Developmental toxicity of N-methyl-2-pyrrolidone in rats following inhalation exposure

Human biomonitoring guidance values (HBM-GVs) for priority substances under the HBM4EU initiative - New values derivation for deltamethrin and cyfluthrin and overall results

The European Initiative HBM4EU aimed to further establish human biomonitoring across Europe as an important tool for determining population exposure to chemicals and as part of health-related risk assessments, thus making it applicable for policy advice. Not only should analytical methods and survey design be harmonized and quality assured, but also the evaluation of human biomonitoring data. For the health-related interpretation of the data within HBM4EU, a strategy for deriving health-based human biomonitoring guidance values (HBM-GVs) for both the general population and workers was agreed on. On this basis, HBM-GVs for exposure biomarkers of 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), phthalates (diethyl hexyl phthalate (DEHP), di-n-butyl phthalate (DnBP), diisobutyl phthalate (DiBP), butyl benzyl phthalate (BBzP), and bis-(2-propylheptyl) phthalate (DPHP)), bisphenols A and S, pyrethroids (deltamethrin and cyfluthrin), solvents (1-methyl-2-pyrrolidone (NMP), 1-ethylpyrrolidin-2-one (NEP), N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC)), the heavy metal cadmium and the mycotoxin deoxynivalenol (DON) were developed and assigned a level of confidence. The approach to HBM-GV derivations, results, and limitations in data interpretation with special focus on the pyrethroids are presented in this paper.

An evaluation of reproductive toxicity studies and data interpretation of N-methylpyrrolidone for risk assessment: An expert panel review

An expert panel was assembled to evaluate reproductive toxicology study data and their application to health risk assessment to provide input on the data quality, interpretation, and application of data from three multi-generation reproductive toxicity studies of N-methylpyrrolidone (NMP). Panelists were engaged using a double-blinded, modified Delphi format that consisted of three rounds. Key studies were scored using the U.S. Environmental Protection Agency's (EPA) questions and general considerations to guide the evaluation of experimental animal studies for systematic review. The primary conclusions of the panel are that one of the studies (Exxon, 1991) is not a high-quality study due to several design flaws that includes: (1) exceedance of the maximum tolerable dose in the high dose group; (2) failure to adjust feed concentrations of NMP during the lactation period, resulting in NMP doses that were 2- to 3-fold higher than nominal levels; and/or (3) underlying reproductive performance problems in the strain of rats used. For these reasons, the panel recommended that this study should not be considered for quantitative risk assessment of NMP. Exclusion of this study, and its corresponding data for male fertility and female fecundity, from the quantitative risk assessment results in a change in the identification of the most sensitive endpoint. Instead, changes in rat fetal/pup body weight, an endpoint previously selected by EPA, was identified as an appropriate basis for human health risk assessment based on a consideration of the best available science and weight of scientific evidence supported by the NMP toxicity database.

Workplace environmental exposure level guide: n-Methyl-2-pyrrolidone

n-Methyl-2-pyrrolidone (NMP) is a widely used solvent with a mild amine-like odor that can exist in a vapor or aerosol at moderate temperatures. In humans, NMP was reported to induce weak and transient eye irritation and headache. NMP was not a dermal sensitizer and has a low acute toxicity via oral, dermal, and inhalation routes. NMP was not genotoxic/mutagenic in a battery of in vitro and in vivo studies. Furthermore, NMP was not carcinogenic in rats although species-specific liver tumors were identified in mice. Chronic studies in the rat provided a NOAEL of 10 ppm (40 mg/m³) causing only minor effects in males (slightly reduced mean body weight) at 100 ppm (400 mg/m³). Developmental toxicity was considered the critical endpoint (decreased fetal body weights at non-maternally toxic doses). Benchmark dose and PBPK models were utilized to derive an internal dose of 350-470 mg·h/L as a NOAEL for this response and a human equivalent air concentration of 350-490 ppm. With the application of adjustment factors, an 8-h time-weighted average WEEL value of 15 ppm (60 mg/m³) was derived and is expected to provide a significant margin of safety against any potential adverse health effects in workers. To address the potential for respiratory irritation, a short-term exposure level of 30 ppm (120 mg/m³) was derived, and a skin notation is assigned because of the contribution of dermal absorption to the systemic toxicity of NMP.

