Computational Exposure Science: An Emerging Discipline to Support 21st-Century Risk Assessment.

BACKGROUND: Computational exposure science represents a frontier of environmental science that is emerging and quickly evolving. OBJECTIVES: In this commentary, we define this burgeoning discipline, describe a framework for implementation, and review some key ongoing research elements that are advancing the science with respect to exposure to chemicals in consumer products. DISCUSSION: The fundamental elements of computational exposure science include the development of reliable, computationally efficient predictive exposure models; the identification, acquisition, and application of data to support and evaluate these models; and generation of improved methods for extrapolating across chemicals. We describe our efforts in each of these areas and provide examples that demonstrate both progress and potential. CONCLUSIONS: Computational exposure science, linked with comparable efforts in toxicology, is ushering in a new era of risk assessment that greatly expands our ability to evaluate chemical safety and sustainability and to protect public health. CITATION: Egeghy PP, Sheldon LS, Isaacs KK, Özkaynak H, Goldsmith M-R, Wambaugh JF, Judson RS, Buckley TJ. 2016. Computational exposure science: an emerging discipline to support 21st-century risk assessment. Environ Health Perspect 124:697-702; http://dx.doi.org/10.1289/ehp.1509748.

A biomonitoring framework to support exposure and risk assessments.

BACKGROUND: Biomonitoring is used in exposure and risk assessments to reduce uncertainties along the source-to-outcome continuum. Specifically, biomarkers can help identify exposure sources, routes, and distributions, and reflect kinetic and dynamic processes following exposure events. A variety of computational models now utilize biomarkers to better understand exposures at the population, individual, and sub-individual (target) levels. However, guidance is needed to clarify biomonitoring use given available measurements and models. OBJECTIVE: This article presents a biomonitoring research framework designed to improve biomarker use and interpretation in support of exposure and risk assessments. DISCUSSION: The biomonitoring research framework is based on a modified source-to-outcome continuum. Five tiers of biomonitoring analyses are included in the framework, beginning with simple cross-sectional and longitudinal analyses, and ending with complex analyses using various empirical and mechanistic models. Measurements and model requirements of each tier are given, as well as considerations to enhance analyses. Simple theoretical examples are also given to demonstrate applications of the framework for observational exposure studies. CONCLUSION: This biomonitoring framework can be used as a guide for interpreting existing biomarker data, designing new studies to answer specific exposure- and risk-based questions, and integrating knowledge across scientific disciplines to better address human health risks.

Review of pesticide urinary biomarker measurements from selected US EPA children's observational exposure studies.

Children are exposed to a wide variety of pesticides originating from both outdoor and indoor sources. Several studies were conducted or funded by the EPA over the past decade to investigate children's exposure to organophosphate and pyrethroid pesticides and the factors that impact their exposures. Urinary metabolite concentration measurements from these studies are consolidated here to identify trends, spatial and temporal patterns, and areas where further research is required. Namely, concentrations of the metabolites of chlorpyrifos (3,5,6-trichloro-2-pyridinol or TCPy), diazinon (2-isopropyl-6-methyl-4-pyrimidinol or IMP), and permethrin (3-phenoxybenzoic acid or 3-PBA) are presented. Information on the kinetic parameters describing absorption and elimination in humans is also presented to aid in interpretation. Metabolite concentrations varied more dramatically across studies for 3-PBA and IMP than for TCPy, with TCPy concentrations about an order of magnitude higher than the 3-PBA concentrations. Temporal variability was high for all metabolites with urinary 3-PBA concentrations slightly more consistent over time than the TCPy concentrations. Urinary biomarker levels provided only limited evidence of applications. The observed relationships between urinary metabolite levels and estimates of pesticide intake may be affected by differences in the contribution of each exposure route to total intake, which may vary with exposure intensity and across individuals.

Assessing the quantitative relationships between preschool children's exposures to bisphenol A by route and urinary biomonitoring.

