Suitability of S-phenyl mercapturic acid and trans-trans-muconic acid as biomarkers for exposure to low concentrations of benzene

Leukemia risk assessment of exposure to low-levels of benzene based on the linearized multistage model

Objectives

To assess leukemia risk in occupational populations exposed to low levels of benzene.

Methods

Leukemia incidence data from the Chinese Benzene Cohort Study were fitted using the Linearized multistage (LMS) model. Individual benzene exposure levels, urinary S-phenylmercapturic acid (S-PMA) and trans, trans-muconic acid (t, t-MA) were measured among 98 benzene-exposed workers from factories in China. Subjects were categorized into four groups by rounding the quartiles of cumulative benzene concentrations (< 3, 3-5, 5-12, ≥12 mg/m3·year, respectively). The risk of benzene-induced leukemia was assessed using the LMS model, and the results were validated using the EPA model and the Singapore semi-quantitative risk assessment model.

Results

The leukemia risks showed a positive correlation with increasing cumulative concentration in the four exposure groups (excess leukemia risks were 4.34, 4.37, 4.44 and 5.52 × 10-4, respectively; Ptrend < 0.0001) indicated by the LMS model. We also found that the estimated leukemia risk using urinary t, t-MA in the LMS model was more similar to those estimated by airborne benzene compared to S-PMA. The leukemia risk estimated by the LMS model was consistent with both the Singapore semi-quantitative risk assessment model at all concentrations and the EPA model at high concentrations (5-12, ≥12 mg/m3·year), while exceeding the EPA model at low concentrations (< 3 and 3-5 mg/m3·year). However, in all four benzene-exposed groups, the leukemia risks estimated by these three models exceeded the lowest acceptable limit for carcinogenic risk set by the EPA at 1 × 10-6.

Conclusion

This study demonstrates the utility of the LMS model derived from the Chinese benzene cohort in assessing leukemia risk associated with low-level benzene exposure, and suggests that leukemia risk may occur at cumulative concentrations below 3 mg/m3·year.

Human Urinary Metabolomics as Biomarkers in Tobacco Users: A Systematic Review

Aim

Urine as a biofluid has been rarely used as a diagnostic fluid in oral diseases. The article aims to systematically review the utility of human urinary carcinogen metabolites as an approach for obtaining important information about tobacco and cancer.

Materials and Methods

The following article reviews the use of urine and its metabolites as biomarkers in various lesions of the oral cavity including oral squamous cell carcinoma and as a screening method in evaluating tobacco and its components. A bibliographic comprehensive search was carried out in the main databases: PUBMED, SciELO, Google Scholar, VHL, and LILACS for articles that were published from 1985 to 2020. The inclusion criteria were "urinary metabolites," "oral cancer/HNSCC," "body fluids," "tobacco," and "metabolomics." A total of 55 articles were collected which included laboratory studies, systematic reviews, and literature of urinary metabolites in tobacco users.

Results

Most of the studies carried out show accurate results with high sensitivity of urinary metabolite biomarkers in individuals with tobacco-based habits and lesions caused by them.

Conclusion

The review indicates that urinary metabolite analysis demonstrates its applicability for the diagnosis and prognosis of disease. Urine is a remarkable and useful biofluid for routine testing and provides an excellent resource for the discovery of novel biomarkers, with an advantage over tissue biopsy samples due to the ease and less invasive nature of collection.

Biological exposure indices of occupational exposure to benzene: A systematic review

The current study aimed to systematically review the studies concerning the biological monitoring of benzene exposure in occupational settings. A systematic literature review was conducted in Scopus, EMBASE, Web of Science, and Medline from 1985 through July 2021. We included peer-reviewed original articles that investigated the association between occupational exposure to benzene and biological monitoring. We identified 4786 unique citations, of which 64 cross-sectional, one case-control, and one cohort study met our inclusion criteria. The most studied biomarkers were urinary trans-trans muconic acid, S- phenyl mercapturic acid, and urinary benzene, respectively. We found the airborne concentration of benzene as a key indicator for choosing a suitable biomarker. We suggest considering urinary benzene at low (0.5-5.0 TLV), urinary SPMA and TTMA at medium (5.0-25 and 25-50 TLV, respectively), and urinary phenol and hydroquinone and catechol at very high concentrations (500 and 1000 TLV ≤, respectively). Genetic polymorphism of glutathione S-transferase and oral intake of sorbic acid have confounding effects on the level of U-SPMA and U-TTMA, respectively. The airborne concentration, smoking habit, oral consumption of sorbic acid, and genetic polymorphism of workers should be considered in order to choose the appropriate indicator for biological monitoring of benzene exposure.

Human biomonitoring of low-level benzene exposures

Historically, benzene has been widely used in a large variety of applications. Occupational exposure limits (OELs) were set for benzene as it was found to be acutely toxic, causing central nervous system depression at high exposures. OELs were lowered when it was discovered that chronic exposure to benzene could cause haematotoxicity. After confirmation that benzene is a human carcinogen causing acute myeloid leukaemia and possibly other blood malignancies, OEL were further lowered. The industrial application of benzene as solvent is almost completely discontinued but it is still used as feedstock for the production of other materials, such as styrene. Occupational exposure to benzene may also occur since it is present in crude oil, natural gas condensate and a variety of petroleum products and because benzene can be formed in combustion of organic material. In the past few years, lower OELs for benzene in the range of 0.05-0.25 ppm have been proposed or were already established to protect workers from benzene-induced cancer. The skin is an important potential route of exposure and relatively more important at lower OELs. Consequently, human biomonitoring - which integrates all exposure routes - is routinely applied to control overall exposure to benzene. Several potential biomarkers have been proposed and investigated. For compliance check of the current low OELs, urinary S-phenylmercapturic acid (S-PMA), urinary benzene and blood benzene are feasible biomarkers. S-PMA appears to be the most promising biomarker but proper validation of biomarker levels corresponding to airborne benzene concentrations below 0.25 ppm are needed.

Using Urinary Biomarkers to Estimate the Benzene Exposure Levels in Individuals Exposed to Benzene

Urinary benzene metabolites trans, trans-muconic acid (t, t-MA), and S-phenyl mercapturic acid (S-PMA) are often used as biomarkers of internal exposure to benzene. However, there are few reports on using urinary benzene metabolites to estimate airborne benzene concentrations in individuals exposed to benzene. In this study, t, t-MA, and S-PMA were analyzed by UPLC-MS/MS, and a simple pharmacokinetic model was used to calculate the daily intake (DI) of benzene based on the levels of urinary t, t-MA, and S-PMA in occupational individuals. The back-calculated airborne benzene levels (BCABL) were obtained from the DI of benzene. Among the exposed subjects (n = 84), the median BCABL (3.67 mg/m³) based on t, t-MA was very close to the median level of measured airborne benzene (3.27 mg/m³, p = 0.171), and there was no effect of smoking or dietary habits on t, t-MA-based BCABL. In the control subjects (n = 49), the levels of measured airborne benzene were all below the quantitation limit (0.024 mg/m³), and the BCABL (0.002-0.25 mg/m³) calculated by S-PMA was close to this background level. Our study suggests that the t, t-MA-based BCABL can reflect the actual airborne benzene level in a range of 1.10-86.91 mg/m³ and that the S-PMA-based BCABL is more reliable for non-professional benzene exposure.

