The determination of chronic toxicity based only in fish survival is enough?

Alexandre Arenzon, C De Lorenzo, N J Coimbra, U H Schulz


In Brazil, the evaluation of short-term chronic effects on fish follows ABNT NBR 15499/2007. It can be conducted with two species: Danio rerio or Pimephales promelas. In the analysis with P. promelas, results are obtained by evaluating survival and growth of the organisms. However, when D. rerio is used, only the survival is evaluated. The objective of this paper is to assess whether the observed chronic toxicity on growth can always be extrapolated from the survival data, as suggested by ABNT NBR 15499/2007. 687 chronic tests with P. promelas were conducted. Three groups of results were observed: samples with toxicity effect only on growth, samples with toxicity effect only on survival and samples that showed toxicity effect on the survival and growth, simultaneously. The toxicity solely on the survival of organisms was observed in 56% and 31% of the tests for environmental samples and effluents, respectively. Analyzing the effluent tests where toxicity was detected on the survival, 32% also showed toxicity on growth. The toxic effect on the growth represented merely 44% of the environmental samples and 37% of the effluent samples. Therefore, chronic toxicity evaluations based exclusively on the survival of organisms may produce false negative results, especially when mortality is not detected at all.

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