Biological monitoring of occupational exposure to N,N-dimethylformamide - the effects of co-exposure to toluene or dermal exposure

Objectives: The objective of this study is to assess the exposure and intak e dose of N,N-dimethylformamide (DMF) and the correlation between them, acc ording to the type of exposure for the workers in the DMF industry. Methods : We monitored 345 workers occupationally exposed to DMF, from 15 workshops in the synthetic fiber, fiber coating, synthetic leather and paint manufac turing industries. Ambient monitoring was carried out with personal sampler s to monitor the external exposure. Biological monitoring was done to deter mine the internal dose by analyzing N-methylformamide (NMF) in end-shift ur ine. Work procedure and exposure type of each DMF workshop was carefully su rveyed, to classify workers by exposure type according to work details. Wor kers were classified into three groups (GroupA: continuous and direct expos ure through inhalation and skin; Group B: intermittent and short-term expos ure through inhalation and skin; Group C: continuous and indirect exposure mostly through inhalation).Results: Geometric mean of DMF concentration in air was 2.62 (CSD 5.30) ppm and that of NMF in urine was 14.50 (GSD 3.89) m g/l. In the case of continuous absorption through inhalation and dermal exp osure (Group A), the value of NMF in urine corresponding to 10 ppm of DMF w as 45.3 mg/l (r = 0.524, n = 178), 39.1 mg/g creatinine (r = 0.424), while it was 37.7mg/l (r=0.788, n=37), 24.2mg/g creatinine (r = 0.743) in the cas e of absorption mostly through inhalation (Group C). Creatinine correction reduced the correlation between two parameters. Conclusion: The NMF in urin e corresponding to 10 ppm DMF, of the dermal and inhalation exposure group was 39.1 mg/g creatinine (r = 0.424, n = 178), while that of the inhalation exposure-only group was 24.2 mg/g creatinine (r = 0.743. n = 37). Co-expos ure with toluene reduced the NMF excretion in urine.