External Exposure to BTEX, Internal Biomarker Response, and Health Risk Assessment of Nonoccupational Populations near a Coking Plant in Southwest China

Benzene, toluene, ethylbenzene and xylene isomers (BTEX) have raised increasing concern due to their adverse effects on human health. In this study, a coking factory and four communities nearby were selected as the research area. Atmospheric BTEX samples were collected and determined by a preconcentrator GC-MS method. Four biomarkers in the morning urine samples of 174 participants from the communities were measured by LC-MS. The health risks of BTEX exposure via inhalation were estimated. This study aimed to investigate the influence of external BTEX exposure on the internal biomarker levels and quantitatively evaluate the health risk of populations near the coking industry. The results showed that the average total BTEX concentration in residential area was 7.17 ± 7.24 μg m^-3. Trans,trans-muconic acid (T,T-MA) was the urinary biomarker with the greatest average level (127 ± 285 μg g^-1 crt). Similar spatial trends can be observed between atmospheric benzene concentration and internal biomarker levels. The mean values of the LCR for male and female residents were 2.15 × 10^-5 and 2.05 × 10^-5, respectively. The results of the risk assessment indicated that special attention was required for the non-occupational residents around the area.

Urinary Acrylonitrile Metabolite Concentrations Before and after Smoked, Vaporized, and Oral Cannabis in Frequent and Occasional Cannabis Users

Cannabis use through smoking, vaping, or ingestion is increasing, but only limited studies have investigated the resulting exposure to harmful chemicals. N-acetyl-S-(2-cyanoethyl)-L-cysteine (2CYEMA), a urinary metabolite of acrylonitrile, a possible carcinogen, is elevated in the urine of past-30-day cannabis users compared to non-cannabis users. Five frequent and five occasional cannabis users smoked and vaped cannabis on separate days; one also consumed cannabis orally. Urine samples were collected before and up to 72 h post dose and urinary 2CYEMA was quantified. We compared 2CYEMA pre-exposure levels, maximum concentration, time at maximum concentration for occasional versus frequent users following different exposure routes, and measured half-life of elimination. Smoking cannabis joints rapidly (within 10 min) increased 2CYEMA in the urine of occasional cannabis users, but not in frequent users. Urine 2CYEMA did not consistently increase following vaping or ingestion in either study group. Cigarette smokers had high pre-exposure concentrations of 2CYEMA. Following cannabis smoking, the half-lives of 2CYEMA ranged from 2.5 to 9.0 h. 2CYEMA is an effective biomarker of cannabis smoke exposure, including smoke from a single cannabis joint, however, not from vaping or when consumed orally. When using 2CYEMA to evaluate exposure in cannabis users, investigators should collect the details about tobacco smoking, route of consumption, and time since last use as possible covariates.

Benzene Exposure and Biomarkers in Alveolar Air and Urine Among Deck Crews on Tankers Transporting Gasoline

INTRODUCTION

Increased rates of leukaemia have been found among tanker crews. Occupational exposures to the leukomogen benzene during loading, unloading, and tank cleaning are possible causes. Studies on older types of tankers carrying gasoline with most handling being done manually have revealed important exposures to benzene. Our study explores benzene exposures on tankers with both automatic and manual systems. Correlations between benzene exposure and benzene in alveolar air (AlvBe), benzene in urine (UBe), and trans,trans-muconic acid (ttMA) in urine were investigated.

METHODS

Forty-three male seafarers (22 deck crewmembers and 21 not on deck) on five Swedish different product and chemical tankers transporting 95- or 98-octane gasoline were investigated between 1995 and 1998. The tankers used closed systems for the loading and unloading of gasoline but stripping and tank cleaning were done manually. Benzene in respiratory air was measured using personal passive dosimeters during a 4-h work shift. Samples for biomarker analyses were collected pre- and post-shift. Smoking did occur and crewmembers did not use any respiratory protection during work.

RESULTS

The average 4-h benzene exposure level for exposed was 0.45 mg m-3 and for non-exposed 0.02 mg m-3. Benzene exposure varied with type of work (range 0.02-143 mg m-3). AlvBe, UBe, and ttMA were significantly higher in post-shift samples among exposed and correlated with exposure level (r = 0.89, 0.74, and 0.57, respectively). Smoking did not change the level of significance among exposed.

DISCUSSION

Benzene in alveolar air, unmetabolized benzene, and ttMA in urine are potential biomarkers for occupational benzene exposure. Biomarkers were detectable in non-exposed, suggesting benzene exposure even for other work categories on board tankers. Work on tankers carrying gasoline with more or less closed handling of the cargo may still lead to significant benzene exposure for deck crewmembers, and even exceed the Swedish Occupational Exposure Limit (OEL; 8-h time-weighted average [TWA]) of 1.5 mg m-3.

Development of a UPLC-ESI-MS/MS method to measure urinary metabolites of selected VOCs: Benzene, cyanide, furfural, furfuryl alcohol, 5-hydroxymethylfurfural, and N-methyl-2-pyrrolidone

We report on the development of an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for simultaneously measuring eight biomarkers of volatile organic compound (VOC) exposure, with potential application to e-cigarette aerosol biomonitoring. Phenylmercapturic acid (PMA) and trans, trans-muconic acid (tt-MA) are metabolites of benzene; 2-aminothiazoline-4-carboxylic acid (ATCA) is a metabolite of cyanide; N-2-furoylglycine (N2FG) is a metabolite of furfural and furfuryl alcohol; 5-hydroxymethylfuroic acid (HMFA), 5-hydroxymethyl-2-furoylglycine (HMFG), and 2,5-furandicarboxylic acid (FDCA) are metabolites of 5-hydroxymethylfurfural; and 5-hydroxy-N-methylpyrrolidone (5HMP) is a metabolite of N-methyl-2-pyrrolidone. A pentafluorophenyl-modified silica column was used for chromatographic separation. The overall run time for the method is about 6 min per sample injection. The method has low to sub-nanograms per milliliter sensitivity, linearity over 3 orders of magnitude, and precision and accuracy within 15%. The method was used to measure human urine samples. Results showed that people with known benzene exposure (daily cigarette smokers) had higher levels of tt-MA and PMA compared with non-smokers. The method is advantageous for high-throughput analysis of selected VOC metabolites in large-scale, population-based studies such as the National Health and Nutrition Examination Survey (NHANES). Quantifying these urinary biomarkers is important to public health efforts to understand human exposure to VOCs from various sources, including tobacco products and electronic nicotine delivery systems.

Comparison of personal air benzene and urine t,t-muconic acid as a benzene exposure surrogate during turnaround maintenance in petrochemical plants

Previous studies have shown that biomarkers of chemicals with long half-lives may be better surrogates of exposure for epidemiological analyses, leading to less attenuation of the exposure-disease association, than personal air samples. However, chemicals with short half-lives have shown inconsistent results. In the present study, we compared pairs of personal air benzene and its short-half-life urinary metabolite trans,trans-muconic acid (t,t-MA), and predicted attenuation bias of theoretical exposure-disease association. Total 669 pairs of personal air benzene and urine t,t-MA samples were taken from 474 male workers during turnaround maintenance operations held in seven petrochemical plants. Maintenance jobs were classified into 13 groups. Variance components were calculated for personal air benzene and urine t,t-MA separately to estimate the attenuation of the theoretical exposure-disease association. Personal air benzene and urine t,t-MA showed similar attenuation of the theoretical exposure-disease association. Analyses for repeated measurements showed similar results, while in analyses for values above the limits of detection (LODs), urine t,t-MA showed less attenuation of the theoretical exposure-disease association than personal air benzene. Our findings suggest that there may be no significant difference in attenuation bias when personal air benzene or urine t,t-MA is used as a surrogate for benzene exposure.

Ln(III)-Functionalized Metal-Organic Frameworks Hybrid System: Luminescence Properties and Sensor for trans, trans-Muconic Acid as a Biomarker of Benzene

By application of a straightforward postsynthetic modification strategy, a luminescent lanthanide-based MOFs hybrid material, Tb(III)@MOF-SO₃^-, is first fabricated by loading Tb(III) ions into the pores of Zn-based MOF-SO₃^-. This hybrid system is constructed on notable and specific luminous sensitization of MOF-SO₃^- to Tb(III) ions. The further study shows that bi-metal-loaded Eu(III)/Tb(III)@MOF-SO₃^- exhibits a Tb(III)-induced luminescence of Eu(III) ions, and the emissions of it all fall in the white region by altering the ratio of Eu(III)/Tb(III) ions and the excitation wavelengths. A kind of white-lighting thin film based on Eu(III)/Tb(III)@MOF-SO₃^- exhibits dazzling white light when excited at 295 nm ( X = 0.338, Y = 0.323). Furthermore, the Tb(III)@MOF-SO₃^- is first developed as a fluorescence sensor specifically toward biomarker of benzene, trans, trans-muconic acid ( tt-MA), based on fluorescence quenching. This reusable sensor with high water tolerance and photostability displays excellent selectivity and sensitivity with a detection limit as low as 0.1 ppm, while being provided with the high antijamming of other urinary chemicals. These results make the sensor has the potential for the practical detection of tt-MA in a urine system. The possible quenching mechanisms are also investigated in detail.

Urinary 1-Hydroxypyrene and t, t-Muconic ACID as Biomarkers of Exposure to Environmental Pollutants in Two Areas in Italy (Epic-Florence and Ragusa)

Aims and background

Several chemical compounds included in the group of polycyclic aromatic hydrocarbons (PAH) and benzene are well-known human carcinogens present in the atmosphere of polluted urban areas. Major sources include vehicle traffic and industrial emissions, but also cigarette smoke. Genotoxic damage derived from exposure to PAHs can be measured in healthy adults by specific assays as PAH-DNA adducts. In the frame of EPIC-Italy, we recently carried out a cross-sectional study in different areas of the country (Palli et al., Int J Cancer, 87: 444-451, 2000) and showed that mean DNA adduct levels varied considerably among different centers, being highest in Florence (a large metropolitan area in Tuscany) and lowest in Ragusa (a small town in Sicily).

Methods

A subgroup of EPIC volunteers, representative of these two local cohorts, agreed to collect 24-h urine samples, and we measured the excretion of two potential biomarkers of exposure to environmental pollutants: t,t-muconic acid (MA), a metabolite of benzene, and 1-hydroxypyrene (1-OHP), a metabolite of pyrene. Overall, 69 24-h urine samples were available for analyses.

Results

The absolute amounts of 1-OHP and MA excreted in the 24-h urine samples were 169.6 ng and 33.8 μg, respectively. Urinary excretion of both metabolites did not vary according to age or area of residence. Strongly significant differences emerged when current smokers were compared to non-smokers for 1-OHP (P = 0.0001) and MA (P = 0.01), thus confirming that smokers are directly exposed to PAHs and benzene from tobacco smoke, with a dose-dependent effect particularly evident for MA. Multivariate analyses showed positive associations of 1-OHP excretion with male sex, low education and being overweight but not with residence in two areas with contrasting levels of urban pollution; MA excretion tended to be higher in Florence.

Conclusions

These two urinary metabolites are strongly related to tobacco smoke and do not appear to represent reliable biomarkers of exposure to environmental pollutants in the general population.

Endocrine disrupting chemicals, 4-nonylphenol, bisphenol A and butyl benzyl phthalate, impair metabolism of estradiol in male and female rats as assessed by levels of 15α-hydroxyestrogens and catechol estrogens in urine

Bisphenol A (BPA), 4-nonylphenol (NP) and butyl benzyl phthalate (BBP), termed endocrine-disrupting chemicals, are known to mimic estrogen activity. The effects of these chemicals on 17β-estradiol (E₂ ) metabolism in vivo in rats were examined. Male and female rats were given NP (250 mg kg^-1  day^-1 ), BPA (250 μg kg^-1  day^-1 ) or BBP (500 mg kg^-1  day^-1 ) by gavage for 14 days, followed by a single intraperitoneal injection of E₂ (5 mg kg^-1 ) on the final day. The urinary excretion over 72 hours of 2-hydroxyestrone 1-N-acetylcysteine thioether, 2-hydroxyestrone 4-N-acetylcysteine thioether, 4-hydroxyestrone 2-N-acetylcysteine thioether, 2-hydroxy-17β-estradiol (2-OHE₂ ), 2-hydroxyestrone (2-OHE₁ ), 4-hydroxy-17β-estradiol, 4-hydroxyestrone, 15α-hydroxyestriol (E₄ ), 15α-hydroxy-17β-estradiol and 15α-hydroxyestrone was measured. Increases in urinary excretion of 2-OHE₁ and decreases in E₄ were observed in males treated with NP or BBP. Decreases in urinary excretion of 2-OHE₂ and E₄ were observed in males treated with BPA. Decreases in urinary excretion of 2-OHE₁ and 2-OHE₂ were observed in females treated with BBP. Normalized liver and weights were increased in both sexes treated with NP or BBP. Histologic observations revealed marked changes in the distal tubules and collecting ducts in the kidneys of rats exposed to NP and BBP, and hypertrophy in the hepatocytes of the centrilobular zone of the liver. No BPA-related effects on organ weight and on liver or kidney histopathology were found. These results suggest that the 14 day oral dosing of NP and BBP disrupted E₂ metabolism, resulting from marked morphological and functional alterations in the liver and kidneys. In addition, BPA could induce metabolic and endocrine disruption.

Occupational benzene exposure from vehicular sources in India and its effect on hematology, lymphocyte subsets and platelet P-selectin expression

Benzene exposure from vehicular sources and its health impact are relatively unexplored in India. We have investigated in this study hematology and lymphocyte subsets of 25 petrol pump attendants, 25 automobile service station workers and 35 controls matched for age, sex and socioeconomic conditions. The participants were non-smoking males of Kolkata (former Calcutta) in eastern India. Compared with controls, the workers had 3.8- times more trans,trans-muconic acid in urine, suggesting higher level of benzene exposure. The exposed subjects had decreased erythrocyte, hemoglobin, lymphocyte and platelet levels, but increased neutrophil, band cells, RBC aniso-poikilocytosis and target cells. In addition, CD4+, CD8+ and CD19+ cells were decreased by 37, 20 and 47% respectively, but CD 16+ 56+ NK cells were increased by 20%. P-selectin expression on platelet surface of the workers was significantly elevated ( P < 0.05), indicating upregulation of platelet activity. In summary, the study revealed high level of benzene exposure from vehicular sources in India, and the exposed subjects had hematological and immunological alterations. Toxicology and Industrial Health 2007; 23: 167—175.

Evaluation of Biomarkers of Exposure in Smokers Switching to a Carbon-Heated Tobacco Product: A Controlled, Randomized, Open-Label 5-Day Exposure Study

Introduction:

Tobacco harm reduction aims to provide reduced risk alternatives to adult smokers who would otherwise continue smoking combustible cigarettes (CCs). This randomized, open-label, three-arm, parallel-group, single-center, short-term confinement study aimed to investigate the effects of exposure to selected harmful and potentially harmful constituents (HPHCs) of cigarette smoke in adult smokers who switched to a carbon-heated tobacco product (CHTP) compared with adult smokers who continued to smoke CCs and those who abstained from smoking for 5 days.

Methods:

Biomarkers of exposure to HPHCs, including nicotine and urinary excretion of mutagenic material, were measured in 24-hour urine and blood samples in 112 male and female Caucasian smokers switching from CCs to the CHTP ad libitum use. Puffing topography was assessed during product use.

Results:

Switching to the CHTP or smoking abstinence (SA) resulted in marked decreases from baseline to Day 5 in all biomarkers of exposure measured, including carboxyhemoglobin (43% and 55% decrease in the CHTP and SA groups, respectively). The urinary excretion of mutagenic material was also markedly decreased on Day 5 compared with baseline (89% and 87% decrease in the CHTP and SA groups, respectively). No changes in biomarkers of exposure to HPHCs or urinary mutagenic material were observed between baseline and Day 5 in the CC group.

Conclusions:

Our results provide clear evidence supporting a reduction in the level of exposure to HPHCs of tobacco smoke in smokers who switch to CHTP under controlled conditions, similar to that observed in SA.

Implications:

The reductions observed in biomarkers of exposure to HPHCs of tobacco smoke in this short-term study could potentially also reduce the incidence of cancer, cardiovascular and respiratory diseases in those smokers who switch to a heated tobacco product.

Biomarkers of susceptibility following benzene exposure: influence of genetic polymorphisms on benzene metabolism and health effects

Benzene is a ubiquitous occupational and environmental pollutant. Improved industrial hygiene allowed airborne concentrations close to the environmental context (1-1000 µg/m(3)). Conversely, new limits for benzene levels in urban air were set (5 µg/m(3)). The biomonitoring of exposure to such low benzene concentrations are performed measuring specific and sensitive biomarkers such as S-phenylmercapturic acid, trans, trans-muconic acid and urinary benzene: many studies referred high variability in the levels of these biomarkers, suggesting the involvement of polymorphic metabolic genes in the individual susceptibility to benzene toxicity. We reviewed the influence of metabolic polymorphisms on the biomarkers levels of benzene exposure and effect, in order to understand the real impact of benzene exposure on subjects with increased susceptibility.

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.

Benzene oxide is a substrate for glutathione S-transferases

Benzene is a known human carcinogen which must be activated to benzene oxide (BO) to exert its carcinogenic potential. BO can be detoxified in vivo by reaction with glutathione and excretion in the urine as S-phenylmercapturic acid. This process may be catalyzed by glutathione S-transferases (GSTs), but kinetic data for this reaction have not been published. Therefore, we incubated GSTA1, GSTT1, GSTM1, and GSTP1 with glutathione and BO and quantified the formation of S-phenylglutathione. Kinetic parameters were determined for GSTT1 and GSTP1. At 37 °C, the putative Km and Vmax values for GSTT1 were 420 μM and 450 fmol/s, respectively, while those for GSTP1 were 3600 μM and 3100 fmol/s. GSTA1 and GSTM1 did not exhibit sufficient activity for determination of kinetic parameters. We conclude that GSTT1 is a critical enzyme in the detoxification of BO and that GSTP1 may also play an important role, while GSTA1 and GSTM1 seem to be less important.

Neurobehavioral performance in adolescents is inversely associated with traffic exposure

On the basis of animal research and epidemiological studies in children and elderly there is a growing concern that traffic exposure may affect the brain. The aim of our study was to investigate the association between traffic exposure and neurobehavioral performance in adolescents. We examined 606 adolescents. To model the exposure, we constructed a traffic exposure factor based on a biomarker of benzene (urinary trans,trans-muconic acid) and the amount of contact with traffic preceding the neurobehavioral examination (using distance-weighted traffic density and time spent in traffic). We used a Bayesian structural equation model to investigate the association between traffic exposure and three neurobehavioral domains: sustained attention, short-term memory, and manual motor speed. A one standard deviation increase in traffic exposure was associated with a 0.26 standard deviation decrease in sustained attention (95% credible interval: -0.02 to -0.51), adjusting for gender, age, smoking, passive smoking, level of education of the mother, socioeconomic status, time of the day, and day of the week. The associations between traffic exposure and the other neurobehavioral domains studied had the same direction but did not reach the level of statistical significance. The results remained consistent in the sensitivity analysis excluding smokers and passive smokers. The inverse association between sustained attention and traffic exposure was independent of the blood lead level. Our study in adolescents supports the recent findings in children and elderly suggesting that traffic exposure adversely affects the neurobehavioral function.

Metabolic polymorphisms and biomarkers of effect in the biomonitoring of occupational exposure to low-levels of benzene: state of the art

Current levels of occupational exposure to benzene, a genotoxic human carcinogen, in Western countries are reduced by two-three orders of magnitude (from ppm to ppb) as compared to the past. However, as benzene toxicity is strongly dependent on biotransformation and recent evidence underlines a higher efficiency of bio-activation pathways at lower levels of exposure, toxic effects at low doses could be higher than expected, particularly in susceptible individuals. Currently, biological monitoring can allow accurate exposure assessment, relying on sensitive and specific enough biomarkers of internal dose. The availability of similarly reliable biomarkers of early effect or susceptibility could greatly improve the risk assessment process to such an extent that risk could even be assessed at the individual level. As to susceptibility biomarkers, functional genetic polymorphisms of relevant biotransformation enzymes may modulate the risk of adverse effects (NQO1) and the levels of biomarkers of internal dose, in particular S-phenylmercapturic acid (GSTM1, GSTT1, GSTA1). Among biomarkers of early effect, genotoxicity indicators, although sensitive in some cases, are too aspecific for routine use in occupational health surveillance programmes. Currently only the periodical blood cell count seems suitable enough to be applied in the longitudinal monitoring of effects from benzene exposure. Novel biomarkers of early effect are expected from higher collaboration among toxicologists and clinicians, also using advanced "omics" techniques.

Reduction of DNA mismatch repair protein expression in airway epithelial cells of premenopausal women chronically exposed to biomass smoke

Biomass burning is a major source of indoor air pollution in rural India. This study examined whether chronic inhalation of biomass smoke causes change in the DNA mismatch repair (MMR) pathway in the airway cells. For this, airway cells exfoliated in sputum were collected from 72 premenopausal nonsmoking rural women (median age 34 years) who cooked with biomass (wood, dung, crop residues) and 68 control women who cooked with cleaner fuel liquefied petroleum gas (LPG) for the past 5 years or more. The levels of particulate matters with diameters less than 10 and 2.5 μm (PM10 and PM2.5) in indoor air were measured by real-time aerosol monitor. Benzene exposure was monitored by measuring trans,trans-muconic acid (t,t-MA) in urine by high-performance liquid chromatography with ultraviolet detector. Generation of reactive oxygen species (ROS) and level of superoxide dismutase (SOD) in airway cells were measured by flow cytometry and spectrophotometry, respectively. Immunocytochemical assay revealed lower percentage of airway epithelial cells expressing MMR proteins mutL homolog 1 (MLH1) and mutS homolog 2 (MSH2) in biomass-using women compared to LPG-using controls. Women who cooked with biomass had 6.7 times higher level of urinary t,t-MA, twofold increase in ROS generation, and 31 % depletion of SOD. Indoor air of biomass-using households had three times more particulate matters than that of controls. ROS, urinary t,t-MA, and particulate pollution in biomass-using kitchen had negative correlation, while SOD showed positive correlation with MSH2 and MLH1 expression. It appears that chronic exposure to biomass smoke reduces MMR response in airway epithelial cells, and oxidative stress plays an important role in the process.

A simple HPLC method to determine urinary phenylmercapturic acid and its application to gasoline station attendants to biomonitor occupational exposure to benzene at less than 1 ppm

The objective of this study was to establish a hand-saving method to measure phenylmercapturic acid (PMA) and to examine urinary PMA as a marker of occupational exposure to benzene at levels less than 1 ppm. A simple HPLC method was developed to analyse PMA by monitoring absorption at 195 nm of the ef? uent from an ODS-3 column with acetonitrile-methanol-perchloric acid-water as a mobile phase. The detection limit of the method was 0.2 μg l(-1) with sufficient reproducibility. The method was applied to end-of-shift urine samples from 70 gasoline station attendants exposed to up to 107 ppb benzene, and 20 non-exposed controls of both sexes. Time-weighted average (TWA) exposure to benzene was measured by diffusive sampling. A regression analysis was applied to examine the quantitative relationship between the intensity of exposure to benzene and PMA in the end-of-shift urine samples. Multiple regression analysis showed no effects of age, sex, smoking and co-exposure to toluene and xylenes on urinary PMA. There was a linear relationship between TWA benzene exposure and urinary PMA (r = 0.60-0.67, P < 0.01). Background PMA in urine of the non-exposed controls was low and scattering of PMA around the regression line was narrow so that those with 20 ppb benzene exposure can be separated from the non-exposed by urinalysis for PMA. Thus, urinary PMA is sensitive enough for biological exposure monitoring of those exposed to less than 1 ppm benzene.

The use of biomonitoring data in exposure and human health risk assessment: benzene case study

Abstract A framework of "Common Criteria" (i.e. a series of questions) has been developed to inform the use and evaluation of biomonitoring data in the context of human exposure and risk assessment. The data-rich chemical benzene was selected for use in a case study to assess whether refinement of the Common Criteria framework was necessary, and to gain additional perspective on approaches for integrating biomonitoring data into a risk-based context. The available data for benzene satisfied most of the Common Criteria and allowed for a risk-based evaluation of the benzene biomonitoring data. In general, biomarker (blood benzene, urinary benzene and urinary S-phenylmercapturic acid) central tendency (i.e. mean, median and geometric mean) concentrations for non-smokers are at or below the predicted blood or urine concentrations that would correspond to exposure at the US Environmental Protection Agency reference concentration (30 µg/m(3)), but greater than blood or urine concentrations relating to the air concentration at the 1 × 10(-5) excess cancer risk (2.9 µg/m(3)). Smokers clearly have higher levels of benzene exposure, and biomarker levels of benzene for non-smokers are generally consistent with ambient air monitoring results. While some biomarkers of benzene are specific indicators of exposure, the interpretation of benzene biomonitoring levels in a health-risk context are complicated by issues associated with short half-lives and gaps in knowledge regarding the relationship between the biomarkers and subsequent toxic effects.

Urinary benzene biomarkers and DNA methylation in Bulgarian petrochemical workers: study findings and comparison of linear and beta regression models

Chronic occupational exposure to benzene is associated with an increased risk of hematological malignancies such as acute myeloid leukemia (AML), but the underlying mechanisms are still unclear. The main objective of this study was to investigate the association between benzene exposure and DNA methylation, both in repeated elements and candidate genes, in a population of 158 Bulgarian petrochemical workers and 50 unexposed office workers. Exposure assessment included personal monitoring of airborne benzene at work and urinary biomarkers of benzene metabolism (S-phenylmercapturic acid [SPMA] and trans,trans-muconic acid [t,t-MA]) at the end of the work-shift. The median levels of airborne benzene, SPMA and t,t-MA in workers were 0.46 ppm, 15.5 µg/L and 711 µg/L respectively, and exposure levels were significantly lower in the controls. Repeated-element DNA methylation was measured in Alu and LINE-1, and gene-specific methylation in MAGE and p15. DNA methylation levels were not significantly different between exposed workers and controls (P>0.05). Both ordinary least squares (OLS) and beta-regression models were used to estimate benzene-methylation associations. Beta-regression showed better model specification, as reflected in improved coefficient of determination (pseudo R(2)) and Akaike's information criterion (AIC). In beta-regression, we found statistically significant reductions in LINE-1 (-0.15%, P<0.01) and p15 (-0.096%, P<0.01) mean methylation levels with each interquartile range (IQR) increase in SPMA. This study showed statistically significant but weak associations of LINE-1 and p15 hypomethylation with SPMA in Bulgarian petrochemical workers. We showed that beta-regression is more appropriate than OLS regression for fitting methylation data.

Reduced exposure evaluation of an Electrically Heated Cigarette Smoking System. Part 1: Non-clinical and clinical insights

The following series of papers presents an extensive assessment of the Electrically Heated Cigarette Smoking System EHCSS series-K cigarette vs. conventional lit-end cigarettes (CC) as an example for an extended testing strategy for evaluation of reduced exposure. The EHCSS produces smoke through electrical heating of tobacco. The EHCSS series-K heater was designed for exclusive use with EHCSS cigarettes, and cannot be used to smoke (CC). Compared to the University of Kentucky Reference Research cigarette 2R4F and a series of commercial CC, mainstream cigarette smoke of both the non-menthol and menthol-flavored EHCSS cigarettes showed a reduced delivery of a series of selected harmful and potentially harmful constituents (HPHC), mutagenic activity determined using the Salmonella typhimurium Reverse Mutation (Ames) assay, and cytotoxicity in the Neutral Red Uptake Assay. Clinical evaluations confirmed reduced exposure to HPHC and excretion of mutagenic material under controlled clinical conditions. Reductions in HPHC exposure were confirmed in a real-world ambulatory clinical study. Potential biomarkers of cardiovascular risk were also reduced under real-world ambulatory conditions. A modeling approach, 'nicotine bridging', was developed based on the determination of nicotine exposure in clinical evaluations which indicated that exposure to HPHC for which biomarkers of exposure do not exist would also be reduced.

Urinary trans, trans-muconic acid and S-phenylmercapturic acid are indicative of exposure to urban benzene pollution during childhood

The aims of the study were to evaluate the feasibility of urinary trans, trans-muconic acid (u-t,t-MA) and urinary S-phenylmercapturic acid (u-SPMA) as markers of exposure to urban benzene pollution for biomonitoring studies performed on children and to investigate the impact that creatinine correction may have on the classification of children exposure status. U-t,t-MA, u-SPMA, u-cotinine, and u-creatinine levels were measured in urine samples of 396 Italian children (5-11 years) living in three areas with different degrees of urbanisation (very, fairly and non-urban). The median u-SPMA levels significantly increased with increased urbanisation: non-urban (0.19 μg/L; 0.22 μg/g creatinine)<fairly urban (0.28 μg/L; 0.28 μg/g creatinine)<very urban group (0.92 μg/L; 0.90 μg/g creatinine). Differences in the levels of u-t,t-MA excretion related to the degree of urbanisation were revealed only by multivariate analyses. Neither u-SPMA nor u-t,t-MA levels were influenced by environmental tobacco smoke (ETS) exposure. Athletic activity during the sampling day was negatively associated with u-SPMA in the model built with u-SPMA adjusted for creatinine, but not in the model where unadjusted u-SPMA was used. This finding demonstrates that u-creatinine correction may alter the results when an independent variable is unrelated to the chemical concentration itself but is related to the u-creatinine levels. These results suggest that both u-SPMA and u-t,t-MA are indicative for assessing environmental benzene exposure in children (exposed and unexposed to ETS) when urine sample is collected at the end of the day. However, u-SPMA is more reliable because u-t,t-MA, also a metabolite of sorbic acid, is less specific for exposure to low levels of benzene. To avoid the possible confounding effect of creatinine correction, it is better to use u-creatinine as additional independent variable in multiple linear regression analyses for evaluating the independent role of the covariates on the variability of u-t,t-MA and u-SPMA levels.

