Biological monitoring of exposure to solvents using the chemical itself in urine: application to toluene.

OBJECTIVE: Biomonitoring of solvents using the unchanged substance in urine as exposure indicator is still relatively scarce due to some discrepancies between the results reported in the literature. Based on the assessment of toluene exposure, the aim of this work was to evaluate the effects of some steps likely to bias the results and to measure urinary toluene both in volunteers experimentally exposed and in workers of rotogravure factories. METHODS: Static headspace was used for toluene analysis. o-Cresol was also measured for comparison. Urine collection, storage and conservation conditions were studied to evaluate possible loss or contamination of toluene in controlled situations applied to six volunteers in an exposure chamber according to four scenarios with exposure at stable levels from 10 to 50 ppm. Kinetics of elimination of toluene were determined over 24 h. A field study was then carried out in a total of 29 workers from two rotogravure printing facilities. RESULTS: Potential contamination during urine collection in the field is confirmed to be a real problem but technical precautions for sampling, storage and analysis can be easily followed to control the situation. In the volunteers at rest, urinary toluene showed a rapid increase after 2 h with a steady level after about 3 h. At 47.1 ppm the mean cumulated excretion was about 0.005% of the amount of the toluene ventilated. Correlation between the toluene levels in air and in end of exposure urinary sample was excellent (r = 0.965). In the field study, the median personal exposure to toluene was 32 ppm (range 3.6-148). According to the correlations between environmental and biological monitoring data, the post-shift urinary toluene (r = 0.921) and o-cresol (r = 0.873) concentrations were, respectively, 75.6 microg/l and 0.76 mg/g creatinine for 50 ppm toluene personal exposure. The corresponding urinary toluene concentration before the next shift was 11 microg/l (r = 0.883). CONCLUSION: Urinary toluene was shown once more time a very interesting surrogate to o-cresol and could be recommended as a biomarker of choice for solvent exposure.

Host factors in occupational diisocyanate asthma: a Swiss longitudinal study.

OBJECTIVE: To investigate the usefulness of surrogates for individual susceptibility to organic diisocyanates in occupational asthma. SUBJECTS: All new cases declared to the Swiss National Accident Insurance Company (SUVA) for establishment of a case for compensable occupational disease during 1993. Sixty-nine persons, of whom three were women, were suspected of having occupational asthma due to isocyanates. Of these, 47 subjects fulfilled the criteria to be accepted as an occupational disease case. METHODS: All subjects were studied clinically and gave a blood sample for the phenotyping of their alpha-antitrypsin status and for immunological studies. The subjects were also given a peroral dose of caffeine for the determination of their N-acetylation capacity. Finally, those with an occupational disease were subjected to the methacholine provocation test. RESULTS: Forty-four persons with occupational disease, out of 47, were heterozygous antitrypsin carriers and/or slow acetylators of primary amines. In the bronchial provocation with methacholine, 12 of these subjects had an unaltered response and seven had a mild reaction, 13 a moderate one and 15 a severe reaction. INTERPRETATION: The study confirms the finding that slow N-acetylators are susceptible to asthma from exposure to common diisocyanate monomers at work. The same applies to heterozygous antitrypsin-phenotype carriers. Thus, the use of these markers may reinforce the diagnostic procedure, but they cannot completely replace the immunological tests.

Validation of self-reported smoking status by simultaneous measurement of carbon monoxide and salivary thiocyanate.

