Fast determination of urinary S-phenylmercapturic acid (S-PMA) and S-benzylmercapturic acid (S-BMA) by column-switching liquid chromatography-tandem mass spectrometry

UBE2L3 promotes benzene-induced hematotoxicity via autophagy-dependent ferroptosis

Benzene is a common environmental pollutant and significant health hazard. Low-dose benzene exposure is common in most industrial settings, and some workers exhibit hematotoxicity characterized by impaired hematopoietic function. Consequently, understanding the early hematopoietic damage and biomarkers associated with low-dose benzene exposure is of critical importance for health risk assessment. Using data from a 5-year prospective cohort study on benzene exposure and the National Center for Biotechnology Information's Gene Expression Omnibus database, we detected significant downregulation of the ubiquitin-conjugating enzyme UBE2L3 (E2) in benzene-exposed subjects compared to control subjects. Liquid chromatography tandem mass spectrometry and co-immunoprecipitation experiments illustrated the binding interaction between UBE2L3 and the ubiquitin-protein ligase ZNF598 (E3). We applied deep learning algorithms to predict candidate interacting proteins and then conducted validation via co-immunoprecipitation experiments, which showed that ZNF598 engages in binding with the autophagy protein LAMP-2. Subsequent overexpression and knockdown of UBE2L3 coupled with immunofluorescence experiments and transmission electron microscopy revealed that UBE2L3 disrupts the ubiquitination-degradation of LAMP-2 by ZNF598, reduces GPX4 expression levels, and activates an autophagy-dependent ferroptosis pathway. It also leads to increased lipid peroxidation, thereby promoting ferroptosis and contributing to the hematotoxicity induced by benzene. In summary, our results suggest that UBE2L3 may be involved in early hematopoietic damage by modulating the autophagy-dependent ferroptosis signaling pathway in benzene-induced hematotoxicity.

Specific CpG sites methylation is associated with hematotoxicity in low-dose benzene-exposed workers

Benzene is a broadly used industrial chemicals which causes various hematologic abnormalities in human. Altered DNA methylation has been proposed as epigenetic biomarkers in health risk evaluation of benzene exposure, yet the role of methylation at specific CpG sites in predicting hematological effects remains unclear. In this study, we recruited 120 low-level benzene-exposed and 101 control male workers from a petrochemical factory in Maoming City, Guangdong Province, China. Urinary S-phenylmercapturic acid (SPMA) in benzene-exposed workers was 3.40-fold higher than that in control workers (P < 0.001). Benzene-induced hematotoxicity was characterized by reduced white blood cells counts and nuclear division index (NDI), along with an increased DNA damage and urinary 8-hydroxy-2'-deoxyguanosine (all P < 0.05). Methylation levels of TRIM36, MGMT and RASSF1a genes in peripheral blood lymphocytes (PBLCs) were quantified by pyrosequencing. CpG site 6 of TRIM36, CpG site 2, 4, 6 of RASSF1a and CpG site 1, 3 of MGMT methylation were recognized as hot CpG sites due to a strong correlation with both internal exposure and hematological effects. Notably, integrating hot CpG sites methylation of multiple genes reveal a higher efficiency in prediction of integrative damage compared to individual genes at hot CpG sites. The negative dose-response relationship between the combined methylation of hot CpG sites in three genes and integrative damage enabled the classification of benzene-exposed individuals into high-risk or low-risk groups using the median cut-off value of the integrative index. Subsequently, a prediction model for integrative damage in benzene-exposed populations was built based on the methylation status of the identified hot CpG sites in the three genes. Taken together, these findings provide a novel insight into application prospect of specific CpG site methylation as epi-biomarkers for health risk assessment of environmental pollutants.

A novel method for the accurate quantification of two isomeric mercapturic acids of 1,3-dichlorobenzene in human urine using isotope dilution online-SPE-LC-MS/MS

1,3-dichlorobenzene (1,3-DCB) is an aromatic solvent that might be formed during thermal decomposition of bis(2,4-dichlorobenzoyl)peroxide used as initiator in silicone rubber production with many workers exposed worldwide. During metabolism of 1,3-DCB, two isomeric mercapturic acids can be formed from ring oxidation of 1,3-DCB in the liver, namely 2,4-dichlorophenylmercapturic acid (24CPhMA) and 3,5-dichlorophenylmercapturic acid (35CPhMA). These urinary mercapturic acids might serve as biomarkers of the toxicologically relevant absorbed dose of 1,3-DCB and have not been determined so far. Thus, we were aimed to develop an analytical method for quantification of these biomarkers. Authentic standards of both mercapturic acids as well as deuterium-labelled analogues were self-synthesized. A method for the quantification of both CPhMAs in human urine using online-SPE LC/MS/MS was developed and validated with an LOQ of 0.1 ng mL-1 for both CPhMAs. The analytes were extracted from urine by online-SPE on a restricted access material phase, transferred to the analytical column and quantified by tandem mass spectrometry. Interday (n = 6) and Intraday (n = 10) precision for both CPhMAs ranged from 1.7 to 4.3 % with accuracies between 99.4 and 109.9 % at concentrations of 0.6 and 3 ng mL-1. We applied the method on post-shift urine samples of 16 workers of the silicone rubber industry with occupational exposure to 1,3-DCB. Both CPhMAs were above LOQ in 15 of 16 urine samples with median levels (range) for 24CPhMA and 35CPhMA of 1.64 ng mL-1 (<0.1 - 8.2 ng mL-1) and 3.98 ng mL-1 (0.36 - 24.1 ng mL-1), respectively. This is the first report on specific urinary mercapturic acids of 1,3-DCB in humans. Our results show that ring oxidation of 1,3-DCB is considered to be a toxicologically relevant metabolic pathway in humans. This might improve risk assessment of 1,3-DCB-emissions in silicone rubber industry.

False positives and false negatives in benzene biological monitoring

Benzene is a commonly used industrial chemical that is a significant environmental pollutant. Occupational health specialists and industrial toxicologists are concerned with determining the exact amount of exposure to chemicals in the workplace. There are two main approaches to assess chemical exposure; air monitoring and biological monitoring. Air monitoring has limitations, which biological monitoring overcomes and could be used as a supplement to it. However, there are several factors that influence biological monitoring results. It would be possible to assess exposure more accurately if these factors were taken into account. This study aimed to review published papers for recognizing and discussing parameters that could affect benzene biological monitoring. Two types of effects can be distinguished: positive and negative effects. Factors causing positive effects will increase the metabolite concentration in urine more than expected. Furthermore, the parameters that decrease the urinary metabolite level were referred to as false negatives. From the papers, sixteen influential factors were extracted that might affect benzene biological monitoring results. Identified factors were clarified in terms of their nature and mechanism of action. It is also important to note that some factors influence the quantity and quality of the influence of other factors. As a result of this study, a decision-making protocol was developed for interpreting the final results of benzene biological monitoring.