Trans, trans-muconic acid as a biomarker of occupational exposure to high-level benzene in China

OBJECTIVE

The work aimed to study the potential correlation between the high-level benzene exposure and its urinary metabolites S-phenylmercapturic acid (SPMA) and trans, trans-muconic acid (t,t-MA) in Chinese shoe-making workers.

METHODS

Individual benzene-exposed levels were determined by gas chromatography analysis, urinary t,t-MA, and urinary SPMA were determined by high performance liquid chromatography-an ultraviolet detector and liquid chromatography/electrospray tandem mass spectrometry method, respectively.

RESULTS

The concentration of benzene ranged from 2.57 to 146.11 mg/m³. And the correlation between benzene and t,t-MA was significantly higher than that of SPMA at the postshift, for example, the correlation coefficient was 0.905 and 0.537 for t,t-MA and SPMA, respectively. Moreover, The relative internal exposure index of t,t-MA (0.28 mg/g Cr: mg/m³) was more similar to the data supplied by American Conference of Governmental Industrial Hygienists compared to the index of SPMA (0.025 mg/g Cr:mg/m³).

CONCLUSIONS

t,t-MA appeared to be a more specific biomarker than SPMA at high-level benzene exposure.

Proposal on limits for chemical exposure in saturation divers' working atmosphere: the case of benzene

Saturation diving is performed under extreme environmental conditions. The divers are confined to a limited space for several weeks under high environmental pressure and elevated oxygen partial pressure. At present, divers are protected against chemical exposure by standard exposure limits only adjusted for the increased exposure length, i.e. from 8 to 24 hours a day and from 5 to 7 days a week. The objective of the present study was to indicate a procedure for derivation of occupational exposure limits for saturation diving, termed hyperbaric exposure limits (HEL). Using benzene as an example, a procedure is described that includes identification of the latest key documents, extensive literature search with defined exclusion criteria for the literature retrieved. Hematotoxicity and leukemia were defined as the critical effects, and exposure limits based upon concentration and cumulative exposure data and corresponding risks of leukemia were calculated. Possible interactions of high pressure, elevated pO₂, and continuous exposure have been assessed, and incorporated in a final suggestion of a HEL for benzene. The procedure should be applicable for other relevant chemicals in the divers' breathing atmosphere. It is emphasized that the lack of interactions from pressure and oxygen indicated for benzene may be completely different for other chemicals.

Chronic inhalation of biomass smoke is associated with DNA damage in airway cells: involvement of particulate pollutants and benzene

This study examined whether indoor air pollution from biomass fuel burning induces DNA damage in airway cells. For this, sputum cells were collected from 56 premenopausal rural women who cooked with biomass (wood, dung, crop residues) and 49 age-matched controls who cooked with cleaner liquefied petroleum gas. The levels of particulate matters with diameters of less than 10 and 2.5 µm (PM(10) and PM(2.5)) in indoor air were measured using a real-time aerosol monitor. Benzene exposure was monitored by measuring trans,trans-muconic acid (t,t-MA) in urine by HPLC-UV. DNA damage was examined by alkaline comet assay in sputum cells. Generation of reactive oxygen species (ROS) and level of superoxide dismutase (SOD) in sputum cells were measured by flow cytometry and spectrophotometry, respectively. Compared with controls, biomass users had 4 times higher tail percentage DNA, 37% more comet tail length and 5 times more Olive tail moment (p < 0.001) in inflammatory and epithelial cells in sputum, suggesting extensive DNA damage. In addition, women who cooked with biomass had 6 times higher levels of urinary t,t-MA and 2-fold higher levels of ROS generation concomitant with 28% depletion of SOD. Indoor air of biomass-using households had 2-4 times more PM(10) and PM(2.5) than that of controls. After controlling potential confounders, positive association was found between DNA damage parameters, particulate pollution, urinary t,t-MA and ROS. Thus, long-term exposure to biomass smoke induces DNA damage in airway cells and the effect was probably mediated, at least in part, by oxidative stress generated by inhaled particulate matter and benzene.

The use of biomarkers in occupational health research, practice, and policy

Biomarkers are potentially useful tools for occupational health and safety research, practice, and policy. However, the full realization of this potential has not been achieved. In this paper, the progress made in these three usage areas is reviewed to identify what efforts can be taken to realize the full promise of biomarkers. Biomarker uses are described by a diverse taxonomy that builds on the categories of exposure, effect and susceptibility, and the continuum between exposure and disease prognosis. The most significant uses of biomarkers in occupational health have been in biological monitoring of workers. Other important uses have been in enhancing research and assessing mechanisms of action of occupational toxicants at low exposures. Seven critical areas will influence the extent to which the potential of biomarkers in occupational health and safety is realized. These include: (1) adequate investment in validation; (2) obtaining international agreement on exposure guidelines; (3) exploring the utility of biomarkers in regulation; (4) applying biomarkers to critical occupational safety and health questions; (5) developing the exposome; (6) utilizing biomarkers to address emerging occupational health issues; and (7) continuing to address the ethical and social justice issues related to biomarkers. Overall, if biomarkers are to make a major contribution to occupational health and safety then a more holistic approach to bringing them from the laboratory to practice will be needed.

Validity of new biomarkers of internal dose for use in the biological monitoring of occupational and environmental exposure to low concentrations of benzene and toluene

OBJECTIVES

This study analyzes the validity of new, more sensitive and specific urinary biomarkers of internal dose, namely, urinary benzene for benzene and urinary toluene and S-benzylmercapturic acid (SBMA) for toluene, to assess their efficacy when compared to traditional biomarkers for biological monitoring of occupational exposure to low concentrations of these two toxic substances.

METHODS

Assessment was made of 41 workers occupationally exposed to benzene and toluene, 18 fuel tanker drivers and 23 filling-station attendants, as well as 31 subjects with no occupational exposure to these toxic substances (controls). Exposure to airborne benzene and toluene was measured using passive Radiello personal samplers worn throughout the work shift. In urine samples collected from all subjects at the end of the workday, both the traditional and the new internal dose biomarkers of benzene and toluene were assessed, as well as creatinine so as to apply suitable adjustments.

RESULTS

Occupational exposure to benzene and toluene resulted significantly higher in the fuel tanker drivers than the filling-station attendants, and higher in the latter than in controls. Significantly higher concentrations of t,t-muconic acid (t,t-MA), S-phenylmercapturic acid (SPMA), urinary benzene, SBMA and urinary toluene were found in the drivers than the filling-station attendants or the controls. Instead, urinary phenol and hippuric acid were not different in the three groups. In the entire sample, airborne benzene and toluene values were significantly correlated, as were the respective urinary biomarkers, showing coefficients ranging from 0.36 to 0.98. Subdividing the subjects by smoking habit, higher coefficients were evident in non-smokers than in smokers; at multiple regression analysis t,t-MA, SPMA and urinary benzene and toluene were dependent on the number of cigarettes smoked daily and on airborne benzene and toluene, respectively. Instead, SBMA was dependent only on airborne toluene.

CONCLUSIONS

Our research confirmed the validity of t,t-MA and SPMA for use in the biological monitoring of exposure to low concentrations of benzene. Urinary benzene showed comparable validity to SPMA; both parameters are affected by smoking cigarettes in the hours before urine collection, so it is best to ask subjects to refrain from smoking for 2 h before urine collection. Urinary toluene was found to be a more specific biomarker than SBMA.

