Biomonitoring of genotoxic risks and haematological changes in workers in rubber industry

Several substances used in rubber processing are known to be of genotoxins and haematotoxins. Such as benzene, phenols, amines amides, naphthalene and benzo(a)pyrene. Twenty-five exposed workers from a rubber factory were compared with twenty-five controls working as administrative staff in the same factory. An elevated level of urinary thioether (mercapturic acid derivatives) a significant elevation in the level of DNA SSB was found among exposed workers in comparison with control group (p < 0.01). A significant increase in the absolute numbers of peripheral leukocytes and in erthrocyte mean cell volume was observed among exposed workers in comparison with controls (p < 0.01), while a significant decrease in the percentage of lymphocytes and eosinophils was found among exposed workers in comparison with controls. However, the percentage of monocytes was not altered. The reported results have justified the use of genotoxic biomarkers in assessing levels of genotoxic exposure in human population groups and as a screening biomarkers in periodic medical examination as a protective measure.     

Sister chromatid exchanges and DNA repair capability in sanitary workers exposed to ethylene oxide: evaluation of the dose-effect relationship

Determination of ethylene oxide (EtO) in the working environment and induction of sister chromatid exchanges (SCE) and unscheduled DNA synthesis (UDS) in peripheral lymphocytes of 10 exposed sanitary workers and 10 control subjects matched for sex, age, and smoking habits are reported. The relationship between the external dose of EtO and the frequency of SCE was determined in the above group and in a group of 41 sanitary workers previously studied. The 10 newly examined workers were exposed to EtO concentrations (1.84 ppm as time-weighted average) intermediate between the high (10.7 ppm) and low (0.35 ppm) levels of exposure of the two previously examined groups (19 and 22 workers, respectively). A statistically significant (p less than 0.002) increase of SCE frequency was observed between the present control and exposed groups. The inducibility of unscheduled DNA synthesis by gamma rays was lower in the lymphocytes of the exposed workers than in controls, but the difference was not statistically significant. A significant relationship between the frequency of SCE and the level of EtO exposure for the three exposed groups was demonstrated by two different statistical methods. It is suggested that the present Italian threshold limit value for EtO (3 ppm) may not protect the exposed workers against possible genotoxic effects and that even a chronic exposure to 1 ppm may not be devoid of genotoxic risk.     

Low level occupational exposure to styrene: its effects on DNA damage and DNA repair

The present study aimed to evaluate the effects of styrene exposure at levels below the recommended standards of the Threshold Limit Value (TLV-TWA(8)) of 20 ppm (ACGIH, 2004) in reinforced-fiberglass plastics workers. Study subjects comprised 50 exposed workers and 40 control subjects. The exposed workers were stratified by styrene exposure levels, i.e. group I (<10 ppm, <42.20 mg/m(3)), group II (10-20 ppm, 42.20-84.40 mg/m(3)), and group III (>20 ppm, >84.40 mg/m(3)). The mean styrene exposure levels of exposed workers were significantly higher than those of the control workers. Biomarkers of exposure to styrene, including blood styrene and the urinary metabolites, mandelic acid (MA) and phenylglyoxylic acid (PGA), were significantly increased with increasing levels of styrene exposure, but were not detected in the control group. DNA damage, such as DNA strand breaks, 8-hydroxydeoxyguanosine (8-OHdG), and DNA repair capacity, were used as biomarkers of early biological effects. DNA strand breaks and 8-OHdG/10(5)dG levels in peripheral leukocytes of exposed groups were significantly higher compared to the control group (P<0.05). In addition, DNA repair capacity, determined by the cytogenetic challenge assay, was lower in all exposed groups when compared to the control group (P<0.05). The expression of CYP2E1, which is involved in styrene metabolism, in all styrene exposed groups, was higher than that of the control group at a statistically significant level (P<0.05). Levels of expression of the DNA repair genes hOGG1 and XRCC1 were significantly higher in all exposed groups than in the control group (P<0.05). In addition to styrene contamination in ambient air, a trace amount of benzene was also found but, the correlation between benzene exposure and DNA damage or DNA repair capacity was not statistically significant. The results obtained from this study indicate an increase in genotoxic effects and thus health risk from occupational styrene exposure, even at levels below the recommended TLV-TWA(8) of 20 ppm.     