Limited published information exists on young children's exposures to bisphenol A (BPA) in the United States using urinary biomonitoring. In a previous project, we quantified the aggregate exposures of 257 preschool children to BPA in environmental and personal media over 48-h periods in 2000-2001 at homes and daycares in North Carolina and Ohio. In the present study for 81 Ohio preschool children ages 23-64 months, we quantified the children's urinary total BPA (free and conjugated) concentrations over these same 48-h periods in 2001. Then, we examined the quantitative relationships between the children's intakes doses of BPA through the dietary ingestion, nondietary ingestion, and inhalation routes and their excreted amounts of urinary BPA. BPA was detected in 100% of the urine samples. The estimated median intake doses of BPA for these 81 children were 109 ng/kg/day (dietary ingestion), 0.06 ng/kg/day (nondietary ingestion), and 0.27 ng/kg/day (inhalation); their estimated median excreted amount of urinary BPA was 114 ng/kg/day. Our multivariable regression model showed that dietary intake of BPA (p = 0.04) and creatinine concentration (p = 0.004) were significant predictors of urinary BPA excretion, collectively explaining 17% of the variability in excretion. Dietary ingestion of BPA accounted for >95% of the children's excreted amounts of urinary BPA.

Adapting concepts from systems biology to develop systems exposure event networks for exposure science research.

Systems exposure science has emerged from the traditional environmental exposure assessment framework and incorporates new concepts that link sources of human exposure to internal dose and metabolic processes. Because many human environmental studies are designed for retrospective exposure evaluations they often do not provide practical toxicological outcome parameters. Our goal was to examine concepts from systems biology research and adapt them to a network approach that maps forward to a perturbation event using two hypothetical examples. The article proposes that environmental exposure studies should not only retrospectively document exposure levels, but also measure biological parameters that can be used to inform relevant systemic changes.

The reliability of using urinary biomarkers to estimate children's exposures to chlorpyrifos and diazinon.

A few studies have reported concurrent levels of chlorpyrifos (CPF) and diazinon (DZN) and their environmentally occurring metabolites, 3,5,6-trichloro-2-pyridinol (TCP) and 2-isopropyl-6-methyl-4-pyrimidinol (IMP), in food and in environmental media. This information raises questions regarding the reliability of using these same metabolites, TCP and IMP, as urinary biomarkers to quantitatively assess the everyday exposures of children to CPF and DZN, respectively. In this study, we quantified the distributions of CPF, DZN, TCP, and IMP in several environmental and personal media at the homes and day-care centers of 127 Ohio preschool children and identified the important sources and routes of their exposures. The children were exposed to concurrent levels of these four chemicals from several sources and routes at these locations. DZN and IMP were both detected above 50% in the air and dust samples. CPF and TCP were both detected in greater than 50% of the air, dust (solid), food, and hand wipe samples. TCP was detected in 100% of the urine samples. Results from our regression models showed that creatinine levels (<0.001), and dietary (P<0.001) and inhalation (P<0.10) doses of TCP were each significant predictors of urinary TCP, collectively explaining 27% of the urinary TCP variability. This information suggests that measurement of urinary TCP did not reliably allow quantitative estimation of the children's everyday environmental exposures to CPF.

Organophosphorus and pyrethroid insecticide urinary metabolite concentrations in young children living in a southeastern United States city.

