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Even if organic solvents can be widely absorbed by the aerosol and dermal route, it has not been assessed in vivo settings in the workplace. So we challenged the measurement and assessment of dermal exposure to skin-annotated organic solvent such as N,N-dimethylformamide (DMF).
Methods
We evaluated dermal exposure of DMF at 82 workers in 12 workshops making synthetic leather with dry-typed coating process. Epidermal cells in hands and neck were sampled using the tape stripping methods in post-shift time. Acetone-treated tapes stripped from the hands of workers were analyzed using gas chromatography-mass selective detector (GC/MSD). The N-methylformamide (NMF) in post-shift spot urine was measured for biological monitoring. The associations for urinary NMF according to the dermal DMF and ambient DMF were analyzed by multiple linear regression.
Results
The exposure level of the disrupted epidermal cells had a significant correlation with urinary NMF. In multiple linear regression tests, the unit increment of dermal DMF and urinary NMF contributed 3.44 and 2.61 respectively in the best-fit model(Y = -3.26 + 3.44x + 2.61z, P<0.001). Dermal DMF adjusted by protein contents showed more fitted relationship with urinary NMF than dermal DMF not adjusted. The adjustment by protein content for dermal sample were proven essential in applying tape stripping method for organic solvent with skin-annotation.
Discussion
The lack of information of dermal DMF can overestimate the contribution of ambient DMF to urinary NMF. Even though, the ambient DMF was below the exposure limit 10 ppm, urinary NMF level reached over biological exposure index 15 mg/L as a result of dermal exposure to DMF. We conclude that dermal exposure of DMF as well as ambient DMF should be considered for biological monitoring of DMF exposure. Therefore, the exposure limit for ambient DMF be reconsidered and the enforcement and adherence to regulations to control dermal exposure should be promoted.