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Volatilization of low vapor pressure – volatile organic compounds (LVP–VOCs) during three cleaning products-associated activities: Potential contributions to ozone formation
Abstract
There have been many studies to reduce ozone formation mostly from volatile organic compound (VOC) sources. However, the role of low vapor pressure (LVP)-VOCs from consumer products remains mostly unexplored and unaddressed. This study explores the impact of high production volume LVP-VOCs on ozone formation from three cleaning products-associated activities (dishwashing, clothes washing, and surface cleaning). We develop a model framework to account for the portion available for ozone formation during the use phase and from the down-the-drain disposal. We apply experimental studies that measured emission rates or models that were developed for estimating emission rates of organic compounds during the use phase. Then, the fraction volatilized (fvolatilized) and the fraction disposed down the drain (fdown-the-drain) are multiplied by the portion available for ozone formation for releases to the outdoor air (fO3|volatilized) and down-the-drain (fO3|down-the-drain), respectively. Overall, for chemicals used in three specific cleaning-product uses, fvolatilized is less than 0.6% for all studied LVP-VOCs. Because greater than 99.4% of compounds are disposed of down the drain during the use phase, when combined with fO3|volatilized and fO3|down-the-drain, the portion available for ozone formation from the direct releases to outdoor air and the down-the-drain disposal is less than 0.4% and 0.2%, respectively. The results from this study indicate that the impact of the studied LVP-VOCs on ozone formation is very sensitive to what occurs during the use phase and suggest the need for future research on experimental work at the point of use.
... The short-term impact is associated with the initial emission of VOCs or SVOCs due to volatilization during product use [24]. For liquid products applied on surfaces, the chemicals in the liquid can evaporate and become gas-phase compounds in the air [20,25]. For spray products applied on surfaces or in the air, aerosol droplets containing the chemicals are formed during product use [26]. ...
... Depending on the mass transfer mechanism and the key parameters considered, existing models for predicting emission of chemicals from HCPs and PCPs can be categorized into three types, i.e., models based on evaporation [20,25,[31][32][33][34][35][36][37], on convective mass transfer [21,22,[38][39][40][41] and on diffusion [17,42,43]. ...
... After the clearance time, the product liquid layer was removed from the model. Compared to the three above-mentioned models, Model E4 simplified evaporation and absorption to zero-order processes, meaning that the evaporation and absorption rates were independent of the chemical concentrations in the air, product liquid and skin, and therefore constant [25,36,37]. The four above-mentioned models address the product emission after one use. ...
Chemicals in household cleaning and personal care products (HCPs and PCPs) can be released into the indoor air primarily during and after product use, leading to human exposures to these chemicals via inhalation and dermal contact. Thus, HCPs and PCPs are a group of important intermittent sources, contributing to chemical emissions in the indoor environment. To characterize emissions more accurately, we reviewed three types of emission models from 17 studies for HCPs and PCPs, i.e., models based on evaporation, on convective mass transfer, and on diffusion. While the three types of models present different levels of complexity, they cover a variety of application scenarios. We also summarized some important input parameters for the models, i.e., the frequency and quantity of use of HCPs and PCPs, and the chemical's evaporation rate and diffusion coefficient. The frequency and quantity of use for many types of products, including shampoo, hand soap and deodorant show some consistency among different studies. Our review of these model inputs reveals a promising basis for further improvement of emission models for HCPs and PCPs.
... There are several exposure models for cleaning product use 23 Some of these models (e.g., Ref. 17) are only capable of calculating exposure of a product from a specific cleaning activity (e.g., daily intake rate of a dish detergent from hand dishwashing). However, the literature on indoor fate and exposure shows that exposures from cleaning product use vary strongly among chemical constituents because chemical properties primarily determine the degree of volatility, the portion disposed down the drain, 24 and dermal permeation. 25 The U.S. EPA Office of Pollution Prevention and Toxics has developed a chemical-specific consumer exposure model (i.e., CEM) to estimate potential exposures from the use of various consumer products, but this model mostly captures the exposure to a user during the use phase (i.e., a time period while a product is being used for cleaning activities). ...
... We did not quantify emissions from this pathway in our study because we lacked sufficient data to develop a model. 24 Similarly, although there may be chemical residues on dishes after dishwasher operation and hand dishwashing, we assume that essentially all of the compounds formulated into dishwashing detergent are either volatilized or disposed down the drain during product use. 24 Because some compounds have a strong tendency to bind to indoor surfaces or organic carbon in dust, 27 we calculate f ventilated to account for both exposure indoors and outdoors, noting that some fraction could be removed from indoor environments via other transport or removal processes (e.g., vacuuming). ...
... 24 Similarly, although there may be chemical residues on dishes after dishwasher operation and hand dishwashing, we assume that essentially all of the compounds formulated into dishwashing detergent are either volatilized or disposed down the drain during product use. 24 Because some compounds have a strong tendency to bind to indoor surfaces or organic carbon in dust, 27 we calculate f ventilated to account for both exposure indoors and outdoors, noting that some fraction could be removed from indoor environments via other transport or removal processes (e.g., vacuuming). ...
We present a screening-level exposure assessment method which integrates exposure from all plausible exposure pathways as a result of indoor residential use of cleaning products. The exposure pathways we considered are (1) exposure to a user during product use via inhalation and dermal, (2) exposure to chemical residues left on clothing, (3) exposure to all occupants from the portion released indoors during use via inhalation and dermal, and (4) exposure to the general population due to down-the-drain disposal via inhalation and ingestion. We use consumer product volatilization models to account for the chemical fractions volatilized to air (fvolatilized ) and disposed down the drain (fdown-the-drain ) during product use. For each exposure pathway, we use a fate and exposure model to estimate intake rates (iR) in mg/kg/day. Overall, the contribution of the four exposure pathways to the total exposure varies by the type of cleaning activities and with chemical properties. By providing a more comprehensive exposure model and by capturing additional exposures from often-overlooked exposure pathways, our method allows us to compare the relative contribution of various exposure routes and could improve high-throughput exposure assessment for chemicals in cleaning products. This article is protected by copyright. All rights reserved.
... For example, a high fraction of organic compounds evaporate from architectural coatings. Most organic compounds in soaps and detergents dissolve in water and end up in sewer systems (20), with negligible amounts emitted from wastewater treatment plants (21). ...
... The ambient and indoor air measurements shown in Fig. 3 constrain primary emissions from VCPs that contributẽ 70% of the OH reactivity from VCPs. Consumer products contain reactive OVOCs and terpenes, which emit upon use, even after accounting for sewer losses (20). ...
Air pollution evolution
Transport-derived emissions of volatile organic compounds (VOCs) have decreased owing to stricter controls on air pollution. This means that the relative importance of chemicals in pesticides, coatings, printing inks, adhesives, cleaning agents, and personal care products has increased. McDonald et al. show that these volatile chemical products now contribute fully one-half of emitted VOCs in 33 industrialized cities (see the Perspective by Lewis). Thus, the focus of efforts to mitigate ozone formation and toxic chemical burdens need to be adjusted.
