Trichloro-compounds in the urine of humans exposed to methyl chloroform at sub-threshold levels

Summary Survey was carried out in 4 intaglio printing factories where methyl chloroform, the sole organic solvent in the entire process, was employed to remove excess ink. The medical interview and clinico-laboratory examinations revealed no dose-consistent adverse effects among the four groups of workers who had been exposed at the average concentrations of 4, 25, 28 and 53 ppm, respectively. Linear relationship was observed between environmental vapour concentrations and total trichloro-compounds levels in the urine of workers exposed. Increased levels of urinary metabolites towards the week-end, together with the biological half-life of 8.7 hrs as measured from the decrease in the urinary metabolites, suggested the storage of methyl chloroform in the body after repeated exposures. Perusal of previous reports as well as present results regarding toxic potency of methyl chloroform supports, with emphasis of possible accumulation, the German threshold of 200 ppm as a tentative value of choice for the time being.A part of this work was presented at the 46th Annual Meeting of the Japanese Association of Industrial Health, Osaka, April 6–8, 1973.