OBJECTIVE: The objective of this study was to determine the validity of tobacco questionnaires when using as gold standard either a single biomarker or a combination of two biomarkers. METHODS: The methods were self-reported smoking compared with salivary thiocyanate and expired carbon monoxide in a 1996, population-based, Swiss survey of 552 men and 565 women. RESULTS: Sensitivity of self-reported smoking relative to salivary thiocynate or carbon monoxide alone was low (38.2% for salivary thiocyanate > or = 100 mg/L, 56.4% for salivary thiocyanate > or = 150 mg/L and 62.6% for carbon monoxide > or = 9 ppm). When defining true positive smokers as people with high concentration of both salivary thiocyanate and carbon monoxide, overall, sensitivity was 88.6% and specificity was 87.2%. In women, sensitivity increased from 85 to 89% when removing subjects exposed to passive smoking. When excluding heavy smokers, sensitivity decreased to 63% in men and to 71% in women. Older women had tendency to misreport smoking. CONCLUSIONS: This comparison of questionnaire data with the simultaneous measurement of salivary thiocyanate and expired carbon monoxide indicates that valid responses can be obtained for self-reported, current smoking in population-based surveys. However, the validity of questionnaires can be underestimated if the gold standard (of exposure to tobacco smoke) is either high levels of carbon monoxide or high levels of salivary thiocyanate.

Isopropanol and methylformate exposure in a foundry: exposure data and neurobehavioural measurements.

OBJECTIVES: The aim of this study was to determine the dose-effect relationship between solvent exposure and acute neurobehavioural effects at the worksite. METHODS: In a balanced design, ten workers in a Swiss foundry were monitored for 15 days at ten different times during work. Urine samples were taken in the morning and at the time of examination, and personal exposure to isopropanol and methylformate was measured with active samplers. Neurobehavioural tests such as postural balance (bipedal, bipedal blind, monopedal), simple reaction time and digit span of the Neurobehavioural Evaluation System (NES2) and a combined memory and reaction-time test, the combi-test, were performed. A rating of well-being, and the last consumption of alcohol, caffeine, nicotine and medication were reported. RESULTS: Average environmental concentrations of isopropanol were at 44 ppm ( +/- 16 ppm), and at 36 ppm (+/-21 ppm) for methylformate. Maximum values of personal exposure to isopropanol reached barely the maximal allowable concentration (MAC) value (400 ppm); the methylformate personal exposure of three workers exceeded the MAC value (100 ppm). Urine concentrations of methanol were high (3.1 +/- 2.3 mg/l in the morning, 7.8 +/- 4.9 mg/l after exposure) compared with the results of other studies; concentrations of isopropanol were rather low (0.88 +/- 0.73 mg/l after exposure). CONCLUSIONS: Nevertheless, between personal exposure and biomonitoring, linear correlation was found. Methylformate exposure correlated with methanol and formic acid concentration in the urine, and isopropanol exposure with its concentration in the urine. With the neurobehavioural tests used, no solvent effect in relation to the dose could be determined.

Experimental exposure to methylformate and its neurobehavioral effects.

OBJECTIVES: The aim of the study was to investigate the acute effects of experimental methylformate exposure on the nervous system. METHODS: In an exposure chamber, 20 subjects were exposed to methylformate at 100 ppm [Swiss maximum allowable concentration (MAC)] for 8 h. The same number of subjects with the same ages (between 20 and 30 years), gender and education level (university) were examined by the same procedure as a control group. The subjects did not know if they were exposed or not. Three times (morning, noon, evening) during these 8 h, mood [Profile of Mood States (POMS)], neurobehavioral performance (reaction, Stroop, nonverbal learning, determination, tracking; Wiener Test System), vision (visual acuity, contrast sensitivity, color sensitivity) and postural sway were tested. During an undemanding test (POMS) and a demanding performance task (determination test), pulse, electromyography (EMG) of the forehead and of the neck were recorded. In the morning and evening spirometry [forced vital capacity (FVC), forced one-second expiration volume (FEV), medium expiration flow (MEF) and peak expiration flow (PEF)] and the odor perception threshold were measured. RESULTS: In the evening, in the exposed group, fatigue was significantly increased and the EMG of the forehead during a demanding task showed a different development during exposure. The other tests showed no significant solvent effect, but 16 of 43 test parameters showed a significant effect of time. CONCLUSIONS: The results of this study indicate a possible effect of methylformate exposure on the subjective feeling of fatigue after 8 h exposure at 100 ppm in young and healthy subjects, without measurable impairment of neurobehavioral performance. We assume that a similar effect in normal work, combined with a heavy workload and shift work, can lead to an impairment of productivity, and increase the risk of accidents.

