[Simultaneous determination for metabolites of benzene compounds in urine by high performance liquid chromatography].

Objective: To describe for the determination of contents of metabolites of benzene compounds in urine sample by high performance liquid chromatography. Methods: After acidification with hydrochloric acid, metabolites in urine were first extracted by acetonitrile and isopropanol (V∶V, 9∶1) with excessive sodium chloride, then gradient separated on a C18 column and then determined by DAD detector. Results: There were good linear relationship between peak areas and injection quality in range of 2.00-100 mg/L (r>0.999). The detection limit and quantitative limit of this method were 4.15-70.7 µg/L and 13.8-235 µg/L respectively. The precision for the analysis of urine was1.78%-8.23% (n =6). The average recovery of metabolites was 85.4%-105.5% at thee spiked levels in the range of 2.00-100 mg/L. Conclusion: The accuracy and reproducibility obtained make this method useful for the biological monitoring of occupational exposure to toluene, xylene, styrene and ethylbenzene.

Direct methyl esterification with 2,2-dimethoxypropane for the simultaneous determination of urinary metabolites of toluene, xylene, styrene, and ethylbenzene by gas chromatography-mass spectrometry.

OBJECTIVES: The purpose of this study was to develop a simple and accurate gas chromatography-mass spectrometry (GC-MS) method for simultaneous determination of four urinary metabolites from four organic solvents, that is, hippuric acid (HA) from toluene, methylhippuric acid (MHA) from xylene, and mandelic acid (MA) and phenylglyoxylic acid (PGA) from styrene or ethylbenzene for biological monitoring. METHODS: The four metabolites were directly methyl-esterified with 2,2-dimethoxypropane and analyzed using GC-MS. The proposed method was validated according to the US Food and Drug Administration guidance. The accuracy of the proposed method was confirmed by analyzing a ClinChek® -Control for occupational medicine (RECIPE Chemicals +Instruments GmbH). RESULTS: Calibration curves showed linearity in the concentration range of 10-1000 mg/L for each metabolite, with correlation coefficients >0.999. For each metabolite, the limits of detection and quantification were 3 mg/L and 10 mg/L, respectively. The recovery was 93%-117%, intraday accuracy, expressed as the deviation from the nominal value, was 92.7%-103.0%, and intraday precision, expressed as the relative standard deviation (RSD), was 1.3%-4.7%. Interday accuracy and precision were 93.4%-104.0% and 1.2%-9.5%, respectively. The analytical values of ClinChek obtained using the proposed method were sufficiently accurate. CONCLUSIONS: The proposed method is a simple and accurate which is suitable for routine analyses that could be used for biological monitoring of occupational exposure to four organic solvents.

Ethylbenzene and styrene exposure in the United States based on urinary mandelic acid and phenylglyoxylic acid: NHANES 2005-2006 and 2011-2012.

Ethylbenzene and styrene are air toxicants with widespread nonoccupational exposure sources, including tobacco smoke and diet. Ethylbenzene and styrene (EB/S) exposure was quantified from their common metabolites measured in spot urine samples obtained from participants (≥6 years old) in the 2005-2006 and 2011-2012 cycles of the National Health and Nutrition Examination Survey (NHANES; N = 4690). EB/S metabolites mandelic acid (MA) and phenylglyoxylic acid (PGA) were measured using ultra-high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). MA and PGA were detected in 98.9% and 90.6% of tested urine specimens, respectively. Exclusive smokers had 2-fold and 1.6-fold higher median urinary MA and PGA, respectively, compared with non-users. Sampleweighted regression analysis among exclusive smokers showed that smoking 0.5 pack cigarettes per day significantly increased MA (+97.9 µg/L) and PGA (+69.3 µg/L), controlling for potential confounders. In comparison, exposure from the median daily dietary intake of grain products increased MA by 1.95 µg/L and was not associated with statistically significant changes in urinary PGA levels. Conversely, consuming vegetables and fruit was associated with decreased MA and PGA. These results confirm tobacco smoke as a major source of ethylbenzene and styrene exposure for the general U.S. population.

