Stillbirth after occupational exposure to N-methyl-2 pyrrolidone

A cross-sectional observation of effect of exposure to N-methyl-2-pyrrolidone (NMP) on workers' health

This study was aimed at clarifying the effect of exposure to N-methyl-2-pyrrolidone (NMP) on workers' health. Fifteen male NMP-exposed workers and 15 referent male workers were recruited for this study. Exposure concentrations were assessed by determining NMP in the breathing zones and urinary NMP. Clinical examinations, motor and sensory nerve conduction velocities in the dominant arm, and neurobehavioral tests were carried out. The subjects were asked to complete self-administered questionnaires for subjective symptoms and psychological assessment. The mean NMP exposure concentrations ranged from 0.14 to 0.26 ppm, and urinary NMP levels at the end of each workday ranged from 0.17 to 0.22 mg/l, throughout the work week. In terms of clinical data, motor and sensory nerve conduction velocities, neurobehavioral tests, and subjective symptom assessments, there were no differences and no dose-dependent changes in either the means or the prevalence of abnormal findings between NMP-exposed and referent workers.

Comparative developmental toxicities of the three major metabolites ofN-methyl-2-pyrrolidone after oral administration in rats

The developmental toxicity of the three main metabolites of N-methyl-2-pyrrolidone (NMP) was studied in Sprague-Dawley rats. Pregnant rats were given 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP; 0, 250, 500, 750 or 1000 mg kg(-1) day(-1)), N-methylsuccinimide (MSI; 0, 500, 750, 1000 or 1250 mg kg(-1) day(-1)), or 2-hydroxyN-methylsuccinimide (2-HMSI; 0, 250, 500, 1000 or 1500 mg kg(-1) day(-1)), by gavage, on gestational days (GD) 6-20. No evidence of maternal toxicity was observed in dams given 5-HNMP. Administration of 2-HMSI resulted in overt maternal toxicity at 500 mg kg(-1) day(-1) and higher doses, as indicated by a significant reduction in weight gain and food consumption at the beginning of treatment. There was no evidence of embryo/fetal toxicity in any of the groups treated with 5-HNMP or 2-HMSI. MSI produced marked developmental toxicity in the presence of maternal effects. Maternal body weight gain and food consumption were affected at 750 mg kg(-1) day(-1) MSI, and above. A significant increase in post-implantation loss occurred at 1250 mg kg(-1) day(-1) MSI, and the incidence of fetuses with external or with visceral malformations was significantly increased at 1000 and 1250 mg kg(-1) day(-1) MSI. Malformations mainly consisted of anasarca, cardiovascular defects and diaphragmatic hernia. Fetal weight was significantly reduced at 1000 and 1250 mg kg(-1) day(-1). The incidence of skeletal variations (predominantly cervical ribs, and delayed ossification of skull bones and sternebrae) was significantly elevated at 750 mg kg(-1) day(-1) and higher doses. However, MSI was much less potent than the parent compound. These results indicate that the embryotoxic and teratogenic effects of NMP are not attributable to these metabolites.

Levels of N-methyl-2-pyrrolidone (NMP) and its metabolites in plasma and urine from volunteers after experimental exposure to NMP in dry and humid air

The aim of this study was to investigate if the uptake of N-methyl-2-pyrrolidone (NMP), a widely used industrial chemical, increases after exposure to NMP in humid air compared to dry air. NMP has been described to be an airway irritant and a developmentally toxic compound. Six male volunteers were exposed to NMP, three at the time, for 8h in an exposure chamber. They were each exposed on four different occasions to air levels of 0 and 20mg NMP/m(3) in dry and humid air. Blood and urine were sampled before, during and up to 5 days after the end of the 8-h exposure. Plasma and urine were analysed for NMP and its metabolites, using liquid chromatography-tandem mass spectrometry. There was no statistically significant increase in the total cumulated excretion of NMP and its metabolites in urine after exposure in humid air as compared to dry air. Furthermore, there were no differences in the levels of peak concentrations in either plasma or urine. Also, no differences were found in AUC between the exposures. However, there were large individual differences, especially for the exposure in humid air. A not previously identified metabolite in human, 2-pyrrolidone (2-P), was identified. The results do not support a significantly higher absorption of NMP at exposure in humid air as compared to dry air. However, the large individual differences support the use of biological monitoring for assessment of NMP exposure. In addition, 2-P was confirmed to be an NMP metabolite in humans. This may be of importance for the developmental toxicity of NMP since 2-P have been described to be a reproductively toxic substance.

