二甲基乙酰胺对工人健康的影响

目的 探讨二甲基乙酰胺( DMAC)肝脏毒性的特点及其接触指标.方法 采用分层抽样法选择145名研究对象,对研究对象进行问卷调查和健康检查等,并进行工作场所空气监测,同时采集研究对象每天的班末尿样或者工作周周末班末尿样,并对工作场所空气中DMAC浓度、尿中甲基乙酰胺(NMAC)进行相关回归分析.结果 卷绕岗位空气中DMAC浓度较高,其他岗位工作场所空气中浓度较低;肝功能异常18例,检出率为12.4％,11例(61.1％)发生在接触DMAC第1年内,且主要集中在卷绕岗位;尿中NMAC浓度与空气中DMAC浓度相关(r=0.44,P＜0.01).结论 DMAC短期接触即可造成工人肝功能异常,尿中NMAC可作为DMAC的接触指标.     

二甲基乙酰胺职业接触及与尿中甲基乙酰胺的关系

[目的]探讨职业二甲基乙酰胺（DMAC）接触与尿中甲基乙酰胺（NMAC）的相关性。[方法]对3家氨纶生产企业6个工种201名工人进行空气中DMAC暴露浓度监测及工作周末班末尿样采集,同时对20名纺丝工连续一周空气样品和班末尿样的采集;分别用气相色谱测定空气中DMAC和尿中NMAC含量。[结果]氨纶生产过程中组件清洗工、纺丝工接触DMAC水平最高（P〈0.0033）,中位数分别为32.10、22.02mg/m3,其尿中NMAC浓度较其他工种高（P〈0.0033）,中位数分别为30.09、22.72mg/gCr;工作周末班末尿NMAC含量与空气中DMAC浓度呈直线相关,直线方程为log（U-NMAC）=0.685＋0.455×log（A-DMAC）（r=0.698,P=0.001）;长期DMAC接触者,接触2d后尿中NMAC呈较高水平（P〈0.0033）;个体DMAC接触代谢转化为NMAC的相对内暴露指数（RIE）与DMAC接触浓度呈负相关（rs=-0.781,P=0.001）。[结论]工作周末班末尿NMAC含量与空气中DMAC浓度呈良好对数线性关系。     

Urinary biomarkers of occupational N,N-dimethylformamide (DMF) exposure attributed to the dermal exposure

OBJECTIVE: To evaluate whether the dermal exposure to N,N-dimethylformamide (DMF) exerts significant effects and to determine the unit increment of dermal exposure on the total body burden of two biomarkers in urine: metabolism-required N-methylformamide (U-NMF) and non-metabolized DMF (U-DMF) in actual occupational environments. METHODS: Exposure via respiratory and dermal routes was assessed on an individual basis for 75 workers from four DMF-related factories directly exposed to DMF. Respiratory exposure was determined by breathing-zone sampling for a full-work shift, and dermal exposure was assessed on the palms and forearms of both hands by an adhesive tape-patch method. U-NMF and U-DMF collected immediately postshift were measured. RESULTS: The average concentrations of airborne DMF, DMF on hands and on forearms, U-NMF, and U-DMF (GM) were 1.51 ppm, 0.04 microg/cm(2), 0.03 microg/cm(2), 0.47 mg/l, and 0.38 mg/l, respectively. In multiple linear regression tests, only airborne DMF and DMF on hands remained significantly (P<0.001) associated with U-NMF and U-DMF. Based on model estimates, the unit increment of hands' exposure (microg/cm(2)) could contribute to 0.53 and 0.46 mg/l of the increment of U-NMF and U-DMF, respectively, given a daily occupational airborne exposure to DMF at about 1.5 ppm. CONCLUSIONS: Dermal exposure provides a substantial contribution to the total body burden of DMF. A control remedy such as the enforcement of wearing impermeable gloves by workers occupationally exposed to DMF should be implemented with the highest priority.     

