Assessing the risk of biomagnification: a physiological approach

In the recent past several methods have been developed for the calculation of quality criteria for surface water. The most important ones are: 1. the application of an extrapolation factor which depends on the number of toxicity data available; 2. the application of an extrapolation factor which is based on the log-logistic distribution of a (large) set of toxicity data; and 3. the use of NOEC for the most sensitive species. All methods hitherto lack a satisfying approach for the risk of biomagnification. The present study envisages an introduction of an improvement applicable to existing methods. It has specifically been developed for the marine environment. In its actual stage the study is limited to birds. The method is based on the use of NOECs (No Observed Effect Concentrations) in food of birds, which represent an important risk group for biomagnification. Because of the considerable difference in food composition and energy budgets between laboratory and field animals a correction factor has been derived which covers both. The factor includes the energy content of grain fodder (laboratory) and prey organisms (field) and the difference in energy expenditure between both groups of birds. The NOECs corrected by this factor can be used for the estimation of maximum permissible concentrations in food by existing methods, from which criteria for water are derived. The correction for biomagnification presented here should be improved in many respects. Its presentation envisages stimulation of further discussion and research in this field.