Further examination of log Pow-based procedures to estimate biological occupational exposure limits.

OBJECTIVES: To test the reliability of the procedures (described in a previous article) for estimation of biological occupational exposure limits (BOELs). METHODS: Data on four organic solvents (styrene, ethyl benzene, isopropyl alcohol and tetrachloroethylene) were obtained from recent publications and added to previously cited data for 10 organic solvents. Regression analysis was used for statistical evaluation. RESULTS AND DISCUSSION: The previously reported results obtained using 10 solvents were reproduced by the analysis with 14 solvents. Repeated randomized division of the 14 sets into two subgroups of equal size followed by statistical comparisons did not show a significant difference between two regression lines. This reproducibility suggests that the procedures used to estimate BOELs may be applicable across many solvents, and this may be of particular benefit for protecting the health of workers who work with skin-penetrating solvents.

Biomonitoring of styrene occupational exposures: Biomarkers and determinants.

INTRODUCTION: High styrene exposures are still experienced in various occupational settings, requesting regular exposure assessments. The aims of this study were to study occupational exposures in various industrial sectors and to determine factors influencing styrene urinary metabolites levels. METHODS: Biomonitoring was conducted in 141 workers from fiberglass-reinforced plastic (FRP) manufacture, thermoplastic polymers production, vehicle repair shops and cured-in-place pipe lining (CIPP). Urinary styrene (StyU) as well as Mandelic (MA) / Phenyglyoxylic Acids (PGA) were quantified at the beginning and at the end of week, and multivariate linear regression models were used. RESULTS: StyU levels revealed very low, rarely exceeding 3 µg.L-1. Highest concentrations of MA + PGA were observed in FRP sector, with levels reaching up to 1100 mg.g-1 of creatinine. Factors influencing end-of-week MA + PGA concentrations were levels at the beginning of week, open molding processes, proximity to the emission source, respiratory protection, styrene content in raw materials. Elevated levels were also observed during CIPP process, whereas thermoplastic injection and vehicle repair shop workers exhibited much lower exposures. CONCLUSIONS: Intervention on process (decreasing styrene proportion, using closed molding), protective equipment (local exhaust ventilation, respiratory protection) and individual practices (stringent safety rules) are expected to decrease occupational exposures. Urinary MA + PGA remain the most appropriate biomarkers for occupational biomonitoring.

Ion-pair-based hollow-fiber liquid-phase microextraction combined with high-performance liquid chromatography for the simultaneous determination of urinary benzene, toluene, and styrene metabolites.

In the current study, a novel technique for extraction and determination of trans,trans-muconic acid, hippuric acid, and mandelic acid was developed by means of ion-pair-based hollow fiber liquid-phase microextraction in the three-phase mode. Important factors affecting the extraction efficiency of the method were investigated and optimized. These metabolites were extracted from 10 mL of the source phase into a supported liquid membrane containing 1-octanol and 10% w/v of Aliquat 336 as the ionic carrier followed by high-performance liquid chromatography analysis. The organic phase immobilized in the pores of a hollow fiber was back-extracted into 24 µL of a solution containing 3.0 mol/L sodium chloride placed inside the lumen of the fiber. A very high preconcentration of 212- to 440-fold, limit of detection of 0.1-7 µg/L, and relative recovery of 87-95% were obtained under the optimized conditions of this method. The relative standard deviation values for within-day and between-day precisions were calculated at 2.9-8.5 and 4.3-11.2%, respectively. The method was successfully applied to urine samples from volunteers at different work environments. The results demonstrated that the method can be used as a sensitive and effective technique for the determination of the metabolites in urine.

Styrene-associated health outcomes at a windblade manufacturing plant.