Pesticide metabolites are routinely measured in the urine of children in the United States. Although the sources of these metabolites are believed to include residues in food from agricultural applications and residues from applications in everyday environments (e.g., homes), few studies have been able to demonstrate an association between indoor residential pesticide applications and pesticide metabolite concentrations. To better quantify the effects of potential risk factors related to demographics, household characteristics, occupation, and pesticide use practices on urinary biomarker levels, we performed a study in a city (Jacksonville, Florida) previously determined to have elevated rates of pesticide use. We enrolled a convenience sample of 203 children ranging in age from 4 to 6 years; their caregivers completed a questionnaire and the children provided a urine sample, which was analyzed for a series of organophosphorus and pyrethroid insecticide metabolites. The questionnaire responses substantiated much higher pesticide use for the study participants as compared to other studies. Urinary metabolite concentrations were approximately an order of magnitude higher than concentrations reported for young children in other studies. Few statistically significant differences (at the p<0.05 level) were observed, however, several trends are worth noting. In general, mean urinary pesticide metabolite concentrations were higher for males, Caucasians, and those children living in homes with an indoor pesticide application occurring within the past four weeks. Comparing the urinary pesticide metabolite concentrations in this study to those reported in the NHANES and GerES studies showed that the children living in Jacksonville had substantially higher pyrethroid pesticide exposures than the general populations of the United States and Germany. Further research is needed in communities where routine pesticide use has been documented to obtain information on the most important routes and pathways of exposure and to develop the most effective strategies for reducing pesticide exposures for children.

Assessment of a pesticide exposure intensity algorithm in the agricultural health study.

The accuracy of the exposure assessment is a critical factor in epidemiological investigations of pesticide exposures and health in agricultural populations. However, few studies have been conducted to evaluate questionnaire-based exposure metrics. The Agricultural Health Study (AHS) is a prospective cohort study of pesticide applicators who provided detailed questionnaire information on their use of specific pesticides. A field study was conducted for a subset of the applicators enrolled in the AHS to assess a pesticide exposure algorithm through comparison of algorithm intensity scores with measured exposures. Pre- and post-application urinary biomarker measurements were made for 2,4-D (n=69) and chlorpyrifos (n=17) applicators. Dermal patch, hand wipe, and personal air samples were also collected. Intensity scores were calculated using information from technician observations and an interviewer-administered questionnaire. Correlations between observer and questionnaire intensity scores were high (Spearman's r=0.92 and 0.84 for 2,4-D and chlorpyrifos, respectively). Intensity scores from questionnaires for individual applications were significantly correlated with post-application urinary concentrations for both 2,4-D (r=0.42, P<0.001) and chlorpyrifos (r=0.53, P=0.035) applicators. Significant correlations were also found between intensity scores and estimated hand loading, estimated body loading, and air concentrations for 2,4-D applicators (r-values 0.28-0.50, P-values<0.025). Correlations between intensity scores and dermal and air measures were generally lower for chlorpyrifos applicators using granular products. A linear regression model indicated that the algorithm factors for individual applications explained 24% of the variability in post-application urinary 2,4-D concentration, which increased to 60% when the pre-application urine concentration was included. The results of the measurements support the use of the algorithm for estimating questionnaire-based exposure intensities in the AHS for liquid pesticide products. Refinement of the algorithm may be possible using the results from this and other measurement studies.

Urinary biomarker, dermal, and air measurement results for 2,4-D and chlorpyrifos farm applicators in the Agricultural Health Study.

A subset of private pesticide applicators in the Agricultural Health Study (AHS) epidemiological cohort was monitored around the time of their agricultural use of 2,4-dichlorophenoxyacetic acid (2,4-D) and O,O-diethyl-O-3,5,6-trichloro-2-pyridyl phosphorothioate (chlorpyrifos) to assess exposure levels and potential determinants of exposure. Measurements included pre- and post-application urine samples, and patch, hand wipe, and personal air samples. Boom spray or hand spray application methods were used by applicators for 2,4-D products. Chlorpyrifos products were applied using spray applications and in-furrow application of granular products. Geometric mean (GM) values for 69 2,4-D applicators were 7.8 and 25 microg/l in pre- and post-application urine, respectively (P<0.05 for difference); 0.39 mg for estimated hand loading; 2.9 mg for estimated body loading; and 0.37 microg/m(3) for concentration in personal air. Significant correlations were found between all media for 2,4-D. GM values for 17 chlorpyrifos applicators were 11 microg/l in both pre- and post-application urine for the 3,5,6-trichloro-2-pyridinol metabolite, 0.28 mg for body loading, and 0.49 microg/m(3) for air concentration. Only 53% of the chlorpyrifos applicators had measurable hand loading results; their median hand loading being 0.02 mg. Factors associated with differences in 2,4-D measurements included application method and glove use, and, for hand spray applicators, use of adjuvants, equipment repair, duration of use, and contact with treated vegetation. Spray applications of liquid chlorpyrifos products were associated with higher measurements than in-furrow granular product applications. This study provides information on exposures and possible exposure determinants for several application methods commonly used by farmers in the cohort and will provide information to assess and refine exposure classification in the AHS. Results may also be of use in pesticide safety education for reducing exposures to pesticide applicators.

