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Reason Foundation

The Environmental Impact of Soil Contamination

Bioavailability, Risk Assessment and Policy Implications

Raymond C. Loehr
August 1, 1996

Executive Summary

Sites which contain contaminated soils are common. While the need to protect human health and the environment at these sites is rarely debated, there are questions about the magnitude of risk posed by the chemicals in such soils and about the cleanup levels that should be achieved. Currently, soil cleanup levels are based on chemical- or media-specific criteria or guidelines, or on limits stemming from risk-based analyses. Chemical availability—the ability of a chemical to reach and adversely affect human health and the environment—is rarely taken into consideration with these approaches.

Recently, however, knowledge about the availability of chemicals in soils—i.e. leachability, mobility, rate of release, and relative toxicity—has increased. There is now considerable weight-of-evidence information from laboratory and field data indicating that for certain common situations—i.e., after chemicals have “weathered” over time, or after bioremediation has been performed—organic chemicals in soils may not be readily available for uptake by organisms, may not have an adverse impact on human health or the environment, and may not require costly remediation.

In this study, the issues associated with chemical bioavailability are presented and discussed, along with a review of current data on the availability of organic chemicals in both treated and untreated soils. The primary conclusions of this study are:


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