BACKGROUND: Health risks of using styrene to manufacture windblades for the green energy sector are unknown. METHODS: Using data collected from 355 (73%) current windblade workers and regression analysis, we investigated associations between health outcomes and styrene exposure estimates derived from urinary styrene metabolites. RESULTS: The median current styrene exposure was 53.6 mg/g creatinine (interquartile range: 19.5-94.4). Color blindness in men and women (standardized morbidity ratios 2.3 and 16.6, respectively) was not associated with exposure estimates, but was the type previously reported with styrene. Visual contrast sensitivity decreased and chest tightness increased (odds ratio 2.9) with increasing current exposure. Decreases in spirometric parameters and FeNO, and increases in the odds of wheeze and asthma-like symptoms (odds ratios 1.3 and 1.2, respectively) occurred with increasing cumulative exposure. CONCLUSIONS: Despite styrene exposures below the recommended 400 mg/g creatinine, visual and respiratory effects indicate the need for additional preventative measures in this industry.

Biomonitoring for Exposure Assessment to Styrene in the Fibreglass Reinforced Plastic Industry: Determinants and Interferents.

Fifty-eight workers exposed to styrene were monitored in four fibreglass reinforced plastic industries of Central Italy. The aim of the study was to explore the factors that can influence the levels of styrene exposure biomarkers of the workers and the aspects that might interfere with the exposure assessment measures, such as the co-exposure to acetone. Personal monitoring of professional exposure to airborne styrene and acetone was carried out by Radiello samplers and GC/MS analysis. Biological monitoring was performed by the determination of urinary metabolites, mandelic (MA), and phenylglyoxylic (PGA) acids with HPLC/MS/MS and unmetabolized styrene in saliva and venous blood by HS/GC/MS. The median values of the four sites ranged between 24.1 to 94.0mg m(-3) and 7.3 to 331.1mg g(-1) creatinine for airborne styrene and MA + PGA, respectively. A good linear correlation was found between styrene in air and its urinary metabolites (r = 0.854). The median value for airborne styrene was found to exceed the (Threshold Limit Value - Time Weighted Average) of 85 mg m(-3) in one site for all the workers and in two if only moulders are considered. The multiple linear regression model showed that the determinants of urinary MA + PGA excretion were the type of process, workers' tasks, level of acetone co-exposure, and the use of respiratory protection devices. Data show that the simultaneous exposure to acetone modify the styrene metabolism with a reduction in the levels of (MA + PGA) excreted. A significant linear log-correlation was found between salivary levels of styrene and blood concentration (r = 0.746) sampled at the same t x time.

Influence of genetic polymorphisms of styrene-metabolizing enzymes on the levels of urinary biomarkers of styrene exposure.

Styrene exposure is still present in different occupational settings including manufacture of synthetic rubber, resins, polyesters and plastic. The aim of this work was to investigate the effects of polymorphic genes CYP2E1, EPHX1, GSTT1, and GSTM1 on the urinary concentrations of the styrene metabolites mandelic acid (MA), phenylglyoxylic acid (PGA) and on the concentration ratios between (MA+PGA) and urinary styrene (U-Sty) and airborne styrene (A-Sty), in 30 workers from two fiberglass-reinforced plastic manufacturing plants and 26 unexposed controls. Personal air sampling and biological monitoring results revealed that sometimes exposure levels exceeded both the threshold limit value (TLV) and the biological exposure index (BEI) suggested by the American Conference of Governmental Industrial Hygienists. A significantly reduced excretion of styrene metabolites (MA+PGA) in individuals carrying the CYP2E1*5B and CYP2E1*6 heterozygote alleles, with respect to the homozygote wild type, was observed only in the exposed group. A reduction was also detected, in the same group, in subjects carrying the slow allele EPHX1 (codon 113), through the lowering of (MA+PGA)/urinary styrene concentration ratio. In addition, the ratio between MA+PGA and the personal airborne styrene concentration appeared to be modulated by the predicted mEH activity, in the exposed group, as evidenced by univariate linear regression analysis. Our results confirm some previous hypotheses about the role of the polymorphism of genes coding for enzymes involved in the styrene detoxification pathway: this may significantly reduce the levels of excreted metabolites and therefore it must be taken into account in the interpretation of the biological monitoring results for occupational exposure.

[Association between GSTP1, GSTM1, GSTT1 genetic polymorphisms and urinary styrene phenyl hydroxyethyl mercapturic acids level].