Exposure as part of a systems approach for assessing risk.

BACKGROUND: The U.S. Environmental Protection Agency is facing large challenges in managing environmental chemicals with increasingly complex requirements for assessing risk that push the limits of our current approaches. To address some of these challenges, the National Research Council (NRC) developed a new vision for toxicity testing. Although the report focused only on toxicity testing, it recognized that exposure science will play a crucial role in a new risk-based framework. OBJECTIVE: In this commentary we expand on the important role of exposure science in a fully integrated system for risk assessment. We also elaborate on the exposure research needed to achieve this vision. DISCUSSION: Exposure science, when applied in an integrated systems approach for risk assessment, can be used to inform and prioritize toxicity testing, describe risks, and verify the outcomes of testing. Exposure research in several areas will be needed to achieve the NRC vision. For example, models are needed to screen chemicals based on exposure. Exposure, dose-response, and biological pathway models must be developed and linked. Advanced computational approaches are required for dose reconstruction. Monitoring methods are needed that easily measure exposure, internal dose, susceptibility, and biological outcome. Finally, population monitoring studies are needed to interpret toxicity test results in terms of real-world risk. CONCLUSION: This commentary is a call for the exposure community to step up to the challenge by developing a predictive science with the knowledge and tools for moving into the 21st century.

Adult and children's exposure to 2,4-D from multiple sources and pathways.

In this study, we investigated the 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide exposures of 135 preschool-aged children and their adult caregivers at 135 homes in North Carolina (NC) and Ohio (OH). Participants were randomly recruited from six NC and six OH counties. Monitoring was performed over a 48-h period at the participants' homes. Environmental samples included soil, outdoor air, indoor air, and carpet dust. Personal samples collected by the adult caregivers concerning themselves and their children consisted of solid food, liquid food, hand wipe, and spot urine samples. All samples were analyzed for 2,4-D (free acid form) by gas chromatography/mass spectrometry. 2,4-D was detected in all types of environmental samples but most often in carpet dust samples, with detection frequencies of 83% and 98% in NC and OH, respectively. The median level of 2,4-D in the carpet dust samples was about three times higher in OH homes compared to NC homes (156 vs. 47.5 ng/g, P<0.0002). For personal samples, 2,4-D was more frequently detected in the hand wipe samples from OH participants (>48%) than from NC participants (<9%). Hand wipe levels at the 95th percentile were about five times higher for OH children (0.1 ng/cm(2)) and adults (0.03 ng/cm(2)) than for the NC children (0.02 ng/cm(2)) and adults (<0.005 ng/cm(2)). 2,4-D was detected in more than 85% of the child and adult urine samples in both states. The median urinary 2,4-D concentration was more than twice as high for OH children compared to NC children (1.2 vs. 0.5 ng/ml, P<0.0001); however, the median concentration was identical at 0.7 ng/ml for both NC and OH adults. The intraclass correlation coefficient of reliability for an individual's urinary 2,4-D measurements, estimated from the unadjusted (0.31-0.62) and specific gravity-adjusted (0.37-0.73) values, were somewhat low for each group in this study. The variability in urinary 2,4-D measurements over the 48-h period for both children and adults in NC and OH suggests that several spot samples were needed to adequately assess these participants' exposures to 2,4-D in residential settings. Results from this study showed that children and their adult caregivers in NC and OH were likely exposed to 2,4-D through several pathways at their homes. In addition, our findings suggest that the OH children might have been exposed to higher levels of 2,4-D through the dermal and nondietary routes of exposure than the NC children and the NC and OH adults.