Urinary methanol and formic acid as indicators of occupational exposure to methyl formate.

OBJECTIVE: To evaluate the validity of methanol (MeOH) and formic acid (FA) in urine as biological indicators of methyl formate (MF) exposure in experimental and field situations. METHODS: The subjects were 28 foundrymen and two groups of volunteers (20 control and 20 exposed). Exposure assessment of the workers was performed by personal air and biological monitoring. Methyl formate vapour collected on charcoal tube was analysed by gas chromatography. The concentration of MF in the exposure chamber (volunteer-study) was monitored by two independent methods [flame ionisation detection (FID) and Fourier transformation infra-red detection (FTIR)]. Urinary metabolites (MeOH and FA) were analysed separately by headspace gas chromatography. RESULTS: The volunteers exposed to 100 ppm MF vapour at rest for 8 h excreted 3.62 +/- 1.13 mg MeOH/l (mean +/- SD) at the end of the exposure. This was statistically different (P < 0.001) from pre-exposure MeOH excretion (2.15 +/- 0.80 mg/1), or from that of controls (1.69 +/- 0.48 mg/l). The urinary FA excretion was 32.2 +/- 11.3 mg/g creatinine after the exposure, which was statistically different (P < 0.001) from pre-exposure excretion (18.0 +/- 9.3 mg/g creatinine) or that of controls (13.8 +/- 7.9 mg/g creatinine). In foundrymen, the urinary FA excretion after the 8 h workshift exposure to a time weighted average (TWA) concentration of 2 to 156 ppm MF showed a dose-dependent increase best modelled by a polynomial function. The highest urinary FA concentration was 129 mg/g creatinine. The pre-shift urinary FA of the foundrymen (18.3 +/- 5.6 mg/g creatinine) did not differ from that of controls (13.8 +/- 7.9 mg/g creatinine). The urinary MeOH excretion of the foundrymen after the shift, varied from < 1 to 15.4 mg/l, while the correlation with the preceding MF exposure was poor. The foundrymen excreted more (P = 0.01) FA (2.12 +/- 3.56 mg/g creatinine) after the workshift than experimentally, once-exposed volunteers (0.32 +/- 0.11 mg/g creatinine) at a similar inhaled MF level of 1 ppm). CONCLUSIONS: In spite of its high background level in non-exposed subjects, urinary FA seems to be a useful biomarker of methyl formate exposure. The question remains as to what is the reason for the differences in chronic and acute exposure respectively.

Propylene glycol monomethyl ether (PGME) occupational exposure. 1. Biomonitoring by analysis of PGME in urine.

An analytical method was developed for the determination of free and conjugated PGME-alpha in urine. The method involves a solid-phase extraction on LC-18 columns and a GC/FID analysis after derivatization with trimethysilylimidazole. The assay was linear (least-squares regression coefficient 0.996), specific, reproducible (intraassay variability 10%, interassay variability 10%), and allowed a high level of PGME recovery (more than 90%). The assay was applied to the analysis of urine samples from three workers who were occupationally exposed to PGME to estimate their exposure. The highest value of PGME concentration in urine was 7.78 mg/l. Air concentrations of PGME ranged between 20 and 40 ppm. A statistically significant correlation was found between measurements of external exposure and PGME in urine. An important fraction of PGME in urine was found to be conjugated.

Neurobehavioural effects of experimental isopropanol exposure.

