Exposure to BTEX is associated with cardiovascular disease, dyslipidemia and leukocytosis in national US population

BACKGROUND

Comprehensive research on the effects of individual benzene, toluene, ethylbenzene, and xylenes (BTEX) and their mixture measured in blood samples, on cardiovascular diseases (CVD) and related risk factors among the general population is limited.

OBJECTIVES

To investigate the effects of blood individual and mixed BTEX on total CVD and its subtypes, lipid profiles, and white blood cell (WBC) count.

METHODS

Survey-weighted multivariate logistic regression was used to examine the associations between blood individual and mixed BTEX with CVD and its subtypes in 17,007 participants from NHANES 1999-2018. The combined effect of BTEX mixture on CVD was estimated using weighted quantile sum modeling and quantile g-computation. Weighted multivariate linear regression assessed the effects of BTEX on lipid profiles and WBC, including its five-part differential count.

RESULTS

In comparison to the reference quartile of BTEX mixture, individuals in the highest quartile had a significantly increased adjusted odds ratio of CVD risk (1.64, 95 % CI: 1.23 to 2.19, P for trend = 0.008). Positive associations were observed for benzene, toluene, ethylbenzene, and m-/p-xylene, demonstrating a monotonically increasing exposure-response relationship. Mixed BTEX was associated with congestive heart failure (CHF), angina pectoris, and heart attack. Individual benzene, toluene, and ethylbenzene were associated with CHF, while toluene, ethylbenzene, and all xylene isomers were linked to angina pectoris. Benzene, toluene, and o-xylene were associated with heart attack. Both mixed and individual BTEX showed positive associations with triglycerides, cholesterol, low-density lipoprotein, and WBC, including its five-part differential count, but a negative relationship with high-density lipoprotein. Subgroup analyses identified modifying effects of smoking, drinking, exercise, BMI, hypertension, and diabetes on the associations between specific toxicants and CVD risk.

CONCLUSIONS

Exposure to BTEX was associated with cardiovascular diseases and cardiovascular risk factors. These findings emphasize the importance of considering blood BTEX levels when assessing cardiovascular health risks.

Co-exposure of petrochemical workers to noise and mixture of benzene, toluene, ethylbenzene, xylene, and styrene: Impact on mild renal impairment and interaction

Epidemiological evidence concerning effects of simultaneous exposure to noise and benzene, toluene, ethylbenzene, xylene, and styrene (BTEXS) on renal function remains uncertain. In 2020, a cross-sectional study was conducted among 1160 petrochemical workers in southern China to investigate effects of their co-exposure on estimated glomerular filtration rate (eGFR) and mild renal impairment (MRI). Noise levels were assessed using cumulative noise exposure (CNE). Urinary biomarkers for BTEXS were quantified. We found the majority of workers had exposure levels to noise and BTEXS below China's occupational exposure limits. CNE, trans, trans-muconic acid (tt-MA), and the sum of mandelic acid and phenylglyoxylic acid (PGMA) were linearly associated with decreased eGFR and increased MRI risk. We observed U-shaped associations for both N-acetyl-S-phenyl-L-cysteine (SPMA) and o-methylhippuric acid (2-MHA) with MRI. In further assessing the joint effect of BTEXS (β, -0.164 [95% CI, -0.296 to -0.033]) per quartile increase in all BTEXS metabolites on eGFR using quantile g-computation models, we found SPMA, tt-MA, 2-MHA, and PGMA played pivotal roles. Additionally, the risk of MRI associated with tt-MA was more pronounced in workers with lower CNE levels (P = 0.004). Multiplicative interaction analysis revealed antagonisms of CNE and PGMA on MRI risk (P = 0.034). Thus, our findings reveal negative dose-effect associations between noise and BTEXS mixture exposure and renal function in petrochemical workers. With the exception of toluene, benzene, xylene, ethylbenzene, and styrene are all concerning pollutants for renal dysfunction. Effects of benzene, ethylbenzene, and styrene exposure on renal dysfunction were more pronounced in workers with lower CNE.

Exposure to benzene, toluene, ethylbenzene, and xylene (BTEX) at Nigeria's petrol stations: a review of current status, challenges and future directions

Introduction

In Nigeria, because of increasing population, urbanization, industrialization, and auto-mobilization, petrol is the most everyday non-edible commodity, and it is the leading petroleum product traded at the proliferating Nigeria's petrol stations (NPSs). However, because of inadequate occupational health and safety (OHS) regulatory measures, working at NPSs exposes petrol station workers (PSWs) to a large amount of hazardous benzene, toluene, ethylbenzene, and xylene (BTEX) compounds.

Methods

Studies on BTEX exposures among Nigerian PSWs are scarce. Thus, constraints in quantifying the health risks of BTEX limit stakeholders' ability to design practical risk assessment and risk control strategies. This paper reviews studies on the OHS of Nigerian PSWs at the NPSs.

Results

Although knowledge, attitude, and practices on OHS in NPSs vary from one Nigeria's study setting to another, generally, safety practices, awareness about hazards and personal protective equipment (PPE), and the use of PPE among PSWs fell below expectations. Additionally, air quality at NPSs was poor, with a high content of BTEX and levels of carbon monoxide, hydrogen sulfide, particulate matter, and formaldehyde higher than the World Health Organization guideline limits.

Discussion

Currently, regulatory bodies' effectiveness and accountability in safeguarding OHS at NPSs leave much to be desired. Understanding the OHS of NPSs would inform future initiatives, policies, and regulations that would promote the health and safety of workers at NPSs. However, further studies need to be conducted to describe the vulnerability of PSWs and other Nigerians who are occupationally exposed to BTEX pollution. More importantly, controlling air pollution from hazardous air pollutants like BTEX is an essential component of OHS and integral to attaining the Sustainable Development Goals (SDG) 3, 7, and 11.

Natural attenuation of BTEX and chlorobenzenes in a formerly contaminated pesticide site in China: Examining kinetics, mechanisms, and isotopes analysis

Groundwater contamination from abandoned pesticide sites is a prevalent issue in China. To address this problem, natural attenuation (NA) of pollutants has been increasingly employed as a management strategy for abandoned pesticide sites. However, limited studies have focused on the long-term NA process of co-existing organic pollutants in abandoned pesticide sites by an integrated approach. In this study, the NA of benzene, toluene, ethylbenzene, and xylene (BTEX), and chlorobenzenes (CBs) in groundwater of a retired industry in China was systematically investigated during the monitoring period from June 2016 to December 2021. The findings revealed that concentrations of BTEX and CBs were effectively reduced, and their NA followed first-order kinetics with different rate constants. The sulfate-reducing bacteria, nitrate-reducing bacteria, fermenting bacteria, aromatic hydrocarbon metabolizing bacteria, and reductive dechlorinating bacteria were detected in groundwater. It was observed that distinct environmental parameters played a role in shaping both overall and key bacterial communities. ORP (14.72%) and BTEX (12.89%) were the main drivers for variations of the whole and key functional microbial community, respectively. Moreover, BTEX accelerated reductive dechlorination. Furthermore, BTEX and CBs exhibited significant enrichment of 13C, ranging from +2.9 to +27.3‰, demonstrating their significance in situ biodegradation. This study provides a scientific basis for site management.

Perioperative exposure to volatile organic compounds in neonates undergoing cardiac surgery

OBJECTIVE

Volatile organic compounds (VOCs) are used in the sterilization and manufacture of medical equipment. These compounds have high vapor pressures with low water solubility and are emitted as gases from solids or liquids. They can be mutagenic, neurotoxic, genotoxic, and/or carcinogenic. Safe limits of exposure are not known for neonates. This study examined determinants of exposure in newborns undergoing cardiac surgery.

METHODS

Twenty metabolites of 16 VOCs (eg, xylene, cyanide, acrolein, acrylonitrile, N, N-dimethylformamide, 1,3-butadiene, styrene, and benzene) were measured as metabolites in daily urine samples collected from 10 neonates undergoing cardiac operations (n = 150 samples). Metabolites were quantified using reversed-phase ultra-high performance liquid chromatography and electrospray ionization tandem mass spectrometry. Repeated measures analysis of covariance was performed for each metabolite to examine associations with use of medical devices.

RESULTS

At least 3 metabolites were detected in every sample. The median number of metabolites detected in each sample was 14 (range, 3-15). In a model controlling for other factors, the use of extracorporeal membrane oxygenation was associated with significantly (P ≤ .05) greater metabolite levels of acrolein, acrylonitrile, ethylene oxide, propylene oxide, styrene, and ethylbenzene. Patients breathing ambient air had greater levels of metabolites of acrolein, xylene, N,N-dimethylformamide, methyl isocyanate, cyanide, 1,3-butadiene (all P ≤ .05).

CONCLUSIONS

Exposure to volatile organic compounds is pervasive in newborns undergoing cardiac surgery. Sources of exposure likely include medical devices and inhalation from the air in the intensive care unit. The contribution of VOC exposure during cardiac surgery in newborns to adverse outcomes warrants further evaluation.