Occupational Exposure to N,N-Dimethylformamide in the Summer and Winter

We evaluated total body burden of N,N-dimethylformamide (DMF) taken through the lung and skin by personal exposure of workers to DMF and urinalysis of N-methylformamide (NMF) and N-acetyl-S(N-methylcarbamoyl)-cysteine (AMCC). A total of 270 workers were engaged in four different jobs in a workplace distant from main production lines emanating high levels of DMF. They were not required to wear any personal protective equipment including respirators or gloves. We found that log-transformed urinary levels of NMF and AMCC increased with an increase in log-transformed concentrations of exposure to DMF. Urinary levels of NMF and AMCC were significantly higher in the summer than the winter, although there was no significant seasonal difference in the concentrations of exposure to DMF. Our findings suggested that the increased urinary levels of NMF and AMCC in the summer resulted in increased skin absorption of DMF due to an increased amount of DMF absorbed by the moisturized skin under humid and hot conditions. Seasonal changes in the relative internal exposure index confirmed the present finding of enhanced summertime skin absorption of DMF. AMCC is thought to be a useful biomarker for assessments of cumulative exposure to DMF over a workweek and for evaluations of workers’ health effects.     

The use of biomarkers of exposure of N,N-dimethylformamide in health risk assessment and occupational hygiene in the polyacrylic fibre industry

Background: N,N-dimethylformamide (DMF) was recently prioritised for field studies by the National Toxicology Program based on the potency of its reproductive toxic effects.

Aims: To measure accurately exposure to DMF in occupational settings.

Methods: In 35 healthy workers employed in the polyacrylic fibre industry, N-methylformamide (NMF) and N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC) in urine, and N-methylcarbamoylated haemoglobin (NMHb) in blood were measured. Workplace documentation and questionnaire information were used to categorise workers in groups exposed to low, medium, and high concentrations of DMF.

Results: All three biomarkers can be used to identify occupational exposure to DMF. However, only the analysis of NMHb could accurately distinguish between workers exposed to different concentrations of DMF. The median concentrations were determined to be 55.1, 122.8, and 152.6 nmol/g globin in workers exposed to low, medium, and high concentrations of DMF, respectively. It was possible by the use of NMHb to identify all working tasks with increased exposure to DMF. While fibre crimpers were found to be least exposed to DMF, persons washing, dyeing, or towing the fibres were found to be highly exposed to DMF. In addition, NMHb measurements were capable of uncovering working tasks, which previously were not associated with increased exposure to DMF; for example, the person preparing the fibre forming solution.

Conclusions: Measurement of NMHb in blood is recommended rather than measurement of NMF and AMCC in urine to accurately assess exposure to DMF in health risk assessment. However, NMF and AMCC are useful biomarkers for occupational hygiene intervention. Further investigations regarding toxicity of DMF should focus on highly exposed persons in the polyacrylic fibre industry. Additional measurements in occupational settings other than the polyacrylic fibre industry are also recommended, since the population at risk and the production volume of DMF are high.

     

Total body burden arising from a week's repeated dermal exposure to N,N-dimethylformamide

Background: Hazardous chemicals and their metabolites may accumulate in the body following repeated airborne exposures and skin contact.

Aims: To estimate the contribution of skin absorption to total body burden of N,N-dimethylformamide (DMF) across a working week in two groups with similar levels of respiratory exposure but dissimilar skin contact.

Methods: Twenty five workers in a synthetic leather (SL) factory, 20 in a copper laminate circuit board (CLCB) factory, and 20 age and sex matched non-DMF exposed subjects, were recruited. Environmental monitoring of DMF exposure via respiratory and dermal routes, as well as biological monitoring of pre-shift urinary N-methylformamide (U-NMF), were performed for five consecutive working days.

Results: Environmental and biological monitoring showed no detectable exposure in controls. The average airborne DMF concentration (geometric mean (GM) 3.98 ppm, geometric standard deviation (GSD) 1.91 ppm), was insignificantly lower for SL workers than for CLCB workers (GM 4.49, GSD 1.84 ppm). Dermal DMF exposure and U-NMF values, however, were significantly higher for SL workers. A significant pattern of linear accumulation was found across a five day work cycle for SL workers but not for CLCB workers.

Conclusions: Dermal exposure to DMF over five consecutive days of occupational exposure can result in the accumulation of a significant DMF body burden. The long term exposure response under both repeated and intermittent conditions of substantial skin exposure is worthy of note.