OBJECTIVES: The study investigated the acute effects of isopropanol exposure at the maximum allowable concentration (MAC) level on the performance of neurobehavioural functions. METHODS: In an exposure chamber 20 healthy subjects aged between 21 and 30 years were exposed to isopropanol at a concentration of 400 ppm (Swiss MAC value) for 8 h. A control group of another 20 subjects of the same age range, gender and education as used in a previous study with methylformate were subjected to the same test procedures without exposure. Mood was measured with the profile of mood states (POMS) in the morning, at noon and in the evening. Neurobehavioural performance tests were administered using the Wiener Test System (Wiener reaction test, Stroop, nonverbal learning, Wiener determination test, "Konturtracking" test), and the digit span test of the Neurobehavioural evaluation system (NES2). A test for postural sway was also conducted. During the POMS and the Wiener determination test the electromyography of the forehead and the left neck muscle as well as the pulse were registered. In the morning and evening spirometry (FVC, FEV, MEF and PEF) and odour threshold were measured. RESULTS: Only postural sway in bipedal standing at noon showed stronger deterioration in the exposed than in the control group when compared with the morning values. The evening values of monopedal standing were also more impaired in the exposed than the control group. In the other tests, no solvent effect could be established. CONCLUSIONS: It can be assumed, that, similar to other alcohols, isopropanol affects postural balance. Our results point to such a disturbance, but because it is the only study so far using the MAC value, any conclusions about safety risks would be premature.

Biological monitoring of tetrahydrofuran: contribution of a physiologically based pharmacokinetic model.

A seven-compartment physiologically based pharmacokinetic (PBPK) model was developed to predict biological levels of tetrahydrofuran under various exposure scenarios. Affinities for the tissue were estimated from measurements of liquid-gas partition coefficients for water, olive oil, and blood. Metabolism was assumed to follow a rapid first order reaction. urinary excretion was simulated considering passive reabsorption of tetrahydrofuran in the tubules. The validity of the model was tested by comparison with available experimental and field data. Agreement was satisfactory with all studies available except one, which showed much higher results than expected. The source of this difference could not be identified, but cannot be explained by different exposure conditions, such as duration, concentration, or physical work load. However, it is recommended that this particular study not be used in the establishment of a biological exposure index. Simulation of repeated occupational exposure with the PBPK model allowed the prediction of biological levels that would be reached after repeated exposure at the American Conference of Governmental Industrial Hygienists' threshold limit value, time-weighted average of 200 ppm. For samples taken at the end of the shift, the PBPK model predicts 5.1 ppm for breath, 57 mumol/L (4.1 mg/L) for venous blood, and 100 mumol/L (7.2 mg/L) for urine.

Lead acetate toxicity in vitro: Dependence on the cell composition of the cultures.

It is well known that exposure to low doses of lead causes long-lasting neurobehavioural deficits, but the cellular changes underlying these behavioural changes remain to be elucidated. A protective role of glial cells on neurons through lead sequestration by astrocytes has been proposed. The possible modulation of lead neurotoxicity by neuron-glia interactions was examined in three-dimensional cultures of foetal rat telencephalon. Mixed-brain cell cultures or cultures enriched in either neurons or glial cells were treated for 10 days with lead acetate (10(-6) m), a concentration below the limit of cytotoxicity. Intracellular lead content and cell type-specific enzyme activities were determined. It was found that in enriched cultures neurons stored more lead than glial cells, and each cell type alone stored more lead than in co-culture. Moreover, glial cells but not neurons were more affected by lead in enriched culture than in co-culture. These results show that neuron-glia interactions attenuate the cellular lead uptake and the glial susceptibility to lead, but they do not support the idea of a protective role of astrocytes.

[Voluntary mercury poisoning: biological consequences and psychiatric significance]. / Intoxication volontaire au mercure: conséquences biologiques et signification psychiatrique.

A young patient suffering from schizophrenia had intense headaches and photophobia which were induced by intra-ocular injections of mercury. The clinical diagnosis was established once foreign bodies were visualized on regular X-rays of the patients skull. The mercury intoxication in combination with the secondary irreversible lesions to the eyes necessitated a bilateral enucleation and the use of a chelating treatment with sodium-dimercapto-1-propane sulfate (DMP). Automutilation is a very rare and dramatic complication of schizophrenia. The psychiatric handling and meaning of such dramatic automutilation is discussed in this case report together with a recent review of the toxicologic treatment of mercury intoxication in humans.

