Ecotoxicological effects at contaminated sites.

Abstract

Contamination sites pose significant environmental hazards for terrestrial and aquatic ecosystems. They are important sources of pollution and may result in ecotoxicological effects on terrestrial, groundwater and aquatic ecosystems. At severely contaminated sites, acute effects occur, but the core problem lies in long-term chronic effects. Ecotoxicological effects occur at all levels of biological organization, from the molecular to the ecosystem level. Not only certain organisms may be affected, but the ecosystems as a whole, both terrestrial and aquatic, in its function and structure. Contaminants at large contaminated sites often share critical properties such as high acute and/or chronic toxicity, high environmental persistence, often high mobility leading to contamination of groundwater, and high lipophilicity leading to bioaccumulation in food webs. Contaminants present at polluted sites occur as mixtures, therefore interactions between individual compounds are of importance. The bioavailability is a key factor for ecotoxicological effects of contaminants. This is demonstrated by a case study on organotins. Organotins belong to the most toxic pollutants known so far for aquatic life. Widespread contamination of harbor sediments occurs globally due to the ongoing use of organotins in antifouling paints in large ships. In lake sediments, tributyl- and triphenyltin are very persistent and bioavailable to biota even after a long time. Bioavailability of these compounds is dependent on pH and organic matter. Organotins are accumulated in sediments, but remobilization occurs when contaminated sediments are disturbed and dredged. A key question in dealing with contaminated sites is the assessment and evaluation of the toxicity of contaminants to the environment. Usually, established OECD tests and whole effluent toxicity tests are performed for an ecotoxicological evaluation and for hazard assessment. However, these assays are often expensive, laborious and sometimes not sensitive enough. As a consequence, we have used fast and reliable in vitro systems such as fish cell lines for the evaluation of sediments and landfill leachates contaminated by polychlorinated hydrocarbons (PAH). Determination of cytotoxicity as a measure for acute toxicity, and induction of cytochrome P4501A (CYP1A) as a biomarker of exposure and toxicity were found to be important measures, which can be used for hazard and risk assessment. We have developed a concept for the ecotoxicological evaluation of PAH contamination based on induction equivalents, which can be applied for aquatic and terrestrial ecosystems. One of the key question and present gaps, however, includes the long-term chronic ecotoxicological effects on soil and aquatic biota, which are largely unknown.