The California Air Resources Board (CARB) is required to consider indoor exposures in assessing the risks to public health posed by compounds being reviewed for classification as toxic air contaminants. This literature review was performed to evaluate the existing data on the potential indoor uses and sources, the indoor concentrations and exposures, and the source emissions of candidate compounds not yet in the formal review process. The study was primarily restricted to organic compounds in Groups IIB and III of the "Toxic Air Contaminant Identification List, February, 1990." Data for 47 individual compounds were reviewed. The body of this report contains a section for each compound or group of closely related compounds in which the data from the literature are summarized and evaluated. Data on indoor concentrations and personal exposures which adequately fulfill the CARB's needs were found only for styrene, xylenes, p-dichlorobenzene and methyl chloroform. These compounds were included in field studies conducted in California by the U.S. EPA. Indoor concentrations for a number of other compounds are being obtained from ongoing field studies sponsored by the CARB. The candidate compounds can generally be classified into three groups according to broad similarities among their likely indoor sources. A number of the compounds may be present in building materials, interior-finish materials, furnishings and various consumer products as minor constituents, such as unreacted monomers and chemical intermediates, additives and contaminants. Emissions from these products and materials may occur under certain circumstances. Some of the compounds are major constituents of expendable consumer products that are available in retail outlets. Exposures to these compounds occur when the products are used indoors. Combustion processes, including sidestream cigarette smoke and wood burning, are indoor sources of other compounds. The data on source emissions of the candidate compounds are very limited. Of all the compounds, p-dichlorobenzene was the only one for which adequate measurements have been made of emission rates from the dominant indoor sources. These sources are moth repellents and room deodorizers in solid form. Recommendations were developed for a multi-component laboratory study to provide data on source emission rates for selected compounds. Three different studies, which parallel the similarities in the sources of the compounds, were defined. Priorities were assigned to these studies and to the individual compounds in each study based on several criteria. In general, compounds in CARB Group II received the highest priority for further investigation. The laboratory study with the highest priority would investigate the potential emissions of volatile candidate compounds that are minor constituents of products and materials. It is suggested the emphasis be placed on measurements of 1,3-butadiene, 1,4-dioxane, ethyl acrylate, propylene oxide, acrylonitrile, the N-nitroso compounds and toluene diisocyanates. The approach would be to screen possible sources for emissions and to measure emission rates for any significant sources using environmental chambers. The study with the next highest priority would investigate emissions of volatile candidate compounds resulting from the use of expendable consumer products. The approach would be to measure emissions while the products are actively being used in a room-size environmental chamber. Products containing 1,4-dioxane should be emphasized. The third study would investigate emissions of compounds in environmental tobacco smoke. Compounds with high priority for this study are 1,3- butadiene, acctaldehyde, hydrazine and the N-nitrosamines.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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