Low-level occupational exposure to BTEX and dyschromatopsia: a systematic review and meta-analysis

Objectives. The present study aimed to assess whether occupational exposure to low concentrations of benzene, toluene, ethylbenzene and xylene (BTEX) is associated with color vision impairment. Methods. We queried PubMed, Scopus, Embase, Web of Science and ProQuest as the main databases, as well as gray literature such as Google Scholar. A random-effects model was used to assess relative risk. A funnel plot was created to assess publication bias. Meta-regression analysis was applied to identify variables that explain the between-study variation in the reported risk estimate. Results. An overall standardized mean difference of 0.529 (95% confidence interval [0.269, 0.788]; p < 0.0001) was obtained in the random-effects model, which corresponded to a medium-size effect. Duration and the levels of exposure to benzene, toluene and xylene were the significant predictors of the magnitude of the combined risk estimate. Chronic exposure to low levels of BTEX was associated with dyschromatopsia determined by the color confusion index. Conclusions. The impairments can occur even at exposures lower than the occupational exposure limits of BTEX. However, there are several flaws in the determination of workers' exposure, which did not allow to establish how low a level of these chemicals can cause color vision impairment.

The Impact of Environmental Benzene, Toluene, Ethylbenzene, and Xylene Exposure on Blood-Based DNA Methylation Profiles in Pregnant African American Women from Detroit

African American women in the United States have a high risk of adverse pregnancy outcomes. DNA methylation is a potential mechanism by which exposure to BTEX (benzene, toluene, ethylbenzene, and xylenes) may cause adverse pregnancy outcomes. Data are from the Maternal Stress Study, which recruited African American women in the second trimester of pregnancy from February 2009 to June 2010. DNA methylation was measured in archived DNA from venous blood collected in the second trimester. Trimester-specific exposure to airshed BTEX was estimated using maternal self-reported addresses and geospatial models of ambient air pollution developed as part of the Geospatial Determinants of Health Outcomes Consortium. Among the 64 women with exposure and outcome data available, 46 differentially methylated regions (DMRs) were associated with BTEX exposure (FDR adjusted p-value < 0.05) using a DMR-based epigenome-wide association study approach. Overall, 89% of DMRs consistently exhibited hypomethylation with increasing BTEX exposure. Biological pathway analysis identified 11 enriched pathways, with the top 3 involving gamma-aminobutyric acid receptor signaling, oxytocin in brain signaling, and the gustation pathway. These findings highlight the potential impact of BTEX on DNA methylation in pregnant women.

Health risk assessment of exposure to benzene, toluene, ethyl benzene, and xylene in shoe industry-related workplaces

Benzene, toluene, ethyl benzene, and xylene (BTEX) are prevalent pollutants in shoe industry-related workplaces. The aim of this study was to assess exposure to BTEX and their carcinogenic and non-carcinogenic risks in shoe-industry-related workplaces. This study was carried out at different shoe manufactures, small shoe workshop units, shoe markets, and shoe stores in Tabriz, Iran in 2021. Personal inhalation exposure to BTEX was measured using the National Institute for Occupational Safety and Health (NIOSH) 1501 method. Carcinogenic and non-carcinogenic risks due to inhalation exposure to BTEX were estimated by United States Environmental Protection Agency (U.S. EPA) method based on Mont Carlo simulation. Results showed that the concentrations of benzene and toluene were higher than the threshold limit value (TLV) in both gluing and non-gluing units of shoe manufactures. The total carcinogenic risk (TCR) due to exposure to benzene and ethyl benzene was considerable in all shoe industry-related workplaces. Also, the hazard index (HI) as a non-carcinogenic index was higher than standard levels in all shoe industry-related workplaces. Therefore, shoe industry-related workers are at cancer and non-cancer risks due to exposure to BTEX. Prevention measures need to be implemented to reduce the concentration of BTEX in shoe industry-related workplaces.

Human Health Risk Assessment of the Photocatalytic Oxidation of BTEX over TiO2/Volcanic Glass

This study demonstrates rapid photocatalytic oxidation of a benzene, toluene, ethylbenzene, and xylene (BTEX) mixture over TiO2/volcanic glass. The assessment of the photocatalytic oxidation of BTEX was conducted under conditions simulating those found in indoor environments affected by aromatic hydrocarbon release. We show, under UV-A intensities of 15 mW/cm2 and an air flow rate of 55 m3/h, that low ppmv levels of BTEX concentrations can be reduced to below detectable levels. Solid-phase microextraction technique was employed to monitor the levels of BTEX in the test chamber throughout the photocatalytic oxidation, lasting approximately 21 h. Destruction of BTEX from the gas phase was observed in the following sequence: o-xylene, ethylbenzene, toluene, and benzene. This study identified sequential degradation of BTEX, in combination with the stringent regulatory level set for benzene, resulted in the air quality hazard indexes (Total Hazard Index and Hazard Quotient) remaining relatively high during the process of photocatalytic oxidation. In the practical application of photocatalytic purification, it is crucial to account for the slower oxidation kinetics of benzene. This is of particular importance due to not only its extremely low exposure limits, but also due to the classification of benzene as a Group 1 carcinogenic compound by the International Agency for Research on Cancer (IARC). Our study underscores the importance of taking regulatory considerations into account when using photocatalytic purification technology.

BTEX in indoor air of barbershops and beauty salons: Characterization, source apportionment and health risk assessment

BACKGROUND

Volatile organic compounds, mainly BTEX, are among the pollutants of concern in beauty salons and barbershops that threaten both staff personnel and clients' health. This study aimed to determine the concentration of BTEX in barbershops and beauty salons and assess the carcinogenic and non-carcinogenic risks based on the actual risk coefficients. Also, possible sources of BTEX were determined.

METHOD

Samples were collected by passive sampling. Quantitative and qualitative measurements of BTEX compounds were performed using gas chromatography-mass spectrometry (GC-MASS). Subsequently, the health risks were assessed according to the US Environmental Protection Agency. SPSS24 software and positive matrix factorization (PMF) analysis were used for statistical analysis and source apportionment respectively.

RESULTS

Toluene is the most abundant compound in beauty salons, with a maximum concentration of 219.4 (μg/m3) in beauty salons. Results indicated that the mean ELCR value estimated for benzene regarding female staff exposure (1.04 × 10-5) was higher than that for men (4.05 × 10-6). Also, ELCR values of ethylbenzene for staff exposure were 2.08 × 10-6 and 3.8 × 10-6 for men and women, respectively, and possess possible carcinogenesis risks.

CONCLUSION

Use of solvents and cosmetic products, improper heating systems, and type of service are the sources that probably contribute to BTEX emissions in beauty salons. It is necessary to follow health guidelines and conduct continuous monitoring for their implementation, in addition to setting a mandated occupational regulation framework or air quality requirements, to improve the health conditions in beauty salons.

Single-chemical and mixture effects of multiple volatile organic compounds exposure on liver injury and risk of non-alcoholic fatty liver disease in a representative general adult population

Evidence on liver injury and non-alcoholic fatty liver disease (NAFLD) from volatile organic compounds (VOCs) exposure is insufficient. A cross-sectional study including 3011 US adults from the National Health and Nutrition Examination Survey was conducted to explore the associations of urinary exposure biomarkers (EBs) for 13 VOCs (toluene, xylene, ethylbenzene, styrene, acrylamide, N,N-dimethylformamide, acrolein, crotonaldehyde, 1,3-butadiene, acrylonitrile, cyanide, propylene oxide, and 1-bromopropane) with liver injury biomarkers and the risk of NAFLD by performing single-chemical (survey weight regression) and mixture (Bayesian kernel machine regression [BKMR] and weighted quantile sum [WQS]) analyses. We found significant positive associations of EBs for toluene and 1-bromopropane with alanine aminotransferase (ALT), EBs for toluene, crotonaldehyde, and 1,3-butadiene with asparate aminotransferase (AST), EBs for 1,3-butadiene and cyanide with alkaline phosphatase (ALP), EBs for xylene and cyanide with hepamet fibrosis score (HFS), EBs for the total 13 VOCs (except propylene oxide) with United States fatty liver index (USFLI), and EBs for xylene, N,N-dimethylformamide, acrolein, crotonaldehyde, and acrylonitrile with NALFD; and significant inverse associations of EBs for ethylbenzene, styrene, acrylamide, acrolein, crotonaldehyde, 1,3-butadiene, acrylonitrile, cyanide, and propylene oxide with total bilirubin, EBs for ethylbenzene, styrene, acrylamide, acrolein, 1,3-butadiene, acrylonitrile, and cyanide with albumin (ALB), EBs for ethylbenzene, styrene, acrylamide, N,N-dimethylformamide, acrolein, crotonaldehyde, 1,3-butadiene, acrylonitrile, cyanide, and propylene oxide with total protein (TP), and EB for 1-bromopropane with AST/ALT (all P-FDR<0.05). In BKMR and WQS, the mixture of VOC-EBs was significantly positively associated with ALT, AST, ALP, HFS, USFLI, and the risk of NAFLD, while significantly inversely associated with TBIL, ALB, TP, and AST/ALT. VOCs exposure was associated with liver injury and increased risk of NAFLD in US adults. These findings highlight that great attention should be paid to the potential risk of liver health damage from VOCs exposure.