Science , this issue p. 760 ; see also p. 744
... See Supplemental Material S3.3 for details. This approach to estimating emission rate was selected as a compromise between the highly conservative approach of assuming all chemical in the product is emitted into the air [26], and attempting to predict scenario-and product-specific time-dependent emission rates, which have high data and computational requirements that make them infeasible for rapid exposure modeling [27][28][29][30][31][32][33][34][35][36][37][38]. Inhalation of dust particles is modeled using the assumption that chemical mass that falls to the floor after use mixes with the dust on the floor and can then become resuspended and inhaled. ...
To estimate potential chemical risk, tools are needed to prioritize potential exposures for chemicals with minimal data. Consumer product exposures are a key pathway, and variability in consumer use patterns is an important factor. We designed Ex Priori, a flexible dashboard-type screening-level exposure model, to rapidly visualize exposure rankings from consumer product use. Ex Priori is Excel-based. Currently, it is parameterized for seven routes of exposure for 1108 chemicals present in 228 consumer product types. It includes toxicokinetics considerations to estimate body burden. It includes a simple framework for rapid modeling of broad changes in consumer use patterns by product category. Ex Priori rapidly models changes in consumer user patterns during the COVID-19 pandemic and instantly shows resulting changes in chemical exposure rankings by body burden. Sensitivity analysis indicates that the model is sensitive to the air emissions rate of chemicals from products. Ex Priori’s simple dashboard facilitates dynamic exploration of the effects of varying consumer product use patterns on prioritization of chemicals based on potential exposures. Ex Priori can be a useful modeling and visualization tool to both novice and experienced exposure modelers and complement more computationally intensive population-based exposure models.
... Other volatile compounds, such as organophosphates for example, are employed as pesticides, flame-retardants in polymers, electric appliances, aircraft and building materials [65][66][67][68]. Moreover, a great amount of cleaning products, like air fresheners, cleaners, furniture polisher, toilet products, laundry detergent, among others, introduce different types of VOCs [69][70][71][72]. In another respect, common VOCs like toluene, benzene, isomers of xylene, and ethylbenzene are frequently used in the production of paints and coatings, leather, rubber, and other synthetic material production that present risk factors upon acute or chronic exposure to high levels of each compound [73][74][75]. ...
Volatile organic compounds (VOCs) that evaporate under standard atmospheric conditions are of growing concern. This is because it is well established that VOCs represent major contamination risks since release of these compounds into the atmosphere can contribute to global warming, and thus, can also be detrimental to the overall health of worldwide populations including plants, animals, and humans. Consequently, the detection, discrimination, and quantification of VOCs have become highly relevant areas of research over the past few decades. One method that has been and continues to be creatively developed for analyses of VOCs is the Quartz Crystal Microbalance (QCM). In this review, we summarize and analyze applications of QCM devices for the development of sensor arrays aimed at the detection of environmentally relevant VOCs. Herein, we also summarize applications of a variety of coatings, e.g., polymers, macrocycles, and ionic liquids that have been used and reported in the literature for surface modification in order to enhance sensing and selective detection of VOCs using quartz crystal resonators (QCRs) and thus QCM. In this review, we also summarize novel electronic systems that have been developed for improved QCM measurements.
... The composition and emissions of chemical products have changed significantly in recent decades in an effort to reduce the ozone (O 3 ) and secondary organic aerosol (SOA) formation potential (Weschler, 2009;CARB, 2015;Shin et al., 2016). For example, water-borne paints are increasingly replacing solvent-borne paints, while, simultaneously, many VOC ingredients are being replaced with water (Matheson, 2002), "exempt" VOCs, or low-vapor-pressure VOCs (LVP-VOCs; Li et al., 2018). ...
The emissions of volatile organic compounds (VOCs) from
volatile chemical products (VCPs) – specifically personal care products,
cleaning agents, coatings, adhesives, and pesticides – are emerging as the
largest source of petroleum-derived organic carbon in US cities. Previous
work has shown that the ambient concentration of markers for most VCP
categories correlates strongly with population density, except for VOCs
predominantly originating from solvent- and water-borne coatings (e.g.,
parachlorobenzotrifluoride (PCBTF) and Texanol®, respectively). Instead, these enhancements were dominated by distinct emission events likely driven by industrial usage patterns, such as
construction activity. In this work, the headspace of a variety of coating
products was analyzed using a proton-transfer-reaction time-of-flight mass
spectrometer (PTR-ToF-MS) and a gas chromatography (GC) preseparation
front end to identify composition differences for various coating types
(e.g., paints, primers, sealers, and stains). Evaporation experiments of
several products showed high initial VOC emission rates, and for the length
of these experiments, the majority of the VOC mass was emitted during the
first few hours following application. The percentage of mass emitted as
measured VOCs (<1 % to 83 %) mirrored the VOC content reported by
the manufacturer (<5 to 550 g L−1). Ambient and laboratory
measurements, usage trends, and ingredients compiled from architectural
coatings surveys show that both PCBTF and Texanol account for ∼10 % of the total VOC ingredient sales and, therefore, can be useful tracers for solvent- and water-borne coatings.
... In addition, the OVOC species such as glycols and glycol ethers are key markers for consumer cleaning products (Shin et al., 2016). Ethanol and isopropanol are common in health care products, cleaning agents, and alcoholic drinking (McDonald et al., 2018). ...
Concentrations of 99 volatile organic compounds (VOCs) were continuously measured online at an urban site in Beijing, China, in January, April, July, and October 2016. Characterization and sources of VOCs and their related changes during days with heavy ozone (O3) pollution were analysed. The total observed concentration of VOCs (TVOCs) was 44.0 ± 28.9 ppbv. The VOC pollution level has decreased in Beijing but remains higher than in other Chinese cities. Alkanes comprised the highest proportion among seven major sampled VOC groups. The concentrations and sources of ambient VOCs showed obvious temporal variations. Six emission sources were identified by the positive matrix factorization (PMF), including biomass burning, coal combustion, gasoline vehicles, diesel vehicles, solvent usage, and biogenic + secondary emissions. The combustion source was the key control factor for VOC reduction in Beijing. From the potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) model, Beijing, Tianjin, Hebei, Shanxi, Inner Mongolia, Shandong, and Henan were identified as major potential source regions of ambient VOCs. O3 formation was sensitive to VOCs in Beijing according to the VOC/NOx ratio (ppbC/ppbv, 8:1 threshold). High- and low-O3 days in July were identified, and high O3 levels were due to both enhanced VOC emission levels and meteorological conditions favourable to the production of O3. These findings provide evidence that the fuel combustion and regional transport have a great impact on concentrations and sources of VOCs in urban Beijing.
... Vo and Morris (2014) standards clearly volatilize at ambient conditions, nearly as rapidly as the traditional high volatility solvents they are meant to replace. Shin et al. (2016) develop and evaluate environmental modeling tools and find that when the LVP-VOC in a consumer product is volatilized from the surface to which it has been applied, greater than 90% is available for photochemical reactions either at the source location or in the downwind areas. ...
Emissions of certain low vapor pressure-volatile organic compounds (LVP-VOCs) are considered exempt to volatile organic compounds (VOC) regulations due to their low evaporation rates. However, these compounds may still play a role in ambient secondary organic aerosol (SOA) and ozone formation. The LVP-VOCs selected for this work are categorized as intermediate-volatility organic compounds (IVOCs) according to their vapor pressures and molecular formulas. In this study, the evaporation rates of 14 select IVOCs are investigated with half of them losing more than 95% of their mass in less than one month. Further, SOA and ozone formation are presented from 11 select IVOCs and 5 IVOC-containing generic consumer products under atmospherically relevant conditions using varying radical sources (NOx and/or H2O2) and a surrogate reactive organic gas (ROG) mixture. Benzyl alcohol (0.41), n-heptadecane (0.38), and diethylene glycol monobutyl ether (0.16) are determined to have SOA yields greater than 0.1 in the presence of NOx and a surrogate urban hydrocarbon mixture. IVOCs also influence ozone formation from the surrogate urban mixture by impacting radical levels and NOx availability. The addition of lab created generic consumer products has a weak influence on ozone formation from the surrogate mixture but strongly affects SOA formation. The overall SOA and ozone formation of the generic consumer products could not be explained solely by the results of the pure IVOC experiments.
... Volatile organic compounds (VOCs), which are precursors to ozone (O 3 ) and particulate matter (PM), play a critical role in air quality. VOCs are emitted from motor vehicles, chemical manufacturing facilities, refineries, factories, consumer and commercial products, and biogenic sources, among numerous other sources [2][3][4][5][6][7]. Pollutants in outdoor air also affect indoor air quality (IAQ). ...
Only limited research has examined the development and application of visible light responsive photocatalytic oxidation (PCO), although such materials have great potential for mitigating concentrations of volatile organic compounds (VOCs) when applied to building surfaces. This study evaluates the performance and characteristics of a visible light responsive photocatalyst, specially, a co-alloyed TiNbON compound with a band energy of 2.3 eV. The PCO material was developed using urea-glass synthesis, characterized by scanning electron microscopy (SEM), diffuse reflectance spectra (DRS), powder X-ray diffraction (PXRD), and Brunauer-Emmett-Teller (BET) methods, and VOC removal efficiency was measured under visible light for toluene (1–5 ppm) at room temperature (21.5 °C) and a range of relative humidity (RH: 25 to 65%), flow rate (0.78 to 7.84 cm/s), and irradiance (42–95 W/m²). A systematic parametric evaluation of kinetic parameters was conducted. In addition, we compared TiNbON with a commercial TiO2-based material under black light, estimated TiNbON’s long-term durability and stability, and tested its ability to thermally regenerate. Using mass transfer and kinetic analysis, three different Langmuir-Hinshelwood (LH) type reaction rate expressions were proposed and evaluated. A LH model considering one active site and competitive sorption of toluene and water was superior to others. The visible-light driven catalyst was able to remove up to 58% of the toluene, generated less formaldehyde than the commercial TiO2, could be fully regenerated at 150 °C, and had reasonable durability and stability. This evaluation of TiNbON shows the potential to remove VOCs and improve air quality for indoor applications. Further research is needed to evaluate the potential for harmful by-products, to identify optimal conditions, and to use field tests to show real-world performance.
... Understanding the increases in ozone production will help improve predictability and reduce ozone pollution by controlling NO x and VOCs emissions. A considerable number of studies on the ozone increases resulting from emissions from vehicles, engines and generators operating using various fuels have been conducted; however, most of these studies were conducted using modeling, computer simulations or direct tailpipe measurements (Mellouki et al., 2015;Shin et al., 2016). To assess the ozone formation potential in the atmosphere and the importance of NMHC precursors, the maximum incremental reactivity (MIR), also known as the maximum ozone incremental reactivity (MOIR) was proposed by Carter in the late 1980s Atkinson, 1987, 1989). ...
Keyword: Ozone increment Biodiesel fuel Emission Vietnam NMHCs NO x a b s t r a c t The consumption of fuel by vehicles emits nitrogen oxides (NO x) and non-methane hydrocarbons (NMHCs) into the atmosphere, which are important ozone precursors. Ozone is formed as a secondary pollutant via photochemical processes and is not emitted directly into the atmosphere. In this paper, the ozone increase resulting from the use of biodiesel and diesel fuels was investigated, and the different ozone formation trends were experimentally evaluated. Known amounts of exhaust gas from a power generator operated using biodiesel and diesel fuels were added to ambient air. The quality of the ambient air, such as the initial NMHC and NO x concentrations, and the irradiation intensity have an effect on the ozone levels. When 30 cm 3 of biodiesel fuel exhaust gas (BFEG) or diesel fuel exhausted gas (DFEG) was added to 18 dm 3 of ambient air, the highest ratios of ozone increase from BFEG compared with DFEG in Japan and Vietnam were 31.2 and 42.8%, respectively, and the maximum ozone increases resulting from DFEG and BFEG compared with the ambient air in Japan were 17.4 and 26.4 ppb, respectively. The ozone increase resulting from the use of BFEG was large and significant compared to that from DFEG under all experimental conditions. The ozone concentration increased as the amount of added exhaust gas increased. The ozone increase from the Jatropha-BFEG was slightly higher than that from waste cooking oil-BFEG.
... Understanding the increases in ozone production will help improve predictability and reduce ozone pollution by controlling NO x and VOCs emissions. A considerable number of studies on the ozone increases resulting from emissions from vehicles, engines and generators operating using various fuels have been conducted; however, most of these studies were conducted using modeling, computer simulations or direct tailpipe measurements (Mellouki et al., 2015; Shin et al., 2016 ). To assess the ozone formation potential in the atmosphere and the importance of NMHC precursors, the maximum incremental reactivity (MIR), also known as the maximum ozone incremental reactivity (MOIR) was proposed by Carter in the late 1980s ( Atkinson, 1987, 1989). ...
Volatile organic compounds (VOCs) can influence air quality and threaten human health; however, the development of an effective method to remediate toxic VOCs is still remain challenge. Herein, a novel silver and Ag2O co-doped TiO2 with fast electron transfer modified by nitrogen doping carbon dots was prepared via a facile chemical precipitation-reduction method. Under 50 min of visible light irradiation, the novel photocatalyst exhibited approximately 50% gaseous toluene degradation efficiency, which was ca. 9.7 times and 2.2 times higher than that of bare TiO2 and silver and Ag2O co-doped TiO2, respectively. Importantly, the photocatalyst also showed a stable structure and good recycling ability after 400 min of photocatalytic degradation with little amount of NCDs. Besides, the up-conversion effect of NCDs could emit high-energetic light and thus generate more e⁻-h⁺ pairs, which could facilitate the SPR effect of Ag and thus showed strong visible light response because of the localized surface plasmon resonance (LSPR) excitation. Thus, the excellent photocatalytic performance could attribute to the synergetic effect of up-conversion effect of NCDs and SPR effect of silver which could both facilitate charge carriers separation and improve visible-light response. Finally, a possible mechanism for the excellent photocatalytic activity was proposed, in which the active species including ·O2⁻, ·OH and h⁺ were generated and contributed to photocatalytic process. The successful fabrication of DACT provides a potential strategy for the treatment of VOCs in practical applications.
