Engineered carbonaceous nanomaterials manufacturers in the United States: Workforce size, characteristics, and feasibility of epidemiologic studies

ArticleinJournal of occupational and environmental medicine / American College of Occupational and Environmental Medicine 53(6 Suppl):S62-7 · June 2011with19 Reads
Impact Factor: 1.63 · DOI: 10.1097/JOM.0b013e31821b1e2c · Source: PubMed
Abstract

Toxicology studies suggest that carbon nanotube (CNT) exposures may cause adverse pulmonary effects. This study identified all US engineered carbonaceous nanomaterial (ECN) manufacturers, determined workforce size and growth, and characterized the materials produced to determine the feasibility of occupational ECN exposure studies. Eligible companies were identified; information was assembled on the companies and nanomaterials they produced; and the workforce size, location, and growth were estimated. Sixty-one companies manufacturing ECN in the United States were identified. These companies employed at least 620 workers; workforce growth was projected at 15% to 17% annually. Most companies produced or used CNT. Half the eligible companies provided information about material dimensions, quantities, synthesis methods, and worker exposure reduction strategies. Industrywide exposure assessment studies appear feasible; however, cohort studies are likely infeasible because of the small, scattered workforce.

    • "...; Dahm et al., 2015) and accompanying human health effects studies (Lee et al., 2015; Schubauer-Berigan et al., 2011) provided insight into types of CNT utilized by industry as well as the downstream applications and..."
      In many cases inhalation is simply not feasible and instillation studies may be necessary, but the overall premise of screening materials with standardized outcomes is an extremely valuable first step. Exposure assessment studies (Dahm et al., 2012; Dahm et al., 2015) and accompanying human health effects studies (Lee et al., 2015; Schubauer-Berigan et al., 2011) provided insight into types of CNT utilized by industry as well as the downstream applications and products containing these materials. These studies provided data on specific preference of materials, level of exposure, years handling a given material, and future direction of the market.
    [Show abstract] [Hide abstract] ABSTRACT: The early incorporation of exposure assessment can be invaluable to help design, prioritize, and interpret toxicological studies or outcomes. The sum total of the exposure assessment findings combined with preliminary toxicology results allows for exposure-informed toxicological study design and the findings can then be integrated, together with available epidemiologic data, to provide health effect relevance. With regard to engineered nanomaterial inhalation toxicology in particular, a single type of material (e.g. carbon nanotube, graphene) can have a vast array of physicochemical characteristics resulting in the potential for varying toxicities. To compound the matter, the methodologies necessary to establish a material adequate for in vivo exposure testing raises questions on the applicability of the outcomes. From insights gained from evaluating carbon nanotubes, we recommend the following integrated approach involving exposure-informed hazard assessment and hazard-informed exposure assessment especially for materials as diverse as engineered nanomaterials: 1) market-informed identification of potential hazards and potentially exposed populations, 2) initial toxicity screening to drive prioritized assessments of exposure, 3) development of exposure assessment-informed chronic and sub-chronic in vivo studies, and 4) conduct of exposure- and hazard-informed epidemiological studies.
    Full-text · Article · Apr 2016 · Journal of Aerosol Science
    • "...ng four distinct industries in which these advanced materials are being produced or used. Berigan et al. (2011) estimated that 44 companies, not including research laboratories or universities, were primary or s..."
      This study provides detailed information on occupational exposures to CNT and CNF from 14 companies (13 CNT facilities, 1 CNF facility); spanning four distinct industries in which these advanced materials are being produced or used. Berigan et al. (2011) estimated that 44 companies, not including research laboratories or universities, were primary or secondary manufacturers of CNT and CNF in the USA, as of 2008–2009. This group, augmented with an additional six companies, formed the sample base for the present study.