Novaluron Has Detrimental Effects on Sperm Functions

Although novaluron is an insect growth regulator with a low mammalian acute toxicity and a low risk to the environment and nontarget organisms, toxic effects of novaluron have been reported. However, no studies have yet evaluated the effect of novaluron on reproduction. Therefore, we examined the effects of novaluron on sperm functions. The spermatozoa of ICR mice were incubated with various concentrations of novaluron to induce capacitation. Then, sperm motion parameters and capacitation status were evaluated using CASA program and H33258/chlortetracycline staining. In addition, PKA activity and tyrosine phosphorylation were evaluated by Western blotting. After exposure, various sperm motion parameters were significantly decreased in a dose-dependent manner. The acrosome reaction was also significantly decreased in the high concentration groups. Sperm viability was significantly reduced at the highest concentration. In addition, PKA activity and tyrosine phosphorylation were also significantly altered. Thus, novaluron affects sperm viability, sperm motility, and motion kinematics during capacitation. Furthermore, it may promote the reduction in acrosome reactions. The physiological suppression of sperm function may depend on abnormal tyrosine phosphorylation via the alteration of PKA activity. Therefore, we suggest that it is necessary to consider reproductive toxicity when using novaluron as a pesticide.

Buprenorphine X-waiver exemption - beyond the basics for the obstetrical provider

Buprenorphine is 1 of 3 medications approved by the US Food and Drug Administration for the treatment of opioid use disorder, and practitioners must obtain a federal waiver to prescribe buprenorphine. Until recently, physicians and advanced practice clinicians were required to complete 8 and 24 hours of training, respectively, before applying for this waiver and to provide psychosocial services when prescribing buprenorphine to ≤30 patients. The US Department of Health and Human Services announced in April 2021 that eligible providers would be exempt from the educational requirement for certification, making the waiver more accessible for those intending to prescribe to ≤30 patients. Here, we reviewed the historic background to the exemption and provided practical guidelines to practitioners caring for obstetrical patients with opioid use disorder who are considering applying for the waiver for the first time. Because the educational requirements will no longer be required for X-waiver application, we reviewed fundamental topics and challenging scenarios that are often reviewed in certification courses.

Solvent-based paint and varnish removers: a focused toxicologic review of existing and alternative constituents

Paint and varnish removers constitute a major potential source of organic solvent exposure to contractors and home improvement enthusiasts. Unfortunately, the leading paint remover formulations have traditionally contained, as major ingredients, chemicals classified as probable human carcinogens (eg, methylene chloride) or reproductive toxicants (eg, N-methylpyrrolidone). In addition, because of its unique toxicology (ie, hepatic conversion to carbon monoxide compounding generic solvent narcosis and arrythmogenesis), high volatility, and rigorous requirements for personal protective equipment, methylene chloride exposures from paint removers have been linked to numerous deaths involving both occupational and consumer usage. The aim of this review is to summarize the known toxicology of solvent-based paint remover constituents (including those found in substitute formulations) in order to provide health risk information to regulators, chemical formulators, and end-users of this class of products, and to highlight any data gaps that may exist.

Subcutaneous Extended-Release Buprenorphine Use in Pregnancy

Background

Opioid use disorder (OUD) in pregnancy is managed by medication-assisted treatment. Sublingual buprenorphine is one option, but subcutaneous extended-release buprenorphine (Sublocade®) is an alternate form administered in monthly injections. Through an extensive literature search, we did not find any prior publication on the use of Sublocade in pregnancy.