Toxicokinetics and metabolism of N-[(14)C]N-methyl-2-pyrrolidone in male Sprague-Dawley rats: in vivo and in vitro percutaneous absorption

Neat N-methyl-2-pyrrolidone (NMP) rapidly penetrated into the skin of male Sprague-Dawley rats after in vivo and in vitro topical application. At the two topical doses tested in vivo, no steady state was observed. The maximal absorption fluxes were 10 and 20 mg/cm(2)/h for 20 microl/cm(2) and 40 microl/cm(2), respectively. Similar results were observed after in vitro topical application of neat [(14)C]NMP (25-400 microl/cm(2)) in fresh full-thickness skin. Whatever the dose tested, the percutaneous absorption fluxes increased with exposure time to reach a maximum value (F(max)) and then decreased. F(max) and the time to reach it (T(max)) increased as the dose increased. At the highest dose, which may be considered as an "infinite dose," the maximal flux (7.7 +/- 1.1 mg/cm(2)/h, n = 12) occurred 6 h after the topical application of NMP. The decrease on percutaneous absorption flux was correlated with the dilution of neat NMP with water from the receptor fluid. A semi-quantitative mathematical model was developed to describe the absorption flux of NMP taking into account the transfer of water through the skin. The K(p) values determined from the different aqueous solutions of NMP (1:1 to 1:32, v/v) were not significantly different. The mean value was 6.4 (10(-3) cm/h) (range, 4.7 to 7.6). Occlusion did not affect the percutaneous absorption flux of neat NMP. Desquamation increased the percutaneous absorption of NMP slightly. The skin did not metabolize NMP. The flux was dependent on the thickness of the skin and was proportional to the concentration of NMP. These findings suggest a passive diffusion of NMP through the skin.

Toxicokinetics and metabolism of N-[14C]methylpyrrolidone in male Sprague-Dawley rats. A saturable NMP elimination process

This study evaluated the toxicokinetics of N-[(14)C]methylpyrrolidone ([(14)C]NMP) after intravenous administration (0.1, 1, 10, 100, and 500 mg/kg, in saline solution) or topical application (20 and 40 micro l/cm(2); 10 cm(2), neat) in haired male Sprague-Dawley rats. Whatever the dose, unchanged NMP was intensively distributed into the body with a volume of distribution of 69% of body weight. After this phase, unchanged NMP declined almost linearly with time for 3 to 4 h after administration and then followed a mono-exponential function (t1/2 = 0.8 h) for the three lowest doses. The maximal plasma level of 5-hydroxy-N-methylpyrrolidone (5-HNMP), the main metabolite, was reached 4 to 6 h later for the three lowest doses and 8 to 24 h later for the highest doses. These findings indicate that the elimination of NMP is governed by a saturable metabolism process. The Michaelis-Menten parameters estimated from plasma levels of unchanged NMP were 2 mM and 3.8 mg/h, respectively. Between 4 and 10% of the administered doses were excreted in the urine as unchanged NMP. Urinary clearance of NMP (0.03 to 0.07 ml/min) indicates intensive tubular reabsorption. 5-HNMP was the main urinary metabolite and accounted for 42 to 55% of the administered doses. Its maximal urinary excretion occurred between 4 and 6 h after administration of the three lowest doses and between 8 and 24 h for the two highest doses. Urinary clearance (0.9 to 1.3 ml/min) was compatible with renal elimination by simple glomerular filtration.

Developmental toxicity of N-methyl-2-pyrrolidone administered orally to rats

The developmental toxicity of N-methyl-2-pyrrolidone (NMP) was studied in Sprague-Dawley rats after oral administration. Pregnant rats were given NMP at doses of 0 (distilled water), 125, 250, 500, and 750 mg/kg/day, by gavage, on gestational days (GD) 6 through 20. Significant decreases in maternal body weight gain and food consumption during treatment, and a reduction in absolute weight gain were observed at 500 and 750 mg/kg. The incidence of resorptions per litter was significantly higher than control at 500 mg/kg, and rose to 91% at 750 mg/kg. Examination of the foetuses revealed treatment-related malformations, including imperforate anus and absence of tail, anasarca, and malformations of the great vessels and of the cervical arches. The incidence of malformed foetuses per litter, and of litters with malformed foetuses was significantly increased at 500 and 750 mg/kg. At 250 mg/kg, one foetus showed malformations similar to those recorded at higher dosages. There was a dose-related decrease in foetal body weights (male, female, and total) that reached statistical significance at 250 mg/kg. A significant increase in incomplete ossification of skull bones and of sternebrae was also present at 500 and 750 mg/kg. In summary, the no-observed-adverse-effect level (NOAEL) for maternal and developmental toxicity was 250 and 125 mg/kg/day, respectively. Thus, oral administration of NMP produced developmental toxicity below maternally toxic levels.