The emissions of volatile organic compounds (VOCs) from volatile chemical products (VCPs) – specifically personal care products, cleaning agents, coatings, adhesives, and pesticides – are emerging as the largest source of petroleum-derived organic carbon in US cities. Previous work has shown that the ambient concentration of markers for most VCP categories correlate strongly with population density except for VOCs predominantly originating from solvent- and water-borne coatings (e.g., parachlorobenzotrifluoride (PCBTF) and Texanol®, respectively). Instead, these enhancements were dominated by distinct emission events likely driven by industrial usage patterns, such as construction activity. In this work, the headspace of a variety of coating products was analyzed using a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) and a gas chromatography (GC) pre-separation front-end to identify composition differences for various coating types (e.g., paints, primers, sealers and stains). Evaporation experiments of several products showed high initial VOC emission rates and for the length of these experiments, the majority of the VOC mass was emitted during the first few hours following application. The percentage of mass emitted as measured VOCs (
The characteristics of volatile organic compounds (VOCs) emitted from several consumer and commercial products (body wash, dishwashing detergent, air freshener, windshield washer fluid, lubricant, hair spray, and insecticide) were studied and compared. The spray products were found to emit the highest amount of VOCs (~96 wt%). In contrast, the body wash products showed the lowest VOC contents (~1.6 wt%). In the spray products, 21.6-96.4 % of the VOCs were propane, iso-butane, and n-butane, which are the components of liquefied petroleum gas. Monoterpene (C10H16) was the dominant component of the VOCs in the non-spray products (e.g., body wash, 53-88 %). In particular, methanol was present with the highest amount of VOCs in windshield washer fluid products. In terms of the number of carbon, the windshield washer fluids, lubricants, insecticides, and hair sprays comprised >95 % of the VOCs in the range C2-C5. The VOCs in the range C6-C10 were predominantly found in the body wash products. The dishwashing detergents and air fresheners contained diverse VOCs from C2 to C11. Besides comprising hazardous VOCs, VOCs from consumer products were also ozone precursors. The ozone formation potential of the consumer and commercial spray products was estimated to be higher than those of liquid and gel materials. In particular, the hair sprays showed the highest ozone formation potential.
Consumers may be exposed to formaldehyde during the use of liquid laundry detergent containing a preservative. The primary objective of this analysis was to present an approach to predict formaldehyde air emissions from a washing machine and the subsequent vapor concentrations in the laundry room air using the U.S. Environmental Protection Agency's (USEPA's) Simulation Tool Kit for Indoor Air Quality and Inhalation Exposure, referred to as the IAQX model. A second objective was to identify key model input parameters for formaldehyde. This analysis recommends use of the IAQX emission Model 52 because it provided the best estimates by correlating the formaldehyde evaporation to the Henry's law constant and to the overall gas-phase mass transfer coefficient that was based on washing machine experimental results. The mass balance estimated that 99.7% of the initial formaldehyde mass in the washing machine was discharged down the drain with the wash water and the rest of the formaldehyde was emitted to the air from the top loading washing machine and the hot air clothes dryer. The predicted formaldehyde exposures were acceptable and much lower than the USEPA proposed targets for non-cancer effects and cancer risk.
REACH (Registration, Evaluation, and Authorization of CHemicals) and other regulations require assessing potential exposure to substances in consumer products in order to determine if the potential risk from the product use is acceptable. In order to assess inhalation exposure due to evaporation of the volatile substance in a consumer product the vapor concentration must be determined. The vapor concentration may be measured or estimated using mathematical modeling. Both options have many advantages and disadvantages but because of the large number of substances and products to be evaluated, modeling is usually the first choice. The primary objective was to present an approach based on sound science to refine an exposure analysis by refining the mass transfer coefficient in the ConsExpo evaporation calculations for use in the subsequent inhalation exposure calculations. This study recommends use of the Sparks et al. (1996)25.
Sparks , L E ,
Tichenor , B A
Chang , J . 1996. Gas-phase mass transfer model for predicting volatile organic compound (VOC) emission rates from indoor pollutant sources. Indoor Air, 6: 31–40. [CrossRef], [Web of Science ®]View all references method for estimating the mass transfer coefficient for indoor evaporation. Three case studies demonstrated the Sparks method provided a better agreement of the predicted vapor concentrations to experimental results than the default mass transfer methods. A second objective was to critically evaluate the two ConsExpo default methods used to estimate the mass transfer coefficient and several limitations were identified.
Surface ozone concentrations at Istanbul during a summer episode in June 2008 were simulated using a high resolution and urban scale modeling system coupling MM5 and CMAQ models with a recently developed anthropogenic emission inventory for the region. Two sets of base runs were performed in order to investigate for the first time the impact of biogenic emissions on ozone concentrations in the Greater Istanbul Area (GIA). The first simulation was performed using only the anthropogenic emissions whereas the second simulation was performed using both anthropogenic and biogenic emissions. Biogenic NMVOC emissions were comparable with anthropogenic NMVOC emissions in terms of magnitude. The inclusion of biogenic emissions significantly improved the performance of the model, particularly in reproducing the low night time values as well as the temporal variation of ozone concentrations. Terpene emissions contributed significantly to the destruction of the ozone during nighttime. Biogenic NMVOCs emissions enhanced ozone concentrations in the downwind regions of GIA up to 25ppb. The VOC/NO(x) ratio almost doubled due to the addition of biogenic NMVOCs. Anthropogenic NO(x) and NMVOCs were perturbed by ±30% in another set of simulations to quantify the sensitivity of ozone concentrations to the precursor emissions in the region. The sensitivity runs, as along with the model-calculated ozone-to-reactive nitrogen ratios, pointed NO(x)-sensitive chemistry, particularly in the downwind areas. On the other hand, urban parts of the city responded more to changes in NO(x) due to very high anthropogenic emissions.
Previous research has indicated that residential washing machines are potential sources of pollution due to the associated use of chemicals found in consumer products, for example, ethanol in laundry detergent and chlorine in bleach.1,2 Washing machines may also emit hazardous air pollutants found in contaminated drinking water. To better understand the extent and impact of chemical emissions from tap water, 26 experiments were completed using a residential washing machine and a cocktail of chemical tracers representing a wide range of physicochemical properties. Variable operating conditions for these experiments included water temperature, amount of clothes present in the machine, water volume, and level of washwater agitation. Chemical stripping efficiencies and mass transfer coefficients were determined during each cycle (fill, wash, and rinse) of a normal washing machine event. Headspace ventilation rates were determined using an isobutylene tracer gas. Mass transfer rates were significantly influenced by operating parameters as exhibited by a wide range of chemical stripping efficiencies. Stripping efficiencies ranged from 0.74 to 36% for acetone, 8.2 to 99% for toluene, 10 to 99% for ethylbenzene, and 6.9 to 100% for cyclohexane.