Ethnic differences in biological monitoring of several organic solvents. I. Human exposure experiment.

OBJECTIVES: In order to improve the reliability of biological monitoring and the development of biological limit values, ethnic differences for several organic solvents were studied in Orientals and Caucasians. METHODS: Six Caucasian and six Oriental volunteers were exposed to each organic solvent in an exposure chamber for 6 h. Exposure concentration to each organic solvent studied was 50 ppm for perchloroethylene, 50 ppm for styrene and 100 ppm for m-xylene, respectively. Biological monitoring was carried out for the parent organic solvents in exhaled air and in blood, and for the metabolites in urine during and after exposure. RESULTS: Caucasians showed higher concentrations of perchloroethylene in exhaled air than Orientals after exposure. But Caucasians showed lower concentrations of styrene in the exhaled air than Orientals during the second half of exposure and after it. Orientals showed lower concentrations of urinary metabolites than Caucasians except for mandelic acid. There were no statistically significant differences in the concentrations of solvent in blood for all three solvents. CONCLUSIONS: Implications of these differences in biological levels, under identical exposure conditions, are discussed in the context of biological monitoring.

Urinary hexane diamine as an indicator of occupational exposure to hexamethylene diisocyanate.

The occupational exposure of 19 men to hexamethylene diisocyanate (HDI) vapour was monitored during one 8-h shift. It ranged from 0.30 to 97.7 micrograms/m3. This was compared with the urinary output of hexane diamine (HDA) liberated by acid hydrolysis from its conjugates in post-shift samples. The excretion varied from 1.36 to 27.7 micrograms g creatinine, and there was a linear association of HDI air concentration with urinary HDA excretion. The validity of the urinary analysis was confirmed by simultaneous blind analysis in another laboratory. The results had an excellent linear concordance. Thus, it seems that while the gas chromatographic-mass spectrometric detection method requires sophisticated apparatus, the results are very useful to occupational health practices. A biological exposure index limit of 19 micrograms HDA/g creatinine in a post-shift urine specimen is proposed as an occupational limit level of HDI monomer (time-weighted average = 75 micrograms/m3). Most importantly, biological monitoring of HDA is sensitive enough to be used at and below the current allowable exposure limit levels.

Time trend and determinants of blood lead levels in a Swiss population over a transition period (1984-1993) from leaded to unleaded gasoline use.

This study analyzes the trend and determinants of blood lead levels in a Swiss region (population 770,000) over the 10-year period following the introduction of unleaded gasoline in 1985. The consumption of unleaded fuel increased rapidly, accounting in 1988 for 36% and in 1992 for 65% of all gasoline sales. Blood lead levels were measured in three representative samples (n = 1700) of the adult population within the framework of a health examination survey carried out in 1984/1985, 1988/1989, and 1992/1993. The geometric mean blood lead levels were, respectively, 0.59, 0.42, and 0.33 mumole/liter in men, 0.41, 0.29, and 0.25 mumole/liter in women. Similar trends have been observed across all age groups, occupational classes, and categories based on smoking, drinking, and dietary habits. The overexposure of city residents, in comparison to village residents, fades out over the observation period. These findings suggest that the changeover from leaded to unleaded gasoline has been the major cause of the blood lead decline. Wine drinking, cigarette smoking, and age appear to be significant determinants of blood lead for both sexes in all three surveys. In contrast, the association is inverse for milk consumption. The multivariate regression analysis shows that wine drinking remains the most important predictor of blood lead, whereas the influence of age increases with time and overcomes the effect of smoking in the third survey.

[Clinical usefulness of phenotyping of alpha 1-antitrypsin]. / Utilité clinique du phénotypage de l'alpha 1-antitrypsine.