HIF-1α/m6A/NF-κB/CCL3 axis-mediated immunosurveillance participates in low level benzene-related erythrohematopoietic development toxicity

Defective erythropoiesis is one of the causes of anemia and leukemia. However, the mechanisms underlying defective erythropoiesis under a low-dose environment of benzene are poorly understood. In the present study, multiple omics (transcriptomics and metabolomics) and methods from epidemiology to experimental biology (e.g., benzene-induced (WT and HIF-1α + ) mouse, hiPSC-derived HSPCs) were used. Here, we showed that erythropoiesis is more easily impacted than other blood cells, and the process is reversible, which involves HIF-1 and NF-kB signaling pathways in low-level benzene exposure workers. Decreased HIF-1α expression in benzene-induced mouse bone marrow resulted in DNA damage, senescence, and apoptosis in BMCs and HSCs, causing disturbances in iron homeostasis and erythropoiesis. We further revealed that HIF-1α mediates CCL3/macrophage-related immunosurveillance against benzene-induced senescent and damaged cells and contributes to iron homeostasis. Mechanistically, we showed that m6A modification is essential in this process. Benzene-induced depletion of m6A promotes the mRNA stability of gene NFKBIA and regulates the NF-κB/CCL3 pathway, which is regulated by HIF-1α/METTL3/YTHDF2. Overall, our results identified an unidentified role for HIF-1α, m6A, and the NF-kB signaling machinery in erythroid progenitor cells, suggesting that HIF-1α/METTL3/YTHDF2-m6A/NF-κB/CCL3 axis may be a potential prevention and therapeutic target for chronic exposure of humans to benzene-associated anemia and leukemia.

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.

Concept for the Evaluation of Carcinogenic Substances in Population-Based Human Biomonitoring

The Human Biomonitoring (HBM) Commission at the German Environment Agency holds the opinion that for environmental carcinogens for which no exposure levels can be assumed and are harmless to health, health-based guidance values corresponding to the classical definition of the HBM-I or HBM-II value cannot be established. Therefore, only reference values have been derived so far for genotoxic carcinogens from exposure data of the general population or subpopulations. The concept presented here opens up the possibility of performing health risk assessments of carcinogenic substances in human biomonitoring, and thus goes decisively beyond the purely descriptive statistical reference value concept. Using the presented method, quantitative dose descriptors of internal exposure can be derived from those of external exposure, provided that sufficient toxicokinetic information is available. Dose descriptors of internal exposure then allow the simple estimate of additional lifetime cancer risks for measured biomarker concentrations or, conversely, of equivalent concentrations for selected risks, such as those considered as tolerable for the general population. HBM data of chronic exposures to genotoxic carcinogens can thus be used to assess the additional lifetime cancer risk referring to the general population and to justify and prioritize risk management measures.

Exposure to benzene, toluene and polycyclic aromatic hydrocarbons in Nunavimmiut aged 16 years and over (Nunavik, Canada) - Qanuilirpitaa 2017 survey

There are numerous volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) that Inuit may be exposed to from combustion, cooking, heating, vehicle exhaust, active and passive smoking and other local sources of contaminants such as oil spills or open-air burning in landfills. To better assess the levels of exposure to these non-persistent chemicals, we measured a suite of benzene, toluene (two VOCs) and PAHs metabolites in pooled urine samples from youth and adults aged 16 years old and over who participated in the Qanuilirpitaa? 2017 Inuit Health Survey (Q2017), a population health survey conducted in Nunavik. A cost-effective pooling strategy was established and 30 different pools from individual urine samples (n = 1266) were created by grouping individual urine samples by sex, age groups and regions. To assess smoking and exposure to second-hand smoke, cotinine levels were measured in individual urine samples. We found that benzene, toluene, all detected PAHs metabolites and cotinine levels were significantly higher in Q2017 compared to adults in the Canadian Health Measure Survey Cycle 4 (2014-2015) or the general U.S population (2015-2016). Moreover, mean levels of one benzene metabolite, S-phenylmercapturic acid, and several PAHs metabolites, 1-naphthol, 2-and 3-hydroxyfluorene, and 4- and 9-hydroxyphenanthrene, known to be associated with smoking habits, were higher in Q2017 compared to reference values (RV₉₅) established for non-smokers in the general Canadian population. Furthermore, benzene and PAHs metabolites were all correlated with cotinine levels. Our results suggest that the high smoking prevalence in Nunavik is an important contributor to the elevated benzene and PAHs exposure. Other local sources may add to that exposure, although we were not able to account for their contribution. These data highlight the importance of regional and community efforts for reducing smoking and to encourage smoke-free homes in Nunavik, while continuing to investigate and reduce other possible local sources of exposure to benzene, toluene and PAHs.

LincRNA-p21 promotes p21-mediated cell cycle arrest in benzene-induced hematotoxicity by sponging miRNA-17-5p

Benzene is widely employed in manufacturing and causes hematotoxic effects and leukemia in humans. A long intergenic noncoding RNA (lincRNA)-microRNA (miRNA)-mRNA coexpression and competing endogenous RNA (ceRNA) regulatory network was constructed by bioinformatics analysis based on a benzene-induced aplastic anemia (BIAA) mouse model. In this population-based study, we observed a trend consistent with that in the BIAA mice: lincRNA-p21 and p21 were upregulated, while miRNA-17-5p expression was downregulated in benzene-exposed workers. Moreover, multiple linear regressions indicated that lincRNA-p21 was negatively associated with white blood cell (WBC) counts. Predictive thresholds of hematotoxicity were identified by ROC curve analysis with S-phenylmercapturic acid (SPMA) and lincRNA-p21 showing a better predictive ability than the other parameters and the combination of SPMA and lincRNA-p21 exhibiting the highest predictive value for hematotoxicity. LincRNA-p21 was predominantly present in the cytoplasm of bone marrow cells (BMCs) and K562 cells as assessed by fluorescence in situ hybridization (FISH). Upon exploring the underlying mechanism by which lincRNA-p21 mediates benzene-induced hematotoxicity, we observed that the negative regulation of 1,4-benzoquinone (1,4-BQ) on cell cycle arrest and inhibition of K562 cell proliferation was partially relieved by lincRNA-p21 knockdown, which can inhibit the expression of P21 and thereby suppress the toxic effects of 1,4-BQ. Finally, dual-luciferase reporter gene and RIP assay showed that, by acting as a sponge, lincRNA-p21 reduced the activity of miRNA-17-5p and consequently increased the expression of p21. In conclusion, our research suggested that benzene induces hematotoxicity via the lincRNA-p21/miRNA-17-5p/p21 signaling which might contribute to the underlying mechanism of lincRNA-p21 in benzene-induced hematotoxicity. Therefore, lincRNA-p21 can serve as a potential biomarker for the early detection of hematopoiesis inhibition in individuals with long-term exposure to low-dose benzene.

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.

The exposures and health effects of benzene, toluene and naphthalene for Chinese chefs in multiple cooking styles of kitchens

Commercial cooking has higher intensity and more severe instantaneous cooking pollution from volatile organic chemicals compared to home cooking, making health risk assessment of occupational exposure for chefs a priority. In this study, chefs from three cooking styles of kitchens, including steaming, frying, and grilling, were selected to investigate the external and internal exposures, health risks and effects of several typical aromatic hydrocarbons (benzene, toluene and naphthalene). Naphthalene was found to be the most concentrated contaminant in air samples among the different kitchens, while benzene had the lowest concentration. The concentration of toluene in frying kitchens was significantly higher than that in steaming kitchens. Air concentrations of toluene in frying kitchens, as well as benzene concentrations in grilling kitchens exceeded the standard level according to indoor air quality standard (GB/T18883-2002). Regarding the metabolites of pollutants in urine, the content of S-benzylmercapturic acids (S-BMA) for frying chefs was significantly higher than that for other cooking styles of chefs, which was consistent with the relatively higher air concentrations of toluene. There was a good correlation between internal and external exposure of the pollutants. The level of oxidative stress was influenced by 2-hydroxynaphthalene (2-OHN) and S-BMA, indicating the potential health risks of these occupational exposed chefs. This study indicates the need to improve the monitoring of typical aromatic hydrocarbons, as well as to investigate their potential health effects in large-scale groups, and improve the ventilation in kitchens.

Gender differences in hematotoxicity of benzene-exposed workers, three cross-sectional studies on 218,061 subjects

Our aim was to analyze the effects of benzene exposure on hematotoxicity in workers, with a focus on gender differences. The study was divided into three parts, and the survey included 218,061 workers. Since 2017, some workers are selected from the total workers each year to explore the possible influencing factors (age, duration of benzene exposure, TWA (8-h time-weighted average) of benzene, SPMA (S-phenylmercapturic acid), MDA (malondialdehyde), 8-OHdG (8-hydroxy-2'-deoxyguanosine) of different hematotoxicity of different genders). The abnormal rate of WBC (white blood cell), ANC (absolute neutrophil count), and platelets of female workers in the benzene exposure group was higher than that of males in the benzene exposure group and also higher than that of the female workers in the control group. Research results in 2019 showed increased SPMA as well as increases their DNA damage including 8-OHdG and MDA in benzene-exposed female workers compared to those in the control female group (all p < 0.05. SPMA, 8-OHdG, and MDA in benzene exposure female workers increased 555%, 183%, and 33.3%, respectively). Female workers are at significantly higher risk for blood system effects of benzene exposure. Therefore, more stringent standards and guidelines may be needed to protect the changing professional population, especially for females.

Magnetic molecularly imprinted polymers for extraction of S-phenylmercapturic acid from urine samples followed by high-performance liquid chromatography

In this study, magnetic molecularly imprinted polymers (MMIPs) were prepared and used as sorbents for extraction of S-phenylmercapturic acid (S-PMA) from urine samples, followed by high-performance liquid chromatography ultraviolet-visible (HPLC-UV/Vis) analysis. The MMIPs were synthesized by the copolymerization reaction of (phenylthio) acetic acid (template molecule), methacrylic acid (functional monomers) and ethylene glycol dimethacrylate (cross-linkers). The morphology, structure property and surface groups of the prepared MMIPs were characterized by scan electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction pattern, thermogravimetric analyses, Brunauer-Emmett-Teller and vibrating sample magnetometer. The selectivity of the MMIPs was investigated in the presence of interferents. Various parameters affecting the S-PMA extraction efficiency were investigated, including MMIPs amount, pH, sample volume, desorption solvent, as well as extraction and desorption time. The obtained optimal parameters were as follows: MMIPs amount (20 mg), pH (3.0), sample volume (5 mL), desorption solvent (methanol/acetic acid [9/1, v/v]), extraction time (30 minutes) and desorption time (2 minutes). The method was validated according to the Food and Drug Administration Guidance for Industry on Bioanalytical Method Validation. The calibration curve for the analyte was linear in the concentration range of 0.030-1.0 mg/L (r = 0.9995). The LOD and LOQ of the method were 0.0080 and 0.0267 mg/L, respectively. The enrichment factor of the MMIPs was 5. The relative standard deviations of intra- and inter-day tests were in the range of 3.8-5.1% and 3.9-6.3%, respectively. The recoveries at three different concentrations of 0.10, 0.50 and 0.80 mg/L ranged between 95.2% and 98.6%. In addition, the MMIPs could be reused for at least eight times. The proposed method was successfully applied to the determination of S-PMA in urine samples. In addition, this developed method could be used as a tool in the early screening and clinical diagnosis of benzene intoxication.

Quantification of a mercapturate metabolite of the biocides methylisothiazolinone and chloromethylisothiazolinone ("M-12") in human urine using online-SPE-LC/MS/MS

Methylisothiazolinone and the reaction mixture of chloromethylisothiazolinone/methylisothiazolinone (MCI/MI, 3 : 1) are broadly used biocides that are contained in many products of everyday life (e.g. cosmetics, wet wipes, etc.). As MI and MCI are able to sensitize (and penetrate) the skin, their application in cosmetic products is of concern. In previous work, we have revealed a background exposure of the general population to MI and/or MCI/MI (3 : 1) by the determination of urinary N-methylmalonamic acid (NMMA) as the main human metabolite. To corroborate these findings, we have now developed a two-dimensional LC/MS/MS method for the quantification of a mercapturic acid metabolite of MI and MCI ((acetylamino){[3-(methylamino)-1-(methylthio)-3-oxopropyl]thio}acetic acid or shortly "M-12") in human urine. This analyte is enriched online using a Strata-X-column and stripped from the urinary matrix. Then, the analyte is back flushed to the analytical column (Phenomenex C18(2), 150 × 4.6 mm) and finally quantified by tandem mass spectrometry with the use of isotopically labelled M-12 as the internal standard. The LOQ for M-12 was 0.2 ng mL-1 urine and sufficient to quantify urinary background levels. Precision within and between series for M-12 in urine at concentrations varying from 0.2 to 5 ng mL-1 ranged from 2.1 to 23.9% and accuracy ranged from 86.3 to 101.8%. Mean accuracy for M-12 in individual urine samples was 94.3% (range: 89.7-102.9%). We applied this method to previously collected 24 h urine samples of 60 persons with no specific exposure to MI and/or MCI/MI (3 : 1). The metabolite M-12 could be quantified in each urine sample. The median and 95th percentile levels for urinary M-12 were determined to be 0.62 and 2.26 ng mL-1, respectively. In these urine samples, the concentrations of the previously determined metabolite NMMA and M-12 correlated well. In the future, we will apply this method to urine samples of a previously conducted human exposure study to explore the additional value of M-12 as a biomarker of exposure to MI and MCI.

Research Progress on Synthesis and Application of Cyclodextrin Polymers

Cyclodextrins (CDs) are a series of cyclic oligosaccharides formed by amylose under the action of CD glucosyltransferase that is produced by Bacillus. After being modified by polymerization, substitution and grafting, high molecular weight cyclodextrin polymers (pCDs) containing multiple CD units can be obtained. pCDs retain the internal hydrophobic-external hydrophilic cavity structure characteristic of CDs, while also possessing the stability of polymer. They are a class of functional polymer materials with strong development potential and have been applied in many fields. This review introduces the research progress of pCDs, including the synthesis of pCDs and their applications in analytical separation science, materials science, and biomedicine.

Reduction in Exposure to Selected Harmful and Potentially Harmful Constituents Approaching Those Observed Upon Smoking Abstinence in Smokers Switching to the Menthol Tobacco Heating System 2.2 for 3 Months (Part 1)

Introduction

The Tobacco Heating System (THS) is a “heat-not-burn” tobacco product designed to generate significantly lower levels of harmful and potentially harmful constituents (HPHCs) and present lower risk of harm than cigarettes. This study assessed the exposure reduction to selected HPHCs in smokers switching to menthol Tobacco Heating System (mTHS) 2.2 compared with smokers continuing smoking menthol cigarettes (mCCs) and smoking abstinence (SA) for 5 days in a confined setting, followed by an 86-day ambulatory period.

Methods

A total of 160 healthy adult US smokers participated in this randomized, three-arm parallel group, controlled clinical study. Biomarkers of exposure to 16 HPHCs were measured in blood and 24-hour urine. Safety was monitored throughout the study. Information was also gathered on product evaluation, product use, subjective effects, and clinical risk markers (co-publication Part 2).

Results

Nicotine uptake was comparable in both exposure groups (mTHS:mCC ratio of 96% on day 90). On day 5, biomarker of exposure levels to other HPHCs were reduced by 51%–96% in the mTHS group compared with the mCC group, and these reductions were sustained for most biomarkers of exposure over ambulatory period. After 90 days of use, the level of satisfaction with mTHS and suppression of urge to smoke were comparable to mCC.

