Abstract

Effluents of tanning industries were recognized as one of the main contaminants of rivers in the Buenos Aires area. Recently, Argentinian legislation, prescribed that the effluents must be submitted to toxicologi cal tests before their release to the rivers. Among these tests the detection of genotoxicity was considered a good choice for the determination of long term ecotoxicity of the treated waste waters. In this work, we report the results obtained when liquid effluents from different processes of leather tanning and finishing were assayed for mutagenicity with the Ames test. We selected an industry that processes 43 tons of leather per day (Curtiembre Giboud Hnos, Buenos Aires, Argentina). Recovery of chromium by precipi tation and secondary waste water treatment is also practiced in this plant. Samples of liquid effluents were obtained from the liming and tanning processes, chromium recuperation plant and from waters released to the river. These samples were either sterilized by filtration with Millipore 0.22 im membranes or concentrated with XAD2 resins before the biological assay. Concentration was carried out as described in a previous paper (Moretton et al. 1991). Two strains of Salmonella typhimurium, TA 98 and TA 100, kindly supplied by Dr Bruce Ames, were used in the biological tests. Detection of mutagenic activity was made using incorporation plate assay (Maron and Ames 1983) for these samples. An in vitro activation system, 59 mix, was incorporated in the assay for the determination of promutagenic activity (Ames et aL 1973).

A highly unspecific toxicity for Salmonella typhimurium was detected in raw water samples from the liming and tanning processes. This effect could be the result of the elevated concentration of contaminants. Nevertheless no mutagenicity was found in the samples. When the concentrates were tested, only the one corresponding to the tanning process resulted in a toxic effect but neither this extract nor the one obtained from waste waters of the liming process were mutagenic in the Salmonella test.

In conclusion, treatment of the tannery waste waters is considered very important to decrease the ecotoxicity of these waters, however the genotoxicity was in general a minor problem.