Biological monitoring of carbon disulphide and phthalate exposure in the contemporary rubber industry

Objectives: We studied the range in urinary levels of 2-thiothiazolidine-4-carboxyl acid (TTCA), a metabolite of CS₂ and phthalic acid (PA), a common metabolite of phthalates, across factories and departments in the contemporary rubber manufacturing industry. Methods: Spot urine samples from 101 rubber workers employed in nine different factories were collected on Sunday and during the workweek on Tuesday, Wednesday and Thursday at ∼4 pm. In total, 386 urine samples were successfully analyzed. Results: Levels of both biomarkers increased significantly by a factor 2 (paired t-test P-value <0.05) during the working week as compared to the Sunday biomarker levels with absolute increases of approximately 70 μg/l and 5 μmol/mol creatinine for PA and TTCA, respectively. Levels in both biomarkers did not differ markedly between working days. Increases seemed to be restricted to specific factories and/or departments (e.g. molding and curing). Conclusions: The results of this study demonstrate that rubber workers in the contemporary rubber industry are exposed to phthalates and low levels of CS₂ (∼0.05 ppm) as measured by PA and TTCA, respectively. Exposures to both compounds are largely driven by specific circumstances in factories. Therefore, when estimating exposures to phthalates and CS₂ detailed information should be collected on the type and amount of phthalate containing ester plasticizers, dithiocarbamates and thiurams used. Preferably, personal exposure data should be collected. In this case, biological monitoring seems a reasonable approach. However, in the case of PA attention should be given to individual background levels as this could lead to a substantial overestimation of the occupational contribution to total phthalate exposure.