Identify Primary Air Pollution Sources of BTEX by Using Positive Matrix Factorization (PMF): A Case Study of Ho Chi Minh City, Vietnam

Ho Chi Minh City (HCMC) is one of the main socioeconomic and financial centers of Vietnam. The city also faces serious air pollution. However, the city polluted with benzene, toluene, ethylbenzene, and xylene (BTEX) has rarely been studied. We used positive matrix factorization (PMF) to analyze BTEX concentrations measured at two sampling locations to identify the main sources of BTEX in HCMC. The locations represented residential area (i.e., To Hien Thanh) and industrial area (i.e., Tan Binh Industrial Park). At the To Hien Thanh location, the average concentrations of benzene, ethylbenzene, toluene, and xylene were 6.9, 14.4, 4.9, and 12.7 µg/m3, respectively. At the Tan Binh location, the average concentrations of benzene, ethylbenzene, toluene, and xylene were 9.8, 22.6, 2.4, and 9.2 µg/m3, respectively. The results showed that PMF was a reliable model for source apportionment in HCMC. Traffic activities were the main sources of BTEX. Besides, industrial activities also contributed to BTEX emissions, especially the location near the industrial park. The majority of BTEXs at the To Hien Thanh sampling site come from traffic sources accounting for 56.2%. Activities from traffic and photochemical reactions (42.7%) and industrial sources (40.5%) were the main sources affecting BTEX emissions at the sampling site of Tan Binh Industrial Park. This study can be used as a reference for mitigation solutions to reduce the BTEX emission in HCMC.

Association between ambient BTEX mixture and neurological hospitalizations: A multicity time-series study in Taiwan

BACKGROUND

Benzene, toluene, ethylbenzene, and xylenes, collectively known as BTEX, are hazardous chemical mixtures, and their neurological health effects have not been thoroughly evaluated. We examined the association between BTEX exposure and neurological hospital admissions.

METHODS

This was a multicity time-series study conducted in five major Taiwanese cities. Daily hospital admission records for diseases of the nervous system from January 1, 2016, to December 31, 2017, were collected from the National Health Insurance Research Database. Ambient BTEX and criteria pollutant concentrations and weather factors were collected from Photochemical Assessment Monitoring Stations. We applied a Poisson generalized additive model (GAM) and weighted quantile sum regression to calculate city-specific effect estimates for BTEX and conducted a random-effects meta-analysis to pool estimates.

RESULTS

We recorded 68 neurological hospitalizations per day during the study period. The daily mean BTEX mixture concentrations were 22.5 µg/m3, ranging from 18.3 µg/m3 in Kaohsiung to 27.0 µg/m3 in Taichung, and toluene (13.6 µg/m3) and xylene (5.8 µg/m3) were the dominant chemicals. Neurological hospitalizations increased by an average of 1.6 % (95 % CI: 0.6-2.6 %) for every interquartile range (15.8 µg/m3) increase in BTEX at lag 0 estimated using a GAM model. A quartile increase in the weighted sum of BTEX exposure was associated with a 1.7 % (95 % CI: 0.6-2.8 %) increase in daily neurological hospitalizations.

CONCLUSION

We found consistent acute adverse effects of BTEX on neurological hospitalizations in Taiwan, with toluene and xylene as the dominant chemicals. These findings aid the development of more targeted public health interventions.

Evaluation of different composting systems on an industrial scale as a contribution to the circular economy and its impact on human health

Due to the production of volatile organic compounds (VOCs), large-scale composting can cause air pollution and occupational health issues. Due to this, it is necessary to determine if the amount generated poses a health risk to plant workers, which can be a starting point for those in charge of composting plant facilities. As a result, the goal of this work is to conduct a thorough analysis of both the physicochemical features and the VOC generation of three large-scale systems. For ten weeks, the three different composting plants were monitored weekly, and VOC identification and quantification were performed using GC-MS gas chromatography. It has been observed that the biggest risk related with VOC formation occurs between the fourth and fifth weeks, when microbial activity is at its peak. Similarly, it has been demonstrated that xylenes and toluene are the ones that are produced in the greatest quantity. Finally, after ten weeks of processing, it was discovered that the material obtained complies with the regulations for the sale of an amendment.Implications: The evaluation and monitoring of the composting processes at an industrial scale is very important, due to the implications they bring. VOCs are produced by the operation of composting facilities with substantial amounts of solid waste, such as the companies in this study. These may pose a health risk to those working in the plants; thus, it is critical to understand where the VOCs occur in the process in order to maintain workers' occupational health measures. This form of evaluation is rare or nonexistent in Colombia, which is why conducting this type of study is critical, as it will provide crucial input into determining when the highest levels of VOC generation occur. These are the ones that may pose a risk at some point, but with proper occupational safety planning, said risk may be avoided. This work has evaluated three composting systems, with different types of waste and mixtures. According to reports, while composting systems continue to produce VOCs and their generation is unavoidable, the potential risk exists only within the plant. These findings can pave the way for the implementation of public policies that will improve the design and operation of composting plants. There is no specific legislation in Colombia for the design and execution of this sort of technology, which allows the use of organic waste.

BTEX in Ambient Air of Zarand, the Industrial City in Southeast of Iran: Concentration, Spatio-temporal Variation and Health Risk Assessment

The existence of several industries in Zarand, a city in Southeastern Iran, caused challenges for the residents about air pollutants and associated health effects. In the present study, the concentration of benzene, toluene, ethylbenzene, and xylene (BTEX), spatio-temporal distribution and related health risks were evaluated. Passive samplers were used to collect 30 samples in the over the hot and cold periods in 2020. The ordinary Kriging method was used to predict the spatio-temporal distribution of BTEXs. Also, the Monte Carlo simulation was used to evaluate the related carcinogenic and non-carcinogenic risks of BTEX for adults. The ranking of mean concentration of overall toluene, xylene, ethylbenzene, and benzene followed as 82.49 ± 26.86, 30.91 ± 14.04, 4.75 ± 3.28, and 0.91 ± 0.18 µg/m3, respectively. The mean value of lifetime carcinogenic risk (LTCR) for residents related to benzene was 7.52 × 10- 6, indicating a negligible carcinogenic risk for them. Furthermore, the ranking of non-carcinogenic risk calculated through hazard quotient (HQ) for investigated BTEX compounds followed as xylene > benzene > toluene > ethylbenzene over the hot period and xylene > toluene > ethylbenzene over the cold period which all points had HQ < 1. Additionally, according to the findings of the sensitivity analysis, the concentration of benzene was the main contributor in increasing the carcinogenic risk. According to our results, it can be stated that the existence of several industries in the study area could not possibly occur the significant carcinogenic and non-carcinogenic risks to the adults residents in the study period. Human studies are recommended to determine definite results.

Emission characteristics of benzene series in FCC flue gas

Benzene series are considered as air pollutants in refineries. However, the emissions of benzene series in fluid catalytic cracking (FCC) flue gas are poorly understand. In this work, we conduct stack tests on three typical FCC units. Benzene series, including benzene, toluene, xylene and ethyl benzene, are monitored in the flue gas. It shows that the coking degree of the spent catalysts affect the emissions of benzene series significantly, and there are four kinds of carbon-containing precursors in the spent catalyst. A fixed-bed reactor is used to conduct the regeneration simulation experiments, and the flue gas is monitored by TG-MS and FTIR. The emissions of toluene and ethyl benzene are mainly emitted in the early and middle stage of the reaction (250-650 °C), while the emission of benzene is mainly detected in the middle and late stage of the reaction (450-750 °C). Xylene group is not detected in the stack tests and regeneration experiments. Higher emissions of benzene series are released from the spent catalyst with lower C/H ratio during regeneration process. With the increase of oxygen content, the emissions of benzene series decrease, and the initial emission temperature is advanced. These insights can improve the refinery's awareness and control of benzene series in the future.

Level of BTEX in the Areas of Domestic Waste Incinerators in Northern Vietnam: A Comprehensive Assessment of Contamination, Composition and Human Health Risk

The trend of the treatment of solid domestic waste by the domestic waste incinerator system is an option to improve waste management and to reduce the negative impacts on the environment and human health. Benzene, toluene, ethylbenzene, and xylenes (o-, m- and p-) (BTEX) are toxic chemical environmental contaminants that are released from different sources such as the domestic waste incinerator system. To determine the concentration of BTEX in the ambient air from these incinerator areas, the research team conducted four sampling campaigns in April, June, September, and November 2021, with a total of 80 samples collected. Concentrations of benzene, toluene, (m,p)-xylenes, o- xylenes and ethylbenzene ranged from 4.53 to 36.75 µg/m³, from 16.29 µg/m³ to 125.36 µg/m³, from 2.82 µg/m³ to 31.45 µg/m³, from 1.42 µg/m³ to 25.61 µg/m³, from 1.32 µg/m³ to 10.79 µg/m³, respectively. As a result of the risk assessment, it was determined that the incinerator's exhaust gas caused secondary environmental damage, impacting the health of not only workers but also people living in nearby communities. On that basis, the article recommends applying a number of management measures to minimize the negative impacts of the operation of the solid waste incinerator on the environment and the health of the workers operating the incinerator.