Ambient volatile organic compounds (VOCs) were continuously measured from February 2013 to October 2014 at an urban site in Wuhan. The characteristics and sources of VOCs and their effect on ozone (O3) formation were studied for the first time. The total VOC levels in Wuhan were relatively low, and of all VOCs, ethane (5.2±0.2 ppbv) was the species with the highest levels. Six sources, i.e., vehicular exhausts, coal burning, liquefied petroleum gas (LPG) usage, the petrochemical industry, solvent usage in dry cleaning/degreasing, and solvent usage in coating/paints were identified, and their contributions to the total VOCs were 27.8±0.9%, 21.8±0.8%, 19.8±0.9%, 14.4±0.9%, 8.5±0.5%, and 7.7±0.4%, respectively. Model simulation of a photochemical box model incorporating the Master Chemical Mechanism (PBM-MCM) indicated that the contribution to O3 formation of the above sources was 23.4±1.3%, 22.2±1.2%, 23.1±1.7%, 11.8±0.9%, 5.2±0.4%, and 14.2±1.1%, respectively. LPG and solvent usage in coating/paints were the sources that showed higher contributions to O3 formation, compared to their contributions to VOCs. The relative incremental reactivity (RIR) analysis revealed that the O3 formation in Wuhan was generally VOC-limited, and ethene and toluene were the primary species contributing to O3 production, accounting for 34.3% and 31.5% of the total RIR-weighted concentration, respectively. In addition, the contribution of CO to the O3 formation was remarkable. The C4 alkanes and alkenes from the LPG usage also significantly contributed to the O3 formation. The results can assist local governments in formulating and implementing control strategies for photochemical pollution.
The Henry's law constant (HLC) and the overall mass transfer coefficient are both important parameters for modeling formaldehyde emissions from aqueous solutions. In this work, the apparent HLCs for formaldehyde aqueous solutions were determined in the concentration range from 0.01% to 1% (w/w) and at different temperatures (23, 40 and 55 °C) by a static headspace extraction method. The aqueous solutions tested included formaldehyde in water, formaldehyde-water with nonionic surfactant Tergitol™ NP-9, and formaldehyde-water with anionic surfactant sodium dodecyl sulfate. Overall, the measured HLCs ranged from 8.33×10-6 to 1.12×10-4 (gas-concentration/aqueous-concentration, dimensionless). Fourteen small chamber tests were conducted with formaldehyde solutions in small pools. By applying the measured HLCs, the formaldehyde overall liquid-phase mass transfer coefficients (KOLs) were determined to be in the range of 8.12×10-5 to 2.30×10-4 m/h, and the overall gas-phase mass transfer coefficients were between 2.84 and 13.4 m/h. The influences of the formaldehyde concentration, temperature, agitation rate, and surfactant on HLC and KOL were investigated. This study provides useful data to support source modeling for indoor formaldehyde originating from the use of household products that contain formaldehyde-releasing biocides.
A new one parameter correlation is developed for evaporation rate (ER) of chemicals as a function of molar mass (M) and vapor pressure (P) that is simpler than existing correlations. It applies only to liquid surfaces that are unaffected by the underlying solid substrate as occurs in the standard ASTM evaporation rate test and to quiescent liquid pools. The relationship has a sounder theoretical basis than previous correlations since ER is correctly correlated with P∙M rather than P alone. The inclusion of M increases the slope of previous logER vs logP regressions to a value close to 1.0 and yields a simpler one parameter correlation, namely ER (µg∙m-2∙h-1) = 1464∙P (Pa)∙M(g∙mol-1) Applications are discussed for the screening level assessment and ranking of chemicals for evaporation rate, such as pesticides, fumigants and hydrocarbon carrier fluids used in pesticide formulations, liquid consumer products used indoors and accidental spills of liquids. The mechanistic significance of the single parameter as a mass transfer coefficient or velocity is discussed.
Unlabelled:
Although widely used in air quality regulatory frameworks, the term "volatile organic compound" (VOC) is poorly defined. Numerous standardized tests are currently used in regulations to determine VOC content (and thus volatility), but in many cases the tests do not agree with each other, nor do they always accurately represent actual evaporation rates under ambient conditions. The parameters (time, temperature, reference material, column polarity, etc.) used in the definitions and the associated test methods were created without a significant evaluation of volatilization characteristics in real world settings. Not only do these differences lead to varying VOC content results, but occasionally they conflict with one another. An ambient evaporation study of selected compounds and a few formulated products was conducted and the results were compared to several current VOC test methodologies: SCAQMD Method 313 (M313), ASTM Standard Test Method E 1868-10 (E1868), and US. EPA Reference Method 24 (M24). The ambient evaporation study showed a definite distinction between nonvolatile, semivolatile, and volatile compounds. Some low vapor pressure (LVP) solvents, currently considered exempt as VOCs by some methods, volatilize at ambient conditions nearly as rapidly as the traditional high-volatility solvents they are meant to replace. Conversely, bio-based and heavy hydrocarbons did not readily volatilize, though they often are calculated as VOCs in some traditional test methods. The study suggests that regulatory standards should be reevaluated to more accurately reflect real-world emission from the use of VOC containing products.
Implications:
The definition of VOC in current test methods may lead to regulations that exclude otherwise viable alternatives or allow substitutions of chemicals that may limit the environmental benefits sought in the regulation. A study was conducted to examine volatility of several compounds and a few formulated products under several current VOC test methodologies and ambient evaporation. This paper provides ample evidence to warrant a reevaluation of regulatory standards and provides a framework for progressive developments based on reasonable and scientifically justifiable definitions of VOCs.
Contaminated tap water may be a source of volatile organic compounds (VOCs) in residential indoor air. To better understand the extent and impact of chemical emissions from this source, a two-phase mass balance model was developed based on mass transfer kinetics between each phase. Twenty-nine experiments were completed using a residential dishwasher to determine model parameters. During each experiment, inflow water was spiked with a cocktail of chemical tracers with a wide range of physicochemical properties. In each case, the effects of water temperature, detergent, and dish-loading pattern on chemical stripping efficiencies and mass transfer coefficients were determined. Dishwasher headspace ventilation rates were also measured using an isobutylene tracer gas. Chemical stripping efficiencies for a single cycle ranged from 18% to 55% for acetone, from 96% to 98% for toluene, and from 97% to 98% for ethylbenzene and were consistently 100% for cyclohexane. Experimental results indicate that dishwashers have a relatively low but continuous ventilation rate (similar to 5.7 L/min) that results in significant chemical storage within the headspace of the dishwasher. In conjunction with relatively high mass transfer coefficients, low ventilation rates generally lead to emissions that are limited by equilibrium conditions after approximately 1-2 min of dishwasher operation.
Dermal and nondietary pathways are possibly important for exposure to pesticides used in residences. Limited data have been collected on pesticide concentrations in residential air and surfaces following application. Models may be useful for interpreting these data and to make predictions about concentrations in the home for other pesticides based on chemical properties. We present a dynamic mass-balance compartment model based on fugacity principles. The model includes air (both gas phase and aerosols), carpet, smooth flooring, and walls as model compartments. Six size fractions of particulate matter with different fate and transport properties are included. We determine the compartmental fugacity capacity and mass-transfer rate coefficients between compartments. We compare model results to chlorpyrifos air and carpet measurements from an independent study. Fora comparison, we run the same simulation for diazinon and permethrin. We quantify the effect of parameter uncertainty and model uncertainties related to the source release rate and conduct a sensitivity analysis to determine which parameters contribute most to output uncertainty. In the model comparison to chlorpyrifos measurements, the model results are of the same order of magnitude as measured values but tend to overpredict the measured data, thus indicating the need for a better understanding of emissions from treated surfaces.