     

二甲基甲酰胺对接触工人肝功能的影响

目的探讨二甲基甲酰胺(DMF)接触浓度、饮酒量及其他因素对DMF接触工人肝功能的影响。方法根据工厂前2年车间空气的监测数据,将DMF分为对照组、低接触组及高接触组。采用问卷调查了解各组研究对象的基本情况及饮酒习惯,采集血样测定肝功能。结果低接触组和高接触组血清丙氨酸转氨酶(ALT)及γ-谷氨酰转肽酶(γ-GT)水平明显高于对照组,高接触组血清天冬氨酸转氨酶(AST)水平高于低接触组;高接触组肝脏指数(Liver index)明显高于对照组和低接触组。多元线性回归分析表明ALT、γ-GT、肝脏指数与接触DMF及体重指数(BMI)相关,ALT还与甘油三酯(TRIG)相关,AST只与工人的饮酒量相关。在肝功能异常者中,有86.7%的AST/ALT比值<1。结论DMF能影响接触工人肝功能,肥胖及饮酒量有一定的协同作用。肝脏指数和AST/ALT比值可作为肝损伤评价和筛选指标。     

二甲基甲酰胺接触工人血清3项脂质过氧化指标的变化

目的探讨二甲基甲酰胺(DMF)作业工人血清丙二醛(MDA)水平、谷胱甘肽过氧化酶(GSH-Px)及超氧化物歧化酶(SOD)活力的变化。方法选取DMF作业工人105人作为接触组,健康献血员30名作为对照组。接触组按接触DMF空气浓度不同分为高浓度组和低浓度组;按接触DMF工作时间不同分为长工龄组和短工龄组。检测各组血清SOD、GSH-Px的活力和MDA水平。结果GSH-Px活力在低浓度组增高、显著高于高浓度组(P<0.05)。SOD活力、MDA水平随DMF浓度的上升呈上升趋势,SOD活力不同浓度组间差异均有显著性(P<0.05),MDA水平低浓度组与高浓度组比较差异有显著性(P<0.05),低浓度组与对照组比较差异无显著性。结论高浓度DMF接触对机体有致脂质过氧化作用,可引起血清GSH-Px的活力下降,MDA水平升高。     

Biological monitoring of workers exposed to N,N-dimethylformamide in the synthetic fibre industry

Objectives: Monitoring of workplace air and biological monitoring of 23 workers exposed to N,N-dimethylformamide (DMF) in the polyacrylic fibre industry was carried out on 4 consecutive days. The main focus of the investigation was to study the relationship between external and internal exposure, the suitability of the metabolites of DMF for biological monitoring and their toxicokinetic behaviour in humans.Methods: Air samples were collected using personal air samplers. The limit of detection (LOD) for DMF using an analytical method recommended by the Deutsche Forschungsgemeinschaft (DFG) was 0.1 ppm. The urinary metabolites, N-hydroxymethyl-N-methylformamide (HMMF), N-methylformamide (NMF), and N-acetyl-S-(N-methylcarbamoyl)-cysteine (AMCC), were determined in one analytical run by gas chromatography with thermionic sensitive detection (GC/TSD). The total sum of HMMF and NMF was determined in the form of NMF. The LOD was 1.0 mg/l for NMF and 0.5 mg/l for AMCC. Results and conclusions: The external exposure to DMF vapour varied greatly depending on the workplace (median 1.74 ppm, range <0.1–159.77 ppm). Urinary NMF concentrations were highest in post-shift samples. They also covered a wide range (<1.0–108.7 mg/l). This variation was probably the result of different concentrations of DMF in the air at different workplaces, dermal absorption and differences in the protective measures implemented by each individual (gloves, gas masks etc.). The urinary NMF concentrations had decreased almost to zero by the beginning of the next shift. The median half-time for NMF was determined to be 5.1 h. The concentrations of AMCC in urine were determined to be in the range from <0.5 to 204.9 mg/l. Unlike the concentrations of NMF, the AMCC concentrations did not decrease during the intervals between the shifts. For the exposure situation investigated in our study, a steady state was found between the external exposure to DMF and the levels of AMCC excreted in urine about 2  days after the beginning of exposure. AMCC is therefore excreted more slowly than NMF. The half-time for AMCC is more than 16 h. Linear regression analysis for external exposure and urinary excretion of metabolites was carried out for a sub-group of 12 workers. External exposure to 10 ppm DMF in air (the current German MAK value) corresponds to an average NMF concentration of about 27.9 mg/l in post-shift urine from the same day and an average AMCC concentration of 69.2 mg/l in pre-shift urine from the following day. NMF in urine samples therefore represents an index of daily exposure to DMF, while AMCC represents an index of the average exposure over the preceding working days. AMCC is considered to be better suited for biomonitoring purposes because (1) it has a longer half-time than NMF and (2) its formation in humans is more closely related to DMF toxicity. Received: 25 June 1999 / Accepted: 2 October 1999     

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

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/m(3)) of the current threshold limit value, the range of the values was from 0.4 to 75.2 mg/m(3). 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=1.384xDMF (mg/m(3))+8.708; r(2)=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)=0.936xDMF (mg/m(3))+7.306; r(2)=0.522 ( P<0.0001).     