OBJECTIVE: To investigate the relationship between genetic polymorphisms of glutathione S-transferase P1 (GSTP1), glutathione S-transferase M1 (GSTM1), and glutathione S-transferase T1 (GSTT1) and urinary level of mercapturic acids of styrene (PHEMAs) in workers exposed to styrene. METHODS: One hundred and twenty-six workers exposed to styrene were selected as exposure group, and 150 workers without styrene exposure as the control group; all the workers came from a locomotive shell production factory in Shandong Province, China. The PCR-RFLP technique was applied to analyze the individual genetic polymorphisms of GSTP1; the multiplex PCR technique was used to investigate the genetic polymorphisms of GSTM1 and GSTT1; the relationship between genetic polymorphisms of GSTP1, GSTM1, and GSTT1 and urinary level of PHEMAs in workers exposed to styrene was statistically analyzed. RESULTS: The three genotypes investigated in the study had a distribution in accordance with the Chinese population. With exposure to high- concentration styrene, the individuals carrying GSTP1 (exon5, A105G) AA genotype (wildtype) had a significantly higher urinary level of PHEMAs (43.58 mg/g) than those with mutant genotypes AG (29.769 mg/g) and GG (30.245 mg/g); the urinary level of PHEMAs in individuals carrying wild-type GSTM1 genotype was significantly higher than that in individuals carrying deficient-type GSTM1 genotype (40.197 mg/g vs 28.866 mg/g, P < 0.05); no significant difference in urinary level of PHEMAs was found between individuals carrying wild-type GSTT1 genotype and deficient-type GSTT1 genotype. There was no significant relationship between the three gene polymorphisms and urinary level of PHEMAs in the control group. CONCLUSION: The genetic polymorphisms of GSTP1 and GSTM1 may be related to urinary level of PHEMAs in workers exposed to styrene.

Otoacoustic emission sensitivity to exposure to styrene and noise.

The ototoxic effect of the exposure to styrene is evaluated, also in the presence of simultaneous exposure to noise, using otoacoustic emissions as biomarkers of mild cochlear damage. Transient-evoked and distortion product otoacoustic emissions were recorded and analyzed in a sample of workers (15 subjects) exposed to styrene and noise in a fiberglass manufacturing facility and in a control group of 13 non-exposed subjects. Individual exposure monitoring of the airborne styrene concentrations was performed, as well as biological monitoring, based on the urinary concentration of two styrene metabolites, the Mandelic and Phenylglyoxylic acids. Noise exposure was evaluated using wearable phonometers, and hearing loss with pure tone audiometry. Due to their different job tasks, one group of workers was exposed to high noise and low styrene levels, another group to higher styrene levels, close to the limit of 20 ppm, and to low noise levels. A significant negative correlation was found between the otoacoustic emission levels and the concentration of the styrene urinary metabolites. Otoacoustic emissions, and particularly distortion products, were able to discriminate the exposed workers from the controls, providing also a rough estimate of the slope of the dose-response relation between otoacoustic levels and styrene exposure.

Occupational styrene exposure induces stress-responsive genes involved in cytoprotective and cytotoxic activities.

OBJECTIVE: The aim of this study was to evaluate the expression of a panel of genes involved in toxicology in response to styrene exposure at levels below the occupational standard setting. METHODS: Workers in a fiber glass boat industry were evaluated for a panel of stress- and toxicity-related genes and associated with biochemical parameters related to hepatic injury. Urinary styrene metabolites (MA+PGA) of subjects and environmental sampling data collected for air at workplace were used to estimate styrene exposure. RESULTS: Expression array analysis revealed massive upregulation of genes encoding stress-responsive proteins (HSPA1L, EGR1, IL-6, IL-1ß, TNSF10 and TNFα) in the styrene-exposed group; the levels of cytokines released were further confirmed in serum. The exposed workers were then stratified by styrene exposure levels. EGR1 gene upregulation paralleled the expression and transcriptional protein levels of IL-6, TNSF10 and TNFα in styrene exposed workers, even at low level. The activation of the EGR1 pathway observed at low-styrene exposure was associated with a slight increase of hepatic markers found in highly exposed subjects, even though they were within normal range. The ALT and AST levels were not affected by alcohol consumption, and positively correlated with urinary styrene metabolites as evaluated by multiple regression analysis. CONCLUSION: The pro-inflammatory cytokines IL-6 and TNFα are the primary mediators of processes involved in the hepatic injury response and regeneration. Here, we show that styrene induced stress responsive genes involved in cytoprotection and cytotoxicity at low-exposure, that proceed to a mild subclinical hepatic toxicity at high-styrene exposure.

