Hexavalent chromium-contaminated soils: options for risk assessment and risk management

Risk assessment involves establishing scientifically defensible dose-response relationships for end points of concern. For Cr(VI)-contaminated soils, this includes conducting dose-response assessments for blood, liver, and kidney toxicity following oral exposure; lung cancer following inhalation exposure; and allergic contact dermatitis following dermal exposure. This dose-response information is then integrated with a site-specific exposure assessment (or default assumptions) in order to develop a site-specific (or generic) soil criterion within the framework of a comprehensive risk characterization. Risk managers develop cleanup standards designed to protect against all possible adverse effects, taking into account these site-specific (or generic) criteria and other factors such as technical feasibility, cost-benefit analyses, and socio-political concerns. Recently a push for cost-benefit analyses of environmental decisions has occurred, further supporting the need for risk assessors to prepare a comprehensive risk characterization, with its attendant uncertainties. These risk assessment and management issues are brought to the forefront by risk assessors and risk managers dealing with Cr(VI)-contaminated soils. This article offers a review and analysis of the risk characterization of Cr(VI)-contaminated soils, showing that the differing toxicities with route of exposures do not necessarily lead to different characterizations or risk. Soil concentrations in the range of 130 to 450 ppm appear to protect against noncancer toxicity from oral exposure, cancer toxicity from inhalation exposure, and allergic contact dermatitis from dermal exposure.