Conclusion

Switching from mCCs to mTHS significantly reduced the exposure to HPHCs to levels approaching those observed in subjects who abstained from smoking for the duration of the study.

Implications

This study compared the impact of switching to mTHS on biomarkers of exposure, relative to continued smoking or SA.

Clinical Significance

Trial Registration

NCT01989156 (ClinicalTrials.gov).

New fully automated gas chromatographic analysis of urinary S-phenylmercapturic acid in isotopic dilution using negative chemical ionization with isobutane as reagent gas

The determination of urinary S-phenylmercapturic acid (S-PMA) represents the most reliable biomarker to monitor the intake risk of airborne benzene. Recently, the European Chemical Agency deliberated new occupational exposure limits for benzene and recommended an S-PMA biological limit value of 2-μg/g creatinine. This limit is an order of magnitude lower than the previous one, and its determination constitutes a challenge in the analytical field. We developed and validated a method that allows the fully automated and sensitive determination of S-PMA by the use of gas-chromatography negative chemical ionization tandem mass spectrometry in isotopic dilution. For negative chemical ionization, we selected a mixture of 1% isobutane in argon as reactive gas, by studying its chemical ionization mechanism and optimal parameters compared with pure isobutane or pure methane. This gas mixture produces a more abundant signal of the target analyte than isobutane or methane, and it extended the operative lifetime of the ion source, enabling us to start a high-throughput approach of the S-PMA analysis. Moreover, energy-resolved mass spectrometry experiments were carried out to refine the MS/MS analysis conditions, testing nitrogen and argon as collision gases. The method optimization was pursued by a chemometric model by using the experimental design. The quantification limit for S-PMA was 0.10 μg/L. Accuracy (between 98.3% and 99.6%) and precision (ranging from 1.6% to 6.4%) were also evaluated. In conclusion, the newly developed assay represents a powerful tool for the robust, reliable, and sensitive quantification of urinary S-PMA, and because of its automation, it is well suited for application in large environmental and biological monitoring.

Influence of benzene exposure, fat content, and their interactions on erythroid-related hematologic parameters in petrochemical workers: a cross-sectional study

BACKGROUND

Ubiquitously distributed benzene is a known hematotoxin. Increasing evidence has suggested that erythroid-related hematologic parameters may be sensitive to benzene exposure. Fat content, which is also closely associated with erythroid-related hematologic parameters, may affect the distribution and/or metabolism of benzene, and eventually benzene-induced toxicity.

METHODS

To explore the influence of benzene exposure, fat content, and their interactions on erythroid-related hematologic parameters, we recruited 1669 petrochemical workers and measured their urinary S-phenylmercapturic acid (SPMA) concentration and erythroid-related hematological parameters. Indices for fat content included body fat percentage (BF%), plasma total cholesterol (TC) and triglycerides (TG), and occurrence of fatty liver.

RESULTS

The dose-response curve revealed U-shaped nonlinear relationships of SPMA with hematocrit (HCT) and mean corpuscular hemoglobin concentration (MCHC) (P-overall < 0.001, and P-nonlinear < 0.015), as well as positive linear associations and r-shaped nonlinear relationships of continuous fat content indices with erythroid-related hematological parameters (P-overall ≤0.005). We also observed modification effects of fat content on the associations between benzene exposure and erythroid-related hematological parameters, with workers of lower or higher BF% and TG more sensitive to benzene-induced elevation of MCHC (P_interaction = 0.021) and benzene-induced decrease of HCT (P_interaction = 0.050), respectively. We also found that some erythroid-related hematologic parameters differed between subgroups of workers with different SPMA levels and fat content combination.

CONCLUSIONS

Our study suggested that benzene exposure, fat content, and their interactions may affect erythroid-related hematological parameters in petrochemical workers in a complex manner that are worthy of further investigation.

Effects of Switching to the Tobacco Heating System 2.2 Menthol, Smoking Abstinence, or Continued Cigarette Smoking on Biomarkers of Exposure: A Randomized, Controlled, Open-Label, Multicenter Study in Sequential Confinement and Ambulatory Settings (Part 1)

Introduction

The menthol Tobacco Heating System 2.2 (mTHS) is a newly developed candidate modified-risk tobacco product intended to reduce exposure to the harmful and potentially harmful constituents (HPHCs) of conventional cigarette (CC) smoke. This study examined the impact of switching to mTHS on biomarkers of exposure to HPHCs relative to menthol CCs (mCCs) and smoking abstinence (SA).

Methods

In this three-arm, parallel-group study, 160 Japanese adult smokers (23–65 years; smoking ≥10 mCCs per day) were randomized to mTHS (n = 78), mCC (n = 42), or SA (n = 40) for 5 days in confinement and 85 days in ambulatory settings. Endpoints included biomarkers of exposure to HPHCs, human puffing topography, safety, and subjective effects of smoking measures.

Results

After 5 days of product use, the concentrations of carboxyhemoglobin, 3-hydroxypropylmercapturic acid, monohydroxybutenyl mercapturic acid, and S-phenylmercapturic acid were 55%, 49%, 87%, and 89% lower (p < .001), respectively, in the mTHS group than in the mCC group. Other biomarkers of exposure (measured as secondary endpoints) were 50%–94% lower in the mTHS group than in the mCC group on day 5. These reductions in the mTHS group were maintained at day 90, similar to the SA group. Switching to mTHS was associated with changes in human puffing topography (shorter puff intervals and more frequent puffs). The urge-to-smoke and smoking satisfaction levels on day 90 were similar in the mTHS and the mCC groups.

Conclusion

Switching from mCCs to mTHS significantly reduced exposure to HPHCs relative to continuing smoking mCCs with concentrations similar to those observed following SA in Japanese adult smokers.

Implications

This randomized study compared the impact of switching to a modified-risk tobacco product candidate mTHS on biomarkers of exposure to HPHCs of cigarette smoke relative to continuing smoking cigarettes or abstaining from smoking in sequential confinement and ambulatory settings. The study showed that switching to mTHS was associated with significant biomarker reductions within 5 days in confinement, these reductions being maintained throughout the ambulatory setting up to day 90. The results provide evidence that switching to mTHS reduces real-life exposure to HPHCs in adult smokers.

Preparation of a new benzylureido-β-cyclodextrin-based column and its application for the determination of phenylmercapturic acid and benzylmercapturic acid enantiomers in human urine by LC/MS/MS

A benzylureido-β-cyclodextrin was synthesized by the reaction of 6-amino-β-cyclodextrin with an active benzyl isocyanate. Then, it was bonded to silica gel by a thiol-ene addition reaction, obtaining a new benzylureido-β-cyclodextrin-based chiral stationary phase (BzCDP). Its chemical structure was characterized by infrared spectroscopy, elemental analysis, and solid-state nuclear magnetic resonance spectroscopy. The BzCDP was successfully used to separate phenylmercapturic acid (PMA) and benzylmercapturic acid (BMA) enantiomers, which were confirmed as biomarkers of exposure to benzene and toluene in human urine. The enantiomeric separations were also optimized through the investigation of related factors. The resolutions of PMA and BMA enantiomers could be up to 2.25 and 2.14, respectively, within 30 min under reversed-phase chromatography. Based on the optimal chromatographic and mass spectrometry conditions, a new LC-MS/MS quantitative method for the PMA and BMA enantiomers was established by negative ion multiple reaction monitoring (MRM) and an isotope-labeled PMA (d²-PMA) as an internal standard. The limits of detection (LODs) of enantiomers were less than 0.17 μg/L for PMA and 0.14 μg/L for BMA, and the averaged recoveries of enantiomers were in the range of 86~100% for PMA and 86~113% for BMA. The method had good reproducibility levels with the RSDs (3.5~11.3% for intra-day and 3.9~13.1% for inter-day). The method was successfully applied to urine testing of 60 painting and printing workers. The results showed that only L-PMA was detected in the urine of the Printers, while a high content of L-PMA (27.5~106 μg/L) and D-PMA (19.9~82.8 μg/L) can be detected simultaneously in the urine of the Painters, indicating that benzene pollution was more serious in this group. The positive rate of BMA was rather higher, indicating that toluene pollution was more common than benzene. BMA also existed in the form of two enantiomers (L-BMA and D-BMA), but the difference between the two types of occupational groups was small. It is a meaningful work to deeply study the existence and content of chiral markers in human urine, which will help to better understand and evaluate the harmful effects of benzene series on human beings. Graphical abstract.

