Air and biological monitoring of solvent exposure during graffiti removal

The European Human Biomonitoring Initiative (HBM4EU): Human biomonitoring guidance values (HBM-GVs) for the aprotic solvents N-methyl-2-pyrrolidone (NMP) and N-ethyl-2-pyrrolidone (NEP)

Toxicologically and/or epidemiologically derived guidance values referring to the internal exposure of humans are a prerequisite for an easy to use health-based interpretation of human biomonitoring (HBM) results. The European Joint Programme HBM4EU derives such values, named human biomonitoring guidance values (HBM-GVs), for priority substances which could be of regulatory relevance for policy makers and have been identified by experts of the participating countries, ministries, agencies and stakeholders at EU and national level. NMP and NEP are such substances for which unresolved policy relevant issues should be clarified by targeted research. Since widespread exposure of the general population in Germany to NMP and NEP was shown for the age groups 3–17 years and 20–29 years, further investigations on exposure to NMP and NEP in other European countries are warranted. The HBM-GVs derived for both solvents focus on developmental toxicity as decisive endpoint. They amount for the sum of the two specific urinary NMP metabolites 5-HNMP and 2-HMSI and likewise of the two specific urinary NEP metabolites 5-HNEP and 2-HESI to 10 mg/L for children and 15 mg/L for adolescents/adults. The values were determined following a consultation process on the value proposals within HBM4EU. A health-based risk assessment was performed using the newly derived HBM-GV_GenPop and exposure data from two recent studies from Germany. The risk assessment revealed that even when considering the combined exposure to both substances by applying the Hazard Index approach, the measured concentrations are below the HBM-GV_GenPop in all cases investigated (i.e., children, adolescents and young adults).

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HBM-GVs are a prerequisite for an easy to use health-based risk assessment of human biomonitoring results.

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For NMP and NEP metabolites in urine, respectively, HBM-GVs were set for children and adolescents/adults.

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First HBM exposure data indicate widespread exposure of German children, adolescents and young adults to NMP and NEP.

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The Hazard Index approach revealed that even when combined exposure to both solvents is assessed, HBM-GVs are not exceeded.

Biological monitoring and health effects of low-level exposure to N-methyl-2-pyrrolidone: a cross-sectional study

PURPOSE

To examine the value of urinary 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) in a population of workers exposed to N-methyl-2-pyrrolidone (NMP) and to look for health effects of exposure to this organic solvent.

METHODS

Airborne NMP was determined according to the NIOSH method. Urinary 5-HNMP and 2-HMSI (after and before next shift) were determined by liquid chromatography with tandem mass spectrometry. Outcomes were effects on lung, kidney, skin and mucous membranes, nervous system, haematopoiesis and liver determined by clinical examination and laboratory measurements. Univariate statistical methods and multiple regressions were used to analyse results. Skin resorption, smoking and other potential confounders were taken into account.

RESULTS

Three hundred twenty-seven workers were eligible out of which 207 workers (63%) participated. Ninety-one of these worked with NMP. Occupational exposure to NMP did often not occur daily and ranged from non-detectable to 25.8 mg/m3 (median = 0.18). Urinary 2-HMSI (mg/l; before next shift) was the best biomarker of exposure to NMP, explaining about 70% of the variance, but most likelihood ratios did not allow for ruling exposure in or out, at these low levels of exposure. Creatinine adjustment did not improve the results clearly. No clear and consistent health effects could be associated with NMP exposure. No indication for a bias due to non-participation was found.

CONCLUSIONS

Biological monitoring, primarily urinary 2-HMSI (mg/l; before next shift), is of value to estimate exposure to NMP even when exposure is irregular and low. Likelihood ratios of urinary 5-HMNP or 2-HMSI are, however, not quite satisfactory at these low levels. No irritant or other health effects were found.

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.

Determination of N-methyl-2-pyrrolidone and its metabolites in urine by micellar electrokinetic chromatography

A fast and accurate micellar electrokinetic capillary chromatography (MEKC) method was developed for monitoring N-methyl-2-pyrrolidone (NMP) exposure. Baseline separation of NMP and its main metabolites: 5-hydroxy-N-methyl-2-pyrrolidone (5HNMP), N-methylsuccinimide (MSI), 2-hydroxy-N-methylsuccinimide (2HMSI), and 2-pyrrolidone (2P) was obtained within 6 min in an uncoated fused silica capillary using 5 mM phosphate buffer and 140 mM sodium dodecyl sulfate (pH 7.1) as background electrolyte (BGE). On-line UV-detection was performed at 200 nm and the applied electric field was 400 V cm−1. Possible interference of BGE-induced system peaks on separation was investigated by computer simulation and no such interference was observed. The developed MEKC method combined with solid phase extraction for sample preparation was successfully applied to the analysis of urine of rats exposed to NMP. The urinary excretion was determined in 0–6 h and 6–24 h specimens collected after an intragastic administration of 308 mg NMP / kg rat body weight. The results of NMP disposition kinetics in rat urine are reported for NMP and metabolites.