    [Show abstract] [Hide abstract] ABSTRACT: Recent evidence has suggested the potential for wide-ranging health effects that could result from exposure to carbon nanotubes (CNT) and carbon nanofibers (CNF). In response, the National Institute for Occupational Safety and Health (NIOSH) set a recommended exposure limit (REL) for CNT and CNF: 1 µg m(-3) as an 8-h time weighted average (TWA) of elemental carbon (EC) for the respirable size fraction. The purpose of this study was to conduct an industrywide exposure assessment among US CNT and CNF manufacturers and users. Fourteen total sites were visited to assess exposures to CNT (13 sites) and CNF (1 site). Personal breathing zone (PBZ) and area samples were collected for both the inhalable and respirable mass concentration of EC, using NIOSH Method 5040. Inhalable PBZ samples were collected at nine sites while at the remaining five sites both respirable and inhalable PBZ samples were collected side-by-side. Transmission electron microscopy (TEM) PBZ and area samples were also collected at the inhalable size fraction and analyzed to quantify and size CNT and CNF agglomerate and fibrous exposures. Respirable EC PBZ concentrations ranged from 0.02 to 2.94 µg m(-3) with a geometric mean (GM) of 0.34 µg m(-3) and an 8-h TWA of 0.16 µg m(-3). PBZ samples at the inhalable size fraction for EC ranged from 0.01 to 79.57 µg m(-3) with a GM of 1.21 µg m(-3). PBZ samples analyzed by TEM showed concentrations ranging from 0.0001 to 1.613 CNT or CNF-structures per cm(3) with a GM of 0.008 and an 8-h TWA concentration of 0.003. The most common CNT structure sizes were found to be larger agglomerates in the 2-5 µm range as well as agglomerates >5 µm. A statistically significant correlation was observed between the inhalable samples for the mass of EC and structure counts by TEM (Spearman ρ = 0.39, P < 0.0001). Overall, EC PBZ and area TWA samples were below the NIOSH REL (96% were <1 μg m(-3) at the respirable size fraction), while 30% of the inhalable PBZ EC samples were found to be >1 μg m(-3). Until more information is known about health effects associated with larger agglomerates, it seems prudent to assess worker exposure to airborne CNT and CNF materials by monitoring EC at both the respirable and inhalable size fractions. Concurrent TEM samples should be collected to confirm the presence of CNT and CNF. Published by Oxford University Press on behalf of the British Occupational Hygiene Society 2015.
    Full-text · Article · Apr 2015 · Annals of Occupational Hygiene
    • "...ed in the handling of CNTs at 61 companies in the U.S. with a projected annual growth of about 22% [7,8]. The growing production and use of CNTs will result in a dramatic increase in occupational and pu..."
      The National Science Foundation projects that by 2020, the CNT industry will employ approximately 6 million workers, 2 million of whom are expected to be in the United States [6]. Currently, a large number of occupational personnel are known to be involved in the handling of CNTs at 61 companies in the U.S. with a projected annual growth of about 22% [7,8]. The growing production and use of CNTs will result in a dramatic increase in occupational and public exposure to engineered nanomaterials.
    [Show abstract] [Hide abstract] ABSTRACT: Given their remarkable properties, carbon nanotubes (CNTs) have made their way through various industrial and medicinal applications and the overall production of CNTs is expected to grow rapidly in the next few years, thus requiring an additional recruitment of workers. However, their unique applications and desirable properties are fraught with concerns regarding occupational exposure. The concern about worker exposure to CNTs arises from the results of recent animal studies. Short-term and sub-chronic exposure studies in rodents have shown consistent adverse health effects such as pulmonary inflammation, granulomas, fibrosis, genotoxicity and mesothelioma after inhalation or instillation of several types of CNTs. Furthermore, physicochemical properties of CNTs such as dispersion, functionalization and particle size can significantly affect their pulmonary toxicity. Risk estimates from animal studies necessitate implementation of protective measures to limit worker exposure to CNTs. Information on workplace exposure is very limited, however, studies have reported that CNTs can be aerosolized and attain respirable airborne levels during synthesis and processing activities in the workplace. Quantitative risk assessments from sub-chronic animal studies recommend the health-based need to reduce exposures below the recommended exposure limit of 1 μg/m3. Practice of prevention measures including the use of engineering controls, personal protective equipment, health surveillance program, safe handling and use, as well as worker training can significantly minimize worker exposure and improve worker health and safety.
    Full-text · Article · Jun 2014
    • "...ed in the handling of CNTs at 61 companies in the U.S. with a projected annual growth of about 22% [7,8]. The growing production and use of CNTs will result in a dramatic increase in occupational and pu..."
      The National Science Foundation projects that by 2020, the CNT industry will employ approximately 6 million workers, 2 million of whom are expected to be in the United States [6]. Currently, a large number of occupational personnel are known to be involved in the handling of CNTs at 61 companies in the U.S. with a projected annual growth of about 22% [7,8]. The growing production and use of CNTs will result in a dramatic increase in occupational and public exposure to engineered nanomaterials.
