Objective: To evaluate whether the dermal exposure to N,N-dimethylformamide (DMF) exerts significant effects and to determine the unit increment of dermal exposure on the total body burden of two biomarkers in urine: metabolism-required N-methylformamide (U-NMF) and non-metabolized DMF (U-DMF) in actual occupational environments. Methods: Exposure via respiratory and dermal routes was assessed on an individual basis for 75 workers from four DMF-related factories directly exposed to DMF. Respiratory exposure was determined by breathing-zone sampling for a full-work shift, and dermal exposure was assessed on the palms and forearms of both hands by an adhesive tape-patch method. U-NMF and U-DMF collected immediately postshift were measured. Results: The average concentrations of airborne DMF, DMF on hands and on forearms, U-NMF, and U-DMF (GM) were 1.51 ppm, 0.04 mg/cm 2 , 0.03 mg/cm 2 , 0.47 mg/l, and 0.38 mg/l, respectively. In multiple linear regression tests, only airborne DMF and DMF on hands remained significantly (Po0.001) associated with U-NMF and U-DMF. Based on model estimates, the unit increment of hands' exposure (mg/cm 2 ) could contribute to 0.53 and 0.46 mg/l of the increment of U-NMF and U-DMF, respectively, given a daily occupational airborne exposure to DMF at about 1.5 ppm. Conclusions: Dermal exposure provides a substantial contribution to the total body burden of DMF. A control remedy such as the enforcement of wearing impermeable gloves by workers occupationally exposed to DMF should be implemented with the highest priority.
Background: Hazardous chemicals and their metabolites may accumulate in the body following repeated airborne exposures and skin contact. Aims: To estimate the contribution of skin absorption to total body burden of N,N-dimethylformamide (DMF) across a working week in two groups with similar levels of respiratory exposure but dissimilar skin contact. Methods: Twenty five workers in a synthetic leather (SL) factory, 20 in a copper laminate circuit board (CLCB) factory, and 20 age and sex matched non-DMF exposed subjects, were recruited. Environmental monitoring of DMF exposure via respiratory and dermal routes, as well as biological monitoring of preshift urinary N-methylformamide (U-NMF), were performed for five consecutive working days. Results: Environmental and biological monitoring showed no detectable exposure in controls. The average airborne DMF concentration (geometric mean (GM) 3.98 ppm, geometric standard deviation (GSD) 1.91 ppm), was insignificantly lower for SL workers than for CLCB workers (GM 4.49, GSD 1.84 ppm). Dermal DMF exposure and U-NMF values, however, were significantly higher for SL workers. A significant pattern of linear accumulation was found across a five day work cycle for SL workers but not for CLCB workers. Conclusions: Dermal exposure to DMF over five consecutive days of occupational exposure can result in the accumulation of a significant DMF body burden. The long term exposure response under both repeated and intermittent conditions of substantial skin exposure is worthy of note.
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