Analysis by isoelectric focusing of serum alpha 1-antitrypsin phenotype of 167 consecutive cases from an occupational health outpatient clinic, from university hospital departments and from private practitioners showed an excessive presence of rare gene alleles S, Z, I and anodal variants compared to their frequencies in blood donors from Lausanne or in the general Swiss population. It seems that analysis has been well grounded in most cases and helps to establish diagnosis in many respiratory diseases, in unexplained liver cirrhosis and even in aortic rupture.

[Occupational exposure to isocyanates and individual susceptibility]. / Exposition professionnelle aux isocyanates et susceptibilité individuelle.

Patients with organic diisocyanate-induced pulmonary disease may be specially susceptible to the toxic effects of agent. Among 11 cases diagnosed in one year, the majority (10/11) were slow acetylators. The same patients were different from the control population in terms of alpha-1-antitrypsin phenotypes. Heterozygous combinations were more frequent than among controls. It seems that the combination of low N-acetylation capacity and a heterozygous alpha-1-antitrypsin predisposes to the disease.

Biological monitoring of occupational exposure to toluene diisocyanate.

The study validated the use of urinary toluene diamine (TDA) in postshift samples as an indicator of preceding 8-h exposure to toluene diisocyanate (TDI). Nine workers exposed in TDI-based polyurethane foam production were studied. Their exposure levels varied in 8-h time-averaged samples from 9.5 to 94 micrograms/m3. The urinary TDA concentrations varied from 6.5 to 31.7 micrograms/g creatinine and they were linearly related to the atmospheric TDI levels. Approximately 20% of TDI is metabolized to diamines but their specificity is remarkable to the extent that by analysis for the 2,4- and 2,6-diamino isomers an idea of the percutaneous absorption may be had.

Detoxification of an aliphatic amine by N-acetylation: experimental and clinical studies.

Incubation of serum serpin (alpha-1-antitrypsin) with 5 mM 1,6-diaminohexane causes significant loss of heterozygotic inhibitor activity. While serpin genes have several alleles, the enzyme complex that acetylates the amine to render it suitable for excretion has primarily two phenotype populations, i.e. slow and fast N-acetylators. This study shows that diacetyl-1,6-diaminohexane does not cause in vitro loss of serpin activity, and that all regional cases (eleven in all) referred to us during one year with a diagnosis of occupational organic diisocyanate asthma were slow acetylators except one who presented a marginally fast reaction type.

Lifestyle and environmental factors as determinants of blood lead levels in a Swiss population.

The determination of blood lead levels was included in a Swiss population survey on cardiovascular risk factors in 1984-1985; 931 men and 843 women aged 25 to 75 years participated in the study. Mean blood lead levels (+/- SD) were 0.63 +/- 0.27 mumole/liter for men and 0.44 +/- 0.19 mumole/liter for women, respectively, with a slight increase with age for both sexes. These values are below the maximum level recommended by the Commission of the European Community in 1977; 18 cases were found with blood lead higher than 1.5 mumole/liter and in six of these, a professional exposure was suspected. Smoking habits, drinking habits, and consumption of dairy products were selected as lifestyle descriptors and educational level, occupational category, and size of the community as sociodemographic indicators. Smoking and alcohol consumption show a direct association with blood lead, consuming dairy products an inverse one. Occupation and level of education are significantly related to blood lead only for men, blue-collar workers and less-educated men being more exposed. A higher blood lead level in cities was only found for women presumably because they stay at home more often than men and are therefore more sensitive to local exposure. In a multiple stepwise logistic regression, the lifestyle indicators showed a consistently stronger effect on blood lead than sociodemographic indicators. For men, smoking has an effect on blood lead for blue-collar workers much stronger than that for nonindustrial employees and may compound in some way the professional exposure to lead. This stresses the fact that interactions between lifestyle and environmental factors on blood lead are significant, complex, and need further investigation.