Research Needs for Rapid Assessments of Chronic Toxicity

Abstract

Chronicity frequently is the most important and sensitive factor in determining the impact of toxicant stress on aquatic biota. However, chronic values are often unavailable or inadequate to provide decisive judgments in hazard assessment. Time and cost constraints involved in generating traditional chronic data also pose equally important problems in basic toxicological research. In assessing rapid means for estimating chronicity, attention is given to predictive models based on structure-activity relationships, extrapolations from acute toxicity data, and use of short chronic (mini-chronic) tests. High priority is placed on further development and evaluation of mini-chronic tests, which have been used successfully to characterize single compounds and complex effluents, evaluate effluent treatability, and determine the effects of point-source discharges on natural receiving waters. Methods most commonly used have involved (1) a five to eight-day fish embryo-larval test, (2) a seven-day cladoceran test, and (3) a seven-day fathead minnow larval growth test. General research needs are summarized as follows: (1) Evaluation of short toxicity tests presently available. This should include accuracy and reproducibility of endpoint determinations and statistical correlations between minichronic data and results obtained using traditional chronic and embryo-larval tests. (2) Design of multiple species tests, in-stream flow-through tests, and other short-term test procedures for estimating chronic effects of complex effluents and single compounds. (3) Determination of the effects of laboratory and field conditions, general water quality characteristics, and selection of animal species on results of mini-chronic tests. (4) Consideration of nonorganismal tests or mathematical models that may be used to estimate chronicity. Such research may include enzyme inhibition tests, QSAR-based modeling, and extrapolations based on acute toxicity data. (5) Investigations of the physiological and biochemical mechanisms involved in acute and chronic toxicity. Analyzing the accuracy and extrapolative value of acute, mini-chronic, and chronic tests data depends in large measure on understanding the pharmacodynamics of toxicants affecting aqautic biota.

Use of an integrated monitoring approach to determine site‐specific effluent metal limits

“…While it is probable that no one monitoring technique will yield an accurate characterization of all effluents, several reasons support the idea that biological monitoring results should overrule chemical-specific results for a given situation. First, biological assessments directly or indirectly assess potential target biota responses to an effluent through sensitive species testing (Birge and Black, 1985) and biological community analyses in the receiving stream in question (Birge et al, 1989). Chemical-specific limits derived from U.S. EPA national criteria may have little relevance to a given site.…”