No increased DNA damage in peripheral lymphocytes of sewage workers as evaluated by alkaline single cell gel electrophoresis.

OBJECTIVES: To study whether sewage workers are exposed to genotoxic substances. An increased risk of cancers among sewage workers has been noted. If this increased risk is due to an exposure to genotoxic agents, primarily DNA damage could be used as a biological marker of exposure. METHODS: In a cross sectional study, DNA damage in peripheral lymphocytes from 35 sewage workers and 30 controls was compared with alkaline single cell gel electrophoresis, a technique for detecting single strand breaks and alkali labile sites in DNA. The controls were selected from among municipal workers matched for age and smoking habit. Information about occupational exposures and possible confounders was collected by means of a questionnaire. RESULTS: No increase in DNA damage was found among the sewage workers when compared with the unexposed controls. CONCLUSIONS: The failure to detect increased damage to DNA in peripheral lymphocytes by alkaline single cell gel electrophoresis suggests that the sewage workers studied here were not exposed to genotoxic agents to a greater extent than other municipal workers. It may be, however, that the lymphocyte is not the appropriate target cell to study, or that sewage workers are exposed to carcinogens which do not damage the genetic material.     

Low level benzene exposure in Sweden: effect on blood elements and body burden of benzene

Measurements for benzene exposure were performed for different work places. In addition, breath benzene concentrations were measured in different occupations in order to establish toxico-kinetics of benzene in man; chromosomal aberrations in lymphocytes of exposed workers were also examined. Smoking appears to result in a large increase in benzene concentration in exhaled breath. The smoke from one cigarette contains 60-80 micrograms of benzene. It was found that exposure levels of 10 ppm are rather uncommon among workers handling gasoline or gasoline equipment. It was concluded that the gasoline load of road tankers cannot be responsible for chromosome changes of the driver, as milk truck drivers showed the same changes. These results did not prove that benzene was the cause of the observed changes. Smoking is the confounding factor, with a potency of at least the same order of magnitude as benzene. In addition, our present knowledge about mechanisms of benzene is not sufficiently developed to permit quantitative conclusions as to the human health risks.     

Methanol in urine as a biological indicator of occupational exposure to methanol vapor

Summary The exposure-excretion relationship and possible health effects of exposure to methanol vapor were studied in 33 exposed workers during the second half of 2 working weeks. Urinary methanol concentrations were also determined in 91 nonexposed subjects. The geometric mean value for methanol in urine samples from the latter was < 2 mg/1 (95% upper limit of normal, < 5 mg/l) when log-normal distribution was assumed. Among the exposed workers, the methanol level in urine samples collected prior to the work shift exceeded the 95% upper limit of normal. The time-weighted average intensity of exposure to methanol vapor was measured using personal sampling devices (in which water severed as an absorbent) in 48 cases of methanol exposure (i.e., 2 of the 33 exposed workers failed to provide urine samples, whereas 17 subjects were examined twice). Methanol concentrations in urine were determined in samples collected at the end of the shift from the 48 exposed cases as well as from 30 nonexposed controls. There was a significant correlation between the exposure to methanol vapor at concentrations of up to 5,500 ppm and the levels of methanol measured in the shift-end urine samples. The calculation indicated that a mean level of 42 mg methanol/l urine (95% confidence range, 26–60 mg/kg) was excreted in the shift-end urine sample following 8 h exposure to methanol at 200 ppm (the current occupational exposure limit). Dimmed vision and nasal irritation were among the most frequent symptoms complained during work. Three cases showing clinical signs of borderline significance were identified.     

