N-Methylsuccinimide in plasma and urine as a biomarker of exposure to N-methyl-2-pyrrolidone

Objective: N-Methyl-2-pyrrolidone (NMP) is a selective and powerful organic solvent. The aim of this study was to investigate whether the NMP metabolite N-methylsuccinimide (MSI) in plasma and urine can be used as a biomarker of exposure to NMP. Methods: Six healthy subjects were exposed to 10, 25, and 50 mg NMP/m³ in an exposure chamber for 8 h. The air levels were monitored by XAD-7 solid sorbent sampling, and analysed by gas chromatography (GC). Plasma and urine were sampled for two days following the exposure, and the levels of MSI were analysed by GC with mass spectrometric detection. Results: The concentration of MSI in plasma and urine rose during the exposure, and reached a peak at about 4 h after the end of the exposure. The concentration then decayed according to a one-compartment model with a half-time of approximately 8 h. About 1% of the inhaled NMP was excreted in urine as MSI. There were very close correlations between the NMP air levels and, on the one hand, the MSI concentrations in plasma collected at the end of exposure (r=0.98), or the urinary MSI concentration collected during the last 2 h of exposure (r=0.96), on the other. Conclusions: MSI in plasma or urine is applicable as a biomarker of exposure to NMP. The concentration in plasma and urine mainly reflects the exposure over one day. Received: 5 May 2000 / Accepted: 1 November 2000