Lack of relationship between occupational exposure to carbon disulfide and endocrine dysfunction: A six-year cohort study of the Japanese rayon workers

Objectives - A six-year prospective cohort study was conducted to clarify whether the current carbon disulfide (CS₂) exposure level is low enough to prevent subclinical health impairment and/or to ameliorate health effects due to previous high exposure. This paper describes the follow-up results, exposure assessment, and effects on the endocrine system. Methods - The study subjects were 432 male workers exposed to CS₂ at one of the 11 rayon factories in Japan and 402 referent workers from the same factories, all of whom were examined in 1992-93. 251 CS₂exposed, 140 former-exposed and 359 referent workers participated in the follow-up survey (follow-up rate 89.9%) in 1998-99. Urinary 2-thiothiazolidine-4carboxylic acid (TTCA) at the end of a shift as internal exposure index and the time-weighted average CS₂ concentration as external exposure index were measured twice a year from 1992-1993. By using various blood indices, we evaluated effects on thyroid, hypophysis, and gonad function, as well as effects on glucose metabolism. Information on potential confounding factors, such as age, smoking and alcohol drinking, were collected and adjusted for. Results When the individual exposure level was represented by arithmetic mean for TTCA and CS₂ concentration, geometric means (SD) of CS₂ workers were 1.61 (1.91) mg/g.crea and 5.02 (1.84) ppm, respectively. There were no exposure-related differences in glucose metabolism or any of the endocrinological indices. Conclusions - No biologically significant effects of CS₂ were found on endocrine function in Japanese rayon manufacturing workers when the average internal and external exposure levels were maintained below the current occupational exposure limit.