Ecotoxicity characterization of dinitrotoluenes and some of their reduced metabolites

in the present study, the toxic effects of 2,4-dinitrotoluene (2,4-DNT), 2, 6-dinitrotoluene (2,6-DNT) and a selection of their respective metabolites were examined and compared to 2,4,6-trinitrotoluene (TNT) using the 15-min Microtox (Vibrio fischeri) and 96-h freshwater green alga (Selenastrum capr icomutum) growth inhibition tests. All of the compounds tested were less to xic than TNT. Using the Microtox assay, 2,6-DNT was more toxic than 2,4-DNT and the order of toxicity for 2,6-DNT and its metabolites was : 2,6-DNT gr eater than or equal to 2A-6NT much greater than 2,6-DAT; whereas that for 2 ,4-DNT was: 4A-2NT > 2A-4NT > 2,4-DNT > 2,4-DAT. For the algal test, 2,4-DN T was more toxic than 2,6-DNT and the order of toxicity for 2,4-DNT and its metabolites was: 2,4-DNT > 2,4-DAT congruent to 4A-2NT = 2A-4NT. The order of toxicity for 2,6-DNT and its reduced metabolites using the algal test w as very similar to the Microtox bioassay. These results demonstrate that th e reduced metabolites of 2,6-DNT tested in this study were less toxic than that of the parent compound, but certain partially reduced metabolites of 2 ,4-DNT can be more toxic than the parent molecule. These data put into ques tion the general hypothesis that reductive metabolism of nitro-aromatics is associated with a sequential detoxification process. (C) 1999 Elsevier Sci ence Ltd. All rights reserved.