An observational study of 127 preschool children at their homes and daycare centers in Ohio: environmental pathways to cis- and trans-permethrin exposure.

The potential exposures of 127 preschool children to the pyrethroid insecticides, cis- and trans-permethrin, in their everyday environments were examined. Participants were recruited randomly from 127 homes and 16 daycare centers in six Ohio (OH) counties. Monitoring was performed over a 48-h period at the children's homes and/or daycare centers. Samples collected included soil, carpet dust, indoor air, outdoor air, diet, hand wipes, surface wipes, transferable residues, and urine. The environmental samples were analyzed for the cis and trans isomers of permethrin, and the urine samples were analyzed for the pyrethroid urinary metabolite, 3-phenoxybenzoic acid (3-PBA), by gas chromatography/mass spectrometry. The isomers were detected most often in the dust (100%) and hand wipe (>78%) samples collected at both homes and daycare centers. The median levels of cis-permethrin (470 and 1010 ng/g) were higher than the median levels of trans-permethrin (344 and 544 ng/g) in the dust samples at both the children's homes and daycare centers, respectively. In the children's hand wipe samples, the median levels of cis- and trans-permethrin were similar, ranging from 0.03 to 0.04 ng/cm(2), at both locations. The urinary metabolite 3-PBA was detected in 67% of the children's urine samples. The median urinary 3-PBA concentration for the children was 0.3 ng/mL, and the maximum value for one child was 33.8 ng/mL. The primary route of the children's exposure to the combined isomers was through dietary ingestion, followed by indirect ingestion. In addition, our calculated aggregate absorbed doses of permethrin accounted for about 60% of the excreted amounts of 3-PBA found in the children's urine. In conclusion, these children were potentially exposed to low levels of permethrin from several sources, and through several pathways and routes.

Pesticides and their metabolites in the homes and urine of farmworker children living in the Salinas Valley, CA.

In support of planning efforts for the National Children's Study, we conducted a study to test field methods for characterizing pesticide exposures to 20 farmworker children aged 5-27 months old living in the Salinas Valley of Monterey County, California. We tested methods for collecting house dust, indoor and outdoor air, dislodgeable residues from surfaces and toys, residues on clothing (sock and union suits), food, as well as spot and overnight diaper urine samples. We measured 29 common agricultural and home use pesticides in multiple exposure media samples. A subset of organophosphorus (OP), organochlorine (OC) and pyrethroid pesticides were measured in food. We also analyzed urine samples for OP pesticide metabolites. Finally, we administered four field-based exposure assessment instruments: a questionnaire; food diary; home inspection; and a self-administered child activity timeline. Pesticides were detected more frequently in house dust, surface wipes, and clothing than other media, with chlorpyrifos, diazinon, chlorthal-dimethyl, and cis- and trans-permethrin detected in 90% to 100% of samples. Levels of four of these five pesticides were positively correlated among the house dust, sock, and union suit samples (Spearman's rho=0.18-0.76). Pesticide loading on socks and union suits was higher for the group of 10 toddlers compared to the 10 younger crawling children. Several OP pesticides, as well as 4,4'-DDE, atrazine, and dieldrin were detected in the food samples. The child activity timeline, a novel, low-literacy instrument based on pictures, was successfully used by our participants. Future uses of these data include the development of pesticide exposure models and risk assessment.

An observational study of the potential exposures of preschool children to pentachlorophenol, bisphenol-A, and nonylphenol at home and daycare.