Should styrene be sampled on the left or right shoulder?--An important question in employee self-assessment

A self-operated personal sampling technique called 'self assessment of exposure' (SAE) has been suggested as an easy method for collecting inhalation exposure data, as the workers themselves are performing the sampling. Employers and employees have raised the question of whether a different estimate of the air concentration is likely to be obtained depending on whether the sampler is fastened at the left or the right shoulder. In order to answer this question, the exposure to styrene vapour in two different small enterprises within the reinforced plastics industry was measured. Seven workers participated and the air sampling was performed by diffusive sampling. We observed no statistically significant difference in the determined air concentration of styrene between the left and right shoulder (P = 0.878). The results strongly indicate that the fastening of a sampler on the left or right shoulder does not produce a difference in the estimation of the inhalation exposure. SAE can thus be used to collect reliable exposure data of styrene vapour. The reliability of SAE will most certainly inspire occupational hygienists, physicians and other experts to involve the workers in repeated exposure measurements. Taking the exposure variability into account, repeated measurements are crucial when evaluating acute and chronic health effects following inhalation exposure to gases and vapours from chemical hazards.     

Toxicity due to 2- and 13-wk inhalation exposures of rats and mice to N, N-dimethylformamide

In order to better characterize the toxicity of N,N-dimethylformamide (DMF) and to provide its basic toxicity data for risk assessment of workers exposed to DMF, F344 rats and BDF1 mice of both sexes were exposed by inhalation (6 h/d x 5 d/wk) to 100, 200, 400, 800 or 1,600 ppm DMF for 2 wk, and 50, 100, 200, 400 or 800 ppm DMF for 13 wk. Three male and 7 female rats died during the 2-wk exposure to 1,600 ppm DMF, but no death of the exposed rats or mice occurred under any other exposure conditions. Massive, focal and single cell necroses were observed in the liver of DMF-exposed rats and mice. The massive necrosis associated with the centrilobular fibrosis occurred at the highest exposure concentration. The single cell necrosis was associated with fragmentation of the nucleoli as well as an increased mitotic figure. The 13-wk exposures of rats and mice to DMF were characterized by increases in the relative liver weight and the incidence of the centrilobular hepatocellular hypertrophy as well as increased serum levels of AST, ALT, LDH, total cholesterol and phospholipid. Lower confidence limits of the benchmark dose yielding the response with a 10% extra risk (BMDL10) were determined for the relative liver weight and the incidence of hepatocellular hypertrophy of the 13-wk exposed animals. The BMDL10 resulted in 1 ppm for the increased relative liver weight of male rats and mice and 17 ppm for the hepatocellular hypertrophy of male mice.     

