optical sizing of single particles in a visual system and measure different particle size fractions, total dust, respirable dust, and particulate matter (PM 2.5 , PM 10 , and PM 1 ) [16]. Light-scattering technologies have become increasingly popular for occupational monitoring purposes [17][18][19]. However, previous studies have shown that these technologies are not as accurate as gravimetric sampling [20], as they are sensitive to the size distribution, shape, angle, and composition of particles [9]. ...
Using an exposure chamber, we investigate the precision of the DustTrak DRX monitor by comparing its results to those obtained from taking traditional gravimetric samples of two stone minerals commonly used in asphalt and lactose powder. We also discuss the possibility of using real-time monitors such as DustTrak DRX for occupational exposure monitoring purposes.
The results are based on 19 days of experiment, each day with measurements collected over 4 h. Compared to the gravimetric samples, the DustTrak DRX overestimated the PM2.5 and respirable dust concentrations, while it underestimated the total dust concentration by a factor of nearly two. However, the ratios, being done for more than one material, between the DustTrak DRX and the gravimetric sample readings varied daily and across the different exposure materials.
Real-time sensors have the potential to excel at identifying exposure sources, evaluating the measured control efficiency, visualizing variations in exposure to motivate workers, and contributing to the identification of measures to be implemented to reduce exposure. For total dust, a correction factor of at least two should be used to bring its readings up to those for the corresponding gravimetric samples. Also, if the DustTrak DRX is used in the initial profiling of occupational exposure, the exposure could be considered acceptable if the readings are well below the occupational exposure limit (OELs) after correction. If the DustTrak DRX readings, after correction, is close to, or above, the accepted exposure concentrations, more thorough approaches would be required to validate the exposure.
... These instruments combine photometric measurements of the particle cloud and optical sizing of single particles in a visual system and measure different particle size fractions, total dust, respirable dust, and particulate matter (PM 2.5 , PM 10 , and PM 1 ) [16]. Light-scattering technologies have become increasingly popular for occupational monitoring purposes [17][18][19]. However, previous studies have shown that these technologies are not as accurate as gravimetric sampling [20], as they are sensitive to the size distribution, shape, angle, and composition of particles [9]. ...
Occupational exposure concentrations are routinely collected using gravimetric samples. However, gravimetric samples typically require a long sampling time, especially when there are low exposure concentrations. While long sampling time may be appropriate to verify compliance with 8-h occupational limit values (OELs), they cannot address exposure's temporal and spatial heterogeneity or provide information on peak exposures present in the work environment. Real-time light scattering sensors enable the possibility of collecting high-resolution, low-cost measurements, quickly identifying peak and short-term concentrations, linking exposure to emission sources, and better understanding within-day variation. These technologies have become increasingly popular also for occupational monitoring purposes. In this presentation, the results of the dust samples collected for a randomized double-blinded controlled human exposure chamber study are presented. In six groups, 24 healthy volunteers were exposed to two common stone minerals, quartz diorite, and rhomb porphyry, in 4-h exposure sessions. To control the exposure in the chamber, personal gravimetric samples of respirable dust and stationary gravimetric samples of total dust, PM2.5, and respiratory dust were collected. Additionally, stationary real-time samples of total dust, respirable dust, PM10, PM2.5, and PM1 were collected continuously using DustTrak TSI model DRX 8533. Despite the many advantages of the real-time sensors, evaluating compliance with OELs should be done with caution. Except for the PM2.5 fraction, a significant difference was observed between the gravimetric and the DustTrak samples. While the DustTrak overestimated the PM2.5 concentrations, the total dust concatenations were underestimated by a factor of almost two compared to the gravimetric samples.
... Of the 55 polymers examined by Lithner et al. (2011), 31 were found to be made of monomers belonging to the highest two of the ranking model's five hazard levels. Workers are also exposed to additives at levels at which adverse health effects may occur (Väisänen et al. 2019;Stefaniak et al. 2021). ...
https://www.unep.org/resources/report/chemicals-plastics-technical-report
The report provides state of knowledge on chemicals in plastics and based on compelling scientific evidence calls for urgent action to address chemicals in plastics as part of the global action on plastic pollution.
Overview of the report:
The “Chemicals in Plastics: A Technical Report” aims to inform the global community about the often-overlooked chemical-related issues of plastic pollution, particularly their adverse impacts on human health and the environment as well as on resource efficiency and circularity. Based on compelling scientific evidence, it further highlights the urgent need to act and outlines possible areas for action. It also aims to support the negotiation process to develop the instrument on plastic pollution based on United Nations Environment Assembly resolution 5/14. The report outlines a set of credible and publicly available scientific studies and initiatives focused on chemicals in plastics and the science-policy interface.
The report was developed by UNEP in cooperation with the Secretariat of the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal, the Rotterdam Convention on the Prior Informed Consent Procedure for Certain Hazardous Chemicals and Pesticides in International Trade, and the Stockholm Convention on Persistent Organic Pollutants, with lead authors from the International Panel on Chemical Pollution, as well as contributions from key experts.
Some key findings:
Based on the latest studies, more than 13,000 chemicals have been identified as associated with plastics and plastic production across a wide range of applications.
Ten groups of chemicals (based on chemistry, uses, or sources) are identified as being of major concern due to their high toxicity and potential to migrate or be released from plastics, including specific flame retardants, certain UV stabilizers, per- and polyfluoroalkyl substances (PFASs), phthalates, bisphenols, alkylphenols and alkylphenol ethoxylates, biocides, certain metals and metalloids, polycyclic aromatic hydrocarbons, and many other non-intentionally added substances (NIAS).
Chemicals of concern have been found in plastics across a wide range of sectors and products value chains, including toys and other children's products, packaging (including food contact materials), electrical and electronic equipment, vehicles, synthetic textiles and related materials, furniture, building materials, medical devices, personal care and household products, and agriculture, aquaculture and fisheries.
Chemicals of concern in plastics can impact our health and our environment: Extensive scientific data on the potential adverse impacts of about 7,000 substances associated with plastics show that more than 3,200 of them have one or more hazardous properties of concern.
Women and children are particularly susceptible to these toxic chemicals. Exposures can have severe or long-lasting adverse effects on several key period of a women’s life and may impact the next generations. Exposures during fetal development and in children can cause, for example, neurodevelopmental / neurobehavioural related disorders. Men are not spared either, with latest research documenting substantial detrimental effects on male fertility due to current combined exposures to hazardous chemicals, many of which are associated with plastics.
Chemicals of concern can be released from plastic along its entire life cycle, during not only the extraction of raw materials, production of polymers and manufacture of plastic products, but also the use of plastic products and at the end of their life, particularly when waste is not properly managed, finding their way to the air, water and soils.
Existing evidence calls for urgent action to address chemicals in plastics as part of the global action on plastic pollution, to protect human health and the environment, and transition to a toxic-free and sustainable circular economy.
UNEP acknowledges the financial support from the Government of Norway, the Government of Sweden and the Government of Switzerland, for the development of the report.
... However, exposure to gaseous and particulate contaminants in other AM methods has gained less attention (Runström Eden et al., 2022;Stefaniak et al., 2021). Exposure to particles and volatile organic compounds (VOCs) has been studied during PBF and BJT (Afshar-Mohajer et al., 2015;Graff et al., 2016;Mellin et al., 2016;Ljunggren et al., 2019;Väisänen et al., 2019;Zisook et al., 2020;Runström Eden et al., 2022). These studies showed that there exists notable exposure to contaminants not only during the 3D printing but especially during pre-and post-processing phases. ...
Particle and gaseous contaminants from industrial scale additive manufacturing (AM) machines were studied in three different work environments. Workplaces utilized powder bed fusion, material extrusion, and binder jetting techniques with metal and polymer powders, polymer filaments, and gypsum powder, respectively. The AM processes were studied from operator’s point of view to identify exposure events and possible safety risks. Total number of particle concentrations were measured in the range of 10 nm to 300 nm from operator’s breathing zone using portable devices and in the range of 2.5 nm to 10 µm from close vicinity of the AM machines using stationary measurement devices. Gas-phase compounds were measured with photoionization, electrochemical sensors, and an active air sampling method which were eventually followed by laboratory analyses. The duration of the measurements varied from 3 to 5 days during which the manufacturing processes were practically continuous. We identified several work phases in which an operator can potentially be exposed by inhalation (pulmonary exposure) to airborne emissions. A skin exposure was also identified as a potential risk factor based on the observations made on work tasks related to the AM process. The results confirmed that nanosized particles were present in the breathing air of the workspace when the ventilation of the AM machine was inadequate. Metal powders were not measured from the workstation air thanks to the closed system and suitable risk control procedures. Still, handling of metal powders and AM materials that can act as skin irritants such as epoxy resins were found to pose a potential risk for workers. This emphasizes the importance of appropriate control measures for ventilation and material handling that should be addressed in AM operations and environment.
... This offers the ability to preconcentrate emissions at lower concentrations while maintaining the dynamic nature of the emissions, which is in contrast to conventional sampling and analysis that deliver only a single snapshot covering the entire accumulation period. 22,23 ■ CONCLUSIONS A novel coupling of a microchamber/thermal extractor system with a real-time proton transfer reaction time-of-flight mass spectrometer instrument was explored as a method to characterize the dynamic emissions of volatile compounds from a model sample. Analyses of the dynamic volatile emissions from 3D-printed cube samples were made directly, either with a prior equilibration period under static conditions or without equilibration. ...
Indoor air is a complex and dynamic mixture comprising manifold volatile organic compounds (VOCs) that may cause physiological and/or psychological discomfort, depending on the nature of exposure. This technical note presents a novel approach to analyze VOC emissions by coupling a microchamber/thermal extractor (μ-CTE) system to a proton transfer reaction-mass spectrometer (PTR-MS). This configuration provides an alternative to conventional emissions testing of small objects. The dynamic emission profiles of VOCs from a representative 3D-printed model are presented as a proof-of-concept analysis. Emission profiles are related to the target compound volatility, whereby 2-propanol and acetaldehyde exhibited the highest emissions and most rapid changes compared to the less volatile vinyl crotonate, 2-hydroxymethyl methacrylate, and mesitaldehyde, which were present at lower concentrations and showed different dynamics. Comparative measurements of the emission profiles of these compounds either with or without prior static equilibration yielded stark differences in their dynamics, albeit converging to similar values after 15 min of sampling time. Further, the utility of this system to determine the time required to capture a specific proportion of volatile emissions over the sampling period was demonstrated, with a mean duration of 8.4 ± 0.3 min to sample 50% of emissions across all compounds. This novel configuration provides a means to characterize the dynamic nature of VOC emissions from small objects and is especially suited to measuring highly volatile compounds, which can present a challenge for conventional sampling and analysis approaches. Further, it represents an opportunity for rapid, targeted emissions analyses of products to screen for potentially harmful volatiles.