Case

Two patients with OUD switched from sublingual buprenorphine to Sublocade. One patient received a total of eight injections and then discovered she was pregnant. Based on ultrasound dating, the last 5 administrations occurred during her pregnancy. The second patient received 6 injections with the last occurring at the time of her last menstrual period. Both declined further injections, as well as oral buprenorphine. Serial urine drug screens remained positive for buprenorphine through delivery in both cases. Neither the mothers nor the neonates experienced withdrawal symptoms or adverse outcomes. No birth anomalies were found. Discussion. Though further research is needed regarding the use of Sublocade in pregnancy, it is likely that other pregnancies will occur during this treatment modality. If this long-acting form of buprenorphine medication is found to be safe, it might play a role in managing some pregnant patients with OUD.

Using physiologically-based pharmacokinetic modeling to assess the efficacy of glove materials in reducing internal doses and potential hazards of N-methylpyrrolidone during paint stripping

A refined risk assessment was conducted to evaluate the efficacy of different glove materials in reducing the potential hazards associated with using paint strippers containing N-methylpyrrolidone (NMP) under the scenarios defined by USEPA's TSCA risk assessment. Three categories of gloves were identified based on measured permeation rates for NMP: (1) minimal protection; (2) moderate protection; and (3) maximal protection. Simulations for eight acute and chronic occupational exposure scenarios identified by USEPA as having a potential hazard (i.e., margins of exposure, MOE, <30) were reassessed for each glove category using PBPK modeling to predict peak (Cmax) and cumulative (AUC) internal doses of NMP. For the acute assessment, the refined MOE values were ≥30 for half of the scenarios for gloves from the moderate protection group category, and all of the scenarios for gloves from the maximal protection category. For the chronic assessment, the refined MOE values were ≥30 for all scenarios except one for gloves from the maximal protection category. The results of this assessment indicate that: (1) the degree of protection provided by gloves from NMP permeation can vary widely depending upon the glove material, NMP formulation, and internal dose measure (with calculated glove protection factors ranging from 1.1 to 1900); and (2) NMP-containing paint strippers can be used safely when appropriate PPE are used. As such, these results can be used to support risk-reduction methods (e.g., product labeling, MSDS instructions on use of appropriate glove materials) as alternatives to banning NMP use under TSCA.

Metabolites of the alkyl pyrrolidone solvents NMP and NEP in 24-h urine samples of the German Environmental Specimen Bank from 1991 to 2014

PURPOSE

The aim of this study was to get a first overview of the exposure to the solvents and reproductive toxicants N-methyl-2-pyrrolidone (NMP) and N-ethyl-2-pyrrolidone (NEP) in Germany. NMP and NEP metabolite concentrations were determined in 540 24-h urine samples of the German Environmental Specimen Bank collected from 1991 to 2014. With these data we were able to investigate NMP/NEP exposures over time and to evaluate associated risks.

METHODS

NMP metabolites 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) and NEP metabolites 5-hydroxy-N-ethyl-2-pyrrolidone (5-HNEP) and 2-hydroxy-N-ethylsuccinimide (2-HESI) were determined by stable isotope dilution analysis using solid phase extraction followed by derivatization (silylation) and GC-EI-MS/MS.

RESULTS

We were able to quantify 5-HNMP and 2-HMSI in 98.0 and 99.6% and 5-HNEP and 2-HESI in 34.8 and 75.7% of the samples. Metabolite concentrations were rather steady over the timeframe investigated, even for NEP which has been introduced as an NMP substitute only in the last decade. Calculated median daily intakes in 2014 were 2.7 µg/kg bw/day for NMP and 1.1 µg/kg bw/day for NEP. For the combined risk assessment of NMP and NEP exposure, the hazard index based on the human biomonitoring assessment I values (HBM I values) was less than 0.1.

CONCLUSIONS

Based on the investigated subpopulation of the German population, individual and combined NMP and NEP exposures were within acceptable ranges in the investigated timeframe. Sources of NEP exposure in the 90s and 00s remain elusive.