Metabolism studies of N,N-Dimethylformamide

Summary In acute 2-h studies male and female rats were exposed to N,N-dimethylformamide concentrations of 209, 87, and 104 ppm with or without anoral dose of ethanol (2.0 g ethanol/kg) prior to inhalation.In a subacute study (2 h/day on 5 consecutive days) with or without an oral administration of ethanol (2.0 g ethanol/kg) before starting the test, the N,N-dimethylformamide concentration was approx. 200 ppm.Acute inhalation studies were performed on male dogs with N,N-dimethylformamide concentrations of 210–240 ppm and oral dose of ethanol (2.0 g ethanol/kg) immediately after or before the exposure.In addition, 4 persons were exposed to N,N-dimethylformamide concentrations of 50–80 ppm for 2 h, with or without preceding oral ethanol administration (19 g ethanol/person).The metabolic behavior of N,N-dimethylformamide and its metabolites (N-methylformamide, formamide) in blood and urine under the influence of ethanol was investigated.Additionally, in the subacute study on rats as well as in the acute studies on persons, the ethanol and acetaldehyde concentration was also determined.A delayed catabolisation of N,N-dimethylformamide was observed in the organism of rats and dogs after the oral administration of 2.0 g ethanol/kg prior to inhalation. This was confirmed by the elevated N,N-dimethylformamide concentration in the blood which decreased very slowly after exposure. After the administration of ethanol, N-methylformamide was not immediately detectable at the end of the inhalation period, but it was only found after a certain time lapse.A small oral dose of 0.2 g ethanol/kg body weight on rats prior to inhalation, did not influence the metabolism of N,N-dimethylformamide.During repeated exposure and daily pretreatment with ethanol, the metabolisation of N,N-dimethylformamide was also inhibited. However, the metabolisation of ethanol seemed also to be influenced by N,N-dimethylformamide.After exposure and preceding administration of ethanol no increase of the N,N-dimethylformamide level in the blood of persons could be found. However, a comparatively lower N-methylformamide concentration in the blood damage of the membrane of the endoplasmic reticulum would be imaginable.After acute ethanol intoxication Rubin et al. (1970) observed a decrease in the cytochrome P-450 activity in rats, which influences the electron transfer system and thus causes a dysfunction of the oxidation chain in the metabolism of foreign substances.Cinti et al. (1973) reported on the interference of high ethanol concentrations with the binding of drug substrates to cytochrome P-450.During repeated DMF exposure to rats, a slight inhibition of the ethanol oxidation was observed. This permits the supposition that it is only a question of concentration as to whether the inhibited metabolisation of the one substance is greater than that of the other.Further experimental studies are planned to establish whether DMF or MF like some other amides (N-butyramide, isobutyramide; Lester, 1970) are able to inhibit ethanol- or acetaldehyde-dehydrogenase.The occasionally observed intolerance reaction in employees exposed to DMF indicates an inhibition of the ethanol oxidation. However, in order to demonstrate this effect, significantly higher DMF exposures than we used in our study on persons are probably necessary. No influence can be expected on the metabolisation of ethanol in man at a DMF-exposure within the MAC range.     

N,N-Dimethylformamide: significance of dermal absorption and adjustment method for urinary N-methylformamide concentration as a biological exposure item

Objectives: To clarify the potential for dermal absorption of N,N-dimethylformamide (DMF) (CAS No. 68-12-2) vapor, and the appropriate adjustment method and the half-lives of urinary concentrations of N-methylformamide (NMF) as the biological exposure item of DMF. Methods: Thirteen healthy male volunteers (mean age: 22.7 years, range: 20–27) were exposed to DMF vapor twice, via both the skin and the lung, for 4 h at concentrations below 10 ppm, the recommended occupational exposure limit set by the Japan Society for Occupational Health, the American Conference of Governmental and Industrial Hygienists, and Deutsche Forschungsgemeinschaft, under conditions of 27 °C and 44% humidity. Each volunteer was exposed to DMF via the skin in a whole-body type exposure chamber and, outside the chamber, via the lung by a respirator connected to the chamber. Exposure levels were 6.2 ± 1.0 ppm in dermal exposure and 7.1 ± 1.0 ppm in inhalation exposure. Urine samples were collected at every opportunity until 72 h after exposure; and NMF, as well as volume, creatinine, and specific gravity were measured. Dermal and inhalation intakes were compared after adjusting concentrations. Results and Conclusions: DMF vapor absorptions via the skin and the lung were estimated to be 40.4 and 59.6%, respectively. Workers need to be aware of the risk of dermal absorption of DMF vapor as well as of the liquid. Though NMF concentrations adjusted by creatinine, specific gravity, and urinary volume showed good correlation with total NMF excretion and the absolute amount of NMF at each sampling time, creatinine-adjusted NMF concentration correlated better than the others. The biological half-life of urinary NMF after dermal exposure, 4.75 ± 1.63 h, was longer than that after respiratory exposure, 2.42 ± 0.63 h. Received: 14 June 2000 / Accepted: 5 October 2000     