[Electronic Shiazo waterpipes: a new source of indoor air pollutants]

BACKGROUND

For some time, a new form of waterpipe smoking has been advertised, where steam stones moistened with aroma fluids (Shiazo) are heated electronically. Since there is no combustion of tobacco, it is often assumed that the produced vapor is not harmful to health. To clarify this issue, we performed a comprehensive inner and outer exposure assessment during the use of an electronic Shiazo waterpipe.

METHODS

Three volunteers smoked an electronic waterpipe operated with nicotine-free Shiazo stones in a thoroughly ventilated room for 2 h. In three smoking sessions, three fluids with different flavorings were vaporized. In parallel, emissions of particles, volatile organic compounds, polycyclic aromatic hydrocarbons (PAH), and metals were measured in indoor air. Within a biomonitoring study, urinary metabolite profiles of air pollutants were checked. For comparison, the components of the Shiazo fluids were also analyzed.

RESULTS

During the smoking sessions, concentrations of formaldehyde, acetaldehyde, glycerine, and propylene glycol rose significantly in the indoor environment. The content of putative carcinogenic PAH in indoor air increased by 42% to 174 ng/m³. Particle number concentrations ranged from 39,968 to 65,610 particles/cm³ (median), with peaks at diameters from 25 to 31 nm. 3‑HPMA, the mercapturic acid metabolite of the pyrolysis product acrolein, was strongly elevated in urine samples of the smokers. All fluids contained high amounts of contact allergens.

CONCLUSIONS

Electronic Shiazo waterpipes release various harmful substances that considerably impact indoor air quality. Compared to conventional waterpipes, the release of pollutants is lower. Nevertheless, smoking with Shiazo waterpipes is a source of health risks for both users and bystanders.

Benzene-induced mouse hematotoxicity is regulated by a protein phosphatase 2A complex that stimulates transcription of cytochrome P4502E1

Chronic benzene exposure is associated with hematotoxicity and the development of aplastic anemia and leukemia. However, the signaling pathways underlying benzene-induced hematotoxicity remain to be defined. Here, we investigated the role of protein phosphatase 2A (PP2A) in the regulation of benzene-induced hematotoxicity in a murine model. Male mice with a hepatocyte-specific homozygous deletion of the Ppp2r1a gene (encoding PP2A Aα subunit) (HO) and matched wildtype (WT) mice were exposed to benzene via inhalation at doses of 1, 10, and 100 ppm for 28 days. Peripheral white blood cell counts and activation of bone marrow progenitors were attenuated in the HO mice, indicating that Ppp2r1a deletion protects against benzene-induced hematotoxicity. Moreover, elevation of urinary S-phenyl mercapturic acid, a benzene metabolite, was much greater in WT mice than in HO mice. Real-time exhalation analysis revealed more exhaled benzene but fewer benzene metabolites in HO mice than in WT mice, possibly because of the down-regulation of Cyp2e1, encoding cytochrome P4502E1, in hepatocytes of the HO mice. Loss-of-function screening disclosed that PP2A complexes containing the B56α subunit participate in regulating Cyp2e1 expression. Notably, PP2A-B56α suppression in HepG2 cells resulted in persistent β-catenin phosphorylation at Ser³³-Ser³⁷-Thr⁴¹ in response to CYP2E1 agonists. In parallel, nuclear translocation of β-catenin was inhibited, concomitant with a remarkable decrease of Cyp2e1 expression. These findings support the notion that a regulatory cascade comprising PP2A-B56α, β-catenin, and Cyp2e1 is involved in benzene-induced hematotoxicity, providing critical insight into the role of PP2A in responses to the environmental chemicals.

Association of PAHs and BTEX exposure with lung function and respiratory symptoms among a nonoccupational population near the coal chemical industry in Northern China

Emissions (particularly aromatic compounds) from coal industries and biomass fuels combustion lead to high health risks for neighboring residents. To investigate the association of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene and 1,2-dimethylbenzene (BTEX) exposure with lung function and respiratory symptoms among adults and children near the coal-chemical industry in Northern China, adults and children from a county dotted with coal chemical industry were chosen as subjects for investigation (investigated area, IR). The control group consisted of adults and children from an agricultural county (control area, CR). The environmental and urinary PAH and BTEX levels of adults and children were determined by isotope dilution liquid chromatography coupled with tandem mass spectrometry. The Mann-Whitney U test and multivariate linear regression models were used to analyze the relationship between pollutant exposure and the respiratory system. The results showed that in an ambient environment, levels of PAHs and BTEX in the IR were significantly higher than those in the CR. Particularly, the concentration profiles for air samples were IR > CR and indoor > outdoor. Both for adults and children, the geometric (GM) concentrations of urinary PAHs and BTEX from the IR were significantly higher than those measured in the CR. Additionally, the urinary PAH exposure level profiles of smokers were higher than those of nonsmokers, indicating that indoor air and smoking were both important nonoccupational exposure sources. The decline of the forced expiratory in the first second (FEV₁, %) and the forced expiratory middle flow rate (FEF_25%) in children were associated with increasing urinary PAH metabolite levels (p < 0.05). The increase in urinary 1-OHN, 3-OHPhe, 4-OHPhe and 1-OHP levels could be linked to a decrease in FEV1 (r = -0.179, p < 0.05) and FEF_25% with the coefficient of -0.166, -0.201 and -0.175 (p < 0.05), respectively. Medical examinations and lung function tests indicated that residents in the IR had higher occurrences of chest inflammation or declining lung function than residents in the CR. Moreover, exposure to PAHs and BTEX could decrease child lung function, though decreased lung function was not observed in adults. Both urinary monitoring and lung function data showed that children were more sensitive to PAH and BTEX exposure than adults.

