Investigations of Indoor and Outdoor Levels of Benzo(a) Pyrene in a Community of Older Homes

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Abstract
Indoor and outdoor air measurements of PM-10 (particulate mass dp < 10 μm) and its benzo (a)pyrene (Bap) content were made daily in 13 residences and 5 nearby sites during one or more of three 14-day periods (Winters 1987 and 1988, and Fall 1988). These are a population of older homes (60+ years) adjacent to a gray-iron foundry. Winter BaP values were ∼ 10 × higher than fall values. Indoor BaP sources in several homes (e.g., cooking, cigarette smoke, a coal stove) led to contaminant levels higher than the ambient concentrations. However, in homes without strong sources, concentrations were very close to outdoor levels. Periods of elevated ambient pollution were readily discernible in the record of virtually all homes. Correlations for indoor-outdoor concentrations (PM-10 and BaP) were statistically significant (p < 0.01) in the majority of homes. Higher BaP concentrations were associated with periods of lower temperatures. There were high degrees of correlation for BaP and PM-10 among outdoor sites. The fraction of BaP in ambient PM-10 (mass ratio BaP/PM-10) was found to be a fairly stable parameter for each season. These factors suggest the predominance of a spatially diffuse source of BaP in the community, such as space heating combustion. The higher BaP/PM-10 ratios were identifiable as an index of indoor sources.