Biochemical responses as indicators of toxic effects of chemicals in ecosystems.

Biochemical responses of animals to environmental chemicals (biochemical biomarkers) can give measures of exposure, and sometimes also toxic effect. They are particularly valuable where they can be used to measure the toxic effects of chemicals in the field, employing non-destructive sampling methods. Measurements of exposure are useful in the case of non-persistent chemicals (e.g. organophosphorus, carbamate, or pyrethroid insecticides) which are difficult or impossible to detect by chemical analysis. They can also be useful to provide an integrated measure of the level of exposure to a group of related chemicals. Biochemical biomarkers are likely to provide a measure of toxic effect, where they are based upon a molecular mechanism which underlies toxicity. A widely-used biochemical biomarker is cholinesterase depression, which may involve destructive sampling (brain acetylcholinesterase) or non-destructive sampling (serum butyrylcholinesterase). For genotoxic chemicals, techniques which measure DNA damage (e.g. detection of DNA adducts) provide a powerful tool in measuring environmental effects. The detection of biochemical changes caused by anticoagulant rodenticides (e.g. abnormal levels of clotting proteins in blood) provides another example of this approach. In general, the development of simple, sensitive, and specific assays that are 'user-friendly' would open the way for much wider use of biochemical biomarkers in environmental monitoring.