A model for non-specific toxicity with aquatic organisms over relatively long periods of exposure time

Experimental data have shown that the internal lethal concentrations of hal obenzenes for aquatic organisms decreased with exposure time. In this paper , a model based on the concept of life expectancy reduction was developed t o describe this relationship. The model was verified with experimental data for fish (Gambusia affinis) and juvenile crab (Porturius pelagicus(L)). It is proposed that long term non-specific toxicity can be measured as the re duction of the life expectancy of the exposed organism per unit internal co ncentration (or volume fraction) of the toxic compound. The model can be us ed to estimate internal lethal concentration at any given exposure period a nd vice versa. The model can also be used to estimate chronic values of the internal concentration, of the toxicants. It provides a useful tool for as sessment of environmental risk of organic compounds in aquatic ecosystems. (C) 1998 Elsevier Science Ltd. All rights reserved.