Enhanced H3K4me3 modifications are involved in the transactivation of DNA damage responsive genes in workers exposed to low-level benzene

In this study, we explore whether altered global histone modifications respond to low-level benzene exposure as well as their association with the hematotoxicity. We recruited 147 low-level benzene-exposed workers and 122 control workers from a petrochemical factory in Maoming City, Guangdong Province, China. The internal exposure marker level, urinary S-phenylmercapturic acid (SPMA), in benzene-exposed workers was 1.81-fold higher than that of the controls (P < 0.001). ELISA method was established to examine the specific histone modifications in human peripheral blood lymphocytes (PBLCs) of workers. A decrease in the counts of white blood cells (WBC), neutrophils, lymphocytes, and monocytes appeared in the benzene-exposed group (all P < 0.05) compared to the control group. Global trimethylated histone 3 lysine 4 (H3K4me3) modification was enhanced in the benzene-exposed group (P < 0.05) and was positively associated with the concentration of urinary SPMA (β = 0.103, P = 0.045) and the extent of DNA damage (% Tail DNA: β = 0.181, P = 0.022), but was negatively associated with the leukocyte count (WBC: β = -0.038, P = 0.023). The in vitro study revealed that H3K4me3 mark was enriched in the promoters of several DNA damage responsive (DDR) genes including CRY1, ERCC2, and TP53 in primary human lymphocytes treated with hydroquinone. Particularly, H3K4me3 modification was positively correlated with the expression of CRY1 in the PBLCs of benzene-exposed workers. These observations indicate that H3K4me3 modification might mediate the transcriptional regulation of DDR genes in response to low-dose benzene exposure.

Gestational exposure to volatile organic compounds (VOCs) in Northeastern British Columbia, Canada: A pilot study

BACKGROUND

Northeastern British Columbia (Canada) is an area of intense hydraulic fracturing for unconventional natural gas exploitation. There have been multiple reports of air and water contamination by volatile organic compounds in the vicinity of gas wells. Although these chemicals are known developmental toxicants, no biomonitoring effort has been carried out in the region.

OBJECTIVE

To evaluate gestational exposure to benzene and toluene in the Peace River Valley, Northeastern British Columbia (Canada).

METHODS

Urine samples were collected over five consecutive days from 29 pregnant women. Metabolites of benzene (s-phenylmercapturic acid (S-PMA) and trans, trans-muconic acid (t,t-MA)) and toluene (s-benzylmercapturic acid (S-BMA)) were measured in pooled urine samples from each participant. Levels of benzene metabolites were compared to those from the general Canadian population and from a biomonitoring study of residents from an area of active gas exploitation in Pavillion, Wyoming (USA). Levels measured in participants from the two recruitment sites, and self-identifying as Indigenous or non-Indigenous, were also compared.

RESULTS

Whereas the median S-PMA level (0.18μg/g creatinine) in our study was similar to that in the general Canadian population, the median t,t-MA level (180μg/g creatinine) was approximately 3.5 times higher. Five women had t,t-MA levels above the biological exposure index® proposed by the American Conference of Governmental Industrial Hygienists. The median urinary S-BMA level in our pilot study was 7.00μg/g creatinine. Urinary metabolite levels were slightly higher in self-identifying Indigenous women, but this difference was only statistically significant for S-PMA.

DISCUSSION

Urinary t,t-MA levels, but not S-PMA levels, measured in our study are suggestive of a higher benzene exposure in participating pregnant women from the Peace River Valley than in the general Canadian population. Given the small sample size and limitations of t,t-MA measurements (e.g., non-specificity), more extensive monitoring is warranted.

Estratégias analíticas com cromatografia e espectrometria de massas para biomonitorização da exposição ao benzeno pela determinação do ácido S-fenilmercaptúrico urinário

Resumo Introdução: o benzeno é uma substância de reconhecida toxicidade e sua biomonitorização torna-se fundamental para a prevenção de danos à saúde humana, principalmente em situações de exposição ocupacional. Dentre os biomarcadores de exposição, o ácido S-fenilmercaptúrico é considerado o único específico, mas, devido a suas baixas concentrações na urina, é requerido o uso de técnicas analíticas sensíveis capazes de quantificar traços. Objetivo: revisar metodologias baseadas na cromatografia e na espectrometria de massas para a determinação do ácido S-fenilmercaptúrico. Método: revisão da literatura sobre a determinação do ácido S-fenilmercaptúrico urinário por técnicas de cromatografia e espectrometria de massas, nas principais bases de dados científicas, considerando o período entre 1951 e 2015. Resultados: 120 documentos serviram como base teórica para a construção desta revisão. A técnica analítica mais empregada foi o acoplamento da cromatografia a líquido com a espectrometria de massas. Contudo, os métodos diferem quanto ao preparo das amostras. Conclusão: o alto custo de aquisição e a manutenção de equipamentos são fatores limitantes para a difusão dos sistemas de cromatografia e espectrometria de massas. No entanto, sua elevada sensibilidade e seletividade faz com que essas técnicas, acopladas, possibilitem elucidar situações de exposição ocupacional e ambiental a poluentes, como o benzeno.

Assessment of the reduction in levels of exposure to harmful and potentially harmful constituents in Japanese subjects using a novel tobacco heating system compared with conventional cigarettes and smoking abstinence: A randomized controlled study in confinement

Smoking conventional cigarettes (CCs) exposes smokers to harmful and potentially harmful constituents (HPHCs). The Tobacco Heating System 2.2 (THS 2.2), a candidate modified risk tobacco product, was developed to reduce or eliminate the formation of HPHCs, while preserving as much as possible the taste, sensory experience, nicotine delivery profile and ritual characteristics of CC. This randomized, controlled, open-label study in confinement for 5 day exposure aimed to demonstrate the reduction in exposure to selected HPHCs, to assess nicotine uptake and subjective effects, in participants switching to THS 2.2 (n = 80) compared to participants continuing smoking CCs (n = 40) and abstaining from smoking (n = 40). The subjects were randomized according to sex and daily CC consumption. The levels of biomarkers of exposure to HPHCs were significantly reduced in participants switching to THS 2.2, compared to CC use. More importantly, the magnitude of exposure reduction observed was close to that which was seen in participants who abstained from smoking for 5 days, while nicotine uptake was maintained. Reduction in urge-to-smoke was comparable between THS and CC groups, however THS 2.2 was slightly less satisfactory than CCs. The new, alternative tobacco product THS 2.2 was well tolerated.

Mercapturic acids: recent advances in their determination by liquid chromatography/mass spectrometry and their use in toxicant metabolism studies and in occupational and environmental exposure studies

This review describes recent selected HPLC/MS methods for the determination of urinary mercapturates that are useful as noninvasive biomarkers in characterizing human exposure to electrophilic industrial chemicals in occupational and environmental studies. High-performance liquid chromatography/mass spectrometry is a sensitive and specific method for analysis of small molecules found in biological fluids. In this review, recent selected mercapturate quantification methods are summarized and specific cases are presented. The biological formation of mercapturates is introduced and their use as indicators of metabolic processing of reactive toxicants is discussed, as well as future trends and limitations in this area of research.

Levels of selected urinary metabolites of volatile organic compounds among children aged 6-11 years

Data from National Health and Nutrition Examination Survey for the years 2011-2012 were used to evaluate variability in the observed levels of 20 urinary metabolites of volatile organic compounds (VOCs) by age, gender, and race/ethnicity among children aged 6-11 years. Exposure to environmental tobacco smoke was positively associated with the levels of selected metabolites of acrylonitrile, 1,3-butadiene, cyanide, and propylene oxide in a dose-response manner. Levels of the selected metabolites of acrolein, acrylonitrile, 1,3-butadiene, styrene, toluene, and xylene decreased with increase in age. Levels of 1-bromopropane decreased with number of rooms in the house but the reverse was true for 1,3-butadiene, carbon-disulfide, and N,N-dimethylformamide. Levels of most of the 20 metabolites did not vary with gender. Non-Hispanic white children had higher adjusted levels of N-Acetyl-S-(3,4-dihydroxybutyl)-L-cysteine (DHBMA), N-Acetyl-S-(N-methylcarbamoyl)-L-cysteine (AMCC), and phenylglyoxylic acid (PGA) than non-Hispanic black children. Non-Hispanic white children had statistically significantly higher adjusted levels of N-Acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA), trans, trans-Muconic acid (MU), and N-Acetyl-S-(N-methylcarbamoyl)-L-cysteine (AMCC) than non-Hispanic Asian children but statistically significantly lower levels of N-Acetyl-S-(n-propyl)-L-cysteine (BPMA) than non-Hispanic Asian children. Non-Hispanic Asian children had the lowest levels of 13 of the 20 metabolites among four major racial/ethnic groups but highest levels for three metabolites. For selected metabolites of acrolein, acrylamide, acrylonitrile-vinyl chloride-ethylene oxide, benzene, 1,3-butadien, crotonaldehyde, cyanide, ethylbenzene-styrene, and toluene, children had statistically significantly higher levels than nonsmoking adults. These results demonstrate how vulnerable children are to being exposed to harmful chemicals like VOCs in their own homes.

