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Objective: A prospective cohort study was designed to clarify the relations between occupational exposure to carbon disulphide (CS2) and its effects on arteriosclerosis in workers in 11 Japanese rayon manufacturing factories. This report is a cross sectional baseline observation in the first study year., Methods: Study subjects were 432 male rayon workers (mean (range) age 35.5 (19.1-47.8); duration of exposure 13.4 (0.3-29.0)) and 402 male referent workers (age 35.8 (18.9-49.8)). Exposure to CS2 was assessed by determining the concentration of 2-thiothiazolidine-4-carboxylic acid (TTCA) in urine. Mean (SD) TTCA was 3.42 (2.73) mg/g creatinine (Cr) (n = 422). About a quarter of the urine samples were > 5 mg/g Cr, a biological exposure index recommended by the American Conference of Governmental Industrial Hygienists. Health effects on arteriosclerosis were evaluated by measuring blood pressure, serum lipids, pulse wave velocity of the aorta, stiffness and blood flow of the carotid artery, and blood coagulation and fibrinolysis indices, and by use of brain magnetic resonance imaging, electrocardiogram (at rest and after exercise), ophthalmograph, and Rose's questionnaire. Information on potential confounding factors was collected by self administered questionnaire., Results: Prevalence of microaneurysm of the retinal artery was significantly higher in workers exposed to CS2 (8.1%) than in referent workers (3.4%), and increased with age. Other examinations did not show any differences between the two groups even after allowance for confounding factors., Conclusions: Significant effects of CS2 on arteriosclerosis were not found in current rayon manufacturing workers, with the exception of induction of microaneurysm of the retinal artery.

A total of 123 male viscose rayon workers who were exposed to carbon disulfide, and an additional 67 workers who were not exposed to any toxic agent in the working environment, underwent a thorough ophthalmological examination. The relationship between exposure and ophthalmological results was analyzed with univariate and multivariate methods. The most striking findings were strong associations between exposure and the 100-HUE color vision score and excess of microaneurysms in the exposed group. The current threshold limit value appeared to protect against these effects.

Microaneurysms are important in the diagnosis of vascular changes caused by carbon disulfide. They can be diagnosed by ophtholmoscopy, angiography or angioscopy. In our opinion even a careful ophthalmoscopic investigation is sufficient for diagnosis, so that angiography is not absolutely necessary for any mass survey. The incidence of microaneurysms correlates with the duration (both daily and total) as well as with the intensity of exposure to carbon disulfide. The quantity correlates closely with the intensity of exposure. The incidence of microaneurysms is not correlated to age; however it was found to be highest in 40-50-year-old men working with staple fibers, whereas in the spinning department it occurred in 50-55-old men. Microaneurysms are found equally frequently in active workers and invalids. There was no difference between the two groups with regard to degenerative changes of the macula. However, the changes found in the eyes of men from the staple fiber department were more pronounced than in those from the spinning department.

In order to clarify the pathogenesis of carbon disulfide retinopathy, fluorescein fundus angiograms were analyzed for 143 workers exposed to CS2 and 40 unexposed workers (reference) from viscose rayon factories. Retinal abnormalities, characterized by saccular microaneurysms, ellipsoidal microaneurysms and loop formation of small vessels, and atrophic/degenerative changes of pigmentary epithelium, were found in workers exposed to CS2. Saccular microaneurysms were found in 45.5% of the CS2 workers and 7.5% of the reference workers (P less than 0.05). Ellipsoidal microaneurysms or loop formation were found in 14.0% of the CS2 workers and 5.0% of the reference workers. Atrophic/degenerative changes of the pigmentary epithelium were found in 32.9% of the CS2 workers and 15.0% of the reference workers (P less than 0.05). Significant correlations were found between the prevalence of these retinal abnormalities and the CS2 exposure index.