Dermal absorption of N,N-dimethylacetamide in human volunteers

Objectives: We investigated the potential for the dermal absorption of N,N-dimethylacetamide (DMAC: CAS No. 127-19-5) vapor, the biological half-life of N-methylacetamide (NMAC) in urine as the biological exposure item of DMAC, and the adjustment method for urinary concentrations. Methods: Twelve healthy male volunteers (mean age 25.2 years, range 21–43 years) were exposed to DMAC for 4 h on two occasions at intervals of 96 h or above. Each volunteer sat inside a whole-body-type exposure chamber for the dermal exposure experiment or outside the chamber for the inhalation exposure experiment. The temperature and relative humidity in the chamber were controlled at approximately 26 °C and 40% in order to keep the skin (90% naked) of the volunteers dry. DMAC concentrations were 6.1 ± 1.3 ppm for dermal exposure and 6.1 ± 1.3 ppm for inhalation exposure. Urine samples were collected from 0 h through 36 h and at 48 h and 72 h after the exposure. Extrapolations from exposure concentrations for 4 h to 10 ppm for 8 h were performed. Results: Mean dermal absorption was estimated to be 40.4% of the total DMAC uptake. The biological half-lives of urinary NMAC were 9.0 ± 1.4 h and 5.6 ± 1.3 h via skin and lung, respectively. Mean NMAC in urine just after 5 consecutive workdays (8 h/day) at 10 ppm DMAC exposure was assumed to be 33.7 mg/g · Cr (18.6–70.0 mg/g · Cr). Creatinine-adjusted NMAC concentration in urine for each volunteer within 12 h after the exposure was more closely correlated with the total excretion amount of NMAC up to 36 h than with urinary-volume-adjusted or specific-gravity-adjusted NMAC concentration in both the dermal and inhalation exposure experiments. Conclusions: DMAC vapor was significantly absorbed through the skin. Estimated NMAC values indicate that 20 mg/g · Cr NMAC seems to be appropriate as the biological exposure index. Received: 6 August 1999 / Accepted: 9 September 1999     

Exposure to solvents in a synthetic leather manufacturing plant

The objective of this study was to evaluate the exposure of synthetic leather workers to dimethylformamide (DMF), epichlorohydrin (ECH) and toluene, in a manufacturing plant. The correlation between biological and environmental monitoring for DMF was also investigated. Environmental monitoring of the three solvents included personal and area sampling based on time of day (morning and afternoon). Urine samples were taken at the end of the shift and urinary N-methylformamide (NMF) was then used to biologically monitor DMF levels. Results for solvent concentrations based on air sampling were considerably higher in area than in personal sampling. Of 41 area samples, 15 (36.6%) and five (12.2%) exceeded permissible exposure levels for DMF and ECH, respectively, compared with 22 (28.6%) and three (3.9%) based on 77 personal samples. Overall, urinary NMF concentrations were lower than the Biological Exposure Index (BEI) suggested by the American Conference of Governmental Industrial Hygienists (ACGIH). A significant correlation (r=0.32; P < 0.05) was found between environmental and biological monitoring. Even though urinary NMF concentration was within permissible levels for Taiwan, the authors recommend that immediate measures be taken to decrease DMF and ECH concentrations in synthetic leather manufacturing plants. Received: 14 June 1999 / Accepted: 20 November 1999     

Occupational dimethylformamide exposure

Summary The relationship between the 8-h time-weighted average (TWA) intensity of exposure toN, N-dimethylformamide (DMF) vapor (with little possibility of skin contact with liquid DMF) and the subsequent excretion ofN-monomethylformamide (MMF) precursor in shift-end urine samples was examined in 116 workers exposed to DMF and 92 workers exposed to DMF in combination with toluene. Urinary MMF level was examined also in 42 non-exposed subjects. The TWA vapor concentration in breathing zone air of each worker was successfully measured by means of a recently developed diffusive sampler in which water was used as an absorbent. The examination of gas chromatographic (GC) conditions for MMF determination showed that the formation of MMF was not saturated when the injection port temperature was set at 200°C, reached a plateau at 250°C, and showed no additional increase at 300°C. There was a linear relationship between DMF in air and MMF in urine with a regression equation ofy =1.65x + 1.69 (r = 0.723,P<0.01), wherey is MMF (unit; mg/l, uncorrected for urine density) in urine andx is DMF (ppm) in air, when only those exposed to DMF were selected, and the injection port temperature was set at 250°C. From this equation, it was possible to estimate that about 10% of the DMF absorbed will be excreted into urine as the MMF precursor. The slope of the regression line was significantly smaller among those exposed to DMF and toluene in combination as compared with those with DMF exposure only.     

A field comparison of inhalable and thoracic size selective sampling techniques.