Co-exposure to polycyclic aromatic hydrocarbons, benzene and toluene and their dose-effects on oxidative stress damage in kindergarten-aged children in Guangzhou, China

Polycyclic aromatic hydrocarbons (PAHs), benzene and toluene (BT) are ubiquitous toxic pollutants in the environment. Children are sensitive and susceptible to exposure to these contaminants. To investigate the potential oxidative DNA damage from the co-exposure of PAHs and BT in children, 87 children (aged 3-6) from a kindergarten in Guangzhou, China, were recruited. Ten urinary PAHs and four BT metabolites, as well as 8-hydroxy-2'-deoxyguanosine (8-OHdG, a biomarker of oxidative DNA damage)in urine, were determined using a liquid chromatography tandem mass spectrometer. The results demonstrated that the levels of PAHs and BT in children from Guangzhou were 2-30 times higher than those in children from the other countries based on a comparison with recent data from the literature. In particular, the difference is more substantial for pyrene and volatile BT. Co-exposure to PAHs and BT could lead to additive oxidative DNA damage. Significant dose-effects were observed between the sum concentration of urinary monohydroxylated metabolites of PAHs (∑OH-PAHs), the sum concentration of the metabolites of BT (∑BT) and 8-OHdG levels. Every one percent increase in urinary PAHs and BT generated 0.33% and 0.02% increases in urinary 8-OHdG, respectively. We also determined that the urinary levels of PAHs and BT were negatively associated with the age of the children. Moreover, significant differences in the levels of ∑OH-PAHs and ∑BT were determined between 3- and 6-year-old children (p<0.05), which may be caused by different metabolism capabilities or inhalation frequencies. In conclusion, exposure to PAHs or BT could lead to oxidative DNA damage, and 8-OHdG is a good biomarker for indicating the presence of DNA damage. There exists a significant dose-effect relationship between PAH exposure, BT exposure and the concentration of 8-OHdG in urine. Toddlers (3-4 years old) face a higher burden of PAH and BT exposure compared with older children.

Benzeno: reflexos sobre a saúde pública, presença ambiental e indicadores biológicos utilizados para a determinação da exposição

O uso indiscriminado de um número cada vez maior de substâncias químicas vem aumentando e a contaminação ambiental associada tem trazido sérias consequências para o sistema público de saúde devido à elevação de danos para a saúde humana. Uma das substâncias que desperta grande interesse devido à contaminação contemporânea é o benzeno, composto aromático classificado pela International Agency for Research on Cancer como reconhecidamente carcinogênico para humanos. O objetivo do presente estudo foi elaborar e discutir um panorama sobre a contaminação por benzeno, seu metabolismo, consequências para a saúde e sua determinação ambiental e biológica a partir de informações existentes na literatura científica. O levantamento de dados possibilitou o acesso a mais de 200 artigos científicos tanto de âmbito nacional quanto internacional, demonstrando a atualidade do tema e a necessidade de minimização da exposição humana a essa substância. A maioria preocupa-se em explorar o metabolismo e investigar indicadores de exposição, muitos já amplamente estudados e com sérias limitações. Contudo, um crescente número de pesquisadores estão empenhados em elucidar fatores relacionados à suscetibilidade e à interferência da exposição no material genético e proteico. Indicadores de exposição inovadores têm sido propostos com o objetivo de complementar as lacunas de informações anteriormente obtidas, contribuindo para o delineamento da estrutura da biologia de sistemas orgânicos frente à exposição ao benzeno.

Biomass fuels and coke plants are important sources of human exposure to polycyclic aromatic hydrocarbons, benzene and toluene

Large amounts of carcinogenic polycyclic aromatic hydrocarbons (PAHs), benzene and toluene (BT) might be emitted from incomplete combustion reactions in both coal tar factories and biomass fuels in rural China. The health effects arising from exposure to PAHs and BT are a concern for residents of rural areas close to coal tar plants. To assess the environmental risk and major exposure sources, 100 coke plant workers and 25 farmers in Qujing, China were recruited. The levels of 10 mono-hydroxylated PAHs (OH-PAHs), four BT metabolites and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the urine collected from the subjects were measured. The 8-OHdG levels in the urine were determined to evaluate the oxidative DNA damage induced by the PAHs and BT. The results showed that the levels of the OH-PAHs, particularly those of 1-hydroxynathalene and 1-hydroxypyrene, in the farmers were 1-7 times higher than those in the workers. The concentrations of the BT metabolites were comparable between the workers and farmers. Although the exact work location within a coke oven plant might affect the levels of the OH-PAHs, one-way ANOVA revealed no significant differences for either the OH-PAHs levels or the BT concentrations among the three groups working at different work sites. The geometric mean concentration (9.17 µg/g creatinine) of 8-OHdG was significantly higher in the farmers than in the plant workers (6.27 µg/g creatinine). The levels of 8-OHdG did not correlate with the total concentrations of OH-PAHs and the total levels of BT metabolites. Incompletely combusted biomass fuels might be the major exposure source, contributing more PAHs and BT to the local residents of Qujing. The estimated daily intakes (EDIs) of naphthalene and fluorene for all of the workers and most of the farmers were below the reference doses (RfDs) recommended by the U.S. Environmental Protection Agency (EPA), except for the pyrene levels in two farmers. However, the EDIs of benzene in the workers and local farmers ranged from 590 to 7239 µg/day, and these levels were 2- to 30-fold higher than the RfDs recommended by the EPA. Biomass fuel combustion and industrial activities related to coal tar were the major sources of the PAH and BT exposure in the local residents. Using biomass fuels for household cooking and heating explains the higher exposure levels observed in the farmers relative to the workers at the nearby coal tar-related industrial facility.

A survey of liquid chromatographic-mass spectrometric analysis of mercapturic acid biomarkers in occupational and environmental exposure monitoring

High-performance liquid chromatography/mass spectrometry (HPLC/MS) is sensitive and specific for targeted quantitative analysis and is readily utilized for small molecules from biological matrices. This brief review describes recent selected HPLC/MS methods for the determination of urinary mercapturic acids (mercapturates) which are useful as biomarkers in characterizing human exposure to electrophilic industrial chemicals in occupational and environmental studies. Electrophilic compounds owing to their reactivity are used in chemical and industrial processes. They are present in industrial emissions, are combustion products of fossil fuels, and are components in tobacco smoke. Their presence in both the industrial and general environments are of concern for human and environmental health. Urinary mercapturates which are the products of metabolic detoxification of reactive chemicals provide a non-invasive tool to investigate human exposure to electrophilic toxicants. Selected recent mercapturate quantification methods are summarized and specific cases are presented. The biological formation of mercapturates is introduced and their use as biomarkers of metabolic processing of electrophilic compounds is discussed. Also, the use of liquid chromatography/tandem mass spectrometry in simultaneous determinations of the mercapturates of multiple parent compounds in a single determination is considered, as well as future trends and limitations in this area of research.

