Leukemia Risk Associated With Low-Level Benzene Exposure

Occupational exposure to benzene and risk of non-Hodgkin lymphoma in an extended follow-up of two population-based prospective cohorts of Chinese men and women

The carcinogenicity of benzene was reevaluated by the International Agency for Research on Cancer in 2017, with the Working Group reaffirming positive yet inconclusive associations with non-Hodgkin lymphoma (NHL). To extend our previous observation of a significant exposure-response for cumulative occupational benzene exposure and NHL risk among Chinese women in a population-based cohort in Shanghai, we extended follow-up of this cohort and pooled the data with a similarly designed population-based cohort of men in Shanghai. Cumulative exposure estimates were derived for 134,449 participants in the pooled analysis by combining ordinal job-exposure matrix intensity ratings with quantitative benzene measurements from an inspection database of Shanghai factories. Associations between benzene exposure metrics and NHL (n = 363 cases including multiple myeloma [MM]) were assessed using Cox proportional hazard models. Ever occupational exposure to benzene in the pooled population was associated with NHL risk (HR = 1.5, 95% CI = 1.2-2.0), and exposure-response relationships were observed for increasing duration (ptrend = .003) and cumulative exposure (ptrend = .003). Associations with ever exposure, duration, and cumulative exposure were similar for NHL with and without MM in the case definition, including lifetime cumulative exposures in the highest quartile (HR = 1.6, 95% CI = 1.1-2.4 with MM included; HR = 1.7, 95% CI = 1.1-2.7 with MM excluded). An elevated risk of the chronic lymphocytic leukemia subtype was suggested in the pooled analyses (HR for ever vs. never exposure = 2.3, 95% CI = 0.9-5.6). These observations provide additional support for a plausible association between occupational benzene exposure and risk of NHL.

Cancer incidence in Swedish oil refinery workers exposed to benzene

BACKGROUND

Oil refinery workers are exposed to benzene, which is a well-known cause of leukaemia, but results on leukaemia in oil refinery workers have been mixed, and the data on workers' exposure is limited. Oil refinery workers are also exposed to asbestos and several studies have shown increased risk of mesothelioma.

AIM

The objective was to investigate cancer incidence, especially leukaemia, at low to moderate exposure to benzene in an update of a previous study of employees at three Swedish oil refineries.

METHODS

Cancer incidence was followed up in 2264 men (1548 refinery operators) employed at three oil refineries in Sweden for at least one year. Job types and employment times were collected from complete company files. A retrospective assessment of the benzene exposure was performed by occupational hygienists in collaboration with the refineries using historic measurements as well as detailed information on changes in the industrial hygiene and technological developments. Cases of cancer were retrieved by a linkage with the Swedish Cancer Register through 35-47 years of follow-up and standardized incidence ratios (SIR) with 95% confidence intervals (CI) were calculated.

RESULTS

In total, 258 tumors had occurred versus 240 expected (SIR 1.07; 95% CI 0.95-1.21). There were 10 cases of leukaemia, all in refinery operators (SIR 2.4; 95% CI 1.18-4.51). There were three cases of pleural mesothelioma, two of which in refinery operators. The mean estimated cumulative benzene exposure for the cases of leukaemia was 7.9 ppm-years (median 4.9, range 0.1-31.1).

DISCUSSION

The study suggests that low to moderate average cumulative benzene exposure increases the risk of leukaemia. Limitations include the modest number of cases and potential misclassification of exposure.

CONCLUSION

The present study indicated an increased risk of leukaemia in male oil refinery workers with low to moderate exposure to benzene.

Long-Term Exposure to Low Concentrations of Ambient Benzene and Mortality in a National English Cohort

Background: Benzene affects human health through environmental exposure in addition to occupational contact. However, few studies have examined the associations between long-term exposure to low concentrations of ambient benzene and mortality risks in nonoccupational settings.Methods: This prospective cohort study consists of 393,042 participants without stroke, myocardial infarction, or cancer at baseline from the UK Biobank. Annual average concentrations of benzene for each year during follow-up were measured using air dispersion models. The main outcomes were all-cause mortality and mortality from specific causes. Cox proportional-hazards models with time-varying exposure measurements were used to estimate the hazard ratios and 95% confidence intervals (CIs) for mortality risks. Restricted cubic spline models were used to estimate exposure-response relationships.Measurements and Main Results: With each interquartile range increase in the average annual concentration of benzene, the adjusted hazard ratios of mortality risk from all causes, cardiovascular disease, cancer, and respiratory disease were 1.26 (95% CI, 1.24-1.27), 1.24 (95% CI, 1.21-1.28), 1.27 (95% CI, 1.25-1.29), and 1.25 (95% CI, 1.20-1.30), respectively. The monotonically increasing exposure-response curves showed no threshold and plateau within the observed concentration range. Furthermore, the effect of benzene exposure on mortality persisted across different subgroups and was somewhat stronger in younger and White people (P for interaction < 0.05).Conclusions: Long-term exposure to low concentrations of ambient benzene significantly increases mortality risk in the general population. Ambient benzene represents a potential threat to public health, and further investigations are needed to support timely pollution regulation and health protection.

Interventional probability of causation (IPoC) with epidemiological and partial mechanistic evidence: benzene vs. formaldehyde and acute myeloid leukemia (AML)

INTRODUCTION

Causal epidemiology for regulatory risk analysis seeks to evaluate how removing or reducing exposures would change disease occurrence rates. We define interventional probability of causation (IPoC) as the change in probability of a disease (or other harm) occurring over a lifetime or other specified time interