ORIGINAL ARTICLE

A six year follow up study of the subclinical effects of carbon disulphide exposure on the cardiovascular system

T Takebayashi¹, Y Nishiwaki¹, T Uemura¹, H Nakashima¹, T Nomiyama¹, H Sakurai², K Omae¹

¹ Department of Preventive Medicine and Public Health, School of Medicine, Keio University, Japan
² Occupational Health Research and Development Center, Japan Industrial Safety and Health Association, Japan

Correspondence to:
Correspondence to:
Dr T Takebayashi
Department of Preventive Medicine and Public Health, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan; ttake{at}sc.itc.keio.ac.jp

Aims: A six year prospective cohort study was conducted to clarify whether the current carbon disulphide (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 effects on the cardiovascular systems.

Methods: The study subjects were 432 male workers exposed to CS₂ and 402 non-exposed workers in Japan, all of whom were examined in 1992–93. A total of 251 CS₂ exposed, 140 formerly exposed, and 359 non-exposed workers participated in the follow up survey (follow up rate 89.9%) in 1998–99. Mean duration of exposure was 19.3 years at the end the study. Mean CS₂ and 2-thiothiazolidine-4-carboxylic acid (TTCA) concentrations were 5.0 ppm and 1.6 mg/g creatinine. Health items examined were serum biochemical indices including lipids and coagulation-fibrinolysis factors, blood pressure, aortic stiffness, ophthalmography, and electrocardiography at rest and after Master’s double 2 step test. Potential confounding factors were adjusted for.

Results: Incidence of ischaemic findings, defined as Minnesota codes I, IV_1–3, V_1–3 (at rest and after the load), or receiving treatment for ischaemia, was significantly higher in the exposed workers, especially for the spinning/refining workers (adjusted OR 2.1; 95% CI 1.1 to 4.0) or the highest quartile of six year mean TTCA (adjusted OR 3.9; 95% CI 1.8 to 8.7), although the observed increase in risk was diminished when rigorous ECG criteria were applied. Incidence of retinal microaneurysm was increased with marginal significance. Among cardiovascular risk factors we examined, only blood pressure values were significantly increased in the exposed workers.

Conclusions: Increased risk of ischaemic electrocardiogram findings among Japanese viscose rayon workers was observed. Although its clinical significance is to be discussed, the current Japanese occupational exposure limit for CS₂, 10 ppm, would be high to prevent subclinical cardiovascular effects in this study population.

Keywords: carbon disulfide; cohort study; cardiovascular system; retinal artery; electrocardiogram; ischaemia; exposure-response relation

Abbreviations: ECG, electrocardiography; LDL, low density lipoprotein; HDL, high density lipoprotein; Lp(a), lipoprotein a; OR, odds ratio; PWV, pulse wave velocity; TTCA, 2-thiothiazolidine-4-carboxylic acid; TWA, time weighted average

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