The Children's Total Exposure to Persistent Pesticides and Other Persistent Organic Pollutants (CTEPP) study investigated the potential exposures of 257 preschool children, ages 1 1/2-5 yr, and their primary adult caregivers to more than 50 anthropogenic chemicals. Field sampling took place in selected counties in North Carolina (NC) and Ohio (OH) in 2000-2001. Over a 48-h period in each child's daycare center and/or home, food, beverages, indoor air, outdoor air, house dust, soil, participants' hand surfaces and urine were sampled. Additional samples-transferable residues, food preparation surface wipes, and hard floor surface wipes-were collected in the approximately 13% of the homes that had pesticide applications within the 7 days prior to field sampling. Three phenols were among the measured chemicals: pentachlorophenol (PCP), bisphenol-A [2,2-bis(4-hydroxyphenyl)propane], and nonylphenol (4-n-nonylphenol). Nonylphenol (NP) was detected in less than 11% of the samples in any medium. Among samples that were collected at all participants' homes and daycare centers, PCP was detected in >50% of indoor air, outdoor air, house dust, and urine samples; bisphenol-A (BPA) was detected in >50% of indoor air, hand wipe, solid food, and liquid food samples. The concentrations of the phenols in the sampled media were measured, and the children's potential exposures and potential absorbed doses resulting from intake through the inhalation, dietary ingestion, and indirect ingestion routes of exposure were estimated. The children's potential exposures to PCP were predominantly through inhalation: 78% in NC and 90% in OH. In contrast, their potential exposures to BPA were predominantly through dietary ingestion: 99%, for children in both states. The children's estimated exposures to PCP, calculated from the amounts excreted in their urine, exceeded their estimated maximum potential intake, calculated from the multimedia PCP concentrations, by a factor greater than 10. This inconsistency for PCP highlights the need for further research on the environmental pathways and routes of PCP exposure, investigation of possible exposures to other compounds that could be metabolized to PCP, and on the human absorption, metabolism, and excretion of this phenol over time periods longer than 48 h.

Exposures of preschool children to chlorpyrifos and its degradation product 3,5,6-trichloro-2-pyridinol in their everyday environments.

As part of the Children's Total Exposure to Persistent Pesticides and Other Persistent Organic Pollutants (CTEPP) study, we investigated the exposures of preschool children to chlorpyrifos and its degradation product 3,5,6-trichloro-2-pyridinol (TCP) in their everyday environments. During this study, the participants were still able to purchase and apply chlorpyrifos at their homes or day care centers. Participants were recruited randomly from 129 homes and 13 day care centers in six North Carolina counties. Monitoring was performed over a 48-h period at the children's homes and/or day care centers. Samples that were collected included duplicate plate, indoor and outdoor air, urine, indoor floor dust, play area soil, transferable residues (PUF roller), and surface wipes (hand, food preparation, and hard floor). The samples were extracted and analyzed by gas chromatography/mass spectrometry. Chlorpyrifos was detected in 100% of the indoor air and indoor floor dust samples from homes and day care centers. TCP was detected at homes and day care centers in 100% of the indoor floor dust and hard floor surface wipe, in >97% of the solid food, and in >95% of the indoor air samples. Generally, median levels of chlorpyrifos were higher than those of TCP in all media, except for solid food samples. For these samples, the median TCP concentrations were 12 and 29 times higher than the chlorpyrifos concentrations at homes and day care centers, respectively. The median urinary TCP concentration for the preschool children was 5.3 ng/ml and the maximum value was 104 ng/ml. The median potential aggregate absorbed dose (ng/kg/day) of chlorpyrifos for these preschool children was estimated to be 3 ng/kg/day. The primary route of exposure to chlorpyrifos was through dietary intake, followed by inhalation. The median potential aggregate absorbed dose of TCP for these children was estimated to be 38 ng/kg/day, and dietary intake was the primary route of exposure. The median excreted amount of urinary TCP for these children was estimated to be 117 ng/kg/day. A full regression model of the relationships among chlorpyrifos and TCP for the children in the home group explained 23% of the variability of the urinary TCP concentrations by the three routes of exposure (inhalation, ingestion, dermal absorption) to chlorpyrifos and TCP. However, a final reduced model via step-wise regression retained only chlorpyrifos through the inhalation route and explained 22% of the variability of TCP in the children's urine. The estimated potential aggregate absorbed doses of chlorpyrifos through the inhalation route were low (median value, 0.8 ng/kg/day) and could not explain most of the excreted amounts of urinary TCP. This suggested that there were other possible sources and pathways of exposure that contributed to the estimated potential aggregate absorbed doses of these children to chlorpyrifos and TCP. One possible pathway of exposure that was not accounted for fully is through the children's potential contacts with contaminated surfaces at homes and day care centers. In addition, other pesticides such as chlorpyrifos-methyl may have also contributed to the levels of TCP in the urine. Future studies should include additional surface measurements in their estimation of potential absorbed doses of preschool children to environmental pollutants. In conclusion, the results showed that the preschool children were exposed to chlorpyrifos and TCP from several sources, through several pathways and routes. .