A residential washing machine was studied in order to determine the extent of chloroform formation following the application of a laundry bleach containing sodium hypochlorite. A dynamic model was also developed to estimate chloroform formation, mass transfer, and gaseous emissions during a typical wash cycle. A series of 22 experiments was completed to determine model parameters, including chemical reaction and mass transfer rate coefficients, as well as headspace air exchange rates. Three additional experiments were completed to evaluate model performance. Experimental and model results suggest that washing machine environments are very conductive to chloroform formation, with chloroform levels frequently exceeding 1 mg/L in washwater. Chloroform stripping efficiencies were observed to be greater than those previously reported for ethanol, but less than those reported for radon. Mass emissions of chloroform to indoor air during a ten-minute wash cycle were predicted to be between 5.3 and 9.8 mg. On a unit activity basis, chloroform emissions associated with hypochlorite-containing bleach addition to washing machines far exceeded emissions from showers. Each source was estimated to emit similar quantities of chloroform on an annual basis. Finally, it was estimated that the use of hypochlorite-containing laundry bleaches may contribute a significant fraction of chloroform mass loadings to municipal wastewater.
Different organic compounds exhibit different propensities for ozone formation. Two approaches were used to study the ozone formation potentials or source reactivities of different anthropogenic organic compounds emission categories in California's South Coast Air Basin (SoCAB). The first approach was based on the combination of total organic gases (TOG) emission speciation profiles and the maximum incremental reactivity (MIR) scale of organic species. The second approach quantified ozone impacts from different emission sources by performing 3-dimensional air quality model sensitivity analysis involving increased TOG emissions from particular sources. The source reactivities derived from these two approaches agree reasonably well for 58 anthropogenic organic compounds emission categories in the SoCAB. Both approaches identify TOG emissions from mobile sources as having the highest reactivity. Source reactivities from both approaches were also combined with TOG emissions from each source category to produce a 2005 reactivity-based anthropogenic TOG emission inventory for the SoCAB. The top five reactivity-based anthropogenic TOG emission sources in the SoCAB during 2005 were: light-duty passenger cars, off-road equipment, consumer products, light-duty trucks category 2 (i.e., 3751–5750 lb), and recreational boats. This is in contrast to the mass-based TOG emission inventory, which indicates that livestock waste and composting emission categories were two of the five largest mass-based anthropogenic TOG emission sources. The reactivity-based TOG emission inventory is an important addition to the mass-based TOG emission inventory because it represents the ozone formation potentials from emission sources and can be used to assist in determining targeted sources for developing organic compounds reduction policies.
This article deals with reactivity and photochemical modeling methods needed to develop emission control strategies for ambient ozone reduction, and with the uncertainties associated with relevant data and methods. Specifically, the article identifies and describes existing reactivity data for volatile organic compound (VOC) emissions from consumer and commercial products (CCF), and methods for developing control strategies for such emissions that take into account emissions reactivities. Existing reactivity data consist of Incremental Reactivity data and KOH-reactivity data. Both types of data are subject to uncertainties associated with• lack of experimental evidence, which is particularly severe for CCP emissions species;• theoretical derivation and/or experimental measurement of reactivity; and• variation of VOC reactivity with ambient conditions.Methods are described for using the reactivity concept to estimate the contribution of CCP emissions to ambient ozone. Also, to comply with one of the requirements of Section 183(e) of the 1990 Clean Air Act Amendments and with current U.S. Environmental Protection Agency policy on reactivity, existing reactivity data were used to classify VOCs into three reactivity classes: "negligibly reactive"; "reactive", and "highly reactive".
Residential clothes washing machines are potential air emission sources for volatile organic compounds (VOCs). The U.S. Environmental Protection Agency has a screening model to predict the potential inhalation exposure to VOC emissions from a washing machine into room air. They also have a refined exposure model that can be extrapolated to evaluate a washing machine. The objectives of this study were to evaluate the screening and refined models and to compare their predictions to experimental results for toluene-contaminated tap water. This study identified a number of important results and it explained why the models over predicted as well as the models’ limitations. The EFAST CEM screening model predicted the peak concentration was 340% of the experimental result and that 90% of the toluene mass was emitted. The refined IAQX model predicted the peak concentration was 35% higher than the experimental value, the TWA-30 minute concentration was 45% higher, and about 30% of the toluene mass was emitted. The screening model provided a quick, conservative exposure result with several limitations. The refined model provided a better estimate of the potential exposure but it required more input data and effort.
A Monte Carlo analysis of indoor ozone levels in four cities was applied to provide guidance to regulatory agencies on setting maximum ozone emission rates from consumer appliances. Measured distributions of air exchange rates, ozone decay rates and outdoor ozone levels at monitoring stations were combined with a steady-state indoor air quality model resulting in emission rate distributions (mg h−1) as a function of % of building hours protected from exceeding a target maximum indoor concentration of 20 ppb. Whole-year, summer and winter results for Elizabeth, NJ, Houston, TX, Windsor, ON, and Los Angeles, CA exhibited strong regional differences, primarily due to differences in air exchange rates. Infiltration of ambient ozone at higher average air exchange rates significantly reduces allowable emission rates, even though air exchange also dilutes emissions from appliances. For Houston, TX and Windsor, ON, which have lower average residential air exchange rates, emission rates ranged from −1.1 to 2.3 mg h−1 for scenarios that protect 80% or more of building hours from experiencing ozone concentrations greater than 20 ppb in summer. For Los Angeles, CA and Elizabeth, NJ, with higher air exchange rates, only negative emission rates were allowable to provide the same level of protection. For the 80th percentile residence, we estimate that an 8-h average limit concentration of 20 ppb would be exceeded, even in the absence of an indoor ozone source, 40 or more days per year in any of the cities analyzed. The negative emission rates emerging from the analysis suggest that only a zero-emission rate standard is prudent for Los Angeles, Elizabeth, NJ and other regions with higher summertime air exchange rates. For regions such as Houston with lower summertime air exchange rates, the higher emission rates would likely increase occupant exposure to the undesirable products of ozone reactions, thus reinforcing the need for zero-emission rate standard.
Volatilisation of crop protection chemicals from soil and crop surfaces is one of a number of processes that may contribute to their dissipation in the environment. Therefore, information on the potential of a chemical to volatilise from these surfaces is required by international and national registration authorities. This paper reports the results of more than 190 experiments, which were carried out with 80 different crop protection chemicals under controlled conditions (laboratory and/or greenhouse) according to the BBA guideline. Percent loss values observed during 24 h after application are reported for 123 soil and 71 crop volatility studies. Generally, volatile losses from crop surfaces were found to be greater than from soil surfaces under comparable experimental conditions. It has been previously proposed that volatile losses from soil surfaces, from crops, and from aqueous systems can be estimated from physico-chemical parameters. The data are therefore analysed to determine whether a correlation exists between volatilisation and physico-chemical parameters, such as vapour pressure, Henry's law constant, water/air and soil/air distribution coefficients. It was found that these parameters can be used to make reasonable predictions of volatile losses from crop and soil surfaces, which can be expected for crop protection chemicals under controlled conditions. Vapour pressure was the best predictor of losses from soil and crops. The use of the soil/air distribution coefficient is an alternative for predicting/estimating the volatility potential of a chemical from soil. Based on direct measurements, no noticeable volatility can be expected from compounds with a vapour pressure below 10(-3) Pa from soil and 10(-4) Pa from crops, this is fully confirmed by indirect measurements. A tiered volatility testing scheme including appropriate trigger values is proposed.