Field Residues and Effects of the Insect Growth Regulator Novaluron and Its Major Co-Formulant N-Methyl-2-Pyrrolidone on Honey Bee Reproduction and Development

Owing to the recent declines in honey bee (Apis mellifera L.) populations, there is a need for field and laboratory studies to investigate threats to pollinator health. This study examines the hypothesis that the organophosphate alternative, Rimon 0.83EC, can have consequences to honey bee health by combining newly acquired field residue data, laboratory bioassays, and colony level feeding studies. Following label rate applications of Rimon 0.83EC to apple trees, average residue concentrations of the active ingredient, novaluron, were found to be 3.38 ppm in tree-collected pollen. Residues of the major co-formulant in Rimon 0.83EC, N-methyl-2-pyrrolidone (NMP), were below the limit of detection in the field, but a growth chamber study described here found that NMP can persist in pollen for up to 7 d with average concentrations of 69.3 ppm. Concurrent larval rearing studies found novaluron and NMP to be toxic to developing honey bees at doses as low as 100 ppb and 100 ppm, respectively. Nucleus colony feeding studies found that chronic exposure to Rimon 0.83EC at doses as low as 200 ppm (18.6 ppm novaluron) can result in interruptions to brood production that can last for up to 2 wk after exposure. Taken together, these data indicate the use of Rimon 0.83EC on blooming flowers is a significant threat to honey bee reproduction, and suggest the need for more strict and clear usage guidelines.

[Guide values for 1-methyl-2-pyrrolidone in indoor air. Report of the German Ad-hoc Working Group on indoor Guidelines of the Indoor Air Hygiene Committee and of the States' Supreme Health Authorities]

The German Ad-hoc Working Group on Indoor Guidelines of the Indoor Air Hygiene Committee and the States' Supreme Health Authorities is issuing indoor air guide values to protect public health. No human studies of sufficient quality are available for health evaluation of 1-methyl-2-pyrrolidone in air. In a well-documented chronic inhalation toxicity study in rats significant impairment of weight gain development has been observed (LOAEC = 400 mg/m(3)). The Working Group used this LOAEC as the point of departure for the derivation of guide value II. The conversion of repeated inhalation to continuous exposure (6-24 h; 5-7 days) used a factor of 5.6. By applying an interspecies factor of 2.5 for toxicodynamics, a factor of 10 to account for individual differences and an additional factor of 2 to include sensitive subgroups, results in a health hazard guide value (RW II) of 1 mg 1-methyl-2-pyrrolidone/m(3) indoor air (rounded). By using the NOAEC of 40 mg/m(3) from the same study and applying the same assessment factors as above a precautionary guide value (RW I) of 0.1 mg 1-methyl-2-pyrrolidone/m(3) is calculated.

Biomonitoring of exposure to N-methyl-2-pyrrolidone in workers of the automobile industry

N-methyl-2-pyrrolidone (NMP) is an important organic solvent for varnishes in industry. NMP has been previously shown to be a developmental toxicant in rodents. This study reports current exposures to NMP in the spraying department of an automobile plant using biological monitoring. Two specific metabolites, 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methyl-succinimide (2-HMSI), were analyzed in 69 urine samples of 14 workers exposed to NMP and 9 nonexposed controls. Three different working tasks ('loading' and 'cleaning' of the sprayer system and 'wiping/packing' of the sprayed materials) and three sampling times (preshift, postshift, and preshift of the following day) were studied in exposed workers. Median exposures of 5-HNMP and 2-HMSI in postshift urine of exposed workers were 0.91 and 0.52mg g(-1) creatinine, respectively, whereas median levels in controls were below the limit of detection. Decreased levels of 5-HNMP were observed in preshift urine samples on the following day (0.39mg g(-1) creatinine) in exposed workers, while the concentration of 2-HMSI did not change (0.49mg g(-1) creatinine). Highest exposures occurred during sprayer cleaning with a maximum level of 8.31mg g(-1) creatinine of 5-HNMP in postshift urine. In contrast to 'wipers/packers', no decrease in 5-HNMP could be observed in preshift urine samples on day 2 of the 'loaders' and 'cleaners'. Overall, exposure in terms of 5-HNMP postshift and 2-HMSI preshift of the following day were well below the current biological limit values of the European Union (70 and 20mg g(-1) creatinine). Our results provide initial data on NMP exposure in the automobile industry and suggest that the analysis of 5-HNMP in preshift samples also provides essential information, particularly in situations involving direct handling of liquid NMP-containing formulations.

