Research Program Area: Health & Exposure
The California Health and Safety Code (HSC) Section 39660.5 requires that indoor exposures to candidate toxic air contaminants (TACS) be considered during risk assessments. The purpose of this study was to generate indoor and personal exposure data to be used by the California Air Resources Board (ARB) for its toxic air contaminants identification process. The overall study was designed to provide the maximum amount of information to the ARB for as many candidate TACs as possible. Personal monitoring, as well as indoor and outdoor microenvironmental monitoring, were performed. Target toxic air pollutants (TAPs) represent a broad range of very volatile organic chemicals (VVOCs), volatile organic chemicals (VOCs), and semivolatile organic chemicals (SOCs). For the, main study, monitoring was conducted during a single season (June 1990) using a probability sample of 128 households and individuals from Woodland, California. Along with field monitoring, information on time/activity patterns and potential source usage within specific microenvironments was collected using questionnaires. Prior to statistical analysis, sampling weights were developed and applied to the chemical concentration and questionnaire results. This approach allowed population estimates to be made for the resulting statistics. For the SOC and outdoor VVOC air concentration data, sample weights were not used due to limited sample size or overall uncertainty in the data. The data were then used to estimate indoor, outdoor and personal air concentrations for a range of volatile, very volatile, and semivolatile toxic air pollutants. They were also used to examine the relationship among toxic air pollutants in various matrices and to investigate the association between air concentrations and potential pollutant sources. Finally, a comparison of activity patterns and pollutant concentrations to other areas in the state was made. As with other air monitoring programs in California, the common volatile organic solvents (l,l,l-trichloroethane, benzene, and the xylenes) were found most often in all types of air samples. They were also found at the highest concentrations. Several other chemicals including perchloroethylene, styrene, p-dichlorobenzene, methylene chloride, acrolein, and di-ethylhexylphlate were frequently or occasionally found in air samples with highest prevalence in indoor or personal air samples. Highest concentrations were reported for methylene chloride and p-dichlorobenzene. A number of other chemicals that had not been monitored on previous programs were included in this study. These were included because of their high priority in the ARB review process. With the exception of methylene chloride, acrolein and di-Z ethylhexylphthalate, these chemicals were rarely or never detected in air samples. For all of the common solvent based TAPs, personal air samples showed the highest concentrations followed by indoor air and then outdoor air samples. Indoor/outdoor air concentration ratios for most of the TAPs were greater than one. Highest ratios were calculated for styrene and p-dichlorobenzene, suggesting strong indoor sources for these two chemicals. Air concentrations for VOCs reported for this study were lower than those reported for other, similar studies in California. This trend was observed for indoor, outdoor, and personal air samples.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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