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VOLATILE ORGANIC COMPOUNDS MEASURED IN DEARS PASSIVE SAMPLERS
Citation:
VETTE, A. F., W. A. MCCLENNY, D. A. WHITAKER, C. W. CROGHAN, C. D. STEVENS, C. RODES, K. OLIVER, H. JACUMIN, AND R. W. WILLIAMS. VOLATILE ORGANIC COMPOUNDS MEASURED IN DEARS PASSIVE SAMPLERS. Presented at International Society of Exposure Analysis Conference, Tucson, AZ, October 30 - November 03, 2005.
Impact/Purpose:
Six objectives have been defined for this study.
(1) To determine the associations between concentrations measured at central site monitors and outdoor residential, indoor residential and personal exposures for selected air toxics, PM constituents, and PM from specific sources.
(2) To describe the physical and chemical factors that affect the relationship between central site monitors and outdoor residential and indoor residential concentrations, including those that affect ambient source impacts.
(3) To identify the human activity factors that influence personal exposures to selected PM constituents and air toxics.
(4) To improve and evaluate models used to characterize and estimate residential concentrations of and human exposures to selected air toxics, PM constituents, and PM from specific sources.
(5) To investigate and apply source apportionment models to evaluate the relationships for PM from specific sources and to determine the contribution of specific ambient sources to residential concentrations and personal exposures to PM constituents and air toxics.
(6) To determine the associations between ambient concentrations of criteria gases (O3, NO2, and SO2) and personal exposures for these gases as well as personal exposures to air toxics, PM constituents, and PM from specific sources.
Description:
A suite of 27 volatile organic compounds (VOCs) were monitored in personal exposures, indoors and outdoors of participant's residences, and at a central community site during the DEARS summer 2004 monitoring season. The list of VOCs focused on compounds typically associated with mobile sources (1,3-butadiene, and BTEX - benzene, toluene, ethylbenzene, and xylenes) and those often associated with industrial or commercial sources such as chlorinated hydrocarbons and other halocarbons as well as other aromatic compounds. Passive diffusion samplers containing Carbopack-X (Supelco) were deployed on a daily basis to capture VOCs during a 24-hour sampling period. Observed BTEX concentrations revealed high temporal variability (std. dev. comparable to mean concentration). For example, personal exposures of benzene ranged from 0.6 to 14.0 ppbv (2.7 1 2.0 ppbv; mean 1 std. dev.); similar variations existed indoors and outdoors for benzene and for concentrations and exposures of toluene, ethylbenzene and xylenes. Levels of 1,3-butadiene were, on average, about two times higher indoors (0.6 1 0.3 ppbv) and in personal exposures (0.8 1 0.3 ppbv) than those measured outdoors (0.3 1 0.2 ppbv). Mean concentrations of BTEX and 1,3-butadiene followed the expected overall trend: personal > indoor > outdoor. There was considerable spatial variability in outdoor concentrations of BTEX and 1,3-butadiene with as much as seven-fold higher concentrations measured at residential outdoor sites as compared to a central community monitor. For most measurements, levels of BTEX and 1,3-butadiene were higher in areas with mobile source impacts. Concentrations of many of the chlorinated and fluorinated compounds were mostly below detection. Notable exceptions were compounds that are used in commercial products for personal care (trichlorofluoromethane), general household use (p-dichlorobenzene - mothballs), and other household products including vinyl flooring (styrene). Consequently, detectable levels of these compounds were mostly found indoors and in personal exposures and were not detected outdoors. Freon-113 levels were nearly uniform in all locations owing to its ubiquitous nature. Perchloroethylene, a solvent widely used for dry cleaning, was also measured in varying quantities, mostly indoors and in personal exposures. Data from winter 2005 monitoring will be presented along with initial source apportionment model results.
Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.