Pesticide volatilization and vapor drift can have adverse effects on non-target, sensitive ecosystems and human health. Four approaches for pesticide volatilization screening based on Fick's Law were investigated. In each approach, vapor pressures or environmentally relevant partition coefficients were used to describe pesticide behavior in an agricultural field system and to predict 24-h cumulative percentage volatilization (CPV24h) losses. The multiphase partitioning approach based on soil-air (Ksoil-air) and water-air (Kwater-air) partition coefficients was found to most accurately model literature-reported pesticide volatilization losses from soils. Results for this approach are displayed on chemical space diagrams for sets of hypothetical Ksoil-air and Kwater-air combinations under different temperature, relative humidity, and soil organic carbon conditions. The CPV24h increased with increasing temperature and relative humidity and with decreasing soil organic carbon content. Pesticides and the conditions under which the greatest volatilization losses exist were easily identified using this visual screening technique.
Because of growing concerns over the potential risks from exposure to airborne pesticides that have acute and chronic human and ecological health impacts, information on concentrations in air downwind of emission sources is being increasingly required, especially in populated areas. A simple and cost-effective approach to estimating downwind air concentrations from emissions was developed by relating physicochemical properties of various pesticides and other organics with their published volatilization rates (flux) from treated soil, plant foliage, and water. The resulting set of ln−ln correlations was used to estimate flux for pesticides with known physicochemical properties. These estimated flux values were used as source strengths in the EPA's SCREEN-2 dispersion model to calculate downwind concentrations near treated fields for time periods soon after application. Using estimated flux values for carbofuran, oxydemeton-methyl, methidathion, azinphos-methyl, and molinate, downwind concentrations were calculated that compared well with concentrations measured near treated fields for these pesticides applied to field crops, orchards, and rice fields. This approach is useful for prioritizing pesticides that pose potential health hazards and for which monitoring should be considered.
Computer model simulations have been carried out to provide information as to how differing aspects of an organic compound's reaction mechanism, and the nature of the environment into which it is emitted, can affect its tendency to promote ozone formation in atmosphere. This is measured by the compound's 'incremental reactivity', which is defined in terms of relative changes in ozone formation and NO oxidation caused by the addition of the compound to the total emissions in a series of standard 'scenarios' to represent air pollution episodes. Incremental reactivities were calculated for a number of representative organics and for several hypothetical species with idealized reaction mechanisms. Six different scenarios were considered, five representing idealized airshed conditions, and one representing conditions of environmental chamber experiments. The ROG/NO(x) ratio was varied from 4 to 40. The results obtained show the relative importance of the various mechanistic, kinetic, and environmental factors in affecting an organic compound's reactivity.
Reliable exposure-based chemical characterization tools are needed to evaluate and prioritize in a rapid and efficient manner the more than tens of thousands of chemicals in current use. This study applies intake fraction (iF), the integrated incremental intake of a chemical per unit of emission, for a suite of indoor released compounds. A fugacity-based indoor mass-balance model was used to simulate the fate and transport of chemicals for three release scenarios: direct emissions to room air and surface applications to carpet and vinyl. Exposure through inhalation, dermal uptake, and nondietary ingestion was estimated. To compute iF, cumulative intake was summed from all exposure pathways for 20 years based on a scenario with two adults and a 1-year-old child who ages through the simulation. Overall iFs vary by application modes: air release (3.1 × 10(-3) to 6.3 × 10(-3)), carpet application (3.8 × 10(-5) to 6.2 × 10(-3)), and vinyl application (9.0 × 10(-5) to 1.8 × 10(-2)). These iF values serve as initial estimates that offer important insights on variations among chemicals and the potential relative contribution of each pathway over a suite of compounds. The approach from this study is intended for exposure-based prioritization of chemicals released inside homes.
The impact of biogenic volatile organic compound (BVOC) emissions on European ozone distributions has not yet been evaluated in a comprehensive way. Using the CHIMERE chemistry-transport model the variability of surface ozone levels from April to September for 4 years (1997, 2000, 2001, 2003) resulting from biogenic emissions is investigated. It is shown that BVOC emissions increased on average summer daily ozone maxima over Europe by 2.5 ppbv (5%). The impact is most significant in Portugal (up to 15 ppbv) and in the Mediterranean region (about 5 ppbv), being smaller in the northern part of Europe (1.3 ppbv north of 47.5°N). The average impact is rather similar for the three summers (1997, 2000, 2001), but is much larger during the extraordinarily hot summer of 2003. Here, the biogenic contribution to surface ozone doubles compared to other years at some locations. Interaction with anthropogenic NOx emissions is found to be a key process for ozone production of biogenic precursors. Comparing the impact of the state-of-the-art BVOC emission inventory compiled within the NatAir project and an earlier, widely used BVOC inventory derived from Simpson et al. [1999. Inventorying emissions from nature in Europe. Journal of Geophysical Research 104(D7), 8113–8152] on surface ozone shows that ozone produced from biogenic precursors is less in central and northern Europe but in certain southern areas much higher e.g. Iberian Peninsula and the Mediterranean Sea. The uncertainty in the regionally averaged impact of BVOC on ozone build-up in Europe is estimated to be ±50%.
A series of environmental chamber experiments have been carried out to investigate the incremental reactivities of selected organics with respect to ozone formation in simulated photochemical smog systems. Varying amounts of a test organic were added to or subtracted from a standard four-hydrocarbon minisurrogate - NO/sub x/ - air mixture to determine, as a function of irradiation time, the resulting changes in the amount of ozone formed and NO consumed, relative to the amount of the organic added. The incremental reactivities of toluene, trans-2-butene, and propene decreased significantly with reaction time, with toluene ultimately becoming negatively reactive; n-butane, ethanol, and tert-butyl methyl ether were always positively reactive; and benzaldehyde was always negatively reactive. The results are reasonably consistent with computer model simulations and indicate that the effect of regulating emissions of an organic on ambient ozone will depend not only on the organics reaction rate but also on its reaction mechanism and the conditions under which it is emitted. 33 references, 8 figures, 3 tables.
Previous research has indicated that residential washing machines are potential sources of pollution due to the associated use of chemicals found in consumer products, for example, ethanol in laundry detergent and chlorine in bleach. Washing machines may also emit hazardous air pollutants found in contaminated drinking water. To better understand the extent and impact of chemical emissions from tap water, 26 experiments were completed using a residential washing machine and a cocktail of chemical tracers representing a wide range of physicochemical properties. Variable operating conditions for these experiments included water temperature, amount of clothes present in the machine, water volume, and level of washwater agitation. Chemical stripping efficiencies and mass transfer coefficients were determined during each cycle (fill, wash, and rinse) of a normal washing machine event. Headspace ventilation rates were determined using an isobutylene tracer gas. Mass transfer rates were significantly influenced by operating parameters as exhibited by a wide range of chemical stripping efficiencies. Stripping efficiencies ranged from 0.74 to 36% for acetone, 8.2 to 99% for toluene, 10 to 99% for ethylbenzene, and 6.9 to 100% for cyclohexane.
