Studies on the toxicity of coal-tar dyes. I. Photodecomposed products of four xanthene dyes and their acute toxicity to fish.

The acute toxicity of photodecomposed products of Erythrosine, Eosine, Phloxine and Rose Bengale were studied, since it was found that toxicity of these dyes to fish increased after the dyes had been photoirradiated. Photodecomposed products of the dyes were isolated and identified with UV, IR, NMR spectra and the acute toxicity of those compounds were determined by TLm test. As results of these studies, it became clear that the toxicity of photodecomposed organic products (dehalogenated compounds of dyes) were lower than the mother compounds. The increases in toxicity of the xanthene dyes by photo-irradiation were attributed to the liberated halogens by irradiation.