Design and sampling methodology for a large study of preschool children's aggregate exposures to persistent organic pollutants in their everyday environments.

Young children, because of their immaturity and their rapid development compared to adults, are considered to be more susceptible to the health effects of environmental pollutants. They are also more likely to be exposed to these pollutants, because of their continual exploration of their environments with all their senses. Although there has been increased emphasis in recent years on exposure research aimed at this specific susceptible population, there are still large gaps in the available data, especially in the area of chronic, low-level exposures of children in their home and school environments. A research program on preschool children's exposures was established in 1996 at the USEPA National Exposure Research Laboratory. The emphasis of this program is on children's aggregate exposures to common contaminants in their everyday environments, from multiple media, through all routes of exposure. The current research project, "Children's Total Exposure to Persistent Pesticides and Other Persistent Organic Pollutants," (CTEPP), is a pilot-scale study of the exposures of 257 children, ages 1(1/2)-5 years, and their primary adult caregivers to contaminants in their everyday surroundings. The contaminants of interest include several pesticides, phenols, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and phthalate esters. Field recruitment and data collection began in February 2000 in North Carolina and were completed in November 2001 in Ohio. This paper describes the design strategy, survey sampling, recruiting, and field methods for the CTEPP study.

Measurement of Indoor Air Emissions from Dry-Process Photocopy Machines.

Presently, no standard test method exists to evaluate the various emissions from office equipment (e.g., ozone, volatile organic compounds, inorganic gases, and particulates) so it is difficult to compare data from different studies.1 As a result, the authors are developing a standardized guidance document for measuring indoor air emissions from office equipment. The ultimate goal is to apply the test method to better understand emissions from office equipment and to develop lower emitting machines. This paper provides background information on indoor air emissions from office equipment with an emphasis on dry-process photocopy machines. The test method is described in detail, along with the results of a study to evaluate the test method using four dry-process photocopy machines. The results from this study indicate that the test method provides acceptable performance for characterizing emissions; that it can adequately identify differences in emissions between machines both in compounds emitted and their emission rates; and that it is capable of measuring both intra- and inter-machine variability in emissions. Challenges and complications were encountered in developing and implementing the test method. These included heat generation, which can cause large increases in chamber temperature; finite paper supplies for photocopy machines, which limit test duration; varying power requirements that may require changes in chamber electrical supply; and remote starting of the machines, which is necessary to maintain chamber integrity. Results show that dry-process photocopy machines can produce emissions of ozone and volatile organic compounds that can potentially have a significant impact on indoor air quality. For the four machines tested in this study, the compounds with the highest emission rates overall were ethylbenzene (28,000 µg/hour), m,p-xylenes (29,000 µg/hour), o-xylene (17,000 µg/hour), 2-ethyl-lhexanol (14,000 µg/hour), and styrene (12,000 fig/hour). Although many of the same compounds tended to be detected in emissions from each of the four photocopiers, the relative contribution of individual compounds varied considerably between machines, with differences greater than an order of magnitude for some compounds.