Hazard assessment of chemical contaminants in soil

Abstract

Disposal practices, incidental spills and leakages and local aerial deposition occurring in the past have lead to local soil pollution. Especially in situations where people lived in or nearby such locations or in polluted nature conservation areas this has created concern about possible adverse effects on human health and the environment. A stepped approach was developed to assess the hazard such locations may pose to the local population and the environment. If a potential exposure to soil contaminants may occur, a preliminary assessment is carried out comparing Maximum Tolerable Exposure Levels (MTEL) derived from toxicological experiments with Environmental Exposure Levels (EEL) calculated using the Human Exposure to Soil Pollutants (HESP) computer model. The HESP model not only calculates the exposure of humans to soil pollutants via various exposure routes, it also calculates equilibrium concentrations of the contaminants within various environmental compartments. This allows comparison of exposure levels with generally accepted ambient environmental exposure standards. If the calculated EEL exceeds the MTEL or an ambient environmental standard, the actual EEL should be measured. If the measured EEL exceeds the MTEL or ambient environmental standard, a hazard is likely, and a risk assessment should be carried out to estimate the probability of a hazard being realised under local circumstances. Hazard assessment for environmental organisms should follow the same principles as for man. Sufficient data to carry out such a hazard assessment however, are not always available. The stepped approach to hazard assessment for man is illustrated using the example compounds DDT, toluene and zinc.