Six year observational cohort study of the effect of carbon disulphide on brain MRI in rayon manufacturing workers

Abstract

Aims: To clarify whether the current occupational exposure limit (OEL) for carbon disulphide (CS 2 ) is low enough to prevent the occurrence of adverse effects on the cerebrovascular system. Methods: A total of 432 male workers exposed to CS 2 and 402 male referent workers in 11 Japanese viscose rayon factories were studied at baseline; 750 of these were followed up. Brain MRI was performed at both baseline and follow up surveys. Changes in the number of hyperintense spots in T2 weighted images (HIS), which point to so-called ''silent cerebral infarctions'', were evaluated over six years. A total of 666 subjects (217 exposed, 125 ex-exposed, and 324 referent subjects) who twice received brain MRI were subjected to analysis. Mean duration of exposure to the end of the study was 19.6 years for the exposed workers. The geometric mean CS 2 (ppm) and TTCA (mg/g creatinine) concentrations for the past six years were 4.9 and 1.6 for all exposed workers, 5.8 and 1.9 for spinning/refining workers, and 2.7 and 0.9 for other exposed workers, respectively. Results: Exposed subjects showed a significantly higher risk for an increase in the number of HIS over six years. Odds ratios adjusted for possible confounders in the exposed and ex-exposed workers were 2.27 (95% CI 1.37 to 3.76) and 1.33 (95% CI 0.70 to 2.54), respectively. No exposure-response relations were observed in a number of analyses among the exposed workers. Conclusions: Exposure to CS 2 under the current Japanese OEL, 10 ppm, might increase the number of HIS in brain MRI. However, results should be interpreted with caution.

Job strain and arteriosclerosis in three different types of arteries among male Japanese factory workers

“…Those with any history of chronic disease such as hypertension, diabetes mellitus, stroke, and cardiovascular disease were excluded from the study at baseline. Details of the study and the results of the cohort study have been described elsewhere (19,20). To investigate the effects of job strain on arteriosclerosis, we added a questionnaire in the follow-up survey of 1998−1999.…”

Changes of median nerve conduction velocity in rayon manufacturing workers: A 6-year cohort study

“…Second, there was a lack of information on previous CS2 exposure concentration. In general, exposure concentrations to hazardous chemicals have been improved by the introduction of effective industrial hygiene control measures in occupational settings, as shown in our previous studies [4][5][6] . The most important question is whether the increased risk that we observed was caused by previous or recent exposure.…”

“…This result indicates that not only previous exposure but also recent exposure had some impact on SCV of the median nerve in this population. Third, although long peripheral nerves, such as the sural nerve, may be more suitable to evaluate the effects of neurotoxins, we measured NCV of the median nerve only due to the limited time allowed for comprehensive health checkups, including examinations of sclerosis of the carotid and aortic arteries, at rest and exercise ECG, ophthalmological test, neurobehavioral examinations, and NCV test at the rayon factories [4][5][6] . If we could examine the long nerves, we could have observed clearer outcomes than those in this study.…”

“…The cohort study design and follow-up details have been described previously 1,2,[4][5][6] . In brief, study subjects at baseline consisted of 432 male workers exposed to CS2 and 402 unexposed male workers, with no medical history of cerebrovascular or cardiovascular diseases as determined using company medical records and a selfadministered questionnaire, in 11 Japanese viscose rayon factories.…”

“…We conducted a 6-year cohort study to comprehensively evaluate CS2 exposure concentration and health effects, including cerebrovascular, cardiovascular, ophthalmological, neurological, neurobehavioral, and endocrinological aspects, at baseline ( 1992-93 ) and follow-up (1998-99) [1][2][3][4][5][6] . The neurological system is considered to be the critical target of CS 2-induced toxicity.…”