Biochemical decomposition of coal-tar dyes II. Acute toxicity of coal-tar dyes and their decomposed products

Abstract

Acute toxicity was tested for 31 compounds including the permitted food tar dyes, raw materials for tar dyes and decomposed products of tar dyes. The eleven dyes showed the acute toxicity. The highest toxicity was observed with the four kinds of halogenated xanthene dyes, and they gave the following 24 and 48 hr medium tolerance limit (TLm) values, respectively: eosin 2,700 and 5,00 mg/liter, erythrosin 1,100 and 900 mg/liter: phloxine 230 and 190 mg/liter: rose bengal 100 and 80 mg/liter. Relating to halogenated derivatives of uranin, the acute toxicity was found as follows in increasing order: rose bengal>phloxine>erythrosin>eosin. Considering the fact that uranin, a non-halogenated precursor for xanthene dyes, is non-toxic, involvement of halogen atoms would cause the acute toxicity to fish. Observation of the fish dying from acutely toxic xanthene dyes showed the coloration of several organs, particularly gills. The respiratory paralysis caused by the dyes binding to gills was thought to be one of the causes of the death. Rose bengal and phloxine showed a remarkably higher acute toxicity to fish under irradiation than in the dark. Deaths of fish increased parallel with the photolysis of the dyes. For inspecting the colors' pollution, the measurement of ultraviolet absorbance value at 254 nm seemed to be employable. Regulation with BOD and COD are not suitable for dyes, becuase the toxicity was observed in the dye solution which had lower BOD or COD values than the limit values prescribed by the law.