Combined Omics Approach Reveals Key Differences between Aerobic and Microaerobic Xylene-Degrading Enrichment Bacterial Communities: Rhodoferax─A Hitherto Unknown Player Emerges from the Microbial Dark Matter

Among monoaromatic hydrocarbons, xylenes, especially the ortho and para isomers, are the least biodegradable compounds in oxygen-limited subsurface environments. Although much knowledge has been gained regarding the anaerobic degradation of xylene isomers in the past 2 decades, the diversity of those bacteria which are able to degrade them under microaerobic conditions is still unknown. To overcome this limitation, aerobic and microaerobic xylene-degrading enrichment cultures were established using groundwater taken from a xylene-contaminated site, and the associated bacterial communities were investigated using a polyphasic approach. Our results show that the xylene-degrading bacterial communities were distinctly different between aerobic and microaerobic enrichment conditions. Although members of the genus Pseudomonas were the most dominant in both types of enrichments, the Rhodoferax and Azovibrio lineages were only abundant under microaerobic conditions, while Sphingobium entirely replaced them under aerobic conditions. Analysis of a metagenome-assembled genome of a Rhodoferax-related bacterium revealed aromatic hydrocarbon-degrading ability by identifying two catechol 2,3-dioxygenases in the genome. Moreover, phylogenetic analysis indicated that both enzymes belonged to a newly defined subfamily of type I.2 extradiol dioxygenases (EDOs). Aerobic and microaerobic xylene-degradation experiments were conducted on strains Sphingobium sp. AS12 and Pseudomonas sp. MAP12, isolated from the aerobic and microaerobic enrichments, respectively. The obtained results, together with the whole-genome sequence data of the strains, confirmed the observation that members of the genus Sphingobium are excellent aromatic hydrocarbon degraders but effective only under clear aerobic conditions. Overall, it was concluded that the observed differences between the bacterial communities of aerobic and microaerobic xylene-degrading enrichments were driven primarily by (i) the method of aromatic ring activation (monooxygenation vs dioxygenation), (ii) the type of EDO enzymes, and (iii) the ability of degraders to respire utilizing nitrate.

Evaluation of Biodegradation of BTEX in the Subsurface of a Petrochemical Site near the Yangtze River, China

The contamination of soil and groundwater with BTEX (benzene, toluene, ethyl benzene, and xylenes) is a common issue at petrochemical sites, posing a threat to the ecosystems and human health. The goal of this study was to evaluate the biodegradation of BTEX in the subsurface of a petrochemical site near the Yangtze River, thus providing scientific basis for bioremediation of the contaminated site. Both molecular analysis of field samples and microcosm study in the laboratory were performed for the evaluation. Soil and groundwater samples were collected from the site. Microcosms were constructed with inoculum from the soil and incubated anaerobically in the presence of nitrate, ferric oxide, manganese oxide, sulfate, and sodium bicarbonate, respectively. The initial concentration of each component of BTEX (benzene, toluene, ethyl benzene, o-xylene) was 4-5 mg/L. Actinobacteria was dominant in the highly contaminated soil, while Proteobacteria was dominant in the slightly contaminated soil and the groundwater. The relative abundances of Firmicutes, Spirochaetes, and Caldiserica were higher in the highly contaminated soil and groundwater samples compared to those in the corresponding slightly contaminated samples. The relative abundances of predicted functions, such as carbohydrate transport and metabolism, nucleotide transport and metabolism, coenzyme transport and metabolism, amino acid transport and metabolism, etc., in the highly contaminated soil and groundwater samples were higher than those in the corresponding slightly contaminated samples. In microcosms, biodegradations of BTEX occurred, and the first-order rate constants in the presence of various electron acceptors had the following order: sulfate (0.08-0.10/d) > sodium bicarbonate (0.07-0.09/d) > ferric oxide (0.04-0.06/d) > nitrate (0.03-0.05/d) > manganese oxide (0.01-0.04/d).

An Innovative Method for BTEX Emission Inventory and Development of Mitigation Measures in Developing Countries-A Case Study: Ho Chi Minh City, Vietnam

Benzene, toluene, ethylbenzene, and xylenes (BTEX) are carcinogenic pollutants. However, the average concentration in 1 h of some pollutants belonging to BTEX, such as benzene, in Ho Chi Minh City (HCMC) is higher than the national standard QCVN 06:2009/BTNMT by about ten times. This research is the first to calculate the emission of BTEX for developing countries on a city scale. This paper developed a method to calculate cold emission factors based on hot emission factors for BTEX. Five spreadsheets developed and calculated these cold emission factors for five vehicle categories. A comprehensive emission inventory (EI) for BTEX was conducted in HCMC to determine the cause of BTEX pollution. An innovative methodology with bottom-up and top-down combination was applied to conduct BTEX EI, in which the EMISENS model was utilized to generate the EI for road traffic sources, and the emission factors method was utilized for other emission sources. Among emission reasons, motorcycles contribute the highest to HCMC air pollution, responsible for 93%, 90%, 98.9%, and 91.5% of benzene, toluene, ethylbenzene, and xylene, respectively. Cars contributed 5%, 6%, 0.8%, and 6.5% of benzene, toluene, ethylbenzene, and xylene, respectively. For LDVs, the emission from benzene, toluene, ethylbenzene, and xylene accounted for 1%, 2%, 0.2%, and 1.9%. The major reasons for point sources were metal production, which had 1%, 2%, and 0.1% for benzene, toluene, ethylbenzene, and xylenes emissions. The area source had a minority emission of total BTEX in Ho Chi Minh City. Our findings can be used to invest in the most significant sources to reduce BTEX in HCMC. Our approach can be applied in similar urban areas in BTEX EI. This research also developed nine measures to reduce BTEX in HCMC for human health protection.

Exposure to Crude Oil-Related Volatile Organic Compounds Associated with Lung Function Decline in a Longitudinal Panel of Children

BACKGROUND

Children in the affected area were exposed to large amounts of volatile organic compounds (VOCs) from the Hebei Spirit oil spill accident.

OBJECTIVES

We investigated the lung function loss from the exposure to VOCs in a longitudinal panel of 224 children 1, 3, and 5 years after the VOC exposure event.

METHODS

Atmospheric estimated concentration of total VOCs (TVOCs), benzene, toluene, ethylbenzene, and xylene for 4 days immediately after the accident were calculated for each village (n = 83) using a modeling technique. Forced expiratory volume in 1 s (FEV₁) as an indicator of airway status was measured 1, 3, and 5 years after the exposure in 224 children 4~9 years of age at the exposure to the oil spill. Multiple linear regression and linear mixed models were used to evaluate the associations, with adjustment for smoking and second-hand smoke at home.

RESULTS

Among the TVOCs (geometric mean: 1319.5 mg/m³·4 d), xylene (9.4), toluene (8.5), ethylbenzene (5.2), and benzene (2.0) were dominant in the order of air concentration level. In 224 children, percent predicted FEV₁ (ppFEV₁), adjusted for smoking and second-hand smoke at home, was 100.7% after 1 year, 96.2% after 3 years, and 94.6% after 5 years, and the loss over the period was significant (p < 0.0001). After 1 and 3 years, TVOCs, xylene, toluene, and ethylbenzene were significantly associated with ppFEV₁. After 5 years, the associations were not significant. Throughout the 5 years' repeated measurements in the panel, TVOCs, xylene, toluene, and ethylbenzene were significantly associated with ppFEV₁.

CONCLUSIONS

Exposure to VOCs from the oil spill resulted in lung function loss among children, which remained significant up to 5 years after the exposure.

Assessing the effect of BTEX on blood and spirometry parameters staff in a petroleum refinery

This study aimed to investigate the impact of BTEX compound on blood and spirometry parameters of staff in the Abadan petroleum refinery (Iran). In 80 staff was examined in terms of BTEX exposure (40 exposed and 40 non-exposed). In this study, the air sampling was carried out according to the NIOSH 1,501 method and an automated hematology analyzer was used to analyze all blood samples to evaluate blood parameters and using a Micro Direct automated computerized spirometer. Spss20 software was used to interpret the performance. According to the obtained results, total BTEX concentrations with the recommended standard level showed that, toluene, ethylbenzene, and xylenes, concentrations in Abadan Oil Refining Company Workers' breathing zone were lower than the TLV-TWA recommended by ACGIH. However, the average concentration of benzene was higher than the allowable limit. Therefore, in this study the effect of benzene on the blood and respiratory parameters of the workers was evaluated, the comparison of the blood and respiratory parameters between the groups of exposed and unexposed workers did not reveal any statistical difference between the groups (p > 0.001). The results showed no statistically significant connection between mean blood and spirometry parameters and benzene exposure. Also, based on results the effect of benzene problems needs to be prevented in employees with adequate engineering and management controls and periodic inspection.

