This study was carried out to identify seasonal variations of urinary concentrations of N-methylformamide (NMF) among workers employed at a synthetic leather factory.

Study subjects consisted of 16 male and 6 female workers who were involved in the direct treatment of dimethylformamide (DMF) in a synthetic leather factory. By using health examination data and the results of air measurements and biologic monitoring conducted in February and July, 2001, we identified seasonal variations of the DMF concentrations in the air and NMF concentrations in urine.

1) In winter and summer, average temperatures at the working sites were 3.2 degrees C and 26.5 degrees C, respectively and average humidities were 35.4 % and 84.5 %, respectively. 2) Airborne DMF concentrations were not significantly different between summer (13.78 ppm) and winter (11.55 ppm). 3) NMF concentrations in urine were found to be significantly higher in summer (96.09 mg/g creatinine) than in winter (31.23 mg/g creatinine) (p<0.001).

The seasonal difference in the urinary excretion values of NMF may be due to increased dermal absorption of DMF with the higher ambient temperature and humidity in summer and the increased area of exposed skin.