Hematotoxocity among Chinese workers heavily exposed to benzene

Benzene is a well-established hematotoxin. However, reports of its effects on specific blood cells have been somewhat inconsistent and the relative toxicity of benzene metabolites on peripheral blood cells in humans has not been evaluated. We compared hematologic outcomes in a cross-sectional study of 44 workers heavily exposed to benzene (median: 31 parts permillion [ppm] as an 8-hr time-weighted average [TWA] and 44 age and gender-matched unexposed controls from Shanghai, China. All hematologic parameters (total white blood cells [WBC], absolute lymphocyte count, platelets, red blood cells, and hematocrit) were decreased among exposed workers compared to controls, with the exception of the red blood cell mean corpuscular volume (MCV), which has higher among exposed subjects. In a subgroup of workers who were not exposed to more than 31 ppm benzene on any of 5 sampling days (n = 11, median 8 hr TWA = 7.6 ppm, range = 1–20 ppm), only the absolute lymphocyte count was significantly different between exposed workers (mean [sd] 1.6 [0.4] x 10³ μL) and controls (1.9 [0.4] x 10³ μL, p = 0.03). Among exposed subjects, a dose-response relationship with various measures of current benzene exposure (i.e., personal air monitoring, benzene metabolites in urine) was present only for the total WBC count, the absolute lymphocyte count, and the MCV. Correlations between benzene metabolites and hematologic parameters were generally similar, although hydroquinone was somewhat more strongly associated with a decrease in the absolute lymphocyte count, and catechol was more strongly associated with an increase in MCV. Morphologic review of peripheral blood slides demonstrated an excess of red blood cell abnormalities (i.e., stomatocytes and target cells) only in the most heavily exposed workers, with no differences in granulocyte, lymphocyte, or platelet morphology noted. Although benzene can affect all the major peripheral blood elements, our results support the use of the absolute lymphocyte count as the most sensitive indicator of benzene-induced hematotoxicity. © 1995 Wiley-Liss, Inc.     

Urinary phenylmercapturic acid as a marker of occupational exposure to benzene

A hand-saving HPLC method to measure urinary phenylmercapturic acid (PMA) was developed which allows about 35 PMA determinations per day. The method involves conversion of pre-PMA to PMA by the addition of sulfuric acid to a urine sample, extraction into an ether-methanol mixture followed by condensation under a nitrogen stream. The condensate was introduced to a ODS-3 column in a HPLC system, and PMA in the column was eluted into a mobile phase of acetonitrile: methanol: perchloric acid: water. The elution of PMA was monitored at 205 nm. One determination will be completed in 40 min. The method was applied to analysis of end-of-shift urine samples from 152 workers exposed up to 210 ppm benzene, 66 workers exposed to a mixture of benzene (up to 116 ppm) and toluene + xylenes (up to 118 ppm), and 131 non-exposed controls of both sexes. A linear regression was established between time-weighted average intensity of exposure to benzene and urinary PMA. From the regression, it was calculated that urinary PMA level will be about 6.4 mg/l after 8-hour exposure to benzene at 100 ppm, and that PMA in urine accounted for about 0.1% of benzene absorbed. No effects of sex, age, and smoking habit of individuals were detected, and the effect of co-exposure to toluene + xylenes at the levels comparable to that of benzene was essentially nil, which indicates an advantage of PMA as a benzene exposure marker over monoto tri-phenolic metabolites or t,t-muconic acid.     