Deep neural networks for simultaneous BTEX sensing at high temperatures

In the study of chemical reactions, it is desirable to have a diagnostic strategy that can detect multiple species simultaneously with high sensitivity, selectivity, and fast time response. Laser-based selective detection of benzene, toluene, ethylbenzene, and xylenes (BTEX) has been challenging due to the similarly broad absorbance spectra of these species. Here, a mid-infrared laser sensor is presented for selective and simultaneous BTEX detection in high-temperature shock tube experiments using deep neural networks (DNN). A shock tube was coupled with a non-intrusive mid-infrared laser source, scanned over 3038.6-3039.8 cm^-1, and an off-axis cavity enhanced absorption spectroscopy (OA-CEAS) setup of ∼ 100 gain to enable trace detection. Absorption cross-sections of BTEX species were measured at temperatures of 1000-1250 K and pressures near 1 atm. A DNN model with five hidden layers of 256, 128, 64, 32, and 16 nodes was implemented to split the composite measured spectra into the contributing spectra of each species. Several BTEX mixtures with varying mole fractions (0-600 ppm) of each species were prepared manometrically and shock-heated to 1000-1250 K and 1 atm, and the composite measured absorbance were split into contributions from each BTEX species using the developed DNN model, and thus make selective determinations of BTEX species. Predicted and manometric mole fractions were in good agreement with an absolute relative error of ∼ 11%. We obtained a minimum detection limit of 0.73-1.38 ppm of the target species at 1180 K. To the best of our knowledge, this work reports the first successful implementation of multispecies detection with a single narrow wavelength-tuning laser in a shock tube with laser absorption spectroscopy.

Evaluation of potential human health risks from exposure to volatile organic compounds in contaminated urban groundwater in the Sava river aquifer, Belgrade, Serbia

The oil pollutant in the Sava River aquifer in the residential area of Belgrade, Serbia was investigated in order to analyze the extent, origin and spatial distribution of the pollution, with the aim to estimate potential human health risks from exposure to the compounds detected. Analytical methods indicated that the dominant compounds in this oil pollutant were gasoline range organic compounds. Benzene, toluene, ethylbenzene and xylenes (BTEX) were identified as compounds of concern and quantified by headspace gas chromatography. The concentrations of benzene measured at all sampling points were higher than the remediation value while the maximum concentrations of BTEX quantified were among the highest concentrations of these compounds reported in the petroleum-contaminated aquifers in the world. The assessment of the human health risks from exposure to BTEX-covered industrial scenario for adult receptors and residential scenario for adult receptors and children. The exposure routes analyzed were dermal contact with and ingestion of contaminated water, considering both cancer and non-cancer effects. The analysis of the lifetime incremental cancer risk indicated the potential for adverse health effects for human exposure at the investigated location, and because of that it was interpreted as an unacceptable risk level or risks of high priority which required immediate consideration for remedial measures at this location. A complete set of mitigation measures was proposed including: groundwater decontamination treatment, installation of filters for tap water, development of the system for monitoring of BTEX in the groundwater and development of the emergency response capacities at this location.

Boosting Electrical Response toward Trace Volatile Organic Compounds Molecules via Pulsed Temperature Modulation of Pt Anchored WO3 Chemiresistor

Insufficient limit of detection (LoD) toward volatile organic compounds (VOCs) hinders the promising applications of metal oxide chemiresistors in emerging air quality monitoring and/or breath analysis. There is an inherent limitation of widely adopted strategies of creating sensitive chemiresistors then operating at the optimized temperature via a continuous heating (CH) mode. Herein, a strategy combining Pt single atoms anchoring (chemical sensitization) with pulsed temperature modulation (PTM, physical sensitization) is proposed. Apart from generating abundant surface asymmetric oxygen vacancy (Pt-V_O -W) active sites at pulsed high temperature (HT) stage, inward diffusion of trace target VOCs across the sensing layer at pulsed low temperature stage (driven by PTM induced concentration gradient), can greatly enhance the charge interaction probability between the generated surface active species and the surrounding VOCs, and thus offers a novel avenue on addressing the bottleneck issue of low LoD by PTM. Triggered by HT of 300 °C, the responses of Pt anchored WO₃ chemiresistor to 1 ppm trimethylamine (TMA) and xylene can be drastically boosted from 1.9 (CH) to 6541.5 (PTM) and 1.5 (CH) to 1001.1 (PTM), respectively. And ultra-low theoretic LoD of 0.78 ppt (TMA) and 0.18 ppt (xylene) are successfully achieved, respectively.

Global preterm births attributable to BTEX (benzene, toluene, ethylbenzene, and xylene) exposure

Epidemiological studies have shown that long-term exposure to toxic volatile organic compounds, such as benzene, toluene, ethylbenzene, and xylene (BTEX), is associated with preterm births (PTB). However, global PTB attributable to long-term BTEX exposure has not been reported in the literature yet. In this study, we employed a global chemical transport model, GEOS-Chem (Goddard Earth Observing System coupled with chemistry), in conjunction with an epidemiological model, to quantify the global country-specific PTB associated with long-term BTEX exposure at the horizontal resolution of 1 km × 1 km for the year 2015. Model simulated surface annual mean BTEX concentrations in GEOS-Chem have been thoroughly evaluated against global in-situ observations, which demonstrated that model simulated BTEX concentrations fairly agreed with observations but tended to be underestimated in India. Our study found that the global annual total PTB attributable to BTEX was 2.01 million [95% confidence interval (95CI): 1.16-2.70 million] in 2015, with largest contributions from India (28.3%), followed by China (27.5%), Pakistan (6.2%), Indonesia (4.2%), Bangladesh (3.7%) and United States (2.3%). The global annual total PTB due to BTEX exposure accounted for 19.6% (95CI: 11.3-26.4%) relative to the global annual total all-cause PTB (10.24 million) in 2015. Our study has significant implications on air pollution mitigation policy associated with country-specific anthropogenic BTEX emission reductions to achieve the benefit of human health.

Characteristics of volatile organic compounds in the metropolitan city of Seoul, South Korea: Diurnal variation, source identification, secondary formation of organic aerosol, and health risk

Atmospheric volatile organic compounds (VOCs) in Seoul, the capital of South Korea, have attracted increased attention owing to their emission, secondary formation, and human health risk. In this study, we collected 24 hourly samples once a month at an urban site in Seoul for a year (a total of 288 samples) using a sequential tube sampler. Analysis results revealed that toluene (9.08 ± 8.99 μg/m³) exhibited the highest annual mean concentration, followed by ethyl acetate (5.55 ± 9.09 μg/m³), m,p-xylenes (2.79 ± 4.57 μg/m³), benzene (2.37 ± 1.55 μg/m³), ethylbenzene (1.81 ± 2.27 μg/m³), and o-xylene (0.91 ± 1.47 μg/m³), indicating that these compounds accounted for 77.8-85.6% of the seasonal mean concentrations of the total (Σ₅₉) VOCs. The concentrations of the Σ₅₉ VOCs were statistically higher in spring and winter than in summer and fall because of meteorological conditions, and the concentrations of individual VOCs were higher during the daytime than nighttime owing to higher human activities during the daytime. The conditional bivariate probability function and concentration weighted trajectory analysis results suggested that domestic effects (e.g., vehicular exhaust and solvents) exhibited a dominant effect on the presence of VOCs in Seoul, as well as long-range atmospheric transport of VOCs. Further, the most important secondary organic aerosol formation potential (SOAFP) compounds included benzene, toluene, ethylbenzene, and m,p,o-xylenes, and the total SOAFP of nine VOCs accounted for 5-29% of the seasonal mean PM_2.5 concentrations. The cancer and non-cancer risks of the selected VOCs were below the tolerable (1 × 10^-4) and acceptable (Hazard quotient: HQ < 1) levels, respectively. Overall, this study highlighted the feasibility of the sequential sampling of VOCs and hybrid receptor modeling to further understand the source-receptor relationship of VOCs.

Human exposure to BTEX emitted from a typical e-waste recycling industrial park: External and internal exposure levels, sources, and probabilistic risk implications

Benzene, toluene, ethylbenzene, and xylene (BTEX) can be released during extensive activities associated with the disposal of electronic waste (e-waste), which might pose deleterious health effects on workers. In this study, pollution profiles of BTEX in air and their urinary excretive profiles in occupational workers were investigated in a typical e-waste recycling industrial park. The results showed that the workers in the park were generally exposed to high levels of BTEX. The median levels of urinary metabolites were approximately 6-orders of magnitude higher than those of unmetabolized BTEX, indicating that pollutants efficiently metabolize at those occupational levels. The analytes presented differential profiles in external and internal exposure. Among the metabolites, significant correlation (p < 0.05) was observed between N-acetyl-S-benzyl-L-cysteine (S-BMA) concentration and atmospheric individual BTEX derived from the e-waste recycling area, suggesting that S-BMA is a potential marker for BTEX exposure to e-waste occupational workers. Notably, 95.2 % of all the workers showed a cumulative carcinogenic risk induced by BTEX exposure via inhalation, with 99.9 % of the carcinogenic risk distribution based on concentration of benzene metabolite (N-acetyl-S-(phenyl)-L-cysteine) exceeding 1.0E-6. This study holds potential in providing valuable inferences for the development of remediation strategies focusing on BTEX exposure reduction to protect workers' health at e-waste recycling industries.

Effects of replacing fish meal with cottonseed protein concentrate on the growth, immune responses, digestive ability and intestinal microbial flora in Litopenaeus vannamei

The effects of cottonseed protein concentrate (CPC) in place of fishmeal on the growth performance, immune response, digestive ability and intestinal microbiota of Litopenaeus vannamei were investigated in this study. L. vannamei (initial body weight: 0.42 ± 0.01g) was fed for 8 weeks by four isonitrogenous and isolipid feeds with CPC replacing fishmeal (FM) at 0% (control), 15% (CPC15), 30% (CPC30) and 45% (CPC45), respectively. At the end of the study, the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR) and protein efficiency ratio (PER) of L. vannamei in CPC15 and CPC30 groups were significantly increased, while the feed conversion ratio (FCR) of L. vannamei in the CPC30 group was significantly reduced when compared with the FM group (P < 0.05). After Vibrio parahaemolyticus infection, the cumulative mortality of L. vannamei in CPC15 within 24 hpi was significantly lower than that of the control group (P < 0.05). When compared with the control group, the activities and expression of the immunity-related enzymes in the hepatopancreas had almost the same obvious change trend in the CPC-containing groups, which indicated that the replacement for fishmeal by CPC led to significant immune response in L. vannamei. Besides, significant up-regulation of the digestive enzyme activities were observed in the CPC-containing groups. Analysis of intestinal microbiota showed that significant difference in alpha diversity existed between the CPC-containing groups and the control group. The relative abundances of several top 10 dominated species at the phylum and genus levels were significantly changed in the CPC-containing groups compared with the control group (P < 0.05). Functional prediction of the microbiota indicated that the pathway of protein digestion and absorption was significantly more abundant while the pathways of nitrotoluene degradation, aminobenzoate degradation, atrazine degradation, dioxin degradation and xylene degradation were significantly less abundant in the CPC-containing groups than the FM group (P < 0.05). In summary, optimal dietary CPC replacement of FM could improve the growth, immunity, digestive capacity and the diversities of the intestinal microbial flora of L. vannamei. However, parts of the functions of the intestinal microbial flora were decline.

Computational Investigations of Metal-Organic Frameworks as Sorbents for BTEX Removal

Sequestration of aromatic volatile organic compounds (VOCs) via metal-organic frameworks (MOFs) as sorbents is a viable means of environmental preservation. In this investigation, we shed light on the key features associated with MOFs that govern the selective uptake of a subclass of VOCs containing benzene, toluene, ethylbenzene, and xylenes (BTEX). We investigate, through a multistep computational framework including ab initio electronic structure and classical molecular dynamics simulations, the energetic and dynamical properties associated with BTEX capture in three MOFs: HKUST-1, ZIF-8, and MIL-53. Our work demonstrates the importance of considering both static and dynamical properties upon introduction of guest molecules in such computational investigations. We elucidate the key geometric factors associated with efficient capture of BTEX compounds and highlight possible postsynthetic modifications that can be used to produce next generation sorbents for BTEX capture.

Biomonitoring of BTEX in primary school children exposed to hookah smoke

Hookah smoking is one of the major indoor sources of benzene, toluene, ethylbenzene, and xylenes (BTEX). This study aimed to investigate the potential exposure to BTEX among primary school children, particularly those exposed to hookah smoke. This cross-sectional study was conducted in Khesht, one of the southwestern cities in Iran, in mid-June 2020. Totally, 50 primary school children exposed to hookah smoke were chosen as the case group and 50 primary school children were selected as the control group. Urinary un-metabolized BTEX was measured by a headspace gas chromatography mass spectrometry (GC-MS). Additionally, a detailed questionnaire was used to gather data and information from the students' parents. The mean levels of urinary benzene, toluene, ethylbenzene, m,p-xylene, and o-xylene were 1.44, 5.87, 2.49, 6.93, and 7.17 μg/L, respectively in the exposed children. Urinary BTEX was 3.93-folds higher in the case group than in the controls (p<0.05). Household cleaning products, the floor on which the house was located, children's sleeping place, and playing outdoors were found to be important factors in predicting urinary BTEX levels. Overall, it was found necessary to avoid indoor smoking to prevent the emission of BTEX compounds via exhaled mainstream smoke and to protect vulnerable non-smokers, especially children, from exposure to second-hand and third-hand smoke.

Indoor exposure levels and risk assessment of volatile organic compounds in residences, schools, and offices in China from 2000 to 2021: A systematic review

The last two decades have witnessed rapid urbanization and economic growth accompanied by severe indoor air pollution of volatile organic compounds (VOCs) in China. However, indoor VOC pollution across China has not been well characterized and documented. This study is a systematic review of field measurements of eight target VOCs (benzene, toluene, xylenes, acetaldehyde, p-dichlorobenzene, butadiene, trichloroethylene, and tetrachloroethylene) in residences, offices, and schools in China from 2000 to 2021. The results show that indoor pollution of benzene, toluene, and xylenes has been more serious in China than in other countries. Spatiotemporal distribution shows lower indoor VOC levels in east and south-east regions and a declining trend from 2000 to 2021. Moving into a dwelling more than 1 year after decoration and improving ventilation could significantly reduce exposure to indoor VOCs. Reducing benzene exposure is urgently needed because it is associated with greater health risks (4.5 × 10^-4 for lifetime cancer risk and 8.3 for hazard quotient) than any other VOCs. The present study enriches the database of indoor VOC levels and provides scientific evidence for improving national indoor air quality standards as well as estimating the attributable disease burden caused by VOCs in China.

Assessing the Biodegradation of BTEX and Stress Response in a Bio-Permeable Reactive Barrier Using Compound-Specific Isotope Analysis

By using compound-specific isotope analysis (CSIA) in combination with high-throughput sequencing analysis (HTS), we successfully evaluated the benzene and toluene biodegradation in a bio-permeable reactive barrier (bio-PRB) and the stress response of the microbial community. Under stress conditions, a greater decline in the biodegradation rate of BTEX was observed compared with the apparent removal rate. Both an increase in the influent concentration and the addition of trichloroethylene (TCE) inhibited benzene biodegradation, while toluene biodegradation was inhibited by TCE. Regarding the stress response, the relative abundance of the dominant bacterial community responsible for the biodegradation of BTEX increased with the influent concentration. However, the dominant bacterial community did not change, and its relative abundance was restored after the influent concentration decreased. On the contrary, the addition of TCE significantly changed the bacterial community, with Aminicenantes becoming the dominant phyla for co-metabolizing TCE and BTEX. Thus, TCE had a more significant influence on the bio-PRB than an increasing influent concentration, although these two stress conditions showed a similar degree of influence on the apparent removal rate of benzene and toluene. The present work not only provides a new method for accurately evaluating the biodegradation performance and microbial community in a bio-PRB, but also expands the application of compound-specific isotope analysis in the biological treatment of wastewater.

Occupational exposure to BTEX and styrene in West Asian countries: a brief review of current state and limits

The aim of introducing occupational exposure limits (OELs) is to use them as a risk management tool in order to protect workers' health and well-being against harmful agents at the workplace. In this review we identify OELs for benzene, toluene, ethylbenzene, xylene (BTEX), and styrene concentrations in air and assess occupational exposure to these compounds through a systematic literature search of publications published in West Asian countries from 1980 to 2021. OELs for BTEX and styrene have been set in Iran and Turkey to levels similar to those in European countries and the US. The search yielded 49 full-text articles that cover studies of exposure assessment in six countries, but most (n=40) regard Iran. Average occupational exposure to benzene of workers in oil-related industries is higher than recommended OEL, while average occupational exposure to other compounds is lower than local OELs (where they exist). Currently, information about levels of occupational exposure to BTEX and styrene is insufficient in West Asian countries, which should be remedied through OEL regulation and application. Furthermore, coherent research is also needed to determine actual levels of occupational exposure, dose-responses, and the economic and technical capacity of local industries to address current issues.

An assessment of spatial distribution and atmospheric concentrations of ozone, nitrogen dioxide, sulfur dioxide, benzene, toluene, ethylbenzene, and xylenes: ozone formation potential and health risk estimation in Bolu city of Turkey

Atmospheric pollutants including ozone, nitrogen dioxide, sulfur dioxide, and BTEX (benzene, toluene, ethylbenzene, and xylenes) compounds were evaluated concerning their spatial distribution, temporal variation, and health risk factor. Bolu plateau where sampling was performed has a densely populated city center, semi-rural areas, and forested areas. Additionally, the ozone formation potentials of BTEXs were calculated, and toluene was found to be the most important compound in ground level ozone formation. The spatial distribution of BTEXs and nitrogen dioxide pollution maps showed that their concentrations were higher around the major roads and city center, while rural-forested areas were found to be rich in ozone. BTEXs and nitrogen dioxide were found to have higher atmospheric concentrations in winter. That was mostly related to the source strength and low mixing height during that season. The average toluene to benzene ratios demonstrated that there was a significant influence of traffic emissions in the region. Although there was no significant change in sulfur dioxide concentrations in the summer and winter seasons of 2017, the differences in the spatial distribution showed that seasonal sources such as domestic heating and intensive outdoor barbecue cooking were effective in the atmospheric presence of this pollutant. The lifetime cancer risk through inhalation of benzene was found to be comparable with the limit value (1 × 10^-6) recommended by USEPA. On the other hand, hazard ratios for BTEXs were found at an acceptable level for different outdoor environments (villages, roadside, and city center) for both seasons.