Pesticide emissions to air have been shown to correlate with compound vapor pressure values taken from the published literature. In the present study, emissions correlations based on vapor pressures derived from chemical property estimation methods are formulated and compared with correlations based on the literature data. Comparison was made by using the two types of correlations to estimate emission rates for five herbicides, a fungicide, and an insecticide, for which field-measured emission rates from treated soil, foliage, and water were available. In addition, downwind concentrations were estimated for two herbicides, three fungicides, four insecticides, and two fumigants, for which concentration measurements had been made near treated sources. The comparison results demonstrated that correlations based on vapor pressures derived from chemical property estimation methods were essentially equivalent to correlations based on literature data. The estimation approach for vapor pressures is a viable alternative to the inherently more subjective process of selecting literature values.
Small chamber tests were conducted to experimentally determine the overall mass transfer coefficient for pollutant emissions from still aqueous solutions under simulated indoor (residential or occupational) environmental conditions. The tests covered six organic compounds with a Henry's constant range from 3.33 x 10(-7) to 3.67 x 10(-3) (atm m(3)/mol). The estimated overall liquid phase mass transfer coefficients for still solutions varied from 1.8 x 10(-6) to 5.7 x 10(-3) m/h; the estimated liquid phase mass transfer coefficients were 9.7 x 10(-3) m/h for the reference compound (oxygen) and 5.00 x 10(-3) to 6.04 x 10-(3) m/h for the test compounds. An empirical model is proposed to estimate the overall mass transfer coefficient, which can be used to predict pollutant emissions from still aqueous solutions (e.g. pools and puddles) in indoor environments.
Dermal and nondietary pathways are possibly important for exposure to pesticides used in residences. Limited data have been collected on pesticide concentrations in residential air and surfaces following application. Models may be useful for interpreting these data and to make predictions about concentrations in the home for other pesticides based on chemical properties. We present a dynamic mass-balance compartment model based on fugacity principles. The model includes air (both gas phase and aerosols), carpet, smooth flooring, and walls as model compartments. Six size fractions of particulate matter with different fate and transport properties are included. We determine the compartmental fugacity capacity and mass-transfer rate coefficients between compartments. We compare model results to chlorpyrifos air and carpet measurements from an independent study. For a comparison, we run the same simulation for diazinon and permethrin. We quantify the effect of parameter uncertainty and model uncertainties related to the source release rate and conduct a sensitivity analysis to determine which parameters contribute most to output uncertainty. In the model comparison to chlorpyrifos measurements, the model results are of the same order of magnitude as measured values but tend to overpredict the measured data, thus indicating the need for a better understanding of emissions from treated surfaces.
Unlabelled:
Experiments were conducted to quantify emissions and concentrations of glycol ethers and terpenoids from cleaning product and air freshener use in a 50-m3 room ventilated at approximately 0.5/h. Five cleaning products were applied full-strength (FS); three were additionally used in dilute solution. FS application of pine-oil cleaner (POC) yielded 1-h concentrations of 10-1300 microg/m3 for individual terpenoids, including alpha-terpinene (90-120), d-limonene (1000-1100), terpinolene (900-1300), and alpha-terpineol (260-700). One-hour concentrations of 2-butoxyethanol and/or d-limonene were 300-6000 microg/m3 after FS use of other products. During FS application including rinsing with sponge and wiping with towels, fractional emissions (mass volatilized/dispensed) of 2-butoxyethanol and d-limonene were 50-100% with towels retained, and approximately 25-50% when towels were removed after cleaning. Lower fractions (2-11%) resulted from dilute use. Fractional emissions of terpenes from FS use of POC were approximately 35-70% with towels retained, and 20-50% with towels removed. During floor cleaning with dilute solution of POC, 7-12% of dispensed terpenes were emitted. Terpene alcohols were emitted at lower fractions: 7-30% (FS, towels retained), 2-9% (FS, towels removed), and 2-5% (dilute). During air-freshener use, d-limonene, dihydromyrcenol, linalool, linalyl acetate, and beta-citronellol) were emitted at 35-180 mg/day over 3 days while air concentrations averaged 30-160 microg/m3.
Practical implications:
While effective cleaning can improve the healthfulness of indoor environments, this work shows that use of some consumer cleaning agents can yield high levels of volatile organic compounds, including glycol ethers--which are regulated toxic air contaminants--and terpenes that can react with ozone to form a variety of secondary pollutants including formaldehyde and ultrafine particles. Persons involved in cleaning, especially those who clean occupationally or often, might encounter excessive exposures to these pollutants owing to cleaning product emissions. Mitigation options include screening of product ingredients and increased ventilation during and after cleaning. Certain practices, such as the use of some products in dilute solution vs. full-strength and the prompt removal of cleaning supplies from occupied spaces, can reduce emissions and exposures to 2-butoxyethanol and other volatile constituents. Also, it may be prudent to limit use of products containing ozone-reactive constituents when indoor ozone concentrations are elevated either because of high ambient ozone levels or because of the indoor use of ozone-generating equipment.
Urban air pollution is comprised of a highly complex mixture of gaseous and particulate components. Much progress has been
made in our understanding of the detailed chemistry and physics of air pollution, but important areas of uncertainty still
remain.
A mass transfer model is proposed to estimate the rates of chemical emissions from aqueous solutions spilled on hard surfaces inside buildings. The model is presented in two forms: a set of four ordinary differential equations and a simplified exact solution. The latter can be implemented in a spreadsheet. User input includes ten parameters, which represent either the properties of the source or those of the building. All of them can be readily obtained. The proposed model is tested against and in good agreement with the measurements of simulated spill events in a room-sized environmental chamber. This model can be used by emergency response planners to estimate the time history of contaminant concentrations in indoor air.
Volatilization of chemicals can be an important form of dissipation in the environment. Rates of evaporative losses from plant and soil surfaces are useful for estimating the potential for food-related dietary residues and operator and bystander exposure, and can be used as source functions for screening models that predict off-site movement of volatile materials. A regression of evaporation on vapor pressure from three datasets containing 82 pesticidal active ingredients and co-formulants, ranging in vapor pressure from 0.0001 to >30,000 Pa was developed for this purpose with a regression correlation coefficient of 0.98.
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The Feasibility of Performing Cumulative Risk Assessments for Mixtures of Disinfection By-products in Drinking Water
- S Epa
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Document for Assessment of Discrete Organic Chemicals: Sustainable Future Summary Assessment
- U S Epa
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Washington, DC. Available at: http://www.epa.gov/sites/production/files/2015-05/documents/05-iad_discretes_june2013.pdf.
Chemical Data Reporting/Inventory Update Reporting
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U.S. EPA, 2015a. Chemical Data Reporting/Inventory Update Reporting. U.S. Environmental Protection Agency, Washington, DC. Available at: http://epa.gov/cdr/.
Estimation Program Interface (EPI) Suite Version 4.1. U.S. Environmental Protection Agency
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Chemical and Product Categories (CPCat) Database. U.S. Environmental Protection Agency
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Setting maximum emission rates from ozone emitting consumer appliances in the United States and Canada
- Morrison