Urinary determination of N-acetyl-S-(N-methylcarbamoyl)cysteine and N-methylformamide in workers exposed to N,N-dimethylformamide

Abstract

Objectives. We conducted this biomonitoring study with the aim of evaluating the correlation between the excretion of N-methylformamide (NMF) (mainly from N-hydroxy-N-methylformamide) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC), and levels of exposure to N,N-dimethylformamide (DMF) among occupationally exposed subjects.

Methods. Exposure levels were determined by personal sampling: breathing zone air samples were collected by means of passive samplers. DMF collected by the charcoal in personal samplers was analysed after extraction with methanol by a gas chromatograph. For the purpose of biological monitoring the levels of NMF and AMCC were measured in pre-shift and post-shift samples. Determinations were carried out by, respectively, gas chromatography and high performance liquid chromatography (HPLC).

Results and conclusions. The mean time-weighted average (TWA) exposure was approximately half (13.5 mg/m³) of the current threshold limit value, the range of the values was from 0.4 to 75.2 mg/m³. Environmental DMF concentrations exhibited a significant correlation with the specific mercapturic acid (AMCC) collected at the end of the working week (AMCC Friday morning mg/l=1.384×DMF (mg/m³)+8.708; r²=0.47; P<0.008]; hence urinary AMCC represents an index of the average exposure during several preceding working days, making it possible to calculate the approximate relationship between DMF uptake and excretion of this metabolite. A significant correlation was found also between the daily excretion of NMF and the corresponding levels of DMF in air. The equation of the regression line was: NMF (mg/g creatinine)=0.936×DMF (mg/m³)+7.306; r²=0.522 (P<0.0001).