We measured inhalable, thoracic, and so-called "total" wood dust exposure in British Columbia lumber mill workers. Particle-size selective sampling was conducted using the GSP and Seven hole inhalable samplers, the PEM thoracic sampler and the 37-mm closed-face cassette "total" sampler. All measurements were full-shift personal samples, obtained from randomly selected workers. We obtained intersampler comparison data for the following pairs of instruments: GSP and 37-mm sampler; GSP and seven-hole sampler (SHS); and PEM and 37-mm sampler. The intersampler measurement ratios were estimated as: GSP/37-mm sampler = 4.2; GSP/SHS = 1.7; and PEM/37-mm sampler = 1.6. The GSP/37-mm sampler ratio is consistent with previously reported findings, while PEM/37-mm sampler and GSP/SHS ratios were both larger than expected. We found that in all comparisons, the measurement ratio had significant variability that was greatest at low ambient dust concentrations. Although it was not possible to attribute the source of the variability to specific sampler types, we concluded that the GSP sampler might be susceptible to "projectile" particles not normally aspirated, and may be vulnerable to direct aspiration of dust from accidentally contacted surfaces. The PEM was designed for environmental monitoring, and it is possible that it is unsuited to the higher particulate concentrations found in some occupational settings. Disparities among inhalable sampling techniques such as that between GSP and SHS should be investigated further in light of the proposed adoption of the inhalable method as an industrial standard.     

A simplified method for determining erythrocyte pyrimidine 5'-nucleotidase (P5N) activity by HPLC and its value in monitoring lead exposure

The method for determining erythrocyte pyrimidine 5'-nucleotidase (P5N EC 3.1.3.5) activity has been simplified using an automated high performance liquid chromatograph (HPLC). The activity determined by the simplified method agreed closely with that obtained by conventional methods. In 161 lead workers P5N activity declined linearly with increasing blood lead concentrations (Pb-B) between 20 and 80 micrograms/100 g, and correlated well with Pb-B (r = -0.87). For the same group of workers, correlation coefficients between Pb-B v ALA-D activity, zinc protoporphyrin, ALA-U, and coproporphyrin were -0.87, 0.73, 0.70, and 0.32, respectively. At Pb-B greater than or equal to 40 micrograms/100 g, the validity of P5N (1.86 at a cut off of 10 less than or equal to units) was higher than that of other indicators examined. P5N activity was fairly stable during the storage of samples for two weeks at 4 degrees C. Determination of P5N activity by this method may be a useful indicator in screening for moderate exposure to lead.     

The effects of co-exposure to methyl ethyl ketone on the biological monitoring of occupational exposure to<Emphasis Type="Italic"> N,N</Emphasis>-dimethylformamide

OBJECTIVES: (1) To assess whether urinary N,N-dimethylformamide (U-DMF) is suitable as a biomarker when co-exposure to methyl ethyl ketone (MEK) exists, and to evaluate whether it is suitable as an exposure biomarker of DMF. (2) To examine whether the co-exposure to MEK affects the characteristics of U-NMF and U-DMF. (3) To investigate if the difference in creatinine-adjusted and non-adjusted measurements of urinary biomarkers of DMF exposure is substantial. METHODS: Personal exposure monitoring of N,N-dimethylformamide (DMF) and MEK on 11 synthetic-leather workers was performed for 5 consecutive days. Daily post-shift urine for each individual was collected and was analyzed for urinary N-methylformamide (U-NMF) and U-DMF levels on both non-adjusted and creatinine-adjusted bases. RESULTS: Both U-NMF and U-DMF showed significant associations with airborne DMF. Positive and significant associations between U-NMF and U-DMF on either a non-adjusted basis or a creatinine-adjusted basis were found. Satisfactory linear associations ( P<0.01) between all kinds of urinary biomarkers and DMF exposure were found. The co-exposure to MEK exerted more effect on the relationship of airborne DMF to U-DMF than to U-NMF. CONCLUSIONS: U-DMF is detectable when occupational DMF exposure is near or below the occupational exposure limit of 10 ppm. In view of the performance of sensitivity, specificity, and positive predictive value, U-NMF, in general, is superior to U-DMF. However, on a par with other findings in this and previous studies, U-DMF might be considered as a complimentary biomarker of exposure to DMF in addition to U-NMF. No distinction between creatinine-adjustment or non-adjustment for urine specimens was found in the biological monitoring of DMF exposure. Further exploration of the influence of co-exposure to MEK at higher exposure is warranted.