BIOLOGICAL MONITORING OF WORKERS EXPOSED TO N-N-DIMETHYLFORMAMIDE .2. DIMETHYLFORMAMIDE AND ITS METABOLITES IN URINE OF EXPOSED WORKERS

N,N-Dimethylformamide (DMF) exposure was monitored in a synthetic leather factory; at the same time, urinary dimethylformamide and its metabolites were measured in urine samples collected before and at the end of workshifts. The study was run during two different periods. During the first phase ten workers were observed for 3 days (Monday, Tuesday and Wednesday) in the same week. In the second phase 16 workers were involved in the study on a Friday and on the following Monday. Urinary DMF, as well as hydroxymethyl-N-methylformamide and hydroxymethylformamide [measured as N-methylformamide (NMF) and formamide, respectively], were measured in all urine samples. Formamide was also measured as a ''physiological'' product in subjects not exposed to dimethylformamide. Environmental exposure to DMF ranged between about 10 and 25 mg/m(3). The unmodified solvent found in urine collected at the end of the exposure was significantly related to the environmental concentrations of DMF; its urinary concentrations were found to range between 0.1 and 1 mg/l. Higher concentrations of NMF (mean 23.3 mg/l) and formamide (24.7 mg/l) were measured in urine samples collected at the end of workshifts. The same concentrations were related to individual exposures to DMF. N-Acetyl-S-(N-methylcarbamoyl)cysteine in the urine of workers exposed to DMF showed a mean concentration of 40.4 mg/l on Friday (before and after the workshift) and a mean concentration of 10.3 mg/l on Monday. Its slow kinetic profile favours its body accumulation during the working week. N,N-dimethylformamide and N-methylformamide in urine collected at the end of the workshift are good markers of current occupational exposure to dimethylformamide, while N-acetyl-S-(N-methylcarbamoyl)cysteine seems a useful biological marker for monitoring repeated exposure to the solvent.