Use of statistical modeling for BTEX prediction in cases of crude oil spill in seawater

Cases of oil spillage and leakage in marine environments are increasing, and generating a need to quickly assess the presence of these contaminants in seawater. This work aims to estimate the concentrations of benzene, toluene, ethylbenzene and xylenes (BTEX) dissolved in seawater in cases of oil spillage using experimental factorial planning. The study factors were oil °API and oil/seawater contact time after spillage. The models obtained were able to satisfactorily estimate BTEX concentrations, with accuracy greater than 99.3% within the ranges studied, with R² correlation coefficients ranging from 0.992 to 0.997. The models presented forecast efficiency higher than 88%, with low relative errors, ranging from 0.1% to 12%. The concentrations of benzene dissolved in seawater found experimentally with only one hour of spillage, for the two types of oils studied, were higher than allowed by Brazilian legislation, demonstrating real environmental risk in cases of spillage of these types of oil into the sea. These results can corroborate the development of a risk assessment in oil spills within the studied ranges and serve as a useful analytical tool for emergencies.

Personal exposure to benzene, toluene, ethylbenzene, and xylenes (BTEXs) mixture and telomere length: a cross-sectional study of the general US adult population

BACKGROUND

Benzene, Toluene, Ethylbenzene, and Xylenes (BTEXs) are a group of aromatic air pollutants from fossil fuels. There is no research on associations of the BTEXs mixture with telomere length (TL), a marker of cellular aging, in the general population.

METHODS

We analyzed a subsample of 549 US adults aged 20-59 years from the National Health and Nutrition Examination Survey 1999-2000. BTEXs samples were collected by passive exposure badges worn by participants for 48-72 h. Levels of BTEXs were measured with gas chromatography/mass spectrometry. Leukocyte TL was measured with qPCR. We used Bayesian Kernel Machine Regression (BKMR) to examine the effect of the BTEXs mixture on TL adjusting for potential confounders. Analyses were stratified by tobacco smoking status (serum cotinine≥10 ng/mL vs. <10 ng/mL).

RESULTS

Levels of personal exposure to BTEXs were detectable in most participants and were relatively higher in the 150 smokers than in the 399 nonsmokers. The BTEXs were moderately or strongly intercorrelated (0.5 < r ≤ 0.9, P < 0.05). All chemicals had weak, inverse correlations with TL (-0.1<r < 0, P > 0.05). In BKMR models among the nonsmokers, the BTEXs mixture was significantly inversely associated with TL at a low range of the BTEXs (20th-65th percentile) but was not associated with TL at a higher range (>65th percentile). Also, we found a U-shape association of benzene and a positive association of ethylbenzene with TL independent of other BTEXs. Among smokers, neither the BTEXs mixture nor any individual BTEXs were significantly associated with TL.

CONCLUSION

Within a low-to-middle range, exposure to the BTEXs mixture may be associated with shorter telomere length in the general nonsmoking population.

BTEX levels in rural households: Heating system, building characteristic impacts and lifetime excess cancer risk assessment

BTEX (benzene, toluene, ethylbenzene, and xylene) are a group of toxic organic compounds that exposure to them can cause adverse short and long terms health effects. We measured the levels of BTEX in the indoor and outdoor air of rural areas in Ardebil, Iran. We further assessed their health risks and determinants parameters. BTEX were sampled by drawing air through activated charcoal tubes, using low flow SKC pumps. Samples were extracted by adding carbon disulfide and analyzed by subjecting the aromatic fraction to GC-FID. The results indicated that the concentrations of BTEX in the indoor air were significantly higher than those of outdoor (p-value<0.05). The mean indoor concentrations of benzene, toluene, ethylbenzene, and xylene were 41.69 ± 30.70, 96.73 ± 60.75, 38.73 ± 33.59, and 59.42 ± 35.99 μg m^-3, while the mean outdoor concentrations of them were 8.94 ± 7.32, 36.93 ± 21.82, 7.66 ± 5.63, and 18.14 ± 10.25 μg m^-3, respectively. The concentrations of BTEX in indoor and outdoor of the rural areas that used kerosene fuel for heating systems were significantly higher than those used natural gas. The results indicated that the tobacco smoke is a notable temporary source of indoor BTEX. The mean inhalation lifetime cancer risk (LTCR) value of benzene for residents of rural houses with the natural gas and kerosene heating systems were 28.6 × 10^-6 and 97.2 × 10^-6, while for ethylbenzene these figures stood out at 29.1 × 10^-6 and 95.8 × 10^-6, respectively. LTCR value for residents who used kerosene fuel for heating was higher than the World Health Organization (WHO) recommended limit.

Continuous VOCs Monitoring in Saturated and Unsaturated Zones Using Thermal Desorber and Gas Chromatography: System Development and Field Application

Subsurface VOC monitoring has been mainly based on manual sampling, transport, and analysis, which would require a sufficient amount of samples to ensure data accuracy and reliability, and additional costs to ensure sample quality. Therefore, a continuous on-site monitoring system is desirable for accurate measurement and subsequent risk assessment. In this study, benzene, toluene, ethylbenzene, and xylene (BTEX) were continuously monitored by the system based on a thermal desorber (TD) and gas chromatography (GC) in an oil-contaminated site that consisted of saturated and unsaturated zones. For the saturated zone, fully automated groundwater sampling and purging processes were performed, and the gasified samples were applied to the TD–GC system. For the unsaturated zone, the gaseous sample in the site was directly applied to the TD–GC system. After verifying the accuracy and precision of the monitoring system, the continuous monitoring system was successfully operated for more than a month in the field. The monitoring system used in this study is applicable to other sites for continuous monitoring, thus providing a scientific background for advanced risk assessment and policy development.

Emission of BTEX compounds from the frying process: Quantification, environmental effects, and probabilistic health risk assessment

Frying is one of the cooking methods which generates mono aromatic hydrocarbons, including benzene, toluene, ethylbenzene, and xylene (BTEX); subsequently, it affects health through carcinogenic (CR) and non-carcinogenic risks (n-CR). However, their environmental effects known by secondary organic aerosols (SOA) and ozone formation potential (OFP) were also attended by many scientists. Therefore, this study quantified the BTEX emissions from 4 types of most commonly used edible oils (canola, corn, sunflower, and blend) under various frying conditions of temperatures and food additives. Furthermore, the effects of the chemicals in the light of health (CR and n-CR) and environment (SOA and OFP) were also investigated. The study results showed that higher temperatures could significantly increase the emissions, while the addition of food ingredients significantly reduces the emissions. The rank order of emitted chemical was obtained as T > B > E > X. The blend had the most emission among oils, followed by, in descending order, corn, sunflower, and canola. In association with environmental effects, the orders of X > T > E > B and T ∼ E > X > B were obtained for OFP and SOA, respectively. THQ for blend, corn, canola, and sunflower oils was higher than 1 (1.76, 1.35, 1.27, and 1.002, respectively), showing a considerable n-CR when the hood was off. In this respect, TCR for the oils (1.78 × 10^-4, 1.45 × 10^-4, 1.39 × 10^-4, and 1.05 × 10^-4, respectively) shown the probable risk for all oils. Moreover, hood switching reduced the risk by about 11-81%.

Seasonal and Diurnal Variations of BTEX in Ambient Air from a Site Impacted by the Oil Industry in Southeast Mexico

Atmospheric concentrations of BTEX were measured in an urban site located in the vicinity of an oil storage-distribution facility in Paraiso, Tabasco, Mexico. Samples were collected during two seasons (nortes 2018 and dry 2019). The relative abundance of BTEX mean concentrations was: toluene (5.24 µg m^-3) > ethylbenzene (3.92 µg m^-3) > m, p-xylene (3.89 µg m^-3) > benzene (2.43 µg m^-3). BTEX concentrations had a clear diurnal and seasonal pattern, showing higher levels during the dry season due to differences in wind conditions, rainfall patterns and temperature. Statistical analysis showed significant positive correlations among BTEX, indicating that these compounds had common sources. Interspecies ratios revealed that BTEX were originated from sources beyond vehicular traffic and that they were influenced by the transport of local air masses. The assessment of lifetime cancer risk showed that the population in the study area is at possible risk of developing cancer.

Benzene, Toluene, Ethylbenzene and Xylene (BTEX) Concentrations in Urban Areas Impacted by Chemical and Petrochemical Industrial Emissions

The Metropolitan Region of Rio de Janeiro is the second largest urban and industrial region in Brazil. While the south and south-east areas are affected by vehicular emissions, the districts and cities located in the northern area are subjected to industrial emissions and have the poorest air quality of the region. In this study, BTEX concentrations were determined in the District of Irajá, a residential area located in the north of the city of Rio de Janeiro, approximately 25 km from the industrial zone, as well as in the District of Jardim Primavera, in the city of Duque de Caxias. The mean values for total BTEX concentrations were 38.4 ± 11.7 and 44.6 ± 29.3 μg m^-3, in Irajá and Jardim Primavera, respectively, which are higher than those previously reported for other areas. The benzene/toluene rates, (approximately 0.5 for both sampling sites), were also higher than typical values that were determined for diesel and gasoline emissions through dynamometer experiments.

