DETERMINING THE RELATIVE HAZARD OF CONTAMINANTS AT SUPERFUND SITES USING CHEMICAL ACTIVITY

In the United States, areas of the environment that have been heavily contaminated by human activity are designated as Superfund sites. Potential Superfund sites undergo extensive remedial investigations to determine the extent of the contamination and the contaminants present that drive the health hazard caused by the contaminated site. For hydrophobic organic contaminants (HOCs) like polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), the bulk concentration of the contaminant in the soil and sediment are generally used to determine the hazard and consequently the risk the contaminants pose to ecological and human health. However, the bulk sediment concentrations of PCBs and PAHs have shown to be a poor predictor of health outcomes in aquatic life in numerous studies. Conversely, when the chemical activity instead of the chemical concentration of the contaminant is quantified, health outcomes are observed in a narrower range of values (e.g., baseline narcosis has been observed at chemical activities in the range of 0.01 to 0.1 in several new studies). To determine the impact of using chemical activity instead of chemical concentrations could have on the outcomes of remedial investigations, the chemical activity of PCBs and PAHs were measured in six samples from four different Superfund sites that had designated only PCBs as a contaminant of concern. The results show that for half of the samples, the chemical activity of PAHs is higher than the chemical activity of PCBs indicating that PAHs might pose a greater risk, and policy regarding the investigation of Superfund sites may need to be updated to reflect the current scientific understanding of exposure risks.