ATSDR evaluation of health effects of benzene and relevance to public health

As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites that have the greatest public health impact. These profiles comprehensively summarize toxicological and environmental information. This article constitutes the release of portions of the Toxicological Profile for Benzene. The primary purpose of this article is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective on the toxicology of benzene. It contains descriptions and evaluations of toxicological studies and epidemiological investigations and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health.

Association between GST genetic polymorphism and dose-related production of urinary benzene metabolite markers, trans, trans-muconic acid and S-phenylmercapturic acid

The urinary benzene metabolites, trans, trans-muconic acid (ttMA) and S-phenylmercapturic acid (SPMA), are widely used as benzene exposure biomarkers. The influence of the glutathione S-transferase (GST) genetic polymorphism on the excretion levels of urinary ttMA and/or SPMA has been investigated. The association between dose-related production of urinary benzene metabolites and benzene exposure level was also reported. However, the association between the dose-related productions of urinary benzene metabolites and GST genetic polymorphism was not described in the literature. The purpose of this study was to investigate the association between the GST genetic polymorphism and dose-related production of the two widely used biomarkers, urinary ttMA and SPMA. Seventy male workers in a chemical factory were measured for their benzene exposure levels and provided blood and urine specimens at the end of work-shift. The atmospheric benzene exposure levels of these workers were determined by passive samplers with gas chromatograph mass spectrometer. The urinary ttMA and SPMA levels were quantitated by an online dual-loop cleanup device with an electrospray ionization tandem mass spectrometer. The analyses of GST genotypes, including M(1), T(1), and P(1), were done using PCR. Mean (+/- SD) of benzene exposure levels in participants was 7.2 +/- 15 ppm. The ttMA and SPMA levels in the high benzene exposure group (> or =1 ppm) were higher than those in the low benzene exposure group (<1 ppm; P < 0.001). Among the GST genotypes investigated in this study, the results showed that only the GSTT1 genotype was related to the level and dose-related production of SPMA. Using SPMA for evaluating benzene exposure, the results suggest that the GSTT1 genetic polymorphism, especially in a comparison study between two populations with different GSTT1 genotype frequencies, should be considered. Additionally, the biological exposure index value of SPMA should be set based on the levels of subjects with GSTT1-deficient genotypes for protection of all subjects.

Evaluation of urinary 1-hydroxypyrene,S-phenylmercapturic acid,trans,trans-muconic acid, 3-methyladenine, 3-ethyladenine, 8-hydroxy-2′-deoxyguanosine and thioethers as biomarkers of exposure to cigarette smoke

The objective was to evaluate the utility of urinary 1-hydroxypyrene (1-OHP), S-phenylmercapturic acid (S-PMA), trans,trans-muconic acid (t,t-MA), 3-methyladenine (3-MeAd), 3-ethyladenine (3-EtAd), 8-hydroxy-2'-deoxyguanosine (8-OHdG) and thioethers as biomarkers for assessing the exposure in adult smokers who switched from smoking conventional cigarettes to candidate potential reduced exposure products (PREP) or who stopped smoking. Two electrically heated smoking systems (EHCSS) were used as prototype cigarettes that have significant reductions in a number of mainstream smoke constituents as measured by smoking machines relative to those from conventional cigarettes. Urine samples were collected from a randomized, controlled, forced-switching study in which 110 adult smokers of a conventional cigarette brand (CC1) were randomly assigned to five study groups. The groups included the CC1 smoking group, a lower-tar conventional cigarette (CC2) smoking group, EHCSS1 group, EHCSS2 group and a no smoking group that were monitored for 8 days. Biomarkers were measured at baseline and day 8. The daily excretion levels of these biomarkers were compared among the groups before and after switching, and the relationships between the daily excretion levels of these biomarkers and cigarette smoking-related exposure were investigated using Pearson product-moment correlation and multiple regression analyses. It was concluded that under controlled study conditions: (1) 1-OHP, S-PMA and t,t-MA are useful biomarkers that could differentiate exposure between smoking conventional and EHCSS cigarettes or between smoking conventional cigarettes and no smoking; between S-PMA and t,t-MA, the former appeared to be more sensitive; (2) 3-MeAd could only differentiate between smoking conventional cigarettes and no smoking; the results for 3-EtAd were not conclusive because contradictory results were observed; (3) 8-OHdG had a questionable association with smoking and therefore the utility of this biomarker for smoking-related exposure could not be established; and (4) urinary excretion of thioethers as a biomarker lacked sensitivity to demonstrate a clear dose-response relationship in conventional cigarette smokers, although it could differentiate the excretion levels between those subjects who smoked a conventional cigarette and those who stopped smoking.

Role of biomarkers in monitoring exposures to chemicals: present position, future prospects

Biomarkers are becoming increasingly important in toxicology and human health. Many research groups are carrying out studies to develop biomarkers of exposure to chemicals and apply these for human monitoring. There is considerable interest in the use and application of biomarkers to identify the nature and amounts of chemical exposures in occupational and environmental situations. Major research goals are to develop and validate biomarkers that reflect specific exposures and permit the prediction of the risk of disease in individuals and groups. One important objective is to prevent human cancer. This review presents a commentary and consensus views about the major developments on biomarkers for monitoring human exposure to chemicals. A particular emphasis is on monitoring exposures to carcinogens. Significant developments in the areas of new and existing biomarkers, analytical methodologies, validation studies and field trials together with auditing and quality assessment of data are discussed. New developments in the relatively young field of toxicogenomics possibly leading to the identification of individual susceptibility to both cancer and non-cancer endpoints are also considered. The construction and development of reliable databases that integrate information from genomic and proteomic research programmes should offer a promising future for the application of these technologies in the prediction of risks and prevention of diseases related to chemical exposures. Currently adducts of chemicals with macromolecules are important and useful biomarkers especially for certain individual chemicals where there are incidences of occupational exposure. For monitoring exposure to genotoxic compounds protein adducts, such as those formed with haemoglobin, are considered effective biomarkers for determining individual exposure doses of reactive chemicals. For other organic chemicals, the excreted urinary metabolites can also give a useful and complementary indication of exposure for acute exposures. These methods have revealed 'backgrounds' in people not knowingly exposed to chemicals and the sources and significance of these need to be determined, particularly in the context of their contribution to background health risks.

Reference values of urinary trans,trans-muconic acid: Italian Multicentric Study

This article reports the results of a study, conducted in the framework of the scientific activities of the Italian Society for Reference Values, aimed at defining reference values of urinary trans,trans-muconic acid (t,t-MA) in the general population not occupationally exposed to benzene. t,t-MA concentrations detected in 376 subjects of the resident population in three areas of Italy, two in central (Florence and southern Tuscany) and one in northern Italy (Padua), by three laboratories, compared by repeated interlaboratory controls, showed an interval of 14.4-225.0 microg/L (5th-95th percentile) and a geometric mean of 52.5 microg/L. The concentrations measured were influenced by tobacco smoking in a statistically significant way: Geometric mean concentrations were 44.8 microg/L and 76.1 microg/Ll in nonsmokers (264 subjects) and smokers (112 subjects), respectively. In the nonsmoking population, a significant influence of gender was found when concentrations were corrected for urinary creatinine, geometric mean concentrations being 36.7 microg/g creatinine in males (128 subjects) and 44.7 microg/g creatinine in females (136 subjects). The place of residence of subjects did not seem to influence urinary excretion of the metabolite, although personal inhalation exposure to benzene over a 24-h period showed slightly higher concentrations in Padua and Florence (geometric means of 6.5 microg/m(3) and 6.6 microg/m(3), respectively) than in southern Tuscany (geometric mean of 3.9 microg/m(3)). Concentration of t,t-MA in urine samples collected at the end of personal air sampling showed little relationship to personal inhalation exposure to benzene, confirming the importance of other factors in determining excretion of t,t-MA when concentrations in personal air samples are very low.