Simultaneous determination of aromatic acid metabolites of styrene and styrene-oxide in rat urine by gas chromatography-flame ionization detection.

A convenient and reliable gas chromatographic method was developed for the simultaneous determination of six aromatic acid metabolites of styrene and styrene-oxide in rat urine; i.e., benzoic (BA), phenylacetic (PAA), mandelic (MA), phenylglyoxylic (PGA), hippuric (HA) and phenylaceturic (PAUA) acids. The method involves a one-pot esterification-extraction procedure, performed directly on urine without prior treatment. Analyses were performed on a RTX-1701 capillary column and the recovered isopropyl esters derivatives were detected by flame ionization detection. The analytical method was validated for selectivity, linearity, detection and quantification limits, recovery and intra-day and inter-day precisions. Calibration curves showed linearity in the range of 8-800 mg/L, except for HA and PAUA (40-800 mg/L). Limits of detection were between 0.2 (PPA) and 7.0 (PAUA) mg/L. The intra-day precisions determined at three concentrations levels were less than 5% for BA, PAA, MA and PGA and 9% for HA and PAUA, respectively. The corresponding mean inter-day precisions for these two groups were 8 and 16%, respectively. The method was successfully applied to quantitatively analyze styrene, styrene-oxide, ethylbenzene and toluene metabolites in urine samples from rats exposed by inhalation to these compounds at levels close to the occupational threshold limit values. Provided that this method can be transposed to human urine, it could have applications as part of biological monitoring for workers exposed to styrene or related compounds.

A reliable method by ultra-performance liquid chromatography coupled with tandem mass spectrometry to quantify and confirm simultaneously the presence of solvent metabolites in workers' urine.

Ultra-performance liquid chromatography coupled with tandem mass spectrometry was used for the biological monitoring of workers occupationally exposed to solvents. The method was developed using a triple quadrupole to investigate the relevant urinary metabolites of styrene, namely mandelic acid and phenylglyoxylic acid. The method provides quantitative and qualitative data to give additional assurance about the nature of the contaminant analyzed in workers' urine. A full scan and a product ion scan were acquired within the chromatographic peak acquired in MRM. For the two metabolites, the repeatability was 96%, the precision ≥97%, and the accuracy ≥93 ± 3%. The quantitative performances were not influenced by the inclusion of simultaneous full scan acquisition as compared to a usual quantitative approach. Footprints of each substance of interest were obtained at each injection, and full scan data can be interrogated for the presence of interferences and other contaminants. The method developed has been submitted to random real samples from both non-occupationally and occupationally exposed workers. The urines of non-occupationally exposed workers were all free of mandelic acid, phenylglyoxylic acid and putative interferences showing the high selectivity of the method. However, the urines of occupationally exposed workers were robustly quantified. The levels of mandelic acid and phenylglyoxylic acid ranged between 0.2 and 9 mM, and the footprints of each metabolite and structural information were acquired in parallel with the quantitative results, thus providing unquestionable data about the nature of the contaminant and the levels reported. The combination of qualitative information acquired simultaneously with quantitative results provides the structural information needed in case of questions, without any harmful effect on the robustness and throughput of the quantitative analysis.

[Biomarkers of occupational and environmental exposure to benzene and styrene determinated by LC-MS/MS]. / Oznaczanie biomarkerów narazenia zawodowego i srodowiskowego na benzen i styren z zastosowaniem techniki LC-MS/MS.

BACKGROUND: Based on the studies performed a sensitive and simple method for the determination of benzene and styrene metabolites in urine has been developed. The developed procedure can be used for biological monitoring of occupational and environmental exposure. MATERIAL AND METHODS: Urine samples for the determination of styrene metabolites (phenylglyoxylic acid--PGA and mandelic acid--MA) were only acidified with formic acid, while those for the determination of benzene metabolite (S-phenyl-mercapturic acid--S-PMA) were additionally extracted with ethyl acetate. The measurement was performed by high performance liquid chromatography--tandem mass spectrometry (HPLC-MS/MS). The quality of our analysis was verified using internal and external quality control. RESULTS: Limit of detection for S-PMA was 0.33 microg/l, for MA--60 microg/l and for PGA--40 microg/l; precision was 2-3% and recovery 94-98%. CONCLUSIONS: The method for the quantification of benzene and styrene metabolites can be used for biological monitoring of occupational and environmental exposure.

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.

Effects of low-level exposure to xenobiotics present in paints on oxidative stress in workers.

Paints are composed of an extensive variety of hazardous substances, such as organic solvents and heavy metals. Biomonitoring is an essential tool for assessing the risk to occupational health. Thus, this study analyzed the levels of biomarkers of exposure for toluene, xylene, styrene, ethylbenzene, and lead, as well as the oxidative stress biomarker alterations in painters of an industry. Lipid peroxidation biomarker (MDA), delta-aminolevulinate dehydratase (ALA-D), nonprotein thyol groups, superoxide dismutase and catalase (CAT) were analyzed in exposed and nonexposed subjects. We estimated which of the paint constituents have the greatest influence on the changes in the biomarkers of oxidative stress in this case of co-exposure. The results demonstrated that despite the fact that all the biomarkers of exposure were below the biological exposure limits, the MDA levels and antioxidant enzyme activities were increased, while nonprotein thyol groups and ALA-D levels were decreased in painters when compared with nonexposed subjects. After statistic test, toluene could be suggested as the principal factor responsible for increased lipid peroxidation and inhibition of ALA-D enzyme; however, further studies on the inhibition of ALA-D enzyme by toluene are necessary.

Assessing variability and comparing short-term biomarkers of styrene exposure using a repeated measurements approach.

The aim of this work is to compare several short-term biomarkers of styrene exposure, namely urinary styrene (StyU), mercapturic acids (M1+M2), mandelic acid (MA), phenylglyoxylic acid (PGA), phenylglycine (PHG), and 4-vinylphenol conjugates (VP), for use as biomarkers of exposure in epidemiologic studies. A repeated measurements protocol (typically 4 measurements per worker over 6 weeks) was applied to measure airborne styrene (StyA) and urinary biomarkers in 10 varnish and 8 fiberglass reinforced plastic workers. Estimated geometric mean personal exposures to StyA were 2.96mg/m(3) in varnish workers and 15.7mg/m(3) in plastic workers. The corresponding levels of StyU, M1+M2, MA, PGA, MA+PGA, PHG and VP were 5.13microg/L, 0.111, 38.2, 22.7, 62.6, 0.978, and 3.97mg/g creatinine in varnish workers and 8.38microg/L, 0.303, 146, 83.4, 232, 2.85 and 3.97mg/g creatinine in plastic workers. Within-worker (sigma(wY)(2)) and between-worker (sigma(bY)(2)) variance components were estimated from the log-transformed data as were the corresponding fold ranges containing 95% of the respective lognormal distributions of daily levels ((w)R(0.95)) and subject-specific mean levels ((b)R(0.95)). Estimates of (w)R(0.95) (range: 4-26) were generally smaller than those of (b)R(0.95) (range: 5-790) for both environmental and biological markers; this indicates that exposures varied much more between workers than within workers in these groups. Since attenuation bias in an estimated exposure-response relationship increases with the variance ratio lambda=sigma(wY)(2)/sigma(bY)(2), we estimated values of lambda for all exposure measures in our study. Values of lambda were typically much less than one (median=0.220) and ranged from 0.089 for M1+M2 in plastic workers to 1.38 for PHG in varnish workers. Since values of lambda were 0.147 and 0.271 for StyA in varnish workers and plastic workers, respectively, compared to 0.178 and 0.210 for MA in the same groups, our results suggest that either air measurements or conventional biomarker measurements (urinary MA) would be comparable surrogates for individual exposures in epidemiologic studies.

