Biological half-lives of chemicals in fishes

Abstract

The biological half-lives were compiled for about 150 priority environmental chemicals that have been reported for fishes. About 25% of the estimates were recalculated from the data reported to provide values that would be more amenable for comparisons for other estimates. About 40% of the estimates presented are based on body burden clearance rates in whole fish which would minimize the influence of 'growth dilution' on half-life estimates. Some estimates for muscle values were also included for comparative purposes. An examination among the estimates generally indicating a range of values has been reported for a specific chemical. Some fo the variability is attributed to interspecies differences, although experimental protocol could be a major contributing factor. Factors such as time interval between cessation of chemical exposure and first sample interval, use of radiolabelled compounds, and use of first- and multi-order kinetics could influence half-life estimates. The influence of biological and environmental variables on half-life estimates was also examined from a limited data base. Estimated half-lives of organic chemicals tend to be longer in fish exposed through dietary rather than waterborne uptake. In contrast, half-lives of elements were longer in fish exposed through water than dietary uptake. Increasing experimental temperatures could decrease half-lives of chemicals in fishes. Other variables such as body weight, pH, and salinity were examined although their influence on half-life estimates was inconclusive. Half-life estimates can be used to evaluate the kinetics of chemicals in aquatic ecosystems. A series of equations is presented that could be used to evaluate reported estimates of half-lives, and assist in planning studies on chemical half-lives in fishes.