A morbidity study of viscose rayon workers exposed to carbon disulphide.

A historical cohort study of the morbidity of CS2 and control workers was carried out in a viscose rayon factory and an adjacent cotton mill. A total of 725 male workers was employed at the two factories on I May 1966. All records of medical treatment received by these men from general practitioners, hospitals, and plant clinics for the period from I May 1966 to 31 December 1970 were obtained from receipts issued by those medical institutions and kept in the health insurance office. The study population was divided into five categories according to the duration and severity of CS2 exposure. Mean ages were found to be almost the same for all five groups (range of means 38a 1-39-0 years). Period prevalence rates of cerebral vascular disease, ischaemic heart disease, hypertensive disease, diabetes mellitus, nephritis and nephrosis, mental disorders, and neurological diseases were calculated for all groups. Renal disease and hypertensive disease were significantly more prevalent in the rayon spinners and cutters with exposure histories of 10 years or more, the most highly exposed group, than in the non-CS2 workers. When the non-CS2 workers and the CS2 workers with negligible exposure are combined and taken as a reference group, ischaemic heart disease was significantly more prevalent in the most highly exposed group than in the reference group. Ratios of period prevalence rates between these two groups were 7-6 for nephritis and nephrosis, 2-3 for ischaemic heart disease, and 1 9 for hypertensive disease. The ratios for cerebrovascular disease, diabetes mellitus, and neurological diseases were larger than 10, but the differences were not statistically significant. Carbon disulphide (CS2) has caused various types of intoxication throughout its history of use in vulcanisation shops and in the viscose rayon industry.1 Chronic vascular diseases, such as atherosclerosis of cerebral arteries,2 ischaemic heart disease,3 4 nephrosclerosis similar to diabetic nephropathy,5-7 and retinal microaneurysms,7 8 have occurred after longterm exposure to CS2. The factors responsible for determining what type of diseases will actually occur in an exposed population are virtually unknown, except that the degree and duration of exposure to CS2 is assumed to play an important part. Yamagata et a16 7 reported 17 cases of CS2 nephrosclerosis found in nine Japanese viscose rayon plants. All the cases manifested overt proteinuria, but the diagnoses were made histopathologically on needle biopsy specimens. Based on these histological findings and Received 2 February 1981 Accepted 2 March 1981 on the absence of clinical and laboratory signs suggestive either of cerebral arteriosclerosis and diabetes mellitus, Yamagata et al concluded that nephrosclerosis can be induced by CS2 as a type of primary chronic intoxication. Other reports from Japan8-1' have found a high prevalence of nephropathy in several viscose rayon factories. In other countries, however, CS2 nephropathy has been generally regarded as an indication of a generalised atherosclerotic process induced by CS2.12 Thus the WHO Task Group on Environmental Health Criteria for Carbon Disulfide'2 considers that renal involvement represents a very late consequence of heavy, protracted exposure to CS2. The present study was undertaken because a unique opportunity was afforded to analyse a complete set of records of the medical treatment given to all employees of a Japanese viscose rayon factory during a period of about five years from 1966 to 1970. In view of the diversity of organs reported