Multimedia analysis of PAHs and nitro-PAH daughter products in the Los Angeles basin

Polycyclic aromatic hydrocarbons (PAHs) that are released into the atmosphere may have health consequences that can be compounded by their nitro-PAH atmospheric transformation products. The available literature suggests that some of the atmospheric nitro-PAH daughter products may increase the overall environmental health risk associated with PAHs. Therefore, an important issue is whether there is merit in considering atmospheric transformation products of air toxins when conducting environmental health-risk analyses. To illustrate the above issue, a comparative analysis of the potential risk that may be imposed by PAHs and their daughter products was carried out for the Los Angeles Basin. The analysis consisted of first assessing the multimedia environmental concentration of selected PAHs and nitro-PAHs using a spatial-compartmental modeling approach coupled with available monitoring data. Multimedia concentrations were then used to estimate chemical media-specific mutagenic densities as well as average daily intake from multiple pathways, followed by cancer risk for the known carcinogens among the study chemicals. The analysis revealed that mutagenic densities of the nitro-PAH daughter products can significantly exceed those of the parent PAHs. The results of this study suggest that there is merit in further investigation of the potential contribution of nitro-PAHs to the overall environmental health risk associated with airborne PAHs.