ESTIMATION OF ECOTOXICOLOGICAL PROTECTION LEVELS FROM NOEC TOXICITY DATA

An extrapolation method is presented for the evaluation of the effect of toxic compounds on all species in a community from single species tests on selected species representing the community. The method assumes log-normal distribution of the toxicity data. By extrapolation, a lower statistical tolerance limit is determined so that one can assert with a certain probability that only a certain percentage of all the species in the community are influenced. The method was tested on ecotoxicological data for 11 aquatic species, and it has been compared with two existing methods when used for a low number of species. The first implies unwarranted assumptions and resulted in considerably higher critical concentrations than the present method when used for a low number of species. The second method applies log-logistic confidence limits and yielded critical concentrations which were in agreement with the presented method.