Environmental and biological monitoring of volatile organic compounds in the workplace

The exposure of workers to volatile organic compounds (VOCs) in the workplace has been evaluated in four different occupations, namely: house painters, varnishing workers, car painters and petrol station workers. The study was carried out by analyzing the ambient air within the workers' breathing zone as well as the alveolar air of these workers, which was selected as the biomarker of exposure. Twenty six VOCs were measured in the air samples. Nearly all target VOCs were found in the ambient air of the workplaces assessed, usually involving in the most abundant compounds, toluene, o-xylene and N-butyl acetate, concentrations between 60 and 51,110 microg m(-3). The same VOCs were found in the alveolar air of workers after their work shift, at concentrations whose amount depended on the compound and occupation involved. Toluene, at concentrations between 90 and 29,840 microg m(-3), o-xylene, between 30 and 12,285 microg m(-3), and N-butyl acetate, between 10 and 8045 microg m(-3), were also the most abundant compounds found in the alveolar air of workers after exposure. The post-work concentrations of VOCs in alveolar air correlated significantly with ambient air concentrations, obtaining correlation coefficients over 0.9 for the compounds studied. Furthermore, a general trend towards greater absorption of benzene derivatives by the human body (the average percentage of absorption is 50%) than that of esters (average percentage of 20%) has been observed in the data obtained throughout the study.

Biomonitoring as a tool in the human health risk characterization of dermal exposure

Dermal exposure is an important factor in risk characterization. In occupational settings it becomes relatively more important because of the continuous reduction in inhalation exposure. In the public health arena, dermal exposure may also form a significant contribution to the total exposure. Dermal exposure, however, is difficult to assess directly because it is determined by a host of factors, which are difficult to quantify. As a consequence, dermal exposure is often estimated by application of models for external exposure. In combination with modeled or measured data for percutaneous penetration, these provide an estimate for the internal exposure that is directly related to the systemic effects. The advantages and drawbacks of EASE (Estimation and Assessment of Substance Exposure) and RISKOFDERM (Risk Assessment of Occupational Dermal Exposure), two models for external exposure that are mentioned in the Technical Guidance Document for the European Union risk assessments performed under the Existing Substances Regulation (EEC/793/93), are discussed. Although new chemicals regulation (REACh, 1907/2006/EC) is now in place in the European Union, the principles applied under the previous legislation do not change and the same models will continue to be used. The results obtained with these models for styrene, 2-butoxyethanol, and 1-methoxy-2-propanol in specific exposure scenarios are compared with an alternative method that uses biomonitoring data to assess dermal exposure. Actual external exposure measurements combined with measured or modeled percutaneous penetration data give acceptable results in risk assessment of dermal exposure, but modeled data of external dermal exposure should only be used if no other data are available. However, if available, biomonitoring should be considered the method of choice to assess (dermal) exposure.

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.

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 experimental exposure study on the uptake and urinary elimination of N-methyl-2-pyrrolidone (NMP) during simulated workplace conditions

A human experimental study was carried out with 16 volunteers to examine the elimination of N-methyl-2-pyrrolidone (NMP) after exposure to the solvent under simulated workplace conditions. The NMP concentrations were 10, 40 and 80 mg/m(3) for 2 x 4 h with an exposure-free interval of 30 min. Additionally, a peak exposure scenario (25 mg/m(3) baseline, 160 mg/m(3) peaks for 4 x 15 min, time-weighted average: 72 mg/m(3)) was tested. The influence of physical activity on the uptake and elimination of NMP was studied under otherwise identical exposure conditions but involving moderate workload on a bicycle ergometer (75 W for 6 x 10 min). The peak times and biological half-lives of urinary NMP and its main metabolites 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) in urine were analysed as well as the interrelationships between exposure and biomarkers. All analytes showed a close correlation between their post-shift peak concentrations and airborne NMP. An exposure to the current German workplace limit value of 80 mg/m(3) under resting conditions resulted in urinary peak concentrations of 2,400 microg/L NMP, 117 mg/g creatinine 5-HNMP and 32 mg/g creatinine 2-HMSI (workload conditions: 3,400 microg/L NMP, 150 mg/g creatinine 5-HNMP, 44 mg/g creatinine 2-HMSI). Moderate workload enhanced the total uptake of NMP by approximately one third. Differences between the estimated and the observed total amount of urinary metabolites point to a significant contribution of dermal absorption on the uptake of NMP. This aspect, together with the influence of physical workload, should be considered for the evaluation of a biological limit value for NMP.