Benzene exposure monitoring of Tunisian workers

To monitor benzene exposure and to check reliability of urinary trans,trans-Muconic Acid (t,t-MA) as a bio-marker of benzene exposure in local conditions, a study was conducted on 30 Tunisian exposed workers (20 tanker fillers and 10 filling station attendants). The analyses were carried out on environmental air and urinary t,t-MA before (t,t-MAA) and at the end of work shift (t,t-MAB). 20 nonoccupationally exposed subjects were also investigated. The average value of environmental benzene concentration was 0.17 ppm. The differences between t,t-MAA and t,t-MAB concentrations and between t,t-MAB and t,t-MA measured in controls (t,t-MAC) were both significant (p < 0.001). Benzene air concentrations were well correlated with t,t-MAB: R = 0.76. In the nonexposed group, average t,t-MA concentrations is significantly higher among smokers than nonsmokers (P < 0.02). Analysis of urinary t,t-MA offers a relatively simple and suitable method for benzene exposure monitoring.     

单细胞凝胶电泳法检测苯作业工人淋巴细胞DNA损伤

目的 用碱性单细胞凝胶电泳技术检测苯作业工人外周血淋巴细胞DNA损伤,研究苯的遗传毒性。方法 采用碱性单细胞凝胶电泳技术。将接苯工人按累积浓度、历史平均浓度和测定当时8h时间加权平均浓度（8hTWA）分组。观察指标包括DNA断裂分级（将DNA断裂损伤细胞按其损伤程度分级）及DNA彗星尾长（彗头末端到彗尾的长度）。结果 接苯工人DNA断裂程度及DNA彗星尾长[Ig(尾长＋1）]两个参数,接苯组按累积浓度、历史平均浓度和8hTWA浓度计算,均明显高于对照组,差异有显著性（P＜0．01）,并有明显的剂量－反应关系。结论 彗星试验能够快速,敏感地检测苯引起的人类淋巴细胞DNA损伤,提示对于检测环境致癌物和致突变物可能是一有用工具。     

Study of some immunological parameters in workers occupationally exposed to benzene

Objective: The aim of the study was to investigate the immunotoxicity of benzene exposure, to establish the correlation between the exposure biomarkers and some immunological parameters, and to assess the possible influence of confounding factors on the results of immunological assay applicable in routine medical surveillance of benzene-exposed workers. Methods: Forty-nine female workers in the shoemaking industry who were exposed to solvent mixtures and 27 nonexposed controls were examined. Workers were exposed to benzene concentrations of up to 15 ppm, and to toluene of up to 50 ppm. Results: Significant differences in the levels of benzene and toluene in blood and phenols in post-shift urine between the exposed and the control group confirmed solvent exposure. The number of B-lymphocytes (P=0.01) was lower in the shoe workers than in the controls. Significant correlation was found between the level of immunoglobulin G and benzene in the work atmosphere, while confounding factors had no impact on immunological values. Conclusion: According to these results, exposure to benzene concentration lower than 15 ppm can induce depression of the circulating B-lymphocyte level and therefore this fact could be used to develop a promising method for health surveillance of benzene-exposed workers. However, considerably more effort in the research on benzene immunotoxicity, especially in the search for suitable health surveillance methods, is still required. Received: 15 July 1999 / Accepted: 22 January 2000     

Evaluation to the exposure to polycyclic aromatic hydrocarbons, benzene, toluene and xylenes in workers in a power plant fueled with heavy oil]

Occupational exposure to polycyclic aromatic hydrocarbons (PAHs) has been demonstrated in many industrial sectors. However, up to date there are few studies in the literature on PAH exposure in thermoelectric power plants. The study was aimed at the evaluation of personal exposure to PAHs in workers of a power plant fueled with heavy oil. Exposure to polycyclic aromatic hydrocarbons (PAHs) and to benzene, toluene and xylenes (BTX) was evaluated on power plant workers exposed to heavy fuel oil; the control group consisted of office workers of the same power plant. Altogether 39 subjects were studied, for a total of 84 days of monitoring. Personal environmental exposure, cutaneous exposure and urinary concentrations of 1-hydroxypyrene (1-OHP), trans,trans-muconic acid (TTMA) and nicotine were measured. Personal environmental exposure to PAHs was very low; only maintenance workers showed exposure to total carcinogenic PAHs significantly higher than controls (median levels 3.05 and 0.88 ng/m3 respectively). All workers showed very low levels of dermal exposure to PAHs (less than 1 ng). The median 1-OHP urinary concentrations were 0.16, 0.11 and 0.08 mumol/mol creatinine in the groups of exposed workers and 0.08 mumol/mol creatinine in the control group. Neither the exposed workers nor the controls showed a significant increase in 1-OHP urinary concentrations across the shift. The regression analysis showed a significant effect of cigarette smoking on urinary 1-OHP, while no association was observed between occupational exposure and diet. Personal environmental exposure levels to BTX were very low. TTMA urinary concentrations of the exposed subjects were similar to those of the controls. No significant increase in the TTMA urinary concentrations was observed across the shift and, as expected, smokers showed higher values than non-smokers. The study did not show a measurable intake of PAHs and BTX in power plant workers that could be ascribed to occupational exposure, thus confirming the efficacy of the protective measures in force.     

Albumin adducts of electrophilic benzene metabolites in benzene-exposed and control workers

BACKGROUND: Metabolism of benzene produces reactive electrophiles, including benzene oxide (BO), 1,4-benzoquinone (1,4-BQ), and 1,2-benzoquinone (1,2-BQ), that are capable of reacting with blood proteins to produce adducts. OBJECTIVES: The main purpose of this study was to characterize relationships between levels of albumin adducts of these electrophiles in blood and the corresponding benzene exposures in benzene-exposed and control workers, after adjusting for important covariates. Because second blood samples were obtained from a subset of exposed workers, we also desired to estimate within-person and between-person variance components for the three adducts. METHODS: We measured albumin adducts and benzene exposures in 250 benzene-exposed workers (exposure range, 0.26-54.5 ppm) and 140 control workers (exposure range < 0.01-0.53 ppm) from Tianjin, China. Separate multiple linear regression models were fitted to the logged adduct levels for workers exposed to benzene < 1 ppm and > or =1 ppm. Mixed-effects models were used to estimate within-person and between-person variance components of adduct levels. RESULTS: We observed nonlinear (hockey-stick shaped) exposure-adduct relationships in log-scale, with inflection points between about 0.5 and 5 ppm. These inflection points represent air concentrations at which benzene contributed marginally to background adducts derived from smoking and from dietary and endogenous sources. Adduct levels were significantly affected by the blood-collection medium (serum or plasma containing either heparin or EDTA), smoking, age, and body mass index. When model predictions of adduct levels were plotted versus benzene exposure > or =1 ppm, we observed marked downward concavity, particularly for adducts of the benzoquinones. The between-person variance component of adduct levels increased in the order 1,2-BQ < 1,4-BQ < BO, whereas the within-person variance components of the three adducts followed the reverse order. CONCLUSIONS: Although albumin adducts of BO and the benzoquinones reflect exposures to benzene > or = 1 ppm, they would not be useful biomarkers of exposure at ambient levels of benzene, which tend to be < 0.01 ppm, or in those working populations where exposures are consistently < 1 ppm. The concavity of exposure-adduct relationships is consistent with saturable metabolism of benzene at air concentrations > 1 ppm. The surprisingly large effect of the blood-collection medium on adduct levels, particularly those of the benzoquinones, should be further investigated.     

Evaluation of sister chromatid exchange and chromosomal aberration frequencies in peripheral blood lymphocytes of gasoline station attendants

Petroleum derivatives constitute a complex mixture of chemicals which contain well-known genotoxicants, such as benzene. Thus, chronic occupational exposure to such derivatives may be considered to possess genotoxic risk. In the present study, frequencies of sister chromatid exchange (SCE); aberrant cells, including numerical and structural chromosomal aberrations; and chromosome aberrations were investigated in peripheral blood lymphocytes from 30 exposed workers (15 smokers and 15 nonsmokers) and 30 controls (15 smokers and 15 nonsmokers). The exposed subjects were employed at 12 different petrol pumping stations in the city of Mersin, Turkey. Urinary phenol levels of exposed workers were found to be significantly higher than those of control subjects. Benzene exposure and cigarette smoking decrease the replication index and mitotic index. There is an interaction between benzene exposure and cigarette smoking for replication index and mitotic index. There is no interaction between cigarette smoking and benzene exposure for chromosomal aberrations. The results indicate that there are significant differences in SCE values in the exposed workers compared to the control individuals (P < 0.01), but there is no difference between smokers and nonsmokers for SCE frequency (P > 0.05). SCE frequency is higher in smokers than in nonsmokers.     