Comparison of benzene exposure in drivers and petrol stations workers by urinary trans,trans-muconic acid in west of Iran

Motor vehicle traffic is the main emission source of benzene. We undertook this study in order to compare benzene exposure and urinary levels of trans,trans-muconic acid (t,t-MA) in taxi drivers and petrol station workers. Air benzene levels were analyzed with gas chromatography using a Flame Ionization Detector. t,t-MA was extracted from urine and analyzed using high performance liquid chromatography. Significant differences in levels of urinary t,t-MA were found in drivers and petrol station workers when compared to a control group (p<0.05). Correlation coefficients between benzene in air and t,t-MA for petrol station workers and drivers were 0.65 and 0.30, respectively. The concentration of benzene in the breathing zone of petrol station workers was 2-3 times higher than drivers, and also 3 times greater than a threshold level (0.5 ppm) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). The lowest benzene concentration at which urinary t,t-MA increased to a measurable level was approximately 0.17 ppm. In conclusion our results suggested that high benzene levels are emitted in petrol stations in west Iran. t,t-MA analysis was able to separate those exposed from the non-exposed benzene group when benzene in the breathing zone of subjects was greater than 0.17 ppm.

A critique of benzene exposure in the general population

Benzene risk assessment indicates that exposure to a time-weighted average (TWA) of 1-5 parts per million (ppm) benzene in ambient air for 40 years is associated with an increased risk of acute myeloid leukemia. Decreased white blood cell count, platelet count and other hematological indices have also been observed in persons exposed to as low as 1 ppm airborne benzene. Evidence from studies worldwide consistently shows elevated levels of benzene biomarkers that are equivalent to 0.1-2 ppm benzene in ambient air, or even higher in the general population without occupational exposure to benzene (including children). The public health significance of these observations depends on to what extent these levels reflect actual benzene exposure, and whether such exposures are life-long or at least occur frequently enough to pose a possible health threat. We reviewed the evidence and discussed possible explanations for these observations. It was concluded that while there is reason to suspect that benzene contributes significantly to elevated levels of biomarkers in the general population, there is growing concern that this cannot be definitively ascertained without concomitant consideration of the role of other factors such as metabolic polymorphisms and sources of biomarkers other than benzene, which have been insufficiently studied to date. Such studies are urgently needed for valid assessment of this potential public health problem.

Relationship between machine-derived smoke yields and biomarkers in cigarette smokers in Germany

In order to determine whether smokers of cigarettes in the contemporary yield ranges of the German market (0.1-1.0mg nicotine, 1-10mg tar) differ in their actual exposure to various smoke constituents, we performed a field study with 274 smokers and 100 non-smokers. The following biomarkers were determined: In 24-h urine: Nicotine equivalents (molar sum of nicotine, cotinine, trans-3'-hydroxycotinine and their respective glucuronides), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL, metabolite of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, NNK), 3-hydroxypropylmercapturic acid (metabolite of acrolein), trans,trans-muconic acid, S-phenylmercapturic acid (metabolites of benzene), 1-hydroxypyrene (metabolite of pyrene); in saliva: Cotinine and trans-3'-hydroxycotinine; in exhaled air: Carbon monoxide; in blood: Methyl-, hydroxyethyl-, cyanoethyl- (biomarker of acrylonitrile) and carbamoylethylvaline (biomarker of acrylamide) hemoglobin adducts. All biomarkers were found to be significantly higher in smokers compared to non-smokers and showed strong correlations with the daily cigarette consumption. Biomarker levels and per cigarette increases in smokers were at most weakly related to the machine-derived smoke yields. It is concluded that machine-derived yields of cigarettes from the contemporary German cigarette market have little or no impact on the actual smoking-related exposure determined by suitable biomarkers.

Urinary biomarkers of 1,3-butadiene in environmental settings using liquid chromatography isotope dilution tandem mass spectrometry

Although, 1,3-butadiene is a known human carcinogen emitted from mobile sources, little is known about traffic-related human exposure to this toxicant. This pilot study was designed to characterize traffic-related environmental exposure to 1,3-butadiene and evaluate its urinary mercapturic acids as biomarkers of exposure in these settings. Personal air samples and multiple urine samples were collected on two separate occasions from three groups of individuals that differed by spatial proximity as well as intensity of traffic: (i) toll collectors, (ii) urban-weekday and (iii) suburban-weekend group. Air samples were analyzed using thermal desorption followed by GC/MS and urine samples were analyzed using isotope dilution liquid chromatography tandem mass spectrometry (ID-LC-MS/MS) for two mercapturic acids of 1,3-butadiene: monohydroxy-3-butenyl mercapturic acid (MHBMA) and 1,2-dihydroxybutyl mercapturic acid (DHBMA). Exposure differed between groups (p<0.05) with median values of 2.38, 1.62 and 0.88 microg/m(3) for toll collectors, the urban-weekday group and the suburban-weekend group, respectively. A refined ID-LC-MS/MS method enabled detection of MHBMA, previously detected only in occupational settings, with high frequency. MHBMA and DHBMA were detected in 95 and 100% of urine samples at levels (mean+/-S.D.) of 9.7+/-9.5, 6.0+/-4.3 and 6.8+/-2.6 ng/mL for MHBMA and 378+/-196, 258+/-133 and 306+/-242 ng/mL for DHBMA for the three different groups, respectively. Mean biomarker levels were higher among the toll collectors compared to the other two groups, however, the differences were not statistically significant (p>0.05). This study is the first to evaluate 1,3-butadiene biomarkers for subtle differences in environmental exposures. However, additional research will be required to ascertain whether the lack of statistical association observed here is real or attributable to unexpectedly small differences in exposure between groups (<1 microg/m(3)), non-specificity of the biomarker at low exposure, and/or small sample size.

Comparison of exposure assessment methods in occupational exposure to benzene in gasoline filling-station attendants

The aim of this study was to assess gasoline filling-station attendants' exposure to benzene and to determine which biological exposure index (BEI), trans,trans-muconic acid (t,t-MA) or S-phenylmercapturic acid (S-PMA), shows better correlation with environmental exposure. Exposure to benzene was measured using passive samplers (Radiello) attached to the collar of the overalls of subjects (n=33) just before the work-shift (approximately 8h); analysis was performed by GC-FID. S-PMA and t,t-MA were determined, respectively, by an immunochemiluminescent assay based on specific monoclonal antibodies and by HPLC-UV at 264 nm. Both methods of biological monitoring were performed on beginning and end-shift urine samples, and expected t,t-MA and S-PMA values were calculated. Smoking habits and life-style were ascertained by means of a questionnaire. Both environmental and biological monitoring data showed that benzene exposure for gasoline filling-station attendants was low when compared with the respective ACGIH limit values (means-benzene: 0.044 mg/m(3); t,t-MA: 171 microg/g creatinine; S-PMA: 2.7 microg/g creatinine). No significant correlation was found between exposure to benzene and t,t-MA or S-PMA excretion data. The use of expected values was also experimented for S-PMA and t,t-MA. This consists of calculating, on the basis of the known half-life of the benzene metabolite, the concentration of that metabolite that a worker should present at the end of the work-shift, the difference between this value and the value actually found is a measure of benzene exposure during work. The use of expected values in biological monitoring did not improve correlations. At these low benzene levels, environmental monitoring seems to be the best method of evaluating individual exposure. However, biological monitoring remains useful, as a mean of assessing group exposure.