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.

Exposure to organic solvents among handicraft car painters: A pilot study in Italy

Car repair painters usually experience long-term exposure to many different solvents. In Italy, the greater part of car painting shops are "handicraft", i.e. 2-5 workers and small premises. Usually workers do not have specific duties, but everyone takes part in all different operations. Moreover, working time is not standardized but varies according to the workload, working methods tend to be traditional, and compliance to individual protection devices is poor. We have hence assessed, on a sample of 8 italian handicraft car painting shops, the exposure levels to solvents, implementing three classic exposure monitoring methods: environmental sampling with charcoal tubes, personal sampling with diffusive charcoal samplers, and urinary determination of unmetabolised solvents. A simple regression analysis was performed to evaluate relationships between the three series of data. The solvents analysed were toluene, ethylbenzene, 1, 2-dichloropropane, n-butylacetate, n-amylacetate, xylene isomers, ethylacetate, and benzene. Benzene was included due to several factors, among others its presence (1% v/v) in the italian unleaded gasoline. Benzene was found in all shops, at levels around or higher than the 8-h time-weighted average limit (8-h TLV-TWA). Other solvents were found in the different shops at various levels, 10(-2) - 10(-1) times the 8-h TLV-TWA. Air concentrations of toluene, n-butylacetate, xylenes, and benzene were positively correlated with urinary levels of the parent compounds, while a negative correlation was found for ethylbenzene. The health implications of workers' exposure level was briefly discussed.

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.

Dermal absorption and urinary elimination of N-methyl-2-pyrrolidone

OBJECTIVES

The dermal absorption of the solvent N-methyl-2-pyrrolidone (NMP) and its elimination in urine was investigated in an experimental study.

METHODS

Seven volunteers were exposed to 1045 mg of liquid NMP under occlusive conditions for 2 h. Urine was collected before, during and up to 72 h after the exposure and analysed for NMP by GC/MS after liquid-liquid extraction. Additionally, the remaining NMP in the pads was determined to estimate the total dermal uptake.

RESULTS

The concentration of NMP in urine increased rapidly after beginning of the exposure up to 1 h after the exposure was completed. A peak concentration of 1,836+/-863 microg/l was observed, the half-life in urine was 3.2 h. About 0.5% of the absorbed dose was excreted metabolically unchanged. An average dermal absorption of 5.5 mg cm(-2) h(-1) was calculated.

CONCLUSIONS

The results of this study show that the percutaneous absorption of NMP may contribute significantly to the overall uptake of the solvent, e.g. in the workplace. Therefore, a biological monitoring of NMP exposed workers is essential for occupational-medical surveillance.

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

The developmental toxicity of inhaled N-methyl-2-pyrrolidone (NMP) was studied in Sprague-Dawley rats. Pregnant rats were exposed whole body to NMP vapours at concentrations of 0, 30, 60 and 120 ppm, 6 h/day, on gestational days (GD) 6 through 20. Maternal body weight gain was significantly decreased at 60 and 120 ppm on GD 6-13 and maternal food consumption was reduced at 120 ppm on GD 13-21. No significant difference in the gestational weight change corrected for the weight of the gravid uterus was observed, whatever NMP concentration. There were no adverse effects on embryo/fetal viability or evidence of teratogenicity at any concentration tested. Fetal toxicity indicated by reduced fetal weight was observed at 120 ppm. Thus, the no-observed-adverse-effect level (NOAEL) for maternal and developmental toxicity was 30 and 60 ppm, respectively.

Dermal exposure to aqueous solutions of N-methyl pyrrolidone

N-methyl pyrrolidone (NMP) is a substance widely used for its strong and selective solvent capacity. The strong potential NMP has for skin absorption makes biological monitoring ideal for exposure assessment. This study looked at brief exposures to NMP in aqueous solutions over a range of concentrations. Two volunteers placed one hand in NMP solutions ranging from 5 to 25% for as long as 15 min followed by urine collection for 48 h. The analyte of interest (analysed by GC-MS) was the NMP metabolite 5-hydroxy-N-methyl pyrrolidone (5-HNMP). Excretion of 5-HNMP was plotted against time and this showed that urine concentrations were at a maximum after about 10 h and 5-HNMP excretion continued for 48 h after exposure. The half-life of excretion was found to be approximately 11 h. The mean correlation between exposure (as a measure of exposure duration and solution concentration) and total 5-HNMP excreted was 0.9297.