Sister chromatid exchanges in peripheral lymphocytes of workers exposed to benzene,trichloroethylene, or tetrachloroethylene,with reference to smoking habits

Summary The frequencies of sister chromatid exchanges (SCE) were studied in peripheral lymphocytes from four groups of solvent workers, i.e. 36 nonsmoking women exposed to benzene at about 50 ppm on the average, 38 men and women (male smokers and nonsmokers, and female nonsmokers) exposed to trichloroethylene (TRI) at 7 ppm, 27 men and women (both smokers and nonsmokers) with tetrachloroethylene (TETRA) exposure, and 19 workers (both smokers and nonsmokers in men, and nonsmokers in women) exposed to a mixture of TRI (at 8 ppm) and TETRA (at 17 ppm) (TRI + TETRA). The results were compared with the findings in control subjects matched by age, sex, smoking habits and place of residence. No significant increase in SCE frequencies was observed in association with exposure to benzene, TRI, TETRA or TRI + TETRA. The SCE frequency was, however, significantly higher in the TRI-, TETRA-or TRI + TETRA-exposed smoking men than in the concurrent nonsmoking controls of the same sex. Possible synergism between solvent exposure and smoking is discussed.     

Excretion of 1,2,4-benzenetriol in the urine of workers exposed to benzene

Urine samples were collected from 152 workers (64 men, 88 women) who had been exposed to benzene, 53 workers (men only) exposed to a mixture of benzene and toluene, and 213 non-exposed controls (113 men, 100 women). The samples were analysed for 1,2,4-benzentriol (a minor metabolite of benzene) by high performance liquid chromatography. The time weighted average solvent exposure of each worker was monitored by diffusive sampling technique. The urinary concentration of 1,2,4-benzentriol related linearly to the intensity of exposure to benzene both in men and women among workers exposed to benzene, and was suppressed by toluene co-exposure among male workers exposed to a mixture of benzene and toluene. A cross sectional balance study in men at the end of the shift of a workday showed that only 0.47% of benzene absorbed will be excreted into urine as 1,2,4-benzenetriol, in close agreement with previous results in rabbits fed benzene. The concentration of 1,2,4-benzenetriol in urine was more closely related to the concentration of quinol than that of catechol. The fact that phenol and quinol, but not catechol, are precursors of 1,2,4-benzentriol in urine was further confirmed by the intraperitoneal injection of the three phenolic compounds to rats followed by urine analysis for 1,2,4-benzenetriol.     

职业性苯暴露反-反式粘糠酸生物接触限值研究

目的研究职业性苯暴露反．反式粘糠酸（t,t—MA）生物接触限值。方法实验室建立生产环境空气中苯浓度的气相色谱检测方法及作业工人尿中t,t—MA含量的高效液相色谱检测方法,并通过检测苯暴露现场工人8h苯暴露水平及班前、班后尿中t,t．MA含量,研究其相关性。结果苯暴露者班前、班后尿中t,t—MA含量与其苯暴露水平有明显的相关关系。班前y（mg／gCr）=0．924＋0．108X（me／m^3）,r=0．62,P〈0．01;班后y（mg／gCr）=2．103＋0．177X（mg／m^3）,r=0．791,P〈0．01。结论根据我国作业场所空气中苯的国家卫生标准,按回归方程推导出职业接触苯生物接触限值,推荐职业暴露苯的生物接触限值为工作班班后尿t,t．MA含量为3．0mg／gCr,下一班班前尿t,t．MA含量为1．5mg／gGr。     

Excretion of 1,2,4-benzenetriol in the urine of workers exposed to benzene.

