Biomarker Of Benzene Exposure Research Articles

Altered Haematological Parameters in Gasoline Station Workers Due to Benzene Exposure

Benzene is harmful to human health and early detection of haematological alterations is important in preventing adverse health effects. This study aimed to investigate the biomarkers of benzene exposure and its effects due to haematological alterations. Gasoline station workers with potential risks according to the biomatrix concerning benzene exposure underwent blood and urine evaluation for the biological monitoring of urinary trans, trans-muconic acid (tt-MA), and haematological and biochemical parameter evaluation. The results were analysed for correlations between biological and haematological effects. The tt-MA biomarker was detected in some workers and approximately 50% of workers had a blood profile that showed abnormal parameters with respect to the haemoglobin (Hb), haematocrit (Hct) and white blood cell parameters, which were outside the normal range. A significant correlation was observed between the tt-MA biomarker’s level and the levels of the haematological and biochemical parameters, which were Hb, Hct, eosinophil, neutrophil, SGOT and blood creatinine. The level of urinary tt-MA as a marker of benzene exposure correlated with haematological and biochemical changes in the blood, suggesting that the gasoline station workers were affected by benzene exposure. Moreover, the current study suggests that early detection of haematological abnormalities may be possible by analysing biomarkers of their effects through regular health surveillance of workers.

Assessment ofurinary 6-hydroxy-2,4-cyclohexadienyl mercapturic acid as a novel biomarker ofbenzene exposure.

Assessing benzene exposure is a public health priority due to its deleterious health effects and ubiquitous industrial and environmental sources of exposure. Phenyl mercapturic acid (PhMA) is a commonly used urinary biomarker to assess benzene exposure. However, recent work has identified significant interlaboratory variation in urinary PhMA concentrations related to methodological differences. In this study, we present urinary 6-hydroxy-2,4-cyclohexadienyl mercapturic acid (pre-PhMA), a metabolite that undergoes acid-catalyzed dehydration to form PhMA, as a novel and specific urinary biomarker for assessing benzene exposure. We developed and validated the first quantitative liquid chromatography-tandem mass spectrometry assay for measuring urinary concentrations of pre-PhMA. The pH effect on the method of ruggedness testing determined that pre-PhMA is stable across the normal human urine pH range and that neutral conditions must be maintained throughout quantification for robust and accurate measurement of urinary pre-PhMA concentrations. The method exhibited below 2 ng/mL sensitivity for pre-PhMA, linearity over three orders of magnitude, and precision and accuracy within 10%. Urinary pre-PhMA concentrations were assessed in 369 human urine samples. Smoking individuals exhibited elevated levels of pre-PhMA compared to non-smoking individuals. Furthermore, the relationship between benzene exposure and urinary pre-PhMA levels was explored by examining the correlation of pre-PhMA with 2-cyanoethyl mercapturic acid, a smoke exposure biomarker. The urinary biomarkers exhibited a positive correlation (r = 0.720), indicating that pre-PhMA levels increased with benzene exposure. The results of this study demonstrate that urinary pre-PhMA is a rugged and effective novel biomarker of benzene exposure that can be widely implemented for future biomonitoring studies.

68 Urinary Biomarkers of Benzene Exposure and Oxidative Damage in Residents of the Oil Extraction Area of Muanda, Dr Congo

Abstract The territory of Muanda, on the Atlantic coastline of the DR Congo, is an area of off-shore and on-shore oil extraction. Following concerns of the local population about the possible environmental and health consequences of these activities, a pilot study was performed in December 2015 to assess, among other issues, the exposure of residents of various relevant locations to oil-derived chemicals. We measured metabolites of benzene (t,t-Muconic Acid, MA, and S-Phenylmercapturic acid, S-PMA) by LC-MS and 8-hydroxy-2’-deoxyguanosine (8-OHdG, as an indicator of DNA damage) by ELISA, in urine spot samples of 53 volunteers (34 adults, 19 children, recruited by convenience sampling) living within areas of oil extraction with flaring (n=27), in an area where petroleum products were handled (n=14), and in a control area in the Mangroves National Park (n=12). Concentrations of both MA and S-PMA were increased among residents of the oil extraction areas (0.23±0.05 mg/L, 1.04±0.30 µg/L, respectively) and petroleum products area (0.32±0.08 mg/L, 1.74±0.63 µg/L, respectively) compared with controls (0.06±0.01 mg/L, 0.40±0.13 µg/L, respectively). Concentrations of of MA and S-PMA correlated with levels of 8-OHdG (RSpearman = 0.37, p<0.01). Our biomonitoring study revealed a low degree of benzene exposure among residents living in the oil extraction and petroleum handling areas compared to a control area. Although the levels of benzene metabolites were low, the positive correlation with 8-OHdG possibly indicates that pollution by hydrocarbons induced oxidative damage in this study population.

A Hybrid Molecularly Imprinted Polymer for Selective Adsorption of Urinary S-Phenylmercapturic Acid

A hybrid molecular imprinted polymer (HMIP) obtained by the organic monomer 4-vinylpyridine (4-VP) and the inorganic precursor tetraethyl orthosilicate (TEOS) was synthesized for the selective extraction of urinary S-phenylmercapturic acid (u-SPMA), a biomarker of benzene exposure. The chemical and structural characterization of the synthetic adsorbent was performed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and textural analysis employing N2 adsorption-desorption isotherms. Selective and adsorptive performance of the imprinted polymers were evaluated by kinetic, isothermal, thermodynamic, and selectivity studies. The kinetic data were well adjusted to pseudo-second order and intraparticle diffusion models, leading to selectivity coefficient (K) value of 0.03 g mg-1 min-1 for HMIP. In addition, the adsorption isotherms were better described by the Sip model achieving a maximum adsorption capacity of 284.81 μg g-1 (at 288.15 K).

Association of metabolites of benzene and toluene with lipid profiles in Korean adults: Korean National Environmental Health Survey (2015–2017)

BackgroundEnvironmental exposure to benzene and toluene is a suspected risk factor for metabolic disorders among the general adult population. However, the effects of benzene and toluene on blood lipid profiles remain unclear. In this study, we investigated the association between urinary blood lipid profiles and metabolites of benzene and toluene in Korean adults.MethodsWe analyzed the data of 3,423 adults from the Korean National Environmental Health Survey Cycle 3 (2015–2017). We used urinary trans,trans-muconic acid (ttMA) as a biomarker of benzene exposure, and urinary benzylmercapturic acid (BMA) as an indicator of toluene exposure. Multivariate logistic regression analyses were performed to explore the association between blood lipid profiles and urinary metabolites of benzene and toluene. Additionally, we examined the linear relationship and urinary metabolites of benzene and toluene between lipoprotein ratios using multivariate regression analyses.ResultsAfter adjusting for covariates, the fourth quartile (Q4) of ttMA [odds ratio (OR) (95% confidence interval, CI = 1.599 (1.231, 2.077)] and Q3 of BMA [OR (95% CI) = 1.579 (1.129, 2.208)] were associated with an increased risk of hypertriglyceridemia. However, the Q4 of urinary ttMA [OR (95% CI) = 0.654 (0.446, 0.961)] and Q3 of urinary BMA [OR (95% CI) = 0.619 (0.430, 0.889)] decreased the risk of a high level of low-density lipoprotein cholesterol (LDL-C). Higher urinary ttMA levels were positively associated with the ratio of triglycerides to high-density lipoproteins [Q4 compared to Q1: β = 0.11, 95% CI: (0.02, 0.20)]. Higher urinary metabolite levels were negatively associated with the ratio of low-density lipoprotein to high-density lipoprotein [Q4 of ttMA compared to reference: β = -0.06, 95% CI: (-0.11, -0.01); Q4 of BMA compared to reference: β = -0.13, 95% CI: (-0.19, -0.08)].ConclusionBenzene and toluene metabolites were significantly and positively associated with hypertriglyceridemia. However, urinary ttMA and BMA levels were negatively associated with high LDL-C levels. These findings suggest that environmental exposure to benzene and toluene disrupts lipid metabolism in humans.

Factors Affecting Adverse Health Effects of Gasoline Station Workers.

This cross-sectional study examined the risk factors affecting adverse health effects from benzene exposure among gasoline station workers in Khon Kean province, Thailand. An interview questionnaire of adverse symptoms relating to benzene toxicity was administered to 151 workers. Area samplings for benzene concentration and spot urine for tt-muconic acid (tt-MA), a biomarker of benzene exposure, were collected. The factors associated with adverse symptoms were analysed by using multiple logistic regression. It was found that these symptoms mostly affected fuelling workers (77.5%), and the detected air benzene reached an action level or higher than 50% of NIOSH REL (>50 ppb). The top five adverse symptoms, i.e., fatigue, headache, dizziness, nasal congestion, and runny nose, were reported among workers exposed to benzene. More specific symptoms of benzene toxicity were chest pain, bleeding/epistaxis, and anaemia. The detected tt-MA of workers was 506.7 ug/g Cr (IQR), which was a value above the BEI and higher than that of asymptomatic workers. Risk factors significantly associated with adverse symptoms, included having no safety training experience (ORadj = 5.22; 95% CI: 2.16–12.58) and eating during work hours (ORadj = 16.08; 95% CI: 1.96–131.74). This study urges the tightening of health and safety standards at gasoline stations to include training and eating restrictions while working in hazardous areas.

Screening of biomarkers in exhaled breath of mice exposed to benzene

Objective: To screen the biomarkers in the exhaled breath of mice exposed to benzene by using exhaled breath online analysis system. Methods: Thirty 8-week-old male C57BL/6 mice were randomly divided into six groups (0, 3, 32, 324, 648, and 1 296 mg/m3) and treated with benzene vapour for 28 days. At the end of the exposure, the peripheral blood cell counts and blood glutathione (GSH) were detected. The content of malondialdehyde (MDA) in HL60 cells treated by mice plasma was examined. Exhaled breath data from mice were collected by Secondary electrospray ionization source high resolution mass spectrometry (SESI-HRMS). Targeted analysis underlying benzene metabolites and oxidative stress metabolites was performed to screen the biomarkers in exhaled breath. Results: After benzene exposure, the number of peripheral blood cells was decreased in different degrees, particularly in the white blood cells (WBC) number. The WBC in 32 and 324 mg/m3 groups was declined by 27.76% and 52.87%, respectively compared to that in control group (P<0.05). Meanwhile, compared with the control group, the GSH content of peripheral blood cells from 324 mg/m3 group decreased by 13.16% (P<0.05). In addition, MDA content was increased by 18.11% in HL60 cells treated with plasma from 324 mg/m3 group mice (P<0.05). The phenol, hydroquinone/catechol, benzenetriol and trans, trans-Muconic acid (t,t-MA) in the exhaled gas of mice could be used as biomarkers for benzene exposure (R2>0.8, P<0.001). The peak intensity of five small molecular metabolites related to oxidative stress (ω-carboxylic fatty acid C5H10O3, ω-carboxylic fatty acid C6H12O3, glutamate, cysteine and MDA) increased with the increase of benzene concentration (P<0.05), which was negatively correlated with WBC decline (P<0.001), suggesting that these molecules mignt be used as biomarkers of benzene-induced toxicity. Conclusions: Phenol, hydroquinone/catechol, benzenetriol and trans, trans-Muconic acid (t,t-MA) in exhaled breath of mice could be used as biomarkers for benzene exposure; ω-carboxylic fatty acid C5H10O3, ω-carboxylic fatty acid C6H12O3, glutamate, cysteine and MDA might be used as markers of benzene-induced toxicity.

Biomarkers of Low-Level Environmental Exposure to Benzene and Oxidative DNA Damage in Primary School Children in Sardinia, Italy.

Background: The main anthropic sources of exposure to airborne benzene include vehicular traffic, cigarette smoke, and industrial emissions. Methods: To detect early genotoxic effects of environmental exposure to benzene, we monitored environmental, personal, and indoor airborne benzene in children living in an urban area and an area near a petrochemical plant. We also used urinary benzene and S-phenylmercapturic acid (S-PMA) as biomarkers of benzene exposure and urinary 8-hydroxydeoxyguanosine (8-OHdG) as a biomarker of early genotoxic effects. Results: Although always below the European Union limit of 5 μg/m3, airborne benzene levels were more elevated in the indoor, outdoor, and personal samples from the industrial surroundings compared to the urban area (p = 0.026, p = 0.005, and p = 0.001, respectively). Children living in the surroundings of the petrochemical plant had urinary benzene values significantly higher than those from the urban area in both the morning and evening samples (p = 0.01 and p = 0.02, respectively). Results of multiple regression modelling showed that age was a significant predictor of 8-OHdG excretion, independent of the sampling hour. Moreover, at the low exposure level experienced by the children participating in this study, neither personal or indoor airborne benzene level, nor personal monitoring data, affected 8-OHdG excretion. Conclusions: Our results suggest the importance of biological monitoring of low-level environmental exposure and its relation to risk of genotoxic effects among children.

Gene-Environment Interactions Between Environmental Response Genes Polymorphisms and Mitochondrial DNA Copy Numbers Among Benzene Workers.

To determine the effect of mitochondrial DNA copy number (mtDNAcn) as a biomarker of benzene exposure. A total of 294 benzene-exposed workers and 102 controls were recruited. Biomarkers of mtDNAcn, cytokinesis-block micronucleus (MN) frequency, and peripheral blood white blood cells (WBC) were detected. Eighteen polymorphism sites in DNA damage repair and metabolic genes were analyzed. Benzene exposure increased mtDNAcn and indicated a dose-response relationship (P < 0.001). mtDNAcn was negatively correlated with WBC count and DNA methylation and positively correlated with MN frequency. The AG type in rs1695 interacted with benzene exposure to aggravate mtDNAcn (β = 0.006, 95% CI: 0, 0.012, P = 0.050). rs13181, rs1695, rs1800975, and GSTM1 null were associated with benzene-induced mtDNAcn. Rs1695 interacted with benzene to increase mitochondrial damage. Benzene exposure increases mtDNAcn levels in benzene-exposed workers.

Analysis of Benzene Exposure in Gas Station Workers Using Trans,Trans-Muconic Acid.

In Brazil, gas station workers are occupationally exposed to the benzene present in gasoline. Brazilian law indicates the use of trans,trans-muconic acid(t,t-MA) as a biomarker of benzene exposure. The aim of this study was to evaluate the level of exposure to benzene in gas station workers, through the quantification of t,t-MA present in urine. A total number of 269 gas station workers divided into 179 filling station attendants exposed by inhalation and dermal route and 90 convenience store workers exposed only by inhalation were included. A control group was formed by 100 office workers, without occupational exposure to benzene. The urinary levels of t,t-MA were evaluated by HPLC with a UV detector. Gas station workers showed higher mean values of t,t-MA (0.204 mg/g creatinine; 95% CI 0.170–0.237) than office workers (0.126 mg/g creatinine; 95% CI 0.0817–0.1693). T,t-MA levels were higher in convenience store workers exposed to gasoline only by inhalation (0.221 mg/g creatinine; 95% CI 0.160–0.282), than in those exposed to gasoline by inhalation and dermal route—filling station attendants (0.195 mg/g creatinine; 95% CI 0.155–0.235). Gas station workers with a higher level of t,t-MA had epistaxis. T,t-MA values were higher in the Downtown (0.15 mg/g creatinine) region’s workers than in the more affluent South Zone region’s workers (0.07 mg/g creatinine). Smoking habits influenced the urinary t,t-MA values, while the frequency of consumption of industrialized and frozen foods showed no influence.

Development of a simple and rapid method for determination of trans, trans-Muconic Acid in human urine using PDLLME preconcentration and HPLC–UV detection

Benzene is a known human carcinogen and monitoring its exposure is very important. trans, trans-Muconic Acid (tt-MA) is an open-ring metabolite product proposed by related regulatory bodies as the best biomarker of benzene exposure. In this study, a new, simple and rapid method was developed for determination of tt-MA in a urine sample using partitioned dispersive liquid–liquid microextraction technique coupled with high-performance liquid chromatography–UV detection. Under the optimal condition, 2000 µL of tetrahydrofuran and 200 µL chloroform were used as disperser and extraction solvent, respectively, for 5 mL sample containing the target analyte. The method was linear in the range of 0.001–10 mg L−1. Method LOD, LOQ, relative standard deviation (RSD) for 3 days and under three concentrations and relative recovery were obtained 0.11 μg L−1, 0.83 µg L−1, 2.02–3.96% and 86–102%, respectively. Therefore, the proposed method with high recovery and easy application is recommended to be used to detect tt-MA in human urine samples.

Biological monitoring of low level exposure to benzene in an oil refinery: Effect of modulating factors

The aim of the study was to investigate the effect of various factors that modulate the metabolism of benzene, including smoking habits, metabolic genotype of GST and co-exposure to toluene, on the levels of three biomarkers, i.e. urinary benzene (UB), S-phenylmercapturic acid (SPMA) and t,t-muconic acid (t,t-MA), in 146 refinery workers exposed to low levels of air benzene (AB) in the range <1.5–529.2 μg/m3 (mean value 32.6 μg/m3).The study confirmed the validity of SPMA as a good biomarker of benzene exposure even at low levels of exposure. It was also confirmed that cigarette smoking is the main confounding factor when assessing biological monitoring data of occupational exposure to AB. Our data indicate that the GSTT1, but not the GSTM1 genotype, significantly increases the urinary levels of SPMA, even at low levels of exposure. It is not known, though, whether subjects with a GSTT1 “null” genotype may be more susceptible to the effects of benzene. Finally, environmental toluene appears to inhibit the metabolism of benzene to SPMA even at low concentrations, also resulting in an underestimation by SPMA levels of the actual exposure of workers to benzene.

EXPOSICIÓN A BENCENO EN UNA POBLACIÓN INFANTIL URBANA DEL NORESTE DE MÉXICO

The aim of this study was to assess the benzene exposure levels in children living in Cadereyta Jimenez in Nuevo Leon state, through determination of urinary trans, trans-muconic acid, a biomarker of benzene exposure. Our results shown that 28 % of the population exceeds the biological exposure index (500 µg/g CR). Considering that benzene is related with hematological malignances it is necessary to undertake studies to assess hematological risks in children living in areas with petrochemical activity.

Separation and quantification of phenolic metabolites using thin-layer chromatography followed by ultraviolet–visible spectroscopy: Urinary biomarkers of benzene exposure

Benzene is an omnipresent liquid in industries. The occupational exposure to benzene leads to the urinary excretion of benzene metabolites, viz., phenol, pyrocatechol, hydroquinone, and trihydroxybenzene, due to its biotransformation. These metabolites are phenolic in nature and considered as immediate biomarkers of benzene exposure. The present work includes the separation and determination of urinary phenolic benzene metabolites by coupling two different techniques. Thin-layer chromatography (TLC) was used as the separation technique to get individually separated spots of all four metabolites, which were further quantified by ultraviolet (UV)–visible spectroscopy at 765 nm. For the development of the separated spots on TLC plate and determination of metabolites by UV–visible spectroscopic method, alkaline Folin‒Ciocalteau reagent was used. Folin‒Ciocalteau reagent is having wide applications for phenol determination and gives blue color with almost all types of phenols. The colored solutions were measur...

Impact of environmental volatile organic compounds on otitis media in children: Correlation between exposure and urinary metabolites

IntroductionVolatile organic compounds (VOCs) induce inflammatory responses. Tobacco smoke contains numerous VOCs and is a risk factor for otitis media effusion (OME); however, no previous studies have investigated the association between VOCs and OME. ObjectivesWe used urinary metabolites and exposure to environmental risk factors to investigate the association between VOC and polycyclic aromatic hydrocarbon exposure and recurrent OME in children. MethodsChildren with recurrent OME who visited the Otorhinolaryngology Department of Seoul National University Hospital between November 2014 and June 2015 were prospectively enrolled in the study. Recurrent OME was defined as more than two OME episodes over a 6-month period lasting longer than 2 months. The control group consisted of children without OME in the last year. Demographic information, including age, sex, and previous medical history was obtained, and endoscopic examinations of the tympanic membrane were performed. Urinary concentrations of 1-hydroxypyrene, 2-naphthol, hippuric acid, trans, trans-muconic acid (t,t-MA), mandelic acid, phenyl glyoxylic acid, and methyl hippuric acid were analyzed using high-performance liquid chromatography/tandem mass spectroscopy. Environmental factors assessed included house type, age, renovations, the presence of furniture <6 months old, proximity to a road, and exposure to passive smoking. ResultsWe enrolled 11 children with OME and 39 controls. Age and sex did not differ between groups. Exposure to passive smoking was significantly more common in the OME group than in the controls (P < 0.001). Urinary concentrations of t.t.-MA were significantly higher in the OME group (126.33 μg/g cr) than in controls (52.661 μg/g cr; P = 0.003). Other metabolites including 1-hydroxypyrene, 2-naphthol, hippuric acid, mandelic acid, phenyl glyoxylic acid, and methyl hippuric acid did not demonstrated significant relation with the OME. ConclusionsLevels of t,t-MA, a biomarker of benzene exposure, were significantly higher in the OME group than in controls. Passive smoking was significantly more common in the OME group. Our findings suggest that high t,t-MA levels which were probably originated from passive smoking and other pollutants could be indicative OME in children.

Development of Hollow-Fiber Liquid-Phase Microextraction Method for Determination of Urinary trans,trans-Muconic Acid as a Biomarker of Benzene Exposure.

For the first time, hollow-fiber liquid-phase microextraction combined with high-performance liquid chromatography–ultraviolet was used to extract trans,trans-muconic acid, in urine samples of workers who had been exposed to benzene. The parameters affecting the metabolite extraction were optimized as follows: the volume of sample solution was 11 mL with pH 2, liquid membrane containing dihexyl ether as the supporter, 15% (w/v) of trioctylphosphine oxide as the carrier, the time of extraction was 120 minutes, and stirring rate was 500 rpm. Organic phase impregnated in the pores of a hollow fiber was extracted into 24 µL solution of 0.05 mol L−1 Na2CO3 located inside the lumen of the fiber. Under optimized conditions, a high enrichment factor of 153–182 folds, relative recovery of 83%–92%, and detection limit of 0.001 µg mL−1 were obtained. The method was successfully applied to the analysis of ttMA in real urine samples.

Exposure to BTEX and Ethers in Petrol Station Attendants and Proposal of Biological Exposure Equivalents for Urinary Benzene and MTBE.

To assess exposure to benzene (BEN) and other aromatic compounds (toluene, ethylbenzene, m+p-xylene, o-xylene) (BTEX), methyl tert-butyl ether (MTBE), and ethyl tert-butyl ether (ETBE) in petrol station workers using air sampling and biological monitoring and to propose biological equivalents to occupational limit values. Eighty-nine petrol station workers and 90 control subjects were investigated. Personal exposure to airborne BTEX and ethers was assessed during a mid-week shift; urine samples were collected at the beginning of the work week, prior to and at the end of air sampling. Petrol station workers had median airborne exposures to benzene and MTBE of 59 and 408 µg m(-3), respectively, with urinary benzene (BEN-U) and MTBE (MTBE-U) of 339 and 780 ng l(-1), respectively. Concentrations in petrol station workers were higher than in control subjects. There were significant positive correlations between airborne exposure and the corresponding biological marker, with Pearson's correlation coefficient (r) values of 0.437 and 0.865 for benzene and MTBE, respectively. There was also a strong correlation between airborne benzene and urinary MTBE (r = 0.835). Multiple linear regression analysis showed that the urinary levels of benzene were influenced by personal airborne exposure, urinary creatinine, and tobacco smoking [determination coefficient (R(2)) 0.572], while MTBE-U was influenced only by personal exposure (R(2) = 0.741). BEN-U and MTBE-U are sensitive and specific biomarkers of low occupational exposures. We propose using BEN-U as biomarker of exposure to benzene in nonsmokers and suggest 1457 ng l(-1) in end shift urine samples as biological exposure equivalent to the EU occupational limit value of 1 p.p.m.; for both smokers and nonsmokers, MTBE-U may be proposed as a surrogate biomarker of benzene exposure, with a biological exposure equivalent of 22 µg l(-1) in end shift samples. For MTBE exposure, we suggest the use of MTBE-U with a biological exposure equivalent of 22 µg l(-1) corresponding to the occupational limit value of 50 p.p.m.

Inhalation exposure or body burden? Better way of estimating risk--An application of PBPK model.

