Ambient air in 18 residences surrounding an aluminum smelter were sampled to study the relationship between indoor and outdoor polycyclic aromatic hydrocarbons (PAHs). Objectives of the study were to quantify the indoor distribution of PAHs, indoor/outdoor (I/O) concentration ratios, and the relationship among PAH compounds. Correlation coefficients inside residences suggested an indoor source of 2-3 ring PAHs and an external source of 4-6 ring PAHs. The I/O ratios of 4-6 ring PAHs for homes without any substantial indoor sources were below unity, indicating that the presence of these PAHs was attributable to the aluminum smelter. Least squares linear regression of the coupled measurements without indoor sources of 5-6 ring PAHs resulted in average infiltration efficiencies (P(PAH)) of 0.49, 0.20, and 0.47 for benzo[a]pyrene, benzo[k]fluoranthene, and benzo[g,h,i]perylene, respectively. These P(PAH) values suggest that simultaneous measurements of indoor and outdoor concentrations of PAHs > 4 rings predominantly associated with the fine fraction of particulate matter could provide useful estimates of particle infiltration efficiency. Overall, study results indicate that when an industrial facility is the main source of outdoor 4-6 ring PAHs, the contribution of facility emissions may greatly exceed indoor sources in nonsmoking residences.

The purpose of this study was to investigate the use of benzo [a]pyrene (B[a]P) relative abundance ratios (RARs) to assess exposure to polycyclic aromatic hydrocarbons (PAHs) in the urban atmospheric air in the vicinity of a horizontal stud Söderberg aluminum reduction facility. The B[a]P RARs refer to the concentration of individual PAHs measured in a given sample divided by the concentration of B[a]P found in the same sample. This study compared the B[a]P RARs calculated for the facility stack and three sites near the Söderberg aluminum smelter for three different sampling periods. Interperiod differences were significant for many of the PAHs, and the differences between the stations proved insignificant at p < 0.05. The differences between each individual station and the facility stack were significant for all PAHs. B[a]P RARs increased in value at the stations compared with the stack, indicating that B[a]P may be degraded or removed from the atmosphere at a rate greater than that of the majority of the measured PAHs. It is concluded that B[a]P and B[a]P RARs may be poor markers of exposure to PAHs in the vicinity of this Söderberg aluminum refinery for the entire mixture of PAHs present in the ambient atmosphere.

The purpose of this study was to characterize atmospheric levels of four- to six-ring polycyclic aromatic hydrocarbons (PAHs) in the vicinity of a horizontal stud Söderberg aluminum smelter in terms of the size distribution of particulate matter (September to December 2002). It was found that the vast majority of the PAHs was associated with particle diameters less than 1 and 3 microm. A profile comparison of the PAH mixture--using benzo[a]pyrene (B[a]P) relative abundance ratios (PAH/B[a]P)--for the cascade impactor filters indicated the formation of a sampling artifact. Overall, the PAH stability scale generated in this study agrees with those produced experimentally for ozone and nitrogen dioxides or developed using other in situ measurement techniques. Correlations of the four- to six-ring PAHs with other atmospheric variables suggested that smelter plume conditions and particle characteristics may play a potentially important role in the overall PAH reactivity. To our knowledge, this is the first study to report a sampling artifact for the four- to six-ring PAHs during in situ high volume sampling under real world conditions.

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