Spatial distribution of BTEX emission and health risk assessment in the ambient air of pars special economic energy zone (PSEEZ) using passive sampling

Benzene, toluene, ethylbenzene and xylene (BTEX) are a challenging group of volatile organic compounds in industrial and energy areas. Since these aromatics may cause serious diseases such as cancer and respiratory illnesses, they must be monitored. Pars Special Economic Energy Zone (PSEEZ) in Iran is the second largest energy zone of the world with numerous gas refineries and petrochemical complexes for producing a wide range of products. This study is focused on determination of BTEX concentration in the whole South Pars area (46 sampling points) which is the active site of PSEEZ using passive sampling. Then, the results of the passive sampling are used for providing spatial distribution of BTEX using GIS. The annual BTEX measurements revealed that benzene and toluene concentration violates the maximum permitted values at numerous points most of which are located in the vicinity of petrochemical complexes. Active sampling in these complexes not only confirms the results of passive sampling, but also suggests a more intensified BTEX pollution in the air quality of the area which reaches as high as 3500 μg.m^-3 and 18,000 μg.m^-3 for benzene and toluene, respectively, being far beyond the acceptable standards. Health risk analysis also confirms the intensity of BTEX at the selected points. This study suggests a reconsideration of the location of non-operational sites and personnel who are more vulnerable to BTEX contamination. Also, BTEX profile provided by GIS in this research gives a suitable plan for relocating.

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.

Diffusive uptake rates for passive air sampling: Application to volatile organic compound exposure during FIREX-AQ campaign

Passive (diffusive) sampling using sorbents is an economical and versatile method of measuring pollutants in air, including volatile organic compounds (VOCs). Diffusive uptake rates (UTRs) are needed for each analyte to obtain average concentrations during a specific passive sampling time duration. Here, a simultaneous active/diffusive ambient air sampling technique on Tenax®TA was employed to measure 24-hours, 7, 14 and 28-days UTRs of up to 27 VOCs, including benzene, toluene, ethylbenzene, xylenes (BTEX), C6-C12 hydrocarbons, benzenes derivatives, tetrachloroethylene, pinenes and limonene. Samples were analyzed via thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) for desired analytes. Seven-day UTR values ranged from 0.17 to 0.59 mL/min and many compounds exhibited a linear relationship with UTR and time duration up to 14 or 28 days. This may be the most comprehensive UTR tabulation of VOCs on Tenax®TA for time periods of 24 hours -28 days available. These rates were applied to VOC data measured during the 2019 NASA/NOAA Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) campaign, with goals to determine the chemical composition of western US wildfire smoke and to assess human exposure to air toxics. Summer 2019 exposure levels of BTEX at five Northwestern cities were low and the cancer risk due to benzene was assessed during FIREX-AQ to be background or 1 × 10^-6. The UTRs derived here can be useful in applications of diffusive sampling, including estimation of sub-chronic to chronic human exposure risk of air toxics and wildfire smoke.

Modeling the environmental, health, and safety aspects of xylene isomer emission from storage tanks in petrochemical industries, Iran

The release of xylene isomers from storage tanks poses a significant threat to petrochemical industries, and their safe transportation and storage is a widely researched topic. This paper focused on modeling the environmental, health, and safety effects of P-xylene and O-xylene leakage from storage tanks via Areal Locations of Hazardous Atmospheres (ALOHA) and Wireless Information System for Emergency Responders (WISER). The meteorological data of the area, characteristics of the tanks, and the roughness of the land surrounding the tanks were used to run the ALOHA model. The dispersion distances of P-xylene and O-xylene toxic and flammable vapor clouds were estimated according to the Immediately Dangerous to Life or Health (IDLH) and lower explosive limit (LEL) criteria. Also, the levels of thermal radiation due to the burning of P-xylene and O-xylene were estimated. The results showed that in the cold seasons, the IDLH was a maximum distance of 62 m and 45 m for P-xylene and O-xylene, respectively. The LEL criteria were 10% with a magnitude of 1100 ppm for a maximum distance of 54 m and 35 m for P-xylene and O-xylene, respectively. The maximum distance of 20 m for O-xylene based on the results of the LEL criteria of 60% (6600 ppm) was attained in the warm seasons. They are potentially lethal within 60 s at 21 m (10.0 kW/m²) when burned. The WISER software predicted the protective distance for xylene isomers to be about 300 m. The results show that creating a protective zone around the P-xylene and O-xylene tanks with a radius of 54 m is necessary to reduce hazards.

Development of a new needle trap-based method for the determination of some volatile organic compounds in the indoor environment

Volatile Organic Compounds (VOCs) are a large group of chemicals mostly found in indoor environments such as homes and workplaces. Long term exposure to certain VOCs can cause symptoms in some individuals and therefore, monitoring and controlling air quality can help better manage chronic respiratory diseases. In this study, we aimed to develop an easy-to-use, economical, in house needle trap-based methodology to detect certain VOCs to be used for public and occupational health. For this purpose, a multi-bed (packed with PDMS/Carbopack-X/Carboxen-1000) needle trap device (NTD) was utilized for sampling, enrichment, and injection of the VOCs into the gas chromatography. The performance of the developed method was investigated for the analysis of the group known as BTEX (benzene, toluene, ethylbenzene and xylene). Operational and instrumental parameters such as sampling flow rate and relative humidity, desorption time and temperature were optimized, and the analytical figures of merit of the proposed method have indicated that very low levels of BTEX in air samples can be easily determined by this new method. Overall results have shown that multi-bed NTD offers a high sensitive procedure for sampling and analysis of BTEX in concentration range of 0.002-0.298 mg/m³ in indoor air.

Influence of the seasonality and of urban variables in the BTEX and PM2.5 atmospheric levels and risks to human health in a tropical coastal city (Fortaleza, CE, Brazil)

The International Agency for Research on Cancer (IARC) classifies benzene in group 1 (carcinogenic to humans). Particulate matter (PM) has recently also been classified in this category. This was an advance toward prioritizing the monitoring of particles in urban areas. The aim of the present study was to assess levels of PM_2.5 and BTEX (benzene, toluene, ethylbenzene, and xylene), the influence of meteorological variables, the planetary boundary layer (PBL), and urban variables as well as risks to human health in the city of Fortaleza, Brazil, in the wet and dry periods. BTEX compounds were sampled using the 1501 method of NIOSH and determined by GC-HS-PID/FID. PM_2.5 was monitored using an air sampling pump with a filter holder and determined by the gravimetric method. Average concentrations of BTEX ranged from 1.6 to 45.5 μg m^-3, with higher values in the wet period, which may be explained by the fact that annual distribution is influenced by meteorological variables and the PBL. PM_2.5 levels ranged from 4.12 to 33.0 μg m^-3 and 4.18 to 86.58 μg m^-3 in the dry and wet periods, respectively. No seasonal pattern was found for PM_2.5, probably due to the influence of meteorological variables, the PBL, and urban variables. Cancer risk ranged from 2.46E^-04 to 4.71E^-03 and 1.72E^-04 to 2.01E^-03 for benzene and from 3.07E^-06 to 7.04E^-05 and 3.08E^-06 to 2.85E^-05 for PM_2.5 in the wet and dry periods, respectively. Cancer risk values for benzene were above the acceptable limit established by the international regulatory agency in both the dry and wet periods. The results obtained of the noncarcinogenic risks for the compounds toluene, ethylbenzene, and xylene were within the limits of acceptability. The findings also showed that the risk related to PM is always greater among smokers than nonsmokers.

Assessment of H2S and BTEX concentrations in ambient air using passive sampling method and the health risks

Wastewater treatment plants (WWTPs) may be a source of nuisance in neighbouring places due to hydrogen sulphide (H₂S) and BTEX (benzene, toluene, ethylbenzene, and xylenes) emissions. In this study, samples were collected from WWTP workplace ambient air and outdoor ambient air around one of the largest WWTPs in Istanbul with a capacity of 250,000 m³/day to evaluate the effects of H₂S and BTEX emissions. Samples were collected in three seasons for 15-day durations: winter (November 2015), spring (May 2015), and summer (August 2016). Average concentrations of H₂S and BTEX were determined as 1.1 and 56.2 µg/m³, respectively. Average concentrations BTEX components were 4.9, 20.7, 6.4, and 24.2 µg/m³, respectively. Health risk assessment for plant workers and local residents was performed for H₂S and BTEX inhalation exposure using the method by USEPA. Results show that H₂S and BTEX emissions do not have harmful effects on human health.

Exposure to BTEX concentration and the related health risk assessment in printing and copying centers

This study was derived to investigation of BTEX (benzene, toluene, ethylbenzene, xylenes) concentrations in printing and copying centers (PCCs) in Ardabil city of Iran. Fifty-three PCCs were randomly selected from all the 136 number of PCCs and BTEX was sampled form their indoor air. The results showed that the concentration of BTEX in the indoor air PCCs is lower than the OELs (occupational exposure limit) in all cases. The obtained mean concentrations of benzene, toluene, ethylbenzene, and xylene were 93.6±63.2, 150.6±99.2, 34.3±16.8, and 29.5±15.2 μg/m³ respectively. Type of printer, number of printing and copying device, and type of ventilation system had significant influence on the BTEX concentration. The mean inhalation lifetime cancer risk (LTCR) value for benzene and ethylbenzene in the indoor air of the PCCs with LaserJet and inkjet printers was 44.4 × 10^-6 and 153.3 × 10^-6, and 23.4×10^-6 and 54.2× 10^-6, respectively, which were higher than EPA (Environmental Protection Agency) and World Health Organization (WHO) recommended limits. The hazard quotient (HQ) of benzene in the indoor air of the PCCs with inkjet printers was >1, which indicates that the non-carcinogenic risks associated with exposure to these compounds are considerable.