Quantitative risk analysis for N-methyl pyrrolidone using physiologically based pharmacokinetic and benchmark dose modeling

Establishing an occupational exposure limit (OEL) for N-methyl pyrrolidone (NMP) is important due to its widespread use as a solvent. Based on studies in rodents, the most sensitive toxic end point is a decrease in fetal/pup body weights observed after oral, dermal, and inhalation exposures of dams to NMP. Evidence indicates that the parent compound is the causative agent. To reduce the uncertainty in rat to human extrapolations, physiologically based pharmacokinetic (PBPK) models were developed to describe the pharmacokinetics of NMP in both species. Since in utero exposures are of concern, the models considered major physiological changes occurring in the dam or mother over the course of gestation. The rat PBPK model was used to determine the relationship between NMP concentrations in maternal blood and decrements in fetal/pup body weights following exposures to NMP vapor. Body weight decrements seen after vapor exposures occurred at lower NMP blood levels than those observed after oral and dermal exposures. Benchmark dose modeling was used to better define a point of departure (POD) for fetal/pup body weight changes based on dose-response information from two inhalation studies in rats. The POD and human PBPK model were then used to estimate the human equivalent concentrations (HECs) that could be used to derive an OEL value for NMP. The geometric mean of the PODs derived from the rat studies was estimated to be 350 mg h/l (expressed in terms of internal dose), a value which corresponds to an HEC of 480 ppm (occupational exposure of 8 h/day, 5 days/week). The HEC is much higher than recently developed internationally recognized OELs for NMP of 10-20 ppm, suggesting that these OELs adequately protect workers exposed to NMP vapor.

Human volunteer study on the inhalational and dermal absorption of N-methyl-2-pyrrolidone (NMP) from the vapour phase

N-Methyl-2-pyrrolidone (NMP) is a versatile organic solvent frequently used for surface cleaning such as paint stripping or graffiti removal. Liquid NMP is rapidly absorbed through the skin but dermal vapour phase absorption might also play an important role for the uptake of the solvent. This particular aspect was investigated in an experimental study with 16 volunteers exposed to 80 mg/m(3) NMP for 8 h under either whole-body, i.e. inhalational plus dermal, or dermal-only conditions. Additionally, the influence of moderate physical workload on the uptake of NMP was studied. The urinary concentrations of NMP and its metabolites 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) were followed for 48 h and analysed by gas chromatography-mass spectrometry (GC-MS). Percutaneous uptake delayed the elimination peak times and the apparent biological half-lives of NMP and 5-HNMP. Under resting conditions, dermal-only exposure resulted in the elimination of 71 +/- 8 mg NMP equivalents as compared to 169 +/- 15 mg for whole-body exposure. Moderate workload yielded 79 +/- 8 mg NMP (dermal-only) and 238 +/- 18 mg (whole-body). Thus, dermal absorption from the vapour phase may contribute significantly to the total uptake of NMP, e.g. from workplace atmospheres. As the concentration of airborne NMP does not reflect the body dose, biomonitoring should be carried out for surveillance purposes.

