Combining novel strategy with kinetic approach in the determination of respective respiration and skin exposure to N,N-dimethylformamide vapor

N,N-dimethylformamide (DMF) could be readily absorbed via skin and inhalation routes. It is difficult, however, to separate the internal dose contribution from skin vapor and inhalation exposure. This study attempts to quantitatively determine the separate skin vapor and inhalation exposure contributions using a semi-actual exposure approach. Six volunteers were tailgated by DMF-exposed employees completely for two exposure scenarios: with and without wearing a respirator. Individual airborne DMF (A-DMF) exposure was evaluated by integrating real-time DMF monitoring and time-activity log. Urinary N-methylformamide (U-NMF) concentrations in 4-h and 8-h one urine sample plus 24-h consecutive urine sample were determined to evaluate the internal DMF exposure dose. The average A-DMF concentrations for all participants were 8.10 (2.75) and 9.52 (3.47) ppm, respectively, for with respirator and without respirator scenarios. Area under the curve of U-NMF throughout 24-h showed 71% and 29% contribution from skin and inhalation exposure, respectively, indicates that the absorbed dose of DMF via skin vapor exposure was much greater than inhalation. In conclusion, the semi-actual approach provides a novel measure to accurately determine the relative skin vapor and inhalation exposure contributions to the internal dose. The skin vapor exposure deserves more attention in the prevention of chemical hazards in the exposed environment.