REGULATORY FOCUS Water-quality-based toxicity testing
Richard M. Dowd EPA is beginning to implement the use of biological monitoring in National Pollutant Discharge Elimination System (NPDES) permits. Two highly relevant documents have just become available: the July draft of the "Technical Support Documents for Water Quality-Based Toxics Control" and "Effluent and Ambient Toxicity Testing and In-Stream Community Response on the Ottawa River, Lima, Ohio" (EPA 600/3-84-080). The latter is the first in a series of research reports on chronic toxicity being prepared as part of EPA's complex effluent toxicity testing study of specific streams. The scientific data from this research program will provide the base for the technical support documents for water-quality-based toxics control. This control approach begins to implement EPA's policy as stated in the March 9, 1984, Federal Register, which encourages the use of an integrated strategy "of both biological and chemical methods to address toxic and non-conventional pollutants from industrial and municipal sources." The policy allows permit limits—stated numerically where appropriate—to be based on effluent toxicity. From EPA's standpoint, a major advantage of this policy is that only the aggregate toxicity of all constituents in a complex effluent need be measured, and this aggregate measure becomes the yardstick for total toxicity reduc0013-936X/84/0916-0281A$01.50/0
tions. This method also offers the advantage of allowing assessment of the bioavailability of individual constituents in an effluent, in that it indicates the results of constituent interactions. Its major disadvantages, according to the agency, are that there are no treatability data for effluent toxicity, and certain test methods are not available in final form. In addition, there are several other issues that must be addressed: the variability of biological toxicity results, the necessity of correlating toxicity measurements with in-stream impacts, the variability of species used for testing, and the behavior of toxicants after discharge into a stream. Each of these issues is addressed at least partly in the first research report on the Ottawa River. Here EPA used a seven-day biological toxicity test for chronic effects on two species, the fathead minnow and Ceriodaphnia. For the fathead minnow, the primary chronic test was the growth rate; for the Ceriodaphnia, it was reproduction—the number of young per adult female. In addition, survival rates were tested in both species. The research report addresses in some detail the variability of the test results and of species sensitivity. It concludes that at least two species are needed to ensure valid results and that the reliability of the chronic test results is adequate. In addition, the study includes field surveys of aquatic life and concludes: "In summary, there is a high correlation between ambient stream toxicity [as measured in these tests] and the number of species, diversity, and community loss of aquatic invertebrates." While this research does not measure toxic chemicals per se and thus does not corroborate observed effects by the presence of toxicants, it is EPA's position that toxicity testing itself provides sufficient (quantitative)
© 1984 American Chemical Society
evidence of the impact of an undifferentiated effluent discharge and that chemical-specific testing is not necessary. Taking such a broad position may eliminate one major problem for EPA—the extensive analytical chemistry that would be required to test each chemical on the lengthy priority pollutants list and to address potential in-stream impacts of each. The proposed toxicity testing, which according to agency sources is relatively inexpensive, could eliminate the need for such individual analyses. EPA is encouraging permit writers, both in the agency and in individual states, to include similar toxicity test requirements in NPDES permits. In fact, several states already incorporate testing for acute toxicity as permit conditions. One of the difficulties in implementing such a policy is that there are no standard methods to translate needed toxicity reductions into engineering controls without first identifying which chemical (s) in a given effluent cause(s) the toxicity. If EPA proceeds with implementation of this toxicity testing policy, significant engineering advances will be needed to relate toxicity-specific effluents to individual constituents where possible, and—in any event—to determine how to reduce total toxicity. Clearly, a next step for EPA should be a careful scientific review and critique of both the research report(s) and the technical support document; the latter also contains recommendations on toxicity testing for chronic health effects testing, which should be reviewed. Richard M. Dowd, PhD, is a Washington, D.C., consultant to Environmental Research and Technology, Inc. Environ. Soi. Techno!., Vol. 18, No. 9, 1984
281A