Characterization of the polyurethanolytic activity of two Alicycliphilus sp. strains able to degrade polyurethane and N-methylpyrrolidone

Two bacterial strains (BQ1 and BQ8) were isolated from decomposed soft foam. These were selected for their capacity to grow in a minimal medium (MM) supplemented with a commercial surface-coating polyurethane (PU) (Hydroform) as the carbon source (MM-PUh). Both bacterial strains were identified as Alicycliphilus sp. by comparative 16S rRNA gene sequence analysis. Growth in MM-PUh showed hyperbolic behavior, with BQ1 producing higher maximum growth (17.8 +/- 0.6 mg.ml(-1)) than BQ8 (14.0 +/- 0.6 mg.ml(-1)) after 100 h of culture. Nuclear magnetic resonance, Fourier transform infrared (IR) spectroscopy, and gas chromatography-mass spectrometry analyses of Hydroform showed that it was a polyester PU type which also contained N-methylpyrrolidone (NMP) as an additive. Alicycliphilus sp. utilizes NMP during the first stage of growth and was able to use it as the sole carbon and nitrogen source, with calculated K(s) values of about 8 mg.ml(-1). Enzymatic activities related to PU degradation (esterase, protease, and urease activities) were tested by using differential media and activity assays in cell-free supernatants of bacterial cultures in MM-PUh. Induction of esterase activity in inoculated MM-PUh, but not that of protease or urease activities, was observed at 12 h of culture. Esterase activity reached its maximum at 18 h and was maintained at 50% of its maximal activity until the end of the analysis (120 h). The capacity of Alicycliphilus sp. to degrade PU was demonstrated by changes in the PU IR spectrum and by the numerous holes produced in solid PU observed by scanning electron microscopy after bacterial culture. Changes in the PU IR spectra indicate that an esterase activity is involved in PU degradation.

Developmental toxic effects ofN-ethyl-2-pyrrolidone administered orally to rats

The developmental toxicity of N-ethyl-2-pyrrolidone (NEP) was studied in Sprague-Dawley rats after oral administration. Pregnant rats were given NEP at doses of 0 (distilled water), 50, 250, 500 and 750 mg kg(-1) day(-1), by gavage (5 ml kg(-1)), on gestational days (GD) 6-20. Maternal toxicity, as evidenced by reduction in body weight gain and food consumption, was observed in all NEP groups at the beginning of treatment (GD 6-9). The incidence of resorptions was significantly increased at 500 mg kg(-1) day(-1), and reached 83% at 750 mg kg(-1) day(-1). There was a dose-related decrease in fetal weight, which was significantly lower than control at 250 mg kg(-1) day(-1) and higher doses. The incidence of malformed fetuses per litter and the number of litters with malformed fetuses were significantly increased at 500 and 750 mg kg(-1) day(-1). Malformations mainly consisted of edema, anal atresia with absent tail, cardiovascular defects and fused cervical arches. Ossification of skull bones and sternebrae was significantly reduced at 500 and 750 mg kg(-1) day(-1). The incidence of supernumerary ribs was significantly elevated at 250 mg kg(-1) day(-1) and higher doses. In conclusion, NEP administered by gavage is embryotoxic and teratogenic at maternal toxic doses.

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.

Human volunteer study on the influence of exposure duration and dilution of dermally applied N-methyl-2-pyrrolidone (NMP) on the urinary elimination of NMP metabolites

OBJECTIVES

N-Methyl-2-pyrrolidone (NMP) is a versatile solvent used in various industrial processes and applications. Apart from its mildly irritating effects on the eyes, the mucous membranes and the skin, NMP has revealed prenatal toxicity in animal experiments after the oral administration of high doses. The dermal absorption of NMP and the urinary elimination of its main metabolites were investigated within an experimental exposure study.

METHODS

Four male volunteers were exposed to liquid NMP under occlusive conditions on the back of one hand with varying exposure times and solvent concentrations. Urine was collected before, during and after the exposure and analysed for the main NMP metabolites 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI).

RESULTS

The urinary concentration of the metabolites upon exposure to undiluted NMP for 2 h increased rapidly with 5-HNMP reaching a maximum at 4-5 h and 2-HMSI after 26-29 h. The application of aqueous NMP solutions resulted in a delay of the peak time for 5-HNMP of approximately 6 h as compared with the undiluted solvent. An average dermal absorption of 5.4+/-1.5 mg NMP cm(-2) h(-1) was calculated for a 2 h exposure to undiluted NMP (6.5+/-2.0 mg NMP cm(-2) h(-1) for a 30 min exposure). Aqueous dilution of NMP to 50% was followed by a decrease of the absorption to 0.9+/-0.5 mg NMP cm(-2) h(-1). NMP metabolite concentrations in the range of the detection limits were found only in isolated urine samples after exposure to 10% NMP in aqueous dilution.