Effect of physical exertion on the biological monitoring of exposure to various solvents following exposure by inhalation in human volunteers: III. Styrene.

This study evaluated the impact of different work load intensities on biological indicators of styrene exposure. Four adult Caucasian men, aged 20 to 44 years, were recruited. Groups of 2-4 volunteers were exposed to 20 ppm of styrene in an exposure chamber according to scenarios involving either aerobic, muscular, or both types of physical exercise for 3 or 7 hr. The target intensities for each 30-min exercise period-interspaced with 15 min at rest-were the following: REST, 38 watts AERO (time-weighted average intensity), 34 watts AERO/MUSC, 49 watts AERO/MUSC, and 54 watts AERO for 7 hr and 22 watts MUSC for 3 hr. End-exhaled air samples were collected at 15 time points during and after 7-hr exposures for the determination of styrene concentrations. Urine samples were collected before the start of exposure, after the first 3 hr of exposure, and at the end of exposure for the determination of mandelic acid (MA) and phenylglyoxilic acid (PGA) concentrations. Compared with exposure at rest, styrene in alveolar air increased by a factor up to 1.7, while the sum of urinary MA and PGA increased by a factor ranging from 1.2 to 3.5, depending on the exposure scenario. Concentrations of biological indicators of styrene fluctuated with physical exertion and were correlated with the magnitude of the physical activity and pulmonary ventilation. Despite the physical exertion effect, urinary concentrations of styrene metabolites after a single-day exposure remain below the current biological exposure index value recommended by ACGIH; therefore, no additional health risk is expected. However, results shows that work load intensities must be considered in the interpretation of biological monitoring data and in the evaluation of the health risk associated with styrene exposure.

Occupational styrene exposure, colour vision and contrast sensitivity: a cohort study with repeated measurements.

OBJECTIVE: Associations between occupational styrene exposures and impairment of visual functions were investigated with a view to answering three questions: (1) are the published findings for colour vision deficiencies and impaired contrast sensitivity to reproduce in a new study approach, (2) if such effects exist, are they related to current or chronic exposures and (3) if effects exist, are there reductions in the effects during an exposure-free period? METHODS: Workers from a boat building plant were examined in groups of current low [n = 97, mean mandelic acid (MA) + phenylglyoxylic acid (PGA) = 51 mg/g creatinine], medium (n = 115, mean = 229 mg/g creatinine) and high (n = 30, mean = 977 mg/g creatinine) level exposure to styrene. Job tenure was about 6 years. In addition, subgroups chronically exposed to low-short (n = 34, lifetime weighted mean 200 mg/g creatinine for 6 years) and high-long (n = 17, mean = 660 mg/g creatinine, 15 years) styrene levels were analysed. The examinations were carried out during normal working days and during the company holidays. Colour vision was investigated with the Lanthony desaturated panel D-15d using the colour confusion index (CCI) as a relevant variable. Contrast sensitivity was investigated with the Vistech charts VCTS 6500 using frequency-related results as well as total scores as variables. Co-variance analyses with repeated measurements and multiple linear regressions were used for statistical analysis. RESULTS: There was no evidence of significant associations between exposure parameters and CCI. This is true for the analyses with all participants as well as for those with the subgroups with high-long versus low-short exposure. Thus, no exposure related changes in the relevant variables were found during the exposure-free period. The analyses for contrast sensitivity show similar results. The largest portions of the variances in both tests were explained by age. German as mother tongue covered a considerable portion of the CCI variances. Education, long-term alcohol use and job tenure explain only partly significant portions of the test variances exhibited. CONCLUSION: Both acute styrene exposure levels of 40 ppm (range of standard deviation up to 54 ppm) and long term exposures to 27 ppm (range of standard deviation up to 44 ppm with higher exposure levels in the past) for a period of about 15 years were not identified as causing elevated risks for the investigated parameters of colour vision and contrast sensitivity. This statement contradicts the published results for styrene-related colour vision deficiencies but it seems to be compatible with published results for contrast sensitivity due to styrene exposure.