Urine samples were collected from 152 workers (64 men, 88 women) who had been exposed to benzene, 53 workers (men only) exposed to a mixture of benzene and toluene, and 213 non-exposed controls (113 men, 100 women). The samples were analysed for 1,2,4-benzentriol (a minor metabolite of benzene) by high performance liquid chromatography. The time weighted average solvent exposure of each worker was monitored by diffusive sampling technique. The urinary concentration of 1,2,4-benzentriol related linearly to the intensity of exposure to benzene both in men and women among workers exposed to benzene, and was suppressed by toluene co-exposure among male workers exposed to a mixture of benzene and toluene. A cross sectional balance study in men at the end of the shift of a workday showed that only 0.47% of benzene absorbed will be excreted into urine as 1,2,4-benzenetriol, in close agreement with previous results in rabbits fed benzene. The concentration of 1,2,4-benzenetriol in urine was more closely related to the concentration of quinol than that of catechol. The fact that phenol and quinol, but not catechol, are precursors of 1,2,4-benzentriol in urine was further confirmed by the intraperitoneal injection of the three phenolic compounds to rats followed by urine analysis for 1,2,4-benzenetriol.     

Determination of low level exposure to volatile aromatic hydrocarbons and genotoxic effects in workers at a styrene plant.

OBJECTIVES--Low exposures to volatile aromatic hydrocarbons and cytogenetic effects in peripheral white blood cells were determined in 25 healthy workers employed in different areas of a styrene production plant in the former German Democratic Republic. The results were compared with 25 healthy unexposed controls (matched for age and sex) employed in the same company. METHODS--The concentrations of aromatic hydrocarbons determined from active air sampling in all areas of the factory (styrene: 73-3540 micrograms/m3 (< 0.01-0.83 ppm); ethylbenzene 365-2340 micrograms/m3 (0.08-0.53 ppm); benzene 73-3540 micrograms/m3 ( < 0.02-1.11 ppm); toluene 54-2960 micrograms/m3 (0.01-0.78 ppm); xylenes 12-94 micrograms/m3 ( < 0.01-0.02 ppm)) were considerably lower than in the pump house ( > 4000 micrograms/m3 styrene, ethylbenzene, benzene, and toluene; > 500 micrograms/m3 xylenes), which was only intermittently occupied for short periods. Passive personal monitoring, biomonitoring of exhaled air and metabolites (mandelic, phenylglyoxylic, trans, trans-muconic, hippuric, o-, m- and p-methylhippuric acids, and phenol) in urine samples collected before and after an eight hour working shift was used to assess individual exposure. Questionnaires and examination of company records showed that the historical exposure was far higher than that measured. Genotoxic monitoring was performed by nuclease P1-enhanced 32P-postlabelling of DNA adducts in peripheral blood monocytes, and DNA single strand breaks, sister chromatid exchange, and micronuclei in lymphocytes. The content of kinetochores in the micronuclei was determined by immunofluorescence with specific antibodies from the serum of CREST patients. RESULTS--No genotoxic effects related to exposure were detected by DNA adducts or DNA single strand breaks and sister chromatid exchange. The only effect related to exposure was an increase in kinetochore positive micronuclei in peripheral lymphocytes; the frequency of total micronuclei in peripheral lymphocytes did not change. Smoking was confirmed by measurement of plasma cotinine, and no confounding effect was found on any of the cytogenetic variables. CONCLUSIONS--Low occupational exposure to styrene, benzene, and ethylbenzene did not induce alterations of genotoxicological variables except kinetochore positive micronuclei. This is the first reported use of the CREST technique for an in vivo study in occupational toxicology, which thus could serve as a valuable and sensitive technique for toxicogenic monitoring.