CONCLUSIONS

NMP is rapidly absorbed across the skin and the dermal route may contribute significantly to the uptake of the solvent. Therefore, a biomonitoring of NMP exposed workers is essential for occupational-medical surveillance. Both urinary metabolites reflect the internal dose after a dermal absorption of NMP and thus qualify as suitable biomarkers for NMP exposure.

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.

Ambient monitoring and biomonitoring of workers exposed to N-methyl-2-pyrrolidone in an industrial facility

OBJECTIVES

The exposure of seven workers and three on-site study examiners to N-methyl-2-pyrrolidone (NMP) was studied in an adhesive bonding compound and glue production facility.

METHODS

Airborne NMP was analysed by personal and stationary sampling on activated charcoal tubes. NMP and its main metabolites, 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI), were analysed in pre-shift and post-shift spot urine samples by gas chromatography-mass spectrometry. The workers were examined with respect to irritation of the eyes, the mucous membranes and the skin, and health complaints before and after the work-shift were recorded.

RESULTS

The time-weighted average concentration of NMP in most work areas varied between 0.2 and 3.0 mg/m3. During the manual cleaning of stirring vessels, valves and tools, 8-h TWA exposures of up to 15.5 mg/m3 and single peak exposures of up to 85 mg/m3) were observed. NMP and its metabolites were detected in two pre-shift urine specimens. NMP and 5-HNMP concentrations in post-shift urine samples of five workers and three on-site study examiners were below 125 microg/g creatinine and 15 mg/g creatinine, respectively, while two vessel-cleaning workers showed significantly higher urinary NMP concentrations of 472 and 711 microg/g creatinine and 5-HNMP concentrations of 33.5 and 124 mg/g creatinine. 2-HMSI was detectable in four post-shift samples (range: 1.6-14.7 mg/g creatinine). The vessel cleaner with the highest NMP exposure reported irritation of the eyes, the upper respiratory tract and headaches.

CONCLUSIONS

The results of this study indicate a relatively low overall exposure to NMP in the facility. An increased uptake of NMP occurred only during extensive manual vessel cleaning. Health complaints associated with NMP exposure were recorded in one case and might be related to an excessive dermal exposure due to infrequent and inadequate use of personal protective equipment.

Concentrations of N-methyl-2-pyrrolidone (NMP) and its metabolites in plasma and urine following oral administration of NMP to rats

The primary aims were to study the metabolism in rats and to determine the biological levels after one oral developmentally toxic dose of N-methyl-2-pyrrolidone (NMP), a widely used industrial chemical. Non-pregnant female Sprague-Dawley rats were given an oral single dose of either a non-toxic dose of 125 mg NMP/kg (group 1) by gavage or a developmentally toxic dose of 500 mg/kg (group 2). Blood plasma (7 rats per time point) and urine (10 rats per time point) were sampled up to 72 h after administration and analyzed using mass spectrometry. In both plasma and urine NMP, 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP), N-methylsuccinimide and 2-hydroxy-N-methylsuccinimide (2-HMSI) and 2-pyrrolidone (2-P) were identified. In urine 48% of the administered dose was recovered as 5-HNMP and 2-5% as 2-HMSI. The total recovery in urine was 53-59%. The peak concentrations for NMP in plasma were 1.2 and 6.9 mmol/l, 0.42 and 0.76 mmol/l for 5-HNMP, 0.07 and 0.31 mmol/l for MSI and for 2-HMSI the concentrations were 0.02 and 0.05 mmol/l for groups 1 and 2, respectively. In summary, the same metabolites were found in rats as in humans and the biological levels were reported for NMP and its metabolites after oral exposure to a developmentally toxic dose and one non-toxic dose of NMP.