The importance of trophic transfer in the bioaccumulation of chemical contaminants in aquatic ecosystems

The U.S. Environmental Protection Agency (EPA) is responsible for establishing Water Quality Criteria which are protective of fresh water and marine life as well as human health. In 1980 the EPA announced the availability of criteria for 65 priority toxic pollutants listed under section 307 (a)(1) of the 1977 amendments of the Clean Water Act. Stara et al. (1980) have reviewed the processes and problems involved in establishing such criteria. They list four levels of toxic effects: (1) acute, subchronic and chronic, (2) mutagenic, (3) teratogenic, and (4) carcinogenic. The latter three are all potentially genotoxic in action. Chemicals causing genetic aberrations theoretically have no threshold (Albert et al. 1977) and therefore a zero-incidence is desirable. Chemicals causing toxic action other than genotoxicity are subject to the establishment of a “No Observable Affect Exposure Level” (NOAEL) (Stara et al. 1980) and therefore have a definable threshold. Often the establishment of zero incidence levels is not feasible for genotoxic materials so risk models must be developed. The “one-hit” model recommended in the EPA’s Interim Cancer Procedures and Guidelines for Health Risk… (1976) has been used for non-threshold risk assessment in the establishment of Water Quality Criteria (EPA 1980), and a modified version was used for chemicals with determinable thresholds. In both models the accuracy of the eventual predicted measure is highly dependent on the reliability of the bioconcentration data which are available in the literature.