Further Investigations on the Evaluation of Exposure to

Metabolic studies were performed on men exposed to nitrobenzene vapour under experimental condi-tions. Absorption was estimated by the analysis of urine for p-nitrophenol. About half as much vapour was absorbed through the skin as through the lungs. In inhalation studies the accumulation of nitrobenzene in the course of repeated exposures was investi-gated. It was found that p-nitrophenol was excreted in the urine in increasing amounts on successive days of exposure, reaching, by the end of a week, levels approximately two and a half times as high as on the first day. The specificity of the p-nitrophenol test on urine was studied using rats. Of all nitro-compounds investigated only chloronitrobenzenes, especially the ortho-isomer, gave interfering compounds in the urine. o-Chloronitrobenzene gave lower results than nitrobenzene by a factor of 3. There are three important ways in which nitro-benzene may be absorbed under industrial condi-tions: as vapour through the lungs; as liquid through the skin; and as vapour through the skin. The first two processes have been investigated experimentall