    Preview · Article · Jan 2014
    • "...ity of the U.S. workforce handling carbonaceous nanomaterials primarily produces or utilizes MWCNT [15]. 2.) Economically, the global market showed that CNT represents 28% of the total engineered nanomat..."
      The inhalation study utilized the MWCNT produced by Hodogaya, commonly referred to as the Mitsui MWCNT or MWNT-7. This particular product was utilized for several reasons: 1.) A majority of the U.S. workforce handling carbonaceous nanomaterials primarily produces or utilizes MWCNT [15]. 2.) Economically, the global market showed that CNT represents 28% of the total engineered nanomaterial market share with MWCNT being 94% of the total CNT production value (http:// www.nanowerk.com/spotlight/spotid=23118.php).
    [Show abstract] [Hide abstract] ABSTRACT: Dosimetry for toxicology studies involving carbon nanotubes (CNT) is challenging because of a lack of detailed occupational exposure assessments. Therefore, exposure assessment findings, measuring the mass concentration of elemental carbon from personal breathing zone (PBZ) samples, from 8 U.S.-based multi-walled CNT (MWCNT) manufacturers and users were extrapolated to results of an inhalation study in mice. Upon analysis, an inhalable elemental carbon mass concentration arithmetic mean of 10.6 mug/m3 (geometric mean 4.21 mug/m3) was found among workers exposed to MWCNT. The concentration equates to a deposited dose of approximately 4.07 mug/d in a human, equivalent to 2 ng/d in the mouse. For MWCNT inhalation, mice were exposed for 19 d with daily depositions of 1970 ng (equivalent to 1000 d of a human exposure; cumulative 76 yr), 197 ng (100 d; 7.6 yr), and 19.7 ng (10 d; 0.76 yr) and harvested at 0, 3, 28, and 84 d post-exposure to assess pulmonary toxicity. The high dose showed cytotoxicity and inflammation that persisted through 84 d after exposure. The middle dose had no polymorphonuclear cell influx with transient cytotoxicity. The low dose was associated with a low grade inflammatory response measured by changes in mRNA expression. Increased inflammatory proteins were present in the lavage fluid at the high and middle dose through 28 d post-exposure. Pathology, including epithelial hyperplasia and peribronchiolar inflammation, was only noted at the high dose. These findings showed a limited pulmonary inflammatory potential of MWCNT at levels corresponding to the average inhalable elemental carbon concentrations observed in U.S.-based CNT facilities and estimates suggest considerable years of exposure are necessary for significant pathology to occur at that level.
    Full-text · Article · Oct 2013 · Particle and Fibre Toxicology
    • "...nner and outer InVS exposure experts and cross-validated with other questionnaires on ENM exposure [14,15] to harmonize it for potential international collaborative studies. ..."
      is designed with aim to address the likelihood of ENM exposure by analysis of the process used to produce or transform ENM at companies pre-selected as of first attention and to establish contacts with company OSH manager and occupational physician for further collaboration (seeFig.1). This questionnaire was reviewed by inner and outer InVS exposure experts and cross-validated with other questionnaires on ENM exposure [14,15] to harmonize it for potential international collaborative studies.
    [Show abstract] [Hide abstract] ABSTRACT: Despite the lack of data on the human health potential risks related to the engineered nanomaterials (ENM) exposure, ENM handling spreads in industry. The French government officially charged the InVS to develop an epidemiological surveillance of workers occupationally exposed to ENM. An initial surveillance plan was proposed on the basis of literature review and discussions with national and international ENM and occupational safety and health (OSH) experts. In site investigations and technical visits were then carried out to build an adequate surveillance system and to assess its feasibility. The current plan consists of a multi-step methodology where exposure registry construction is paramount. Workers potentially exposed to carbon nanotubes (CNT) or nanometric titanium dioxide (TiO2) will be identified using a 3-level approach: 1-identification and selection of companies concerned with ENM exposure (based on compulsory declaration and questionnaires), 2-in site exposure assessment and identification of the jobs/tasks with ENM exposure (based on job-expose matrix, further supplemented with measurements), and 3-identification of workers concerned. Data of interest will be collected by questionnaire. Companies and workers inclusion questionnaires are designed and currently under validation. This registration is at the moment planned for three years but could be extended and include other ENM. A prospective cohort study will be established from this registry, to pursue surveillance objectives and serve as an infrastructure for performing epidemiological and panel studies with specific research objectives.
    Full-text · Article · Apr 2013 · Journal of Physics Conference Series
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