Use of electronic cigarettes (e-cigarettes) impairs indoor air quality and increases FeNO levels of e-cigarette consumers

Despite the recent popularity of e-cigarettes, to date only limited data is available on their safety for both users and secondhand smokers. The present study reports a comprehensive inner and outer exposure assessment of e-cigarette emissions in terms of particulate matter (PM), particle number concentrations (PNC), volatile organic compounds (VOC), polycyclic aromatic hydrocarbons (PAH), carbonyls, and metals. In six vaping sessions nine volunteers consumed e-cigarettes with and without nicotine in a thoroughly ventilated room for two hours. We analyzed the levels of e-cigarette pollutants in indoor air and monitored effects on FeNO release and urinary metabolite profile of the subjects. For comparison, the components of the e-cigarette solutions (liquids) were additionally analyzed. During the vaping sessions substantial amounts of 1,2-propanediol, glycerine and nicotine were found in the gas-phase, as well as high concentrations of PM2.5 (mean 197 μg/m(3)). The concentration of putative carcinogenic PAH in indoor air increased by 20% to 147 ng/m(3), and aluminum showed a 2.4-fold increase. PNC ranged from 48,620 to 88,386 particles/cm(3) (median), with peaks at diameters 24-36 nm. FeNO increased in 7 of 9 individuals. The nicotine content of the liquids varied and was 1.2-fold higher than claimed by the manufacturer. Our data confirm that e-cigarettes are not emission-free and their pollutants could be of health concern for users and secondhand smokers. In particular, ultrafine particles formed from supersaturated 1,2-propanediol vapor can be deposited in the lung, and aerosolized nicotine seems capable of increasing the release of the inflammatory signaling molecule NO upon inhalation. In view of consumer safety, e-cigarettes and nicotine liquids should be officially regulated and labeled with appropriate warnings of potential health effects, particularly of toxicity risk in children.

Direct bioanalytical sample injection with 2D LC–MS

New analytical platforms have been developed in response to the need for attaining increased peak capacity for multicomponent complex analysis with higher sensitivity and characterization of the analytes, and high-throughput capabilities. This review outlines the fundamental principles of target and comprehensive 2D LC method development and encompasses applications of LC–LC and LC × LC coupled to MS in bioanalysis using a variety of online analytical procedures. It also provides a rationale for the usage of the most employed mass analyzers and ionization sources on these platforms.

Simultaneous analysis of 28 urinary VOC metabolites using ultra high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI/MSMS)

Volatile organic compounds (VOCs) are ubiquitous in the environment, originating from many different natural and anthropogenic sources, including tobacco smoke. Long-term exposure to certain VOCs may increase the risk for cancer, birth defects, and neurocognitive impairment. Therefore, VOC exposure is an area of significant public health concern. Urinary VOC metabolites are useful biomarkers for assessing VOC exposure because of non-invasiveness of sampling and longer physiological half-lives of urinary metabolites compared with VOCs in blood and breath. We developed a method using reversed-phase ultra high performance liquid chromatography (UPLC) coupled with electrospray ionization tandem mass spectrometry (ESI/MSMS) to simultaneously quantify 28 urinary VOC metabolites as biomarkers of exposure. We describe a method that monitors metabolites of acrolein, acrylamide, acrylonitrile, benzene, 1-bromopropane, 1,3-butadiene, carbon-disulfide, crotonaldehyde, cyanide, N,N-dimethylformamide, ethylbenzene, ethylene oxide, propylene oxide, styrene, tetrachloroethylene, toluene, trichloroethylene, vinyl chloride and xylene. The method is accurate (mean accuracy for spiked matrix ranged from 84 to 104%), sensitive (limit of detection ranged from 0.5 to 20 ng mL(-1)) and precise (the relative standard deviations ranged from 2.5 to 11%). We applied this method to urine samples collected from 1203 non-smokers and 347 smokers and demonstrated that smokers have significantly elevated levels of tobacco-related biomarkers compared to non-smokers. We found significant (p<0.0001) correlations between serum cotinine and most of the tobacco-related biomarkers measured. These findings confirm that this method can effectively quantify urinary VOC metabolites in a population exposed to volatile organics.

Mercapturic acids derived from toluene in rat urine samples: identification and measurement by gas chromatography-tandem mass spectrometry

Toluene is one of the most widely used CMR chemicals in industry. Worker exposure to this compound is regulated in France, but new, more sensitive methods are required to effectively monitor this exposure. A gas chromatography-tandem mass spectrometry (GC-MS/MS) method was developed and fully validated for the simultaneous determination of urinary toluene mercapturic acids derived from side chain and ring oxidation, i.e., benzylmercapturic acid and the three isomers o-, m- and p-toluylmercapturic acids, respectively. The method involves a simple and efficient two-step preparation procedure consisting of liquid-liquid extraction of the urinary acids followed by a microwave-assisted esterification of the isolated compounds using 2-propanol. The method meets all the required validation criteria: high selectivity, intra-day and inter-day precision ranges between 1.0 % and 12.4 %, with close to 100 % recovery. Linearity has been shown over the reduced concentration range 0.03-0.5 mg/L whereas a multiplicative model (ln-ln transformation) had to be used to describe the full range of concentrations 0.03-20 mg/L. The limits of detection for the four analytes, ranging from 2.8 to 5.5 μg/L, made the method suitable for their identification and quantification in urine from rats inhaling toluene in the 2 to 200 ppm concentration range. All urine samples from exposed rats contained measurable amounts of all metabolites. This is the first time that o- and m-toluylmercapturic acids have been shown to occur. Our results confirm the hypothesis that toluene mercapturic acids derived from ring oxidation exist in three forms.

[Simultaneous determination of four mercapturic acids in human urine using solid phase extraction and liquid chromatography-tandem mass spectrometry]

A method was developed for the simultaneous extraction and determination of four mercapturic acids (MAs), N-acetyl-S-(3,4-dihydroxybutyl)-L-cysteine (DHBMA), N-acetyl-S-(3-hydroxypropyl)-L-cysteine (3-HPMA), N-acetyl-S-(2-carboxyethyl)-L-cysteine ( CEMA) and S-phenylmercapturic acid (SPMA), in human urine using solid phase extraction and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Frozen urine samples were thawed at room temperature, and centrifuged to remove any settled precipitate. The supernatant was then purified and concentrated by a C18 solid phase extraction column, and analyzed by HPLC-MS/MS in the multiple reaction monitoring (MRM) mode for the quantitative analysis. The ranges of recovery for DHBMA, 3-HPMA, CEMA and SPMA spiked in human urine matrix at three concentration levels were 105.6%-124.4%, 102.7%-106.5%, 103.2%-103.9% and 101.7%-104.3%, respectively, with the relative standard deviations of 2.6%-7.7%. The limits of detection (LOD, S/N > or = 3) were 0. 062, 0. 031, 0. 020 and 0. 003 microg/L for DHBMA, 3-HPMA, CEMA and SPMA, respectively. The method was successfully used to detect 4 MAs in 37 human urine samples from smokers and non-smokers. It was found that the contents of 3-HPMA, CEMA and SPMA in the urines from cigarette smokers were about three to six-fold more than those in the urines from the non-smokers.