... DustTrak DXR Aerosol Monitors enable real-time monitoring of various particle fractions at high temporal resolutions (Rivas et al., 2017). These instruments combine photometric measurements of the particle cloud and optical sizing of single particles in a visual system and measure different particle size fractions, total dust, respirable dust, and particulate matter (PM 2.5 , PM 10 (Cavallari et al., 2016;Shao et al., 2021;Väisänen et al., 2019). However, previous studies have shown that these technologies are not as accurate as gravimetric sampling (Wang et al., 2016), as they are sensitive to the size distribution, shape, angle, and composition of particles (Rivas et al., 2017). ...
Using a human exposure chamber, we investigate the reliability of the DustTrak DXR monitor by comparing its results to those obtained from taking traditional gravimetric samples of two stone minerals commonly used in asphalt and lactose powder. We also discuss the possibility of using real-time monitors such as DustTrak for occupational exposure monitoring purposes.
The results are based on 19 days of experiment, each day with measurements collected over 4 h. Compared to the gravimetric samples, the DustTrak overestimated the PM2.5 and respirable dust concentrations, while it underestimated the total dust concentration by a factor of nearly two. However, the ratios, being done for more than one material, between the DustTrak and the gravimetric sample readings varied daily and across the different exposure materials.
Real-time sensors have the potential to excel at identifying exposure sources, evaluating the measured control efficiency, visualizing variations in exposure to motivate workers, and contributing to the identification of measures to be implemented to reduce exposure. For total dust, a correction factor of at least two should be used to bring its readings up to those for the corresponding gravimetric samples. Also, if the DustTrak is used in the initial profiling of occupational exposure, the exposure could be considered acceptable if the readings are well below the occupational exposure limit (OELs) after correction. If the DustTrak readings, after correction, is close to, or above, the accepted exposure concentrations, more thorough approaches would be required to validate the exposure.
... A major group of air emissions from 3D printing is the volatile organic compound (VOC). Experimental studies have reported the VOC emissions during the solidification processes of photocurable liquid resins in SL and DLP processes [29,30]. In addition, VOCs and particulate matters (PMs) have been identified as primary air emissions from FDM platforms with commonly used acrylonitrile butadiene styrene and polylactic acid filaments [31]. ...
4D printing of stimuli-responsive materials extends 3D printing by enabling the fabricated structures to transform their shapes and properties over time in response to external stimuli. Numerous research efforts have been dedicated to developing new smart materials, enhancing material printability, and ensuring time-evolving properties. Meanwhile, the use of smart materials and external stimuli in 4D printing has introduced the possibility of air emissions that can potentially deteriorate the indoor air quality at the workplace and pose continuous health hazards to users during the production and use phases. These potential air emissions caused by 4D printing have not yet been assessed in current literature, leading to unknown occupational hazards and human health effects. This study focuses on stereolithography-based 4D printing with constrained thermo-mechanics and builds an emission model to quantify the volatile organic compound emissions from printing, shape programming, and shape recovery stages. The established model mathematically links the emission characteristics with material compositional design and stimuli-response mechanisms. In addition, shape fixity and recovery abilities, as two key quality measures, are jointly considered to analyze the trade-off between the air emissions and stimuli-response performance of 4D printed parts. Case study results suggest that the methacrylate-based thermo-responsive material with higher glass transition temperature leads to higher air emissions, surpassing the permissible exposure level in the indoor environment. By altering the thermo-temporal conditions, a 61.29% reduction in emission yield can be achieved while ensuring a satisfactory shape memory performance.
... This methodology provides high accuracy and smooth surfaces in a relatively fast and uncostly process. However, the dispensed materials are expensive and messy, and can cause irritation to living tissues [28]. Moreover, heat sterilization is not an option, and products have a limited shelf life. ...
Compared to traditional manufacturing methods, additive manufacturing and 3D printing stand out in their ability to rapidly fabricate complex structures and precise geometries. The growing need for products with different designs, purposes and materials led to the development of 3D printing, serving as a driving force for the 4th industrial revolution and digitization of manufacturing. 3D printing has had a global impact on healthcare, with patient-customized implants now replacing generic implantable medical devices. This revolution has had a particularly significant impact on oral and maxillofacial surgery, where surgeons rely on precision medicine in everyday practice. Trauma, orthognathic surgery and total joint replacement therapy represent several examples of treatments improved by 3D technologies. The widespread and rapid implementation of 3D technologies in clinical settings has led to the development of point-of-care treatment facilities with in-house infrastructure, enabling surgical teams to participate in the 3D design and manufacturing of devices. 3D technologies have had a tremendous impact on clinical outcomes and on the way clinicians approach treatment planning. The current review offers our perspective on the implementation of 3D-based technologies in the field of oral and maxillofacial surgery, while indicating major clinical applications. Moreover, the current report outlines the 3D printing point-of-care concept in the field of oral and maxillofacial surgery.
... This category includes all the parameters that can be changed through the printer software or the MCU. Such parameters typically affect the cost of materials, mechanical properties, shape accuracy, surface quality, energy, and environment, [59][60][61][62][63][64] and include: ...
Fused filament fabrication (FFF) is an additive manufacturing process, which constructs physical items by fused melt material, selectively deposited layer-by-layer through a heated extrusion mechanism. Parameters’ selection and control in FFF are of utmost importance since they significantly affect the surface quality (SQ) and dimensional accuracy (DA) of the FFF printed parts. In the present paper, initially, the FFF process is briefly presented. Next, a cause-and-effect diagram exhibits the process parameters’ categorization with the SQ and DA of the manufactured parts. Then, according to the robust design theory, the process parameters are divided into three classes, i.e., the signal, the control, and the noise. This classification supports the selection of appropriate FFF printers, according to the control parameters, whereas it facilitates the optimization of the SQ and DA of printed parts, concerning the signal parameters. Finally, the impact of each parameter on SQ and DA is presented, supported by an extensive literature review. Overall, the process parameters’ optimization is critical for the SQ and DA. Therefore, they should be adjusted to achieve higher quality and less post-processing work.
... Researchers have extensively studied both particulate and gaseous emissions produced directly from 3D printers during the printing process 26−28 with a focus on ultrafine particle emissions, 29,30 and there are many additional studies examining emissions from other polymeric processes (e.g., plastic recycling in Unwin et al. 31 ). Of particular relevance for this work, Vaïsanen et al. 32 measured gas-phase volatile organic compound (VOC) emissions during the printing process of an SLA Formlabs printer and detected several different compounds in excess of the background. There are, however, no published studies directly characterizing particulate and gaseous emissions from the finished printed parts. ...
Medical shortages during the COVID-19 pandemic saw numerous efforts to 3D print personal protective equipment and treatment supplies. There is, however, little research on the potential biocompatibility of 3D-printed parts using typical polymeric resins as pertaining to volatile organic compounds (VOCs), which have specific relevance for respiratory circuit equipment. Here, we measured VOCs emitted from freshly printed stereolithography (SLA) replacement medical parts using proton transfer reaction mass spectrometry and infrared differential absorption spectroscopy, and particulates using a scanning mobility particle sizer. We observed emission factors for individual VOCs ranging from ∼0.001 to ∼10 ng cm–3 min–1. Emissions were heavily dependent on postprint curing and mildly dependent on the type of SLA resin. Curing reduced the emission of all observed chemicals, and no compounds exceeded the recommended dose of 360 μg/d. VOC emissions steadily decreased for all parts over time, with an average e-folding time scale (time to decrease to 1/e of the starting value) of 2.6 ± 0.9 h.
... 6,[10][11][12]18,[33][34][35][36][37][38][39][40][41][42][43][44][45] In Figure Finally, 8 articles were excluded because at high risk of bias. [46][47][48][49][50][51][52][53] At the end of these steps, 43 articles, all with a low risk of bias, were included in the systematic review. In particular, all the papers All the included articles were grouped according to the studied occupational scenarios as follows: healthcare and research (Table 2), esthetic and wellness (Table 3), industrial (Table 4), fire fighters' and other settings (Table 5). ...
The objectives of the systematic review were to: identify the work sectors at risk for exposure to formaldehyde; investigate the procedures applied to assess occupational exposure; evaluate the reported exposure levels among the different settings. An electronic search of Pubmed, Scopus, Web of Science and ToxNet was carried out for collecting all the articles on the investigated issue published from January 1, 2004 to September 30, 2019. Forty‐three papers were included in the review, and evidenced a great number of occupational scenarios at risk for formaldehyde exposure. All the included studies collected data on formaldehyde exposure levels by a similar approach: environmental and personal sampling followed by chromatographic analyses. Results ranged from not detectable values until to some mg m−3 of airborne formaldehyde. The riskiest occupational settings for formaldehyde exposure were the gross anatomy and pathology laboratories, the hairdressing salons and some specific productive settings, such as wooden furniture factories, dairy facilities and fish hatcheries. Notice that formaldehyde, a well‐known carcinogen, was recovered in air at levels higher than outdoor in almost all the studied scenarios/activities; thus, when formaldehyde cannot be removed or substituted, targeted strategies for exposure elimination or mitigation must be adopted.
... In facilities housing such printers, workers could be exposed to manufactured NMP as well as incidental NMP from uncontrolled process emissions. High concentrations of dust (9.1 mg/m 3 and 2.4 mg/m 3 for powder bed and multi-jet fusion processes, respectively) were reported for post-processing of manufactured products, while during manufacturing dust concentrations were low for both types of 3D printing (less than 0.4 mg/m 3 ) (Väisänen et al. 2019). ...
... 60 (iv) Not immediately approaching a printer if it malfunctions because emissions increase during malfunctions. 60,61 Rather, wait for contaminants to dissipate before fixing the issue. (v) Ensuring that the extruder nozzle and build platform surfaces are cleaned before and after each print job. ...
Material extrusion-type fused filament fabrication (FFF) 3-D printing is a valuable tool for education. During FFF 3-D printing, thermal degradation of the polymer releases small particles and chemicals, many of which are hazardous to human health. In this study, particle and chemical emissions from 10 different filaments made from virgin (never printed) and recycled polymers were used to print the same object at the polymer manufacturer’s recommended nozzle temperature (“normal”) and at a temperature higher than recommended (“hot”) to simulate the real-world scenarios of a person intentionally or unknowingly printing on a machine with a changed setting. Emissions were evaluated in a college teaching laboratory using standard sampling and analytical methods. From mobility sizer measurements, particle number-based emission rates were 81 times higher; the proportion of ultrafine particles (diameter <100 nm) were 4% higher, and median particle sizes were a factor of 2 smaller for hot-temperature prints compared with normal-temperature prints (all p-values <0.05). There was no difference in emission characteristics between recycled and virgin acrylonitrile butadiene styrene and polylactic acid polymer filaments. Reducing contaminant release from FFF 3-D printers in educational settings can be achieved using the hierarchy of controls: (1) elimination/substitution (e.g., training students on principles of prevention-through-design, limiting the use of higher emitting polymer when possible); (2) engineering controls (e.g., using local exhaust ventilation to directly remove contaminants at the printer or isolating the printer from students); (3) administrative controls such as password protecting printer settings and establishing and enforcing adherence to a standard operating procedure based on a proper risk assessment for the setup and use (e.g., limiting the use of temperatures higher than those specified for the filaments used); and (4) maintenance of printers.
... Although current AM machines are usually encapsulated and equipped with exhaust-air filtration, AM workers might be at risk for exposure to metallic particles during handling, use, and disposal of the powders [17][18][19]. The potential human exposure to airborne metalcontaining particulates (including nanoparticles and their aggregates) forming during AM have been associated with an increased risk for respirable tract diseases including asthma and lung inflammation [17][18][19][20][21]. For example, both nickel (Ni) and cobalt (Co) are common metals in AM feedstocks and classified by the European Chemical Agency (ECHA) as respiratory sensitizing materials [ 22 , 23 ]. ...
Exposure to metal particles via the inhalation route unavoidably takes place at occupational settings during additive manufacturing of metals and alloys. This calls for investigations on possible adverse health effects. This study focuses on virgin and reused powders of three iron- and nickel-based alloy powders (316L, IN718, 18Ni300) widely used in additive manufacturing, and dust powder of 18Ni300 generated during laser melting. Investigations were performed from a physico-chemical and toxicological perspective assessing their bioaccessibility in artificial lysosomal fluid (ALF, simulating lung exposure to respirable particles), corrosion behavior, surface morphology and composition, microstructure, hydrodynamic size distribution in ALF, and in-vitro toxicity towards cultured human lung cells. Less than 1 % of the powder mass was dissolved from the passive alloys (316L, IN718) under simulated physiological conditions (pH 4.5, 37°C, 24 h), whereas the 18Ni300 iron-nickel alloy showed an active behavior and dissolved completely. Reused powders of 18Ni300 and IN718 showed no, or only minor, differences in surface oxide composition, metal release pattern, and corrosion behavior compared with virgin powders. After reuse, the 316L powder showed an enrichment of manganese within the outermost surface, an increased corrosion current, increased amounts of released iron and an increased fraction of particles with ferritic microstructure, which increased the extent of particle aggregation. All powders showed low, or negligible, cytotoxic potency and reactive oxygen species formation. Powder bed fusion using laser melting can hence affect the chemical, physical, and surface properties of non-fused powders, which, if reused, could influence the properties of the printed part.
... It can be seen that raw materials (powder, polymer, thermoplastic material, binder, etc.) and the process of creating 3D objects (heating, laser scanning, jetting with high pressure, etc.) may become the sources of harmful fine particles and VOCs. 11,22,23 Overall, despite the continuous development and innovation of 3D printing, its potential environmental pollution risks should be known. With 3D printers becoming more and more common, the releases of PM 2.5 and VOCs into the environment are also increasing, which will cause greater environmental risks. ...
With the growing adoption of additive manufacturing (AM) technology across various industries, concerns regarding the possible release of hazardous volatile organic compound (VOC) emissions have surfaced, particularly in VAT photopolymerization (VPP) processes. This study investigates VOC emissions in VPP AM by implementing machine learning (ML) and advanced digital twins to monitor, predict, and mitigate VOC release. An Industrial Internet of Things (IIoT) sensor network, integrated with an Anycubic Mono X 6 K 3D printer, captured data on critical parameters, including layer thickness, exposure time, and light intensity. Subsequent ML model analysis identified exposure time as a principal factor influencing VOC emissions. A Unity-based digital twin was developed to support proactive process optimization, offering real-time visualization and predictive analytics of emission trends. The system aligns with Industry 4.0 objectives, showing considerable potential to enhance operational efficiency and environmental sustainability in VPP AM. This integrated approach significantly advances environmentally responsible AM practices in industrial settings.
Exposures and emissions of toxic gases, such as carbon monoxide, ammonia, hydrogen sulfide, nitrogen dioxide, sulfur dioxide, and volatile organic compounds at the industrial level, are regulated by legislation or standards. Engineering measures are compulsory to ensure minimal or zero levels of toxic gases are released. Effective and reliable respiratory protective equipment serves as the last line of protection for workers and is equally crucial for control measures. Activated carbon (AC) is a superior material that has been widely used in environmental applications and is commonly employed as a filter material used in gas mask respirators. The goals of this research are to explore recent advancements in AC for adsorbing toxic gases and to conduct an in-depth review of AC usage in gas mask respirator filters, cartridges, or canisters. The preliminary study found that less than 100 articles or journals related to materials used in gas mask filters were published in the past decade. This review also enhances understanding of the significance of AC properties in gas respirator applications and highlights current advancements in carbon materials as gas adsorbents. This review is the first to comprehensively describe AC as a cartridge material, addressing reports in the last 10 years on factors affecting cartridge efficiency, estimation of service life, and testing methods.
Additive manufacturing (AM) is a promising technology for medical applications. This review paper aims to fill this gap by analysing the sustainability aspects of AM, including its environmental, economic, and social implications. The main objective of the review study is to provide dependable and achievable sustainability guidelines for AM by evaluating the advantages, methods of implementation, and obstacles connected with Sustainable Additive Manufacturing (SAM) systems. The review study will enhance our understanding of the environmental impact of AM by providing a more holistic perspective on the technology and its potential consequences.
Metal additive manufacturing (AM) is gaining traction but raises worker health concerns due to micron‐sized powders, including fine inhalable particles. This study explored particle and surface characteristics, electrochemical properties, metal release in artificial lysosomal fluid (ALF), and potential toxicity of virgin and sieved virgin Fe‐based powders, stainless steel (316L), Fe, and two tooling steels. Virgin particles ranged in size from 1 to 100 µm, while sieved particles were within the respirable size range (<5–10 µm). Surface oxide composition differed from bulk composition. The Fe powder showed low corrosion resistance and high metal release due to a lack of protective surface oxide. Sieved particles of 316L, Fe, and one tooling steel released more metals into ALF than virgin particles, with the opposite was observed for the other tooling steel. Sieved particles had no notable impact on cell viability or micronuclei formation in human bronchial epithelial cells. Inflammatory response in human macrophages was generally low, except for the Fe powder and one tooling steel, which induced increased interleukin‐8 (IL‐8/CXCL‐8) and monocyte chemoattractant protein‐1 (MCP‐1/CCL‐2) secretion. This study underscores distinctions between virgin and sieved Fe‐based powders and suggests relatively low acute toxicity.
3D printing is an extensively used manufacturing technique that can pose specific health concerns due to the emission of volatile organic compounds (VOC). Herein, a detailed characterization of 3D printing-related VOC using solid-phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS) is described for the first time. The VOC were extracted in dynamic mode during the printing from the acrylonitrile-styrene-acrylate filament in an environmental chamber. The effect of extraction time on the extraction efficiency of 16 main VOC was studied for four different commercial SPME arrows. The volatile and semivolatile compounds were the most effectively extracted by carbon wide range-containing and polydimethyl siloxane arrows, respectively. The differences in extraction efficiency between arrows were further correlated to the molecular volume, octanol-water partition coefficient, and vapour pressure of observed VOC. The repeatability of SPME arrows towards the main VOC was assessed from static mode measurements of filament in headspace vials. In addition, we performed a group analysis of 57 VOC classified into 15 categories according to their chemical structure. Divinylbenzene-polydimethyl siloxane arrow turned out to be a good compromise between the total extracted amount and its distribution among tested VOC. Thus, this arrow was used to demonstrate the usefulness of SPME for the qualification of VOC emitted during printing in a real-life environment. A presented methodology can serve as a fast and reliable method for the qualification and semi-quantification of 3D printing-related VOC.
Purpose
A positive outlook on the impact of Industry 4.0 (I4.0) on sustainability prevails in the literature. However, some studies have highlighted potential areas of concern that have not yet been systematically addressed. The goal of this study is to challenge the assumption of a sustainable Fourth Industrial Revolution by (1) identifying the possible unintended negative impacts of I4.0 technologies on sustainability; (2) highlighting the underlying motivations and potential actions to mitigate such impacts; and (3) developing and evaluating alternative assumptions on the impacts of I4.0 technologies on sustainability.
Design/methodology/approach
Building on a problematization approach, a systematic literature review was conducted to develop potential alternative assumptions about the negative impacts of I4.0 on sustainability. Then, a Delphi study was carried out with 43 experts from academia and practice to evaluate the alternative assumptions. Two rounds of data collection were performed until reaching the convergence or stability of the responses.
Findings
The results highlight various unintended negative effects on environmental and social aspects that challenge the literature. The reasons behind the high/low probability of occurrence, the severity of each impact in the next five years and corrective actions are also identified. Unintended negative environmental effects are less controversial than social effects and are therefore more likely to generate widely accepted theoretical propositions. Finally, the alternative hypothesis ground is partially accepted by the panel, indicating that the problematization process has effectively opened up new perspectives for analysis.
Originality/value
This study is one of the few to systematically problematize the assumptions of the I4.0 and sustainability literature, generating research propositions that reveal several avenues for future research.
Stereolithography three-dimensional printing is used increasingly in biomedical applications to create components for use in healthcare and therapy. The exposure of patients to volatile organic compounds (VOCs) emitted from cured resins represents an element of concern in such applications. Here, we investigate the biocompatibility in relation to inhalation exposure of volatile emissions of three different cured commercial resins for use in printing a mouthpiece adapter for sampling exhaled breath. VOC emission rates were estimated based on direct analysis using a microchamber/thermal extractor coupled to a proton transfer reaction-mass spectrometer. Complementary analyses using comprehensive gas chromatography-mass spectrometry aided compound identification. Major VOCs emitted from the cured resins were associated with polymerization agents, additives, and postprocessing procedures and included alcohols, aldehydes, ketones, hydrocarbons, esters, and terpenes. Total VOC emissions from cubes printed using the general-purpose resin were approximately an order of magnitude higher than those of the cubes printed using resins dedicated to biomedical applications at the respective test temperatures (40 and 25 °C). Daily inhalation exposures were estimated and compared with daily tolerable intake levels or standard thresholds of toxicological concerns. The two resins intended for biomedical applications were deemed suitable for fabricating an adapter mouthpiece for use in breath research. The general-purpose resin was unsuitable, with daily inhalation exposures for breath sampling applications at 40 °C estimated at 310 μg day-1 for propylene glycol (tolerable intake (TI) limit of 190 μg day-1) and 1254 μg day-1 for methyl acrylate (TI of 43 μg day-1).
Three-dimensional (3D) printing is an additive manufacturing process that increases in application and consumer popularity. Studies with 3D printers have shown that the printing process releases particles and volatile organic compounds (VOCs). This review looked at 50 studies that analyzed the most commonly used printing process in consumer 3D printers, the material extrusion or so-called fused filament fabrication (FFF) method and summarizes the most important results. Although the reviewed studies often used different methods, general assumptions can be drawn: Higher printing temperature resulted in higher emissions, styrene was the main VOC emitted during printing with ABS, the size of released particles was in the nano range and filaments with additives could pose a higher risk due to the possible release of e.g., carbon nanotubes (CNTs). In vivo and in vitro studies showed toxic effects. Thus, we recommend: printing in a separated and ventilated room, using the lowest possible print temperature and be cautious with filaments containing particulate additives.
Direct reading instruments (DRIs) for aerosols have been used in industrial hygiene practice for many years, but their potential has not been fully realized by many occupational health and safety professionals. Although some DRIs quantify other metrics, this article will primarily focus on DRIs that measure aerosol number, size, or mass. This review addresses three applications of aerosol DRIs that occupational health and safety professionals can use to discern, characterize, and document exposure conditions and resolve aerosol related problems in the workplace. The most common application of aerosol DRIs is the evaluation of engineering controls. Examples are provided for many types of workplaces and situations including construction, agriculture, mining, conventional manufacturing, advanced manufacturing (nanoparticle technology and additive manufacturing) and non-industrial sites. Aerosol DRIs can help identify the effectiveness of existing controls and as needed, develop new strategies to reduce potential aerosol exposures. Aerosol concentration mapping (ACM) using DRI data can focus attention on emission sources in the workplace, spatially illustrate the effectiveness of controls and constructively convey concerns to management and workers. Examples and good practices of ACM are included. Video Exposure Monitoring (VEM) is another useful technique in which video photography is synced with the concentration output of an aerosol DRI. This combination allows the occupational health and safety professional to see what tasks, environmental situations and/or worker actions contribute to the aerosol concentration and potential exposure. VEM can help identify factors responsible for temporal variations in concentration. VEM can assist training, engage workers, convince managers about necessary remedial actions and provide for continuous improvement of the workplace environment. Although using DRIs for control evaluation, ACM and VEM can be time-consuming, the resulting information can provide useful data to prompt needed action by employers and employees. Other barriers to adoption include privacy and security issues in some worksites. This review seeks to provide information so occupational health and safety professionals can better understand and effectively use these powerful applications of aerosol DRIs.
In recent years, due to the rapid development of digital dentistry, 3D printing has gradually become an important production tool in dental laboratories and clinics. Professional printing centers and good manufacturing practice (GMP) production plants have been continuously put on the market, and materials with new properties and functions have been continuously entering the market. In the circumstance of high competition, 3D printers are getting more accurate, faster, and inexpensive. This trend brings advantages, but also some disadvantages and safety issues to clinical processes. How to regulate printed devices has always been a topic of common concern of regulatory agencies in various countries. In view of the above situation, this chapter organizes 3D printing-related topics as the object of discussion, including printing workflow management, risk, regulatory supervision, safety, and future trend.
With the advancement of technology and the integration of digital solutions in treatment planning, clinical prognosis and treatment in oral health science have evolved from a classic two-dimensional (2D) method to a sophisticated three-dimensional (3D) technique. The integration of digital technology in oral health science requires digital 3D images as a primary input data. These 3D digital data can be acquired by different modalities like nonionizing methods (desktop scanning, intraoral scanning, face scanning) to capture the 3D surface data of dento-alveolar-facial tissue and the ionizing methods (conventional CT or CBCT) to capture the 3D data of hard tissue (bone and teeth) of the craniofacial region. In this chapter, the basic principles and their application in dentistry in conjunction with 3D printing of digital surface scanning using desktop scanning, intraoral scanning, and facial scanning and the hard tissue scanning using CBCT are discussed. CBCT along with the state of the art newer ethnologies have improved the level of diagnosis and subsequent care to an paralleled level of accuracy, efficiency, and predictability of the treatment. This chapter provides an in-depth practical understanding of the principles and applications of various 3D scanning methods for 3D digital data acquisition of the craniofacial region in the oral health science.Keywords3D imagingIntraoral scanningDesktop scanningFace sackingCone beam computed tomography (CBCT)Computer-aided designing (CAD)3D printing
Tissue engineering and regenerative medicine (TERM) research has advanced significantly with the development of three-dimensional (3D) printing technology. Specifically, 3D bioprinting provides additional benefits and improvement to 3D printing by incorporating the ability to include cells into the process, creating a cell-laden ink, termed bioink. By incorporating cells in conjunction with the superior temporospatial precision of 3D printing, scientists and clinicians have the potential to print live tissues with sophisticated structures and microarchitectures. While 3D bioprinting is still in its early phase, with limited preclinical animal and human studies, it has been proposed as a promising tool for TERM research in many areas of medicine and dentistry, including craniofacial, oral, and dental (DOC) tissue regeneration. This chapter aims to provide a comprehensive overview of major concepts in 3D bioprinting including its armamentarium, types of bioprinters, bioprinting process, clinical applications in craniofacial regeneration, limitations, and future perspectives.Keywords3D bioprinting3D printingAdditive manufacturingTissue engineeringRegenerative medicineCraniofacial tissue regenerationPeriodontal regenerationPulp regenerationDentistryOral surgery
Costochondral grafts (CCG) are considered the best method for condylar reconstruction in young children with Pruzansky/Kaban type IIB and type III HFM. This orthodontic-surgical intervention immediately corrects the facial asymmetry by eliminating the hypoplastic mandible and the negative influence on the normal maxillary growth simultaneously with ramus height restoration. However, CCG precise surgical positioning is a challenge in these patients due to mandibular hypoplasia when the glenoid fossa is difficult to identify, or it might be absent. The aim of the 3D-printed jig is to manage the precise suitable placement position and fixation of the costochondral rib graft in relation to the contralateral unaffected temporomandibular joint and soft tissues. The jig may preserve the rib’s cartilage cap, prevent fractures at the costochondral junction, and result in a decrease in the risk of interference of cartilage growth.KeywordsHemifacial microsomiaPruzansky/Kaban classificationCostochondral graftsTemporomandibular jointJig3D printing3D models3D CT imaging
Material jetting and vat photopolymerization additive manufacturing (AM) processes use liquid resins to build objects. These resins can contain skin irritants and/or sensitizers but product safety data sheets (SDSs) might not declare all ingredients. We characterized elemental and organic skin irritants and sensitizers present in 39 commercial products; evaluated the influence of resin manufacturer, system, color, and AM process type on the presence of irritants and sensitizers; and compared product SDSs to results. Among all products, analyses identified 23 irritant elements, 54 irritant organic substances, 22 sensitizing elements, and 23 sensitizing organic substances; SDSs listed 3, 9, 4, and 6 of these ingredients, respectively. Per product, the number and total mass (an indicator of potential dermal loading) of ingredients varied: five to 17 irritant elements (8.32–4756.65 mg/kg), one to 17 irritant organics (3273 to 356,000 mg/kg), four to 17 sensitizing elements (8.27–4755.63 mg/kg), and one to seven sensitizing organics (15–382,170 mg/kg). Median numbers and concentrations of irritants and sensitizers were significantly influenced by resin system and AM process type. The presence of undeclared irritants and sensitizers in these resins supports the need for more complete information on product SDSs for comprehensive dermal risk assessments.
Biocomposites (BCs) can be used as substitutes for unsustainable polymers in 3D printing, but their safety demands additional investigation as biological fillers may produce altered emissions during thermal processing. Commercial filament extruders can be used to produce custom feedstocks, but they are another source for airborne contaminants and demand further research. These knowledge gaps are targeted in this study. Volatile organic compound (VOC), carbonyl compound, ultrafine particle (UFP), and fine (PM2.5) and coarse (PM10) particle air concentrations were measured in this study as a filament extruder and a 3D printer were operated under office environment using one PLA and four PLA-based BC feedstocks. Estimates of emission rates (ERs) for total VOCs (TVOC) and UFPs were also calculated. VOCs were analyzed with a GC-MS system, carbonyls were analyzed with an LC-MS/MS system, whereas real-time particle concentrations were monitored with continuously operating instruments. VOC concentrations were low throughout the experiment; TVOC ranged between 34-63 µg/m3 during filament extrusion and 41-56 µg/m3 during 3D printing, which represent calculated TVOC ERs of 2.6‒3.6 × 102 and 2.9‒3.6 × 102 µg/min. Corresponding cumulative carbonyls ranged between 60-91 and 190-253 µg/m3. Lactide and miscellaneous acids and alcohols were the dominant VOCs, while acetone, 2-butanone, and formaldehyde were the dominant carbonyls. Terpenes contributed for ca. 20-40% of TVOC during BC processing. The average UFP levels produced by the filament extruder were 0.85 × 102-1.05 × 103 #/cm3, while the 3D printer generated 6.05 × 102-2.09 × 103 #/cm3 particle levels. Corresponding particle ERs were 5.3 × 108-6.6 × 109 and 3.8 × 109-1.3 × 1010 #/min. PM2.5 and PM10 particles were produced in the following average quantities; PM2.5 levels ranged between 0.2-2.2 µg/m3, while PM10 levels were between 5-20 µg/m3 for all materials. The main difference between the pure PLA and BC feedstock emissions were terpenes, present during all BC extrusion processes. BCs are similar emission sources as pure plastics based on our findings, and a filament extruder produces contaminants at comparable or slightly lower levels in comparison to 3D printers.
Particles and volatile organic compounds (VOCs) have been detected emitting from material extrusion 3D printing, which is widely used in nonindustrial environments. However, vat polymerization 3D printing that is also commonly used has yet to be well-characterized for its emissions. In this study, we measured particle and VOC emission rates from stereolithography (SLA) 3D printing during print and post-processing wash and cure processes individually using a standardized testing method for 3D printer emissions in an exposure chamber. We observed minimal particle emissions and identified 30 to over 100 individual VOCs emitted from each operating phase, some of which accumulated after the printing ended. The total VOC emissions from SLA processes were higher than typical levels from material extrusion 3D printing, and the emission rate could be over 4 mg/h. Major VOCs emitted were associated with the resin and chemicals used in print and post-processing procedures, which included esters, alcohols, aldehydes, ketones, aromatics, and hydrocarbons. Emissions from post-processing units were lower than those from printing but also included chemicals with health concerns. The emitted mixture of sensitizers, carcinogens, irritants, and flammable chemicals may present a hazard for indoor air quality and human health. The estimated personal exposure to total VOC and some specific VOCs of concern to human health, like formaldehyde and naphthalene, exceeded the recommended indoor levels (e.g., California Office of Environmental Health Hazard Assessment), potentially causing irritation and other health impacts for 3D printer users.
The EU-project FAST (GA 685825) has developed a 3D printer machine prototype for the manufacture of bone implants (scaffolds), by merging masterbatches of biodegradable polymer poly(ethylene oxide)terephthalate/poly(butylene terephthalate) [PEOT/PBT] doped with nanofillers [reduced graphene oxide (rGO), hydroxyapatite (HA) and magnesium aluminium hydroxide ciprofloxacin hydrotalcite (LDH-CFX)], and atmospheric plasma technology. This paper focus on the safe design strategies identified by FAST to address the risk to health resulting from the potential airborne emission of nano-objects and their aggregates and agglomerates (NOAAs) by the 3D printer prototype, which might result in occupational exposures by inhalation. The work also includes measurements of airborne emissions and occupational exposures carried out during the verification stage of the prototype design. Nanofillers particles (rGO, n-HA, LDH-CFX) were not observed, neither at source nor in the working area, suggesting no release of free nanofillers to the air one they have been embedded in the polymer masterbatch. Additionally, the exposure in the workplace was far below the selected Occupational Exposure Levels (OELs), for total particle number concentration (PNC), dust, elemental carbon (EC) and volatile organic compounds (VOCs). The results showed that, when working with the current prototype in normal operation (for its intended use) and with controls enabled [enclosure with the doors closed and Local Exhaust Ventilation (LEV) activated], the emission from the machine and the worker’s exposure to NOAAs are well controlled.
Particle emissions from multiple fused deposition modeling consumer 3D printers were systematically quantified utilizing an established emission testing protocol (Blue Angel) to allow quantitative exposure assessments for printers operating in different environments. The data are consistent with particle generation from volatilization of the polymer filament as it is heated by the extruder. Typically, as printing begins, a burst of new particle formation leads to the smallest sizes and maximum number concentrations produced throughout the print job. For acrylonitrile butadiene styrene (ABS) filaments, instantaneous concentrations were up to 10⁶ #/cm³ with mean particle sizes of 20 to 40 nm when measured in a well mixed 1 m³ chamber with 1 air change per hour. Particles are continuously formed during printing and the size distribution evolves consistent with vapor condensation and particle coagulation. Particles emitted per mass of filament consumed (particle yield) varied widely due to factors including printer brand, and type and brand of filament. Higher extruder temperatures result in larger emissions. For filament materials tested, average particle number yields ranged from 7.3 × 10⁸ to 5.2 × 10¹⁰ g⁻¹ (approximately 0.65 to 24 ppm), with trace additives apparently driving the large variations. Nanoparticles (diameters less than 100 nm) dominate number distributions, whereas diameters in the range of 200 to 500 nm contribute most to estimated mass. Because 3D printers are often used in public spaces and personal residences, the general public and particularly susceptible populations, such as children, can be exposed to high concentrations of non-engineered nanoparticles of potential toxicity.
Copyright © 2017 American Association for Aerosol Research
Printing devices are known to emit chemicals into the indoor atmosphere. Understanding factors that influence release of chemical contaminants from printers is necessary to develop effective exposure assessment and control strategies. In this study, a desktop fused deposition modeling (FDM) 3-D printer using acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA) filaments and two monochrome laser printers were evaluated in a 0.5 m³ chamber. During printing, chamber air was monitored for vapors using a real-time photoionization detector (results expressed as isobutylene equivalents) to measure total volatile organic compound (TVOC) concentrations, evacuated canisters to identify specific VOCs by off-line gas chromatography-mass spectrometry (GC-MS) analysis, and liquid bubblers to identify carbonyl compounds by GC-MS. Airborne particles were collected on filters for off-line analysis using scanning electron microscopy with an energy dispersive x-ray detector to identify elemental constituents. For 3-D printing, TVOC emission rates were influenced by a printer malfunction, filament type, and to a lesser extent, by filament color; however, rates were not influenced by the number of printer nozzles used or the manufacturer's provided cover. TVOC emission rates were significantly lower for the 3-D printer (49 to 3552 µg h⁻¹) compared to the laser printers (5782 to 7735 µg h⁻¹). A total of 14 VOCs were identified during 3-D printing that were not present during laser printing. 3-D printed objects continued to off-gas styrene, indicating potential for continued exposure after the print job is completed. Carbonyl reaction products were likely formed from emissions of the 3-D printer, including 4-oxopentanal. Ultrafine particles generated by the 3-D printer using ABS and a laser printer contained chromium. Consideration of the factors that influenced the release of chemical contaminants (including known and suspected asthmagens such as styrene and 4-oxopentanal) from a FDM 3-D printer should be made when designing exposure assessment and control strategies.
3-D printing is an additive manufacturing process involving the injection of melted thermoplastic polymers, which are then laid down in layers to achieve a pre-designed shape. The heated deposition process raises concerns of potential aerosol and volatile organic compounds (VOC) emission and exposure. The decreasing cost of desktop 3-D printers has made the use of 3-D printers more acceptable in non-industrial workplaces lacking sufficient ventilation. Meanwhile, little is known about the characteristics of 3-D printing fume emission. The objective of this study was to characterize aerosols and VOC emissions generated from various filaments used with a low-cost 3-D printer in an environmental testing chamber. A pre-designed object was printed in 1.25 hours using eight types of filaments. A scanning mobility particle sizer and an aerodynamic particle sizer were employed to measure the particle size distribution in sub-half-micron fraction (<0.5 µm) and super-half-micron fraction (0.5-20 µm), respectively. VOC concentration was monitored real-time by a photoionization detector and sampled with a tri-sorbent thermal desorption tube, and analyzed by thermal desorption gas chromatography mass spectrometry (TD-GC/MS). Results showed high levels of fume particles emission rate (1.0 × 10(7) to 1.2 × 10(10) #/min) in the sub-half-micron range with mode sizes of 41-83 nm. Particle concentrations peaked during the heat-up and solid layer printing periods. Total VOC concentration in the chamber followed a first-order buildup, with predominant VOC species in the chamber were breakdown and reaction products of the filaments, such as styrene from ABS filaments. These findings and exposure scenario estimation suggest that although the VOC concentrations were much lower than occupational exposure limits, particles with size less than micron might be a concern for users of low-cost 3-D printers due to high respirablity, especially if used in settings without proper guidance and engineering control.
3D printers are currently widely available and very popular among the general public. However, the use of these devices may pose health risks to users, attributable to air-quality issues arising from gaseous and particulate emissions in particular. We characterized emissions from a low-end 3D printer based on material extrusion, using the most common polymers: acrylonitrile-butadiene-styrene (ABS) and polylactic acid (PLA). Measurements were carried out in an emission chamber and a conventional room. Particle emission rates were obtained by direct measurement and modeling, whereas the influence of extrusion temperature was also evaluated. ABS was the material with the highest aerosol emission rate. The nanoparticle emission ranged from 3.7·108 to 1.4·109 particles per second (# s−1) in chamber measurements and from 2.0·109 to 4.0·109 # s−1in room measurements, when the recommended extruder temperature was used. Printing with PLA emitted nanoparticles at the rate of 1.0·107 # s−1 inside the chamber and negligible emissions in room experiments. Emission rates were observed to depend strongly on extruder temperature. The particles’ mean size ranged from 7.8 to 10.5 nanometers (nm). We also detected a significant emission rate of particles of 1 to 3 nm in size during all printing events. The amounts of volatile organic and other gaseous compounds were only traceable and are not expected to pose health risks. Our study suggests that measures preventing human exposure to high nanoparticle concentrations should be adopted when using low-end 3D printers.
Desktop three-dimensional (3D) printers are becoming commonplace in business offices, public libraries, university labs and classrooms, and even private homes; however, these settings are generally not designed for exposure control. Prior experience with a variety of office equipment devices such as laser printers that emit ultrafine particles (UFP) suggests the need to characterize 3D printer emissions to enable reliable risk assessment. The aim of this study was to examine factors that influence particulate emissions from 3D printers and characterize their physical properties to inform risk assessment. Emissions were evaluated in a 0.5-m3 chamber and in a small room (32.7 m3) using real-time instrumentation to measure particle number, size distribution, mass, and surface area. Factors evaluated included filament composition and color, as well as the manufacturer-provided printer emissions control technologies while printing an object. Filament type significantly influenced emissions, with acrylonitrile butadiene styrene (ABS) emitting larger particles than polylactic acid (PLA), which may have been the result of agglomeration. Geometric mean particle sizes and total particle (TP) number and mass emissions differed significantly among colors of a given filament type. Use of a cover on the printer reduced TP emissions by a factor of 2. Lung deposition calculations indicated a threefold higher PLA particle deposition in alveoli compared to ABS. Desktop 3D printers emit high levels of UFP, which are released into indoor environments where adequate ventilation may not be present to control emissions. Emissions in nonindustrial settings need to be reduced through the use of a hierarchy of controls, beginning with device design, followed by engineering controls (ventilation) and administrative controls such as choice of filament composition and color.
Direct human emissions are known to contribute volatile organic compounds (VOCs) to indoor air via various mechanisms. However, few measurements are available that determine the emissions of a full suite of occupant-associated VOCs. We measured occupant-related VOC emissions from engineering students in a classroom using a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS). The dominant compound emitted was a cyclic volatile methylsiloxane (cVMS), decamethylcyclopentasiloxane (D5), which is a major inactive ingredient in some personal care products such as antiperspirants. D5 was found to contribute ~30% of the total indoor VOC mass concentration as measured by the PTR-TOF-MS. Octamethylcyclotetrasiloxane (D4) and dodecamethylcyclohexasiloxane (D6) were detected at one to two orders of magnitude lower abundance. The per-person emission rate of these three cVMS declined monotonically from morning into the afternoon, consistent with expectations for emissions from daily morning applic
In the recent years, printers, especially inkjet printers, have become very commonly used in households, causing significant environment impact. In this paper, a life cycle assessment for an inkjet printer - model HP DeskJet D1360 manufactured in Taiwan, used and disposed in Poland was performed. The system boundaries of this study includes also consumables essential for printer operating: paper and ink as well as electricity consumption. Values for eleven impact categories were provided with the application of the Eco-indicator 99 method, expressing the significant environmental burden. For the whole life cycle the most significant stage is paper usage, followed by the manufacturing of the product and electricity consumption.
Volatile organic compounds (VOCs) are ubiquitous domestic pollutants. Their role in asthma/allergy development and exacerbations is uncertain. This systematic review investigated whether domestic VOC exposure increases the risk of developing and/or exacerbating asthma and allergic disorders. We systematically searched 11 databases and three trial repositories, and contacted an international panel of experts to identify published and unpublished experimental and epidemiological studies. 8455 potentially relevant studies were identified; 852 papers were removed after de-duplication, leaving 7603 unique papers that were screened. Of these, 278 were reviewed in detail and 53 satisfied the inclusion criteria. Critical appraisal of the included studies indicated an overall lack of high-quality evidence and substantial risk of bias in this body of knowledge. Aromatics (i.e. benzenes, toluenes and xylenes) and formaldehyde were the main VOC classes studied, both in relation to the development and exacerbations of asthma and allergy. Approximately equal numbers of studies reported that exposure increased risks and that exposure was not associated with any detrimental effects. The available evidence implicating domestic VOC exposure in the risk of developing and/or exacerbating asthma and allergy is of poor quality and inconsistent. Prospective, preferably experimental studies, investigating the impact of reducing/eliminating exposure to VOC, are now needed in order to generate a more definitive evidence base to inform policy and clinical deliberations in relation to the management of the now substantial sections of the population who are either at risk of developing asthma/allergy or living with established disease.
Copyright ©ERS 2015.
“Click” chemistry has become an efficient avenue to unimolecular polymeric nanoparticles through the self-crosslinking of individual polymer chains containing appropriate functional groups. Herein we report the synthesis of ultra-small (7 nm in size) polymethyl methacrylate (PMMA) nanoparticles (NPs) by the “metal-free” cross-linking of PMMA-precursor chains prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization containing β-ketoester functional groups. Intramolecular collapse was performed by the one-pot reaction of β-ketoester moieties with alkyl diamines in tetrahydrofurane at r.t. (i.e., by enamine formation). The collapsing process was followed by size exclusion chromatography and by nuclear magnetic resonance spectroscopy. The size of the resulting PMMA-NPs was determined by dynamic light scattering. Enamine “click” chemistry increases the synthetic toolbox for the efficient synthesis of metal-free, ultra-small polymeric NPs.
The development of low-cost desktop versions of three-dimensional (3D)
printers has made these devices widely accessible for rapid prototyping
and small-scale manufacturing in home and office settings. Many desktop
3D printers rely on heated thermoplastic extrusion and deposition, which
is a process that has been shown to have significant aerosol emissions
in industrial environments. However, we are not aware of any data on
particle emissions from commercially available desktop 3D printers.
Therefore, we report on measurements of size-resolved and total
ultrafine particle (UFP) concentrations resulting from the operation of
two types of commercially available desktop 3D printers inside a
commercial office space. We also estimate size-resolved
(11.5 nm-116 nm) and total UFP (<100 nm)
emission rates and compare them to emission rates from other desktop
devices and indoor activities known to emit fine and ultrafine
particles. Estimates of emission rates of total UFPs were large, ranging
from
˜2.0 × 1010 # min-1
for a 3D printer utilizing a polylactic acid (PLA) feedstock to
˜1.9 × 1011 # min-1
for the same type of 3D printer utilizing a higher temperature
acrylonitrile butadiene styrene (ABS) thermoplastic feedstock. Because
most of these devices are currently sold as standalone devices without
any exhaust ventilation or filtration accessories, results herein
suggest caution should be used when operating in inadequately ventilated
or unfiltered indoor environments. Additionally, these results suggest
that more controlled experiments should be conducted to more
fundamentally evaluate particle emissions from a wider arrange of
desktop 3D printers.
Studies of unexplained symptoms observed in chemically sensitive subjects have increased the awareness of the relationship between neurological and immunological diseases due to exposure to volatile organic compounds (VOCs). However, there is no direct evidence that links exposure to low doses of VOCs and neurological and immunological dysfunction. We review animal model data to clarify the role of VOCs in neuroimmune interactions and discuss our recent studies that show a relationship between chronic exposure of C3H mice to low levels of formaldehyde and the induction of neural and immune dysfunction. We also consider the possible mechanisms by which VOC exposure can induce the symptoms presenting in patients with a multiple chemical sensitivity.
Exposure to low-toxicity dusts, which have previously been viewed as ‘nuisance dusts’, can cause chronic obstructive pulmonary
disease or other nonmalignant respiratory disease. In Britain, the ‘de facto’ airborne exposure limits for these dusts have
remained unchanged for >30 years; currently, they are 10mg m−3 for inhalable dust and 4mg m−3 for respirable dust. During this time, exposures in industry have decreased and although in the past, many occupational dust
exposures may have exceeded these limits, today this is less likely. However, there is good evidence from epidemiology and
toxicology studies that current dust exposures may still present a risk to workers and that for some of those who are affected,
there are devastating health consequences. Numerous researchers and others have drawn attention to the necessity to control
dust exposures to levels lower than are currently accepted in Britain. It is proposed that until regulators agree on the safe
occupational exposure limits for low-toxicity dusts, health and safety professionals should consider 1mg m−3 of respirable dusts as a more appropriate guideline than the value of 4mg m−3 currently used in Britain.
To better evaluate the health effects and indoor air quality impacts of nanoparticles generated by laser printers, measurements were made to characterize the number concentration, size distribution, morphology, and chemical composition of the emitted nanoparticles as a function of printer distance, idle time, “cold start” state, cartridge states, and number of pages printed. Emitted ion concentrations, nanoparticles, volatile organic compound (VOC) emissions, and toner particles were characterized using multiple analytical techniques. Finally, particle generation mechanisms and emission control strategies are discussed.
This article summarizes the outcome of the discussions at the international workshop on nano reference values (NRVs), which was organized by the Dutch trade unions and employers' organizations and hosted by the Social Economic Council in The Hague in September 2011. It reflects the discussions of 80 international participants representing small- and medium-size enterprises (SMEs), large companies, trade unions, governmental authorities, research institutions, and non-governmental organizations (NGOs) from many European countries, USA, India, and Brazil. Issues that were discussed concerned the usefulness and acceptability of precaution-based NRVs as a substitute for health-based occupational exposure limits (OELs) and derived no-effect levels (DNELs) for manufactured nanoparticles (NPs). Topics concerned the metrics for measuring NPs, the combined exposure to manufactured nanomaterials (MNMs) and process-generated NPs, the use of the precautionary principle, the lack of information about the presence of nanomaterials, and the appropriateness of soft regulation for exposure control. The workshop concluded that the NRV, as an 8-h time-weighted average, is a comprehensible and useful instrument for risk management of professional use of MNMs with a dispersible character. The question remains whether NRVs, as advised for risk management by the Dutch employers' organization and trade unions, should be under soft regulation or that a more binding regulation is preferable.
Efforts to understand and mitigate the health effects of particulate matter (PM) air pollution have a rich and interesting history. This review focuses on six substantial lines of research that have been pursued since 1997 that have helped elucidate our understanding about the effects of PM on human health. There has been substantial progress in the evaluation of PM health effects at different timescales of exposure and in the exploration of the shape of the concentration-response function. There has also been emerging evidence of PM-related cardiovascular health effects and growing knowledge regarding interconnected general pathophysiological pathways that link PM exposure with cardiopulmonary morbidity and mortality. Despite important gaps in scientific knowledge and continued reasons for some skepticism, a comprehensive evaluation of the research findings provides persuasive evidence that exposure to fine particulate air pollution has adverse effects on cardiopulmonary health. Although much of this research has been motivated by environmental public health policy, these results have important scientific, medical, and public health implications that are broader than debates over legally mandated air quality standards.
Various publications indicate that the operation of laser printers and photocopiers may be associated with health effects due to the release of gaseous components and fine and ultrafine particles (UFP). However, only sparse studies are available that evaluate the possible exposure of office workers to printer emissions under real conditions. Therefore, the aim of our study was to assess the exposure of office workers to particulate matter released from laser printers and photocopiers.
Concentrations of fine particles and UFP were measured before, during, and after the operation of laser printing devices in 63 office rooms throughout Germany. Additionally, the particles were characterized by electron microscopy and energy-dispersive X-ray spectroscopy.
A significant increase of fine particles and UFP was identified in ambient workplace air during and after the printing processes. Particle fractions between 0.23 and 20 μm emitted by the office machines significantly affect particle mass concentrations while printing 500 pages, i.e., during the printing process, PM(0.23-20), PM(2.5), and PM(10) concentrations increased in 43 out of the evaluated 62 office rooms investigated. Additionally, a significant increase was observed in submicrometer particles, with median particle number concentrations of 6,503 particles/cm(3) before and 18,060 particles/cm(3) during the printing process.
Our data indicate that laser printers and photocopiers could be a relevant source of fine particles and particularly UFP in office rooms.
Methyl methacrylate (MMA), a widely used monomer in dentistry and medicine has been reported to cause abnormalities or lesions in several organs. Experimental and clinical studies have documented that monomers may cause a wide range of adverse health effects such as irritation to skin, eyes, and mucous membranes, allergic dermatitis, stomatitis, asthma, neuropathy, disturbances of the central nervous system, liver toxicity, and fertility disturbances.
Four groups of 48 male rats each were exposed, nose-only, 6 h/day, 5 days/week, for a total of 4 weeks (i.e. 20 exposures) to aerosols of Nylon respirable-sized, fiber-shaped particulates (RFPs) at concentrations of 0, 4, 15 and 57 f/cm3 (ratio of RFPs:particles = 1:10–20). The samples containing Nylon RFPs were prepared using flock rotary cutters followed by vigorous opening procedures. Following 4 week exposures, the lungs of sham and Nylon-exposed rats were evaluated at 1 day, 1 week, as well as 1, 3, 6 and 12 months after exposure. At each of the post-exposure time points, the lungs of rats were either lavaged (for 3 months after exposure) or infusion fixed for cell proliferation, histopathology and fiber clearance/retention studies. This report contains data obtained during a 6 month post-exposure period. Preliminary results show that the retained mean lung burdens at 1 day after exposure were 1.75 × 107 (high level), 3.4 × 106 (mid level) and 4.8 × 105 (low level) RFPs/lung. Mean lengths and diameters of the Nylon aerosol were 9.8 and 1.6 μm, respectively. There were no significant increases in lung weights or indications of pulmonary inflammation in Nylon-exposed animals versus controls—based on cell differentials, bronchoalveolar lavage (BAL) fluid analyses and chemotaxis activity. More than 90% of the alveolar macrophages recovered by BAL (high level) contained Nylon RFPs or particles within their cytoplasm. Interim histopathological analyses have thus far revealed no adverse lower pulmonary or upper respiratory effects.
Methods development studies were conducted to develop standardized techniques for quantifying respirable organic fiber aerosol exposures in the workplace. The aim of this study was to compare the light microscopy results of aerosolized organic respirable-sized, fiber-shaped particulate (RFP) counts from three different laboratories and from four different individual counters (two in one laboratory). p -Aramid was utilized in these studies as a representative organic fiber-type. Atmospheres of aerosolized p -Aramid RFPs were generated in an inhalation chamber. Fifteen randomly distributed methylcellulose filters were exposed to a p -Aramid aerosol for 5 min at estimated concentrations of 20–30 f/ml. Following completion of exposures, filters were prepared for phase-contrast optical microscopy counting using standard preparation methods. The prepared slides containing a portion of the fiber-exposed filters were first counted at DuPont Haskell Laboratory in the USA, and then the same slides were sent to the Denkendorf Institute in Stuttgart, Germany and finally to the Institute of Occupational Medicine, Edinburgh, Scotland, UK. For quantification of fiber counts, the NIOSH 7400 fiber counting method was used at DuPont Haskell, while a WHO/EURO MMF fiber counting method was utilized in the European laboratories. The results demonstrated that the fiber counts from one laboratory (designated here as Lab 1) had consistently lower counts when compared to another laboratory (i.e. Lab 2) (mean values for the 15 filters = 18.4 ± 4.3 versus 27.7 ± 4.3 f/ml). A third laboratory (Lab 3), with two different counters, was frequently intermediate between the counts of Labs 1 and 2 (24.2 ± 1.1 and 22.1 ± 2.2 f/ml). The differences in fiber counts may be related either to the minor differences in counting rules between the US and European methods and/or to variability among counters. With few exceptions, the intralaboratory variability between counts was lower than the inter-laboratory variability among counts. Studies are ongoing to better assess the expected variability for aerosolized organic RFP counts when comparing the results from one laboratory to another and one method to another (NIOSH versus WHO/EURO MMF).
Efforts to understand and mitigate thehealth effects of particulate matter (PM) air pollutionhave a rich and interesting history. This review focuseson six substantial lines of research that have been pursued since 1997 that have helped elucidate our understanding about the effects of PM on human health. There hasbeen substantial progress in the evaluation of PM health effects at different time-scales of exposure and in the exploration of the shape of the concentration-response function. There has also been emerging evidence of PM-related cardiovascular health effects and growing knowledge regarding interconnected general pathophysiological pathways that link PM exposure with cardiopulmonary morbidiity and mortality. Despite important gaps in scientific knowledge and continued reasons for some skepticism, a comprehensive evaluation of the research findings provides persuasive evidence that exposure to fine particulate air pollution has adverse effects on cardiopulmonaryhealth. Although much of this research has been motivated by environmental public health policy, these results have important scientific, medical, and public health implications that are broader than debates over legally mandated air quality standards.
A symposium on the mechanisms of action of inhaled airborne particulate matter (PM), pathogenic particles and fibers such as silica and asbestos, and nanomaterials, defined as synthetic particles or fibers less than 100 nm in diameter, was held on October 27 and 28, 2005, at the Environmental Protection Agency (EPA) Conference Center in Research Triangle Park, North Carolina. The meeting was the eighth in a series of transatlantic conferences first held in Penarth, Wales, at the Medical Research Council Pneumoconiosis Unit (1979), that have fostered long-standing collaborations between researchers in the fields of mineralogy, cell and molecular biology, pathology, toxicology, and environmental/occupational health.
The goal of this meeting, which was largely supported by a conference grant from the NHLBI, was to assemble a group of clinical and basic research scientists who presented and discussed new data on the mechanistic effects of inhaled particulates on the onset and development of morbidity and mortality in the lung and cardiovascular system. Another outcome of the meeting was the elucidation of a number of host susceptibility factors implicated in adverse health effects associated with inhaled pathogenic particulates.
New models and data presented supported the paradigm that both genetic and environmental (and occupational) factors affect disease outcomes from inhaled particulates as well as cardiopulmonary responses. These future studies are encouraged to allow the design of appropriate strategies for prevention and treatment of particulate-associated morbidity and mortality, especially in susceptible populations.
Fused deposition modeling (FDM™) 3‐dimensional printing uses polymer filament to build objects. Some polymer filaments are formulated with additives, though it is unknown if they are released during printing. Three commercially‐available filaments that contained carbon nanotubes (CNTs) were printed with a desktop FDM™ 3‐D printer in a chamber while monitoring total particle number concentration and size distribution. Airborne particles were collected on filters and analyzed using electron microscopy. Carbonyl compounds were identified by mass spectrometry. The elemental carbon content of the bulk CNT‐containing filaments was 1.5 to 5.2 wt%. CNT‐containing filaments released up to 10¹⁰ ultrafine (d <100 nm) particles/g printed and 10⁶ to 10⁸ respirable (d ~0.5 to 2 μm) particles/g printed. From microscopy, 1% of the emitted respirable polymer particles contained visible CNTs. Carbonyl emissions were observed above the limit of detection (LOD) but were below the limit of quantitation (LOQ). Modeling indicated that for all filaments, the average proportional lung deposition of CNT‐containing polymer particles was 6.5%, 5.7%, and 7.2% for the head airways, tracheobronchiolar, and pulmonary regions, respectively. If CNT‐containing polymer particles are hazardous, it would be prudent to control emissions during use of these filaments.
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Background:
3D printers emit potentially hazardous ultrafine particles and volatile organic compounds. Workers using 3D printing technologies may be at risk of respiratory illness from occupational exposure.
Aims:
To assess whether 3D printing is associated with health effects in occupational users.
Methods:
This was a preliminary survey. Workers in 17 companies using 3D printing, including commercial prototyping businesses, educational institutions and public libraries, in the Greater Toronto Area, Canada, were asked to complete survey questionnaires concerning demographic, occupational and health information. Associations between self-reported health history variables and occupational characteristics were examined by chi-square and Fisher's exact tests.
Results:
Among 46 surveyed workers, 27 (59% of participants) reported having respiratory symptoms at least once per week in the past year. Working more than 40 h per week with 3D printers was significantly associated with having been given a respiratory-related diagnosis (asthma or allergic rhinitis) (P < 0.05). We observed a wide variation in occupational hygiene practices in the 17 printing workplaces that we surveyed.
Conclusions:
Our finding of frequently reported respiratory symptoms suggests a need for additional studies on exposed workers in this field.
Additive manufacturing (AM), commonly known as “three-dimensional (3D) printing,” is the process of joining materials to make objects from 3D model data, usually layer by layer. AM provides a cost-effective and time-efficient way to fabricate products with complicated geometries and advanced material properties and functionality. Based on the 2014 National Science Foundation (NSF) Workshop on Environmental Implications of Additive Manufacturing, this paper outlines potential environmental implications of AM related to key issues including energy use, occupational health, waste, lifecycle impact, and cross-cutting and policy issues, in terms of their current state-of-the-art, research needs, and recommendations, respectively.
Background:
Three-dimensional (3D) printing is being increasingly used in manufacturing and by small business entrepreneurs and home hobbyists. Exposure to airborne emissions during 3D printing raises the issue of whether there may be adverse health effects associated with these emissions.
Aims:
We present a case of a worker who developed asthma while using 3D printers, which illustrates that respiratory problems may be associated with 3D printer emissions.
Case report:
The patient was a 28-year-old self-employed businessman with a past history of asthma in childhood, which had resolved completely by the age of eight. He started using 10 fused deposition modelling 3D printers with acrylonitrile-butadiene-styrene filaments in a small work area of approximately 3000 cubic feet. Ten days later, he began to experience recurrent chest tightness, shortness of breath and coughing at work. After 3 months, his work environment was modified by reducing the number of printers, changing to polylactic acid filaments and using an air purifier with an high-efficiency particulate air filter and organic cartridge. His symptoms improved gradually, although he still needed periodic treatment with a salbutamol inhaler. While still symptomatic, a methacholine challenge indicated a provocation concentration causing a 20% fall in FEV1 (PC20) of 4 mg/ml, consistent with mild asthma. Eventually, his symptoms resolved completely and a second methacholine challenge after symptom resolution was normal (PC20 > 16 mg/ml).
Conclusions:
This case indicates that workers may develop respiratory problems, including asthma when using 3D printers. Further investigation of the specific airborne emissions and health problems from 3D printing is warranted.
Three-dimensional (3D) printers are known to emit aerosols, but questions remain about their composition and the fundamental processes driving emissions. The objective of this work was to characterize aerosol emissions from the operation of a fuse-deposition modeling 3D printer. We modeled the time- and size-resolved emissions of submicron aerosols from the printer in a chamber study, gained insight into the chemical composition of emitted aerosols using Raman spectroscopy, and measured potential for exposure to aerosols generated by 3D printers under real-use conditions in a variety of indoor environments. Average aerosol emission rates ranged from ~108 to ~1011 particles min-1, and rates varied over the course of a print job. Acrylonytrile-butadiene-styrene (ABS) filaments generated the largest number of aerosols and wood-infused polylactic acid (PLA) filaments generated the smallest amount. Emission factors ranged from 6×108 to 6×1011 per gram of printed part, depending on the type of filament used. For ABS, the Raman spectra of the filament and printed part were indistinguishable while the aerosol spectra lacked important peaks corresponding to styrene and acrylonitrile, which are both present in ABS. This observation suggests that aerosols are not a result of volatilization and subsequent nucleation of ABS or direct release of ABS aerosols.
Most desktop 3D printers designed for the consumer market utilize a plastic filament extrusion and deposition process to fabricate solid objects. Previous research has shown that the operation of extrusion-based desktop 3D printers can emit large numbers of ultrafine particles (UFPs: particles less than 100 nm) and some hazardous volatile organic compounds (VOCs), although very few filament and printer combinations have been tested to date. Here we quantify emissions of UFPs and speciated VOCs from five commercially available desktop 3D printers utilizing up to nine different filaments using controlled experiments in a test chamber. Median estimates of time-varying UFP emission rates ranged from ~108 to ~1011 #/min across all tested combinations, varying primarily by filament material and, to a lesser extent, bed temperature. The individual VOCs emitted in the largest quantities included caprolactam from nylon-based and imitation wood and brick filaments (ranging from ~2 to ~180 μg/min), styrene from acrylonitrile butadiene styrene (ABS) and high-impact polystyrene (HIPS) filaments (~10 to ~110 μg/min), and lactide from polylactic acid (PLA) filaments (~4 to ~5 μg/min). Results from a screening analysis of the potential exposures to these products in a typical small office environment suggest caution should be used when operating many of the printer and filament combinations in enclosed or poorly ventilated spaces or without the aid of a combined gas and particle filtration system.
Emissions from a desktop 3D printer based on fused deposition modeling (FDM) technology were measured in a test chamber and indoor air was monitored in office settings. Ultrafine aerosol (UFA) emissions were higher while printing a standard object with polylactic acid (PLA) than with acrylonitrile butadiene styrene (ABS) polymer (2.1 × 10⁹ vs. 2.4 × 10⁸ particles/min). Prolonged use of the printer led to higher emission rates (factor 2 with PLA and 4 with ABS, measured after seven months of occasional use).
UFA consisted mainly of volatile droplets, and some small (100–300 nm diameter) iron containing and soot-like particles were found. Emissions of inhalable and respirable dust were below the limit of detection (LOD) when measured gravimetrically, and only slightly higher than background when measured with an aerosol spectrometer. Emissions of volatile organic compounds (VOC) were in the range of 10 µg/min. Styrene accounted for more than 50% of total VOC emitted when printing with ABS; for PLA, methyl methacrylate (MMA, 37% of TVOC) was detected as the predominant compound. Two polycyclic aromatic hydrocarbons (PAH), fluoranthene and pyrene, were observed in very low amounts. All other analyzed PAH, as well as inorganic gases and metal emissions except iron (Fe) and zinc (Zn), were below the LOD or did not differ from background without printing.
A single 3D print (165 min) in a large, well-ventilated office did not significantly increase the UFA and VOC concentrations, whereas these were readily detectable in a small, unventilated room, with UFA concentrations increasing by 2,000 particles/cm³ and MMA reaching a peak of 21 µg/m³ and still being detectable in the room even 20 hr after printing.
This study evaluated the emissions characteristics of hazardous material during fused deposition modeling type 3D printing. Particulate and gaseous materials were measured before, during, and after 3D printing in an exposure chamber. One ABS and two PLA (PLA1 and PLA2) cartridges were tested three times. For online monitoring, a scanning mobility particle sizer, light scattering instrument, and total volatile organic compound (TVOC) monitor were employed and a polycarbonate filter and various adsorbent tubes were used for offline sampling. The particle concentration of 3D printing using ABS material was 33-38 times higher than when PLA materials were used. Most particles were nanosize (<100 nm) during ABS (96%) and PLA1 (98%) use, but only 12% were nanosize for PLA2. The emissions rates were 1.61 1010 ea/min and 1.67 1011 ea/g cartridge with the ABS cartridge and 4.27-4.89 108 ea/min and 3.77-3.91x109 ea/g cartridge with the PLA cartridge. TVOCs were also emitted when the ABS was used (GM; 155 ppb, GSD; 3.4), but not when the PLA cartridges were used. Our results suggest that more research and sophisticated control methods, including the use of less harmful materials, blocking emitted containments, and using filters or adsorbents, should be implemented.
As an indicator of general indoor air quality in industrial facilities, the concentrations of total volatile organic compounds (TVOC) were determined in the workplaces of 37 industry sectors during the years of 2006–2011. For comparison, the TVOC levels in office-type workplaces were also determined. Based on the results, the TVOC target and guideline values are proposed for industrial workplaces. The geometric mean and median concentrations in the industrial workplaces were 778 and 845 µg/m3, respectively, while the 90th, 25th percentiles were, respectively, 6616 and 270 µg/m3. In the office-type environments, the geometric mean and median concentrations were 55 and 50 µg/m3, and the 90th and 25th percentiles were 230 and 27 µg/m3. Based on the measured TVOC distributions and the target values previously set, we propose a TVOC target value of 300 µg/m3 and guideline value of 3000 µg/m3 for the general indoor air in industrial workplaces. The concentration of 3000 µg/m3 could be achieved with reasonable measures by most industry sectors, but does not guarantee that the inhalation exposure to volatile organic compounds in the occupational environments is free from health concerns or perceived discomfort. Therefore, when reasonably achievable, a TVOC concentration close to or below the target value is recommended. This would make the TVOC levels in industrial facilities similar to those in the non-occupational indoor environments.
Chemical storage rooms located near engineered nanomaterials (ENMs) workplaces can be a significant source of unintentional nanoaerosol generation. A new incidental nanoparticle source was identified and characterized in a chemical storage room located at an ENMs workplace. Stationary and mobile measurements using on-line instruments and chemical analysis of volatile organic compounds (VOCs) were carried out to identify the source. The number of nanoaerosols emitted from the chemical storage room was found to be several orders of magnitude higher than that existing in the ENMs workplace. VOC analysis showed that the accumulated precursors and oxygenated VOCs in the chemical storage room could be attributed to incidental particle formation via gas-to-particle conversion. We stress the importance of identification of the incidental nanoaerosols to allow characterization of the nanoaerosols at ENMs workplaces, and to estimate additional nanoaerosols exposure, which was previously unknown. Hazardous chemical substances in the workplace have been regulated in many countries; however, most of the regulations are focused on gas-phase or liquid-phase substances. The present study emphasizes the importance of secondary pollutants in particulate form that can be generated from the gas or liquid phase of hazardous chemical substances.
Copyright © 2015 Elsevier B.V. All rights reserved.
Objectives:
Thermoplastics may contain a wide range of additives and free monomers, which themselves may be hazardous substances. Laboratory studies have shown that the thermal decomposition products of common plastics can include a number of carcinogens and respiratory sensitizers, but very little information exists on the airborne contaminants generated during actual industrial processing. The aim of this work was to identify airborne emissions during thermal processing of plastics in real-life, practical applications.
Methods:
Static air sampling was conducted at 10 industrial premises carrying out compounding or a range of processes such as extrusion, blown film manufacture, vacuum thermoforming, injection moulding, blow moulding, and hot wire cutting. Plastics being processed included polyvinyl chloride, polythene, polypropylene, polyethylene terephthalate, and acrylonitrile-butadiene-styrene. At each site, static sampling for a wide range of contaminants was carried out at locations immediately adjacent to the prominent fume-generating processes.
Results:
The monitoring data indicated the presence of few carcinogens at extremely low concentrations, all less than 1% of their respective WEL (Workplace Exposure Limit). No respiratory sensitizers were detected at any sites.
Conclusions:
The low levels of process-related fume detected show that the control strategies, which employed mainly forced mechanical general ventilation and good process temperature control, were adequate to control the risks associated with exposure to process-related fume. This substantiates the advice given in the Health and Safety Executive's information sheet No 13, 'Controlling Fume During Plastics Processing', and its broad applicability in plastics processing in general.
The present feature article highlights the preparation of polymeric nanoparticles and initial attempts towards mimicking the structure of natural biomacromolecules by single chain folding of well-defined linear polymers through covalent and non-covalent interactions. Initially, the discussion focuses on the synthesis and characterization of single chain self-folded structures by non-covalent interactions. The second part of the article summarizes the folding of single chain polymers by means of covalent interactions into nanoparticle systems. The current state of the art in the field of single chain folding indicates that covalent-bond-driven nanoparticle preparation is well advanced, while the first encouraging steps towards building reversible single chain folding systems by the use of mutually orthogonal hydrogen-bonding motifs have been made.
The relation of chronic respiratory symptoms and pulmonary function to formaldehyde (HCHO) in homes was studied in a sample of 298 children (6–15 years of age) and 613 adults. HCHO measurements were made with passive samplers during two 1-week periods. Data on chronic cough and phlegm, wheeze, attacks of breathlessness, and doctor diagnoses of chronic bronchitis and asthma were collected with self-completed questionnaires. Peak expiratory flow rates (PEFR) were obtained during the evenings and mornings for up to 14 consecutive days for each individual. Significantly greater prevalence rates of asthma and chronic bronchitis were found in children from houses with HCHO levels 60–120 ppb than in those less exposed, especially in children also exposed to environmental tobacco smoke. In children, levels of PEFR decreased linearly with HCHO exposure, with the estimated decrease due to 60 ppb of HCHO equivalent to 22% of PEFR level in nonexposed children. The effects in asthmatic children exposed to HCHO below 50 ppb were greater than in healthy ones. The effects in adults were less evident: decrements in PEFR due to HCHO over 40 ppb were seen only in the morning, and mainly in smokers.
A total of 100 workers, 86 from the glass-fibre-reinforced plastics (GRP) industry, 11 from polystyrene production and 3 from polyester resin coating manufacture, were examined for occupational skin hazards and for evaluation of skin protection. The workers had been exposed to many chemicals. Those working in the GRP industry had also been exposed to glass fibre and to dust produced by finishing work. 94% used protective gloves. 22 workers, all employed in the GRP industry, had contracted occupational skin disorders. 6 had allergic and 12 irritant contact dermatitis. 4 workers had an accidental injury caused by a peroxide catalyst, fire, hot air and constant mechanical friction. Allergic dermatoses were due to natural rubber (latex) (4 cases) in protective gloves, phenol-formaldehyde resin (1 case) and cobalt naphthenate (1 case). Irritant hand dermatoses (5 cases) were caused by the combined hazardous effect of unsaturated polyester or vinyl ester resins, organic solvents, glass fibre and dust from finishing work on the skin. Other cases of irritant dermatoses (7 cases) were due to the dust, promoted by mechanical friction of clothes. Skin disorders in the GRP industry were common (26%) but the symptoms were mild and only 3 patients had been on sick leave because of occupational skin disease.
Acrylates are compounds used in a variety of industrial fields and their use is increasing. They have many features which make them superior to formerly used chemicals, regarding both their industrial use and their possible health effects. Contact sensitization is, however, one of their well known adverse health effects but they may also cause respiratory symptoms. We report on 18 cases of respiratory disease, mainly asthma, caused by different acrylates, 10 cases caused by cyanoacrylates, four by methacrylates and two cases by other acrylates.
The effects on health of prolonged but low level exposure to carbon monoxide (CO) are unclear. Studies of carbon monoxide exposure focus mainly on short term effects in experimental settings, or on long term effects in cases of accidental poisoning. Exposures in long term case studies are often of unknown levels and duration. Patients are sometimes exposed to short periods of acute intoxication, in addition to the low level, chronic exposure; thus the difficulty in determining which type of exposure is responsible for any subsequent health problems. Anecdotal evidence suggests that chronic exposure to CO may produce mild neurological effects. Although there are as yet no conclusive studies showing such a correlation, the evidence in its favour is accumulating.
The effects of severe exposure to carbon monoxide are well understood. The very effective competition of carbon monoxide with oxygen for binding sites on haemoglobin with the subsequent left shift of the dissociation curve leads to a reduction in both oxygen transport and release. This produces a range of effects on health. In 1999, a WHO expert group reviewed the subject and reported their conclusions in Environmental Health Criteria 213, Carbon Monoxide .1 A short account has been provided by the Expert Panel on Air Quality Standards.2 Severe poisoning, leading to a period of unconsciousness, may lead to neurological damage that may be long lasting, though eventual recovery seems to be the general rule. The mechanisms underlying the neurological damage are imperfectly known, but are thought to include an inflammatory response that may be initiated during the reperfusion or recovery phase when blood with increasing levels of oxygen flows into tissues that had hitherto been severely hypoxic. Reperfusion injury is known to play a part in the damage produced by myocardial infarction.3 Free radical release may lead to …
Objectives:
The critical health effects of formaldehyde exposure include sensory irritation and the potential to induce tumours in the upper respiratory tract. In literature, a concentration as low as 0.24 ppm has been reported to be irritating to the respiratory tract in humans. Nasal tumour-inducing levels in experimental animals seem to be 1-2 orders of magnitude larger. In this paper, the subjectively measured sensory irritation threshold levels in humans are discussed in line with findings obtained in animal experiments. In addition, a Benchmark dose (BMD) analysis of sensory irritation was used to estimate response incidences at different formaldehyde concentrations.
Methods:
Data on respiratory irritation and carcinogenicity of formaldehyde were retrieved from public literature and discussed. BMD analysis was carried out on human volunteer studies using the US-EPA BMD software.
Results:
Subjective measures of irritation were the major data found in humans to examine sensory (eye and nasal) irritation; only one study reported objectively measured eye irritation. On a normalized scale, mild/slight eye irritation was observed at levels 1 ppm, and mild/slight respiratory tract irritation at levels 2 ppm. With the BMD software, it was estimated that at a level of 1 ppm, only 9.5% of healthy volunteers experience 'moderate' (i.e., annoying) eye irritation (95% upper confidence limit). An important factor modulating the reported levels of irritation and health symptoms most probably includes the perception of odour intensity. In several studies, the 0-ppm control condition was missing. From the results of the long-term inhalation toxicity studies in experimental animals, a level of 1 ppm formaldehyde has been considered a NOAEL for nasal injury.
Conclusions:
Sensory irritation is first observed at levels of 1 ppm and higher. From both human and animal studies, it was concluded that at airborne levels for which the prevalence of sensory irritation is minimal both in incidence and degree (i.e., <1 ppm), risks of respiratory tract cancer are considered to be negligibly low.
Indoor Air Quality: A Comprehensive Reference Book
- M Maroni
- B Seifert
- T Lindvall
Maroni, M., Seifert, B., and Lindvall, T.: Indoor Air Quality: A Comprehensive Reference Book.
Amsterdam Elsevier, 1995.
Wohlers Report; 3D Printing and Additive Manufacturing State of the Industry
- T Wohlers
- I Campbell
- O Diegel
- J Kowen
- J Caffrey
Wohlers, T., Campbell, I., Diegel, O., Kowen, J., and Caffrey, J.: Wohlers Report; 3D Printing
and Additive Manufacturing State of the Industry: Annual Worldwide Progress Report. Colorado,
USA: Wohlers Associates, Inc., 2017.
WHO Guidelines for Indoor Air Quality: Selected Pollutants. World Health Organization
- D A Kaden
- C Mandin
- G D Nielsen
- P Wolkoff
Kaden, D. A., Mandin, C., Nielsen, G. D., and Wolkoff, P.: WHO Guidelines for Indoor Air
Quality: Selected Pollutants. World Health Organization, 2010.