We aim to establish a new way for estimating the risk from internal dose or body burden due to exposure of benzene in human subject utilizing physiologically based pharmacokinetic (PBPK) model. We also intend to verify its applicability on human subjects exposed to different levels of benzene. We estimated personal inhalation exposure of benzene for two occupational groups namely petrol pump workers and car drivers with respect to a control group, only environmentally exposed. Benzene in personal air was pre-concentrated on charcoal followed by chemical desorption and analysis by gas chromatography equipped with flame ionization detector (GC-FID). We selected urinary trans,trans-muconic acid (t,t-MA) as biomarker of benzene exposure and measured its concentration using solid phase extraction followed by high performance liquid chromatography (HPLC). Our estimated inhalation exposure of benzene was 137.5, 97.9 and 38.7 μg/m(3) for petrol pump workers, car drivers and environmentally exposed control groups respectively which resulted in urinary t,t-MA levels of 145.4±55.3, 112.6±63.5 and 60.0±34.9 μg g(-1) of creatinine, for the groups in the same order. We deduced a derivation for estimation of body burden from urinary metabolite concentration using PBPK model. Estimation of the internal dose or body burden of benzene in human subject has been made for the first time by the measurement of t,t-MA as a urinary metabolite using physiologically based pharmacokinetic (PBPK) model as a tool. The weight adjusted total body burden of benzene was estimated to be 17.6, 11.1 and 5.0 μg kg(-1) of body weight for petrol pump workers, drivers and the environmentally exposed control group, respectively using this method. We computed the carcinogenic risk using both the estimated internal benzene body burden and external exposure values using conventional method. Our study result shows that internal dose or body burden is not proportional to level of exposure rather have a non-linear relationship. At a higher exposure level such as for occupational exposure of petrol pump workers and drivers, the conventionally estimated risk is higher than risk estimated from internal body burden. Likewise, for environmental exposure the conventional risk estimation predict lower level than estimated in our study. This emphasizes the importance of body burden and to consider it as a key parameter while estimating health risk at varying level of exposure.

Overexpression of G6PD and HSP90 Beta in Mice with Benzene Exposure Revealed by Serum Peptidome Analysis.

The small peptides representation of the original proteins are a valuable source of information that can be used as biomarkers involved in toxicity mechanism for chemical exposure. The aim of this study is to investigate serum peptide biomarkers of benzene exposure. C57BL/6 mice were enrolled into control group and benzene groups of 150 and 300 mg/kg/d Serum peptides were identified by mass spectrometry using an assisted laser desorption ionization/time of flight mass spectrometry (MS). Differential peptide spectra were obtained by tandem mass spectrometry and analyzed by searching the International Protein Index using the Sequest program. Forty-one peptide peaks were found in the range of 1000–10,000 Da molecular weight. Among them, seven peaks showed significantly different expression between exposure groups and control group. Two peptide peaks (1231.2 and 1241.8), which showed a two-fold increase in expression, were sequenced and confirmed as glucose 6-phosphate dehydrogenase (G6PD) and heat shock protein 90 Beta (HSP90 Beta), respectively. Furthermore, the expression of the two proteins in liver cells showed the same trend as in serum. In conclusion, G6PD and HSP90 beta might be the candidate serum biomarkers of benzene exposure. It also provided possible clues for the molecular mechanism of benzene-induced oxidative stress.

Urinary biomarkers of exposure and of oxidative damage in children exposed to low airborne concentrations of benzene

The aim of this work was to evaluate the oxidative damage to nucleic acids in children (5–11 years) associated with exposure to environmental pollutants and tobacco smoke (ETS). For each subject, urinary sampling was done twice (evening and next morning) to measure by tandem LC–MS–MS such oxidated products of nucleic acids as 8-oxo-7,8-dihydro-2’-deoxyguanosine (8-oxodGuo), 8-oxo-7,8-dihydroguanosine (8-oxoGuo), and 8-oxo-7,8-dihydroguanine (8-oxoGua). Methyl tert-butyl ether (U-MTBE), benzene (U-Benz), and its metabolites (t,t-muconic and S-phenylmercapturic acids, t,t-MA and S-PMA, respectively) were determined as biomarkers of exposure to air pollution, and cotinine as a biomarker of exposure to ETS.Biomarkers of exposure (S-PMA and U-MTBE) and of DNA oxidation (8-oxodGuo) were dependent on the urbanization and industrialization levels and increased in the evening sample as compared to next morning (p<0.05). In both evening and next morning samples, 8-oxodGuo and 8-oxoGuo correlated with each other (r=0.596 and r=0.537, respectively, p<0.01) and with biomarkers of benzene exposure, particularly S-PMA (r=0.59 and r=0.45 for 8-oxodGuo and r=0.411 and r=0.383 for 8-oxoGuo, p<0.01). No such correlations were observed for U-MTBE and cotinine. Multiple linear regression analyses showed that 8-oxodGuo was positively associated with S-PMA at both sampling times (β=0.18 and β=0.14 for evening and next morning sampling, respectively; p<0.02) and weakly with U-MTBE (β=0.07, p=0.020) only in the evening urines. These results suggest that the selected biomarkers of exposure to benzene, particularly S-PMA, are good tracers of exposure to complex mixtures of oxidative pollutants and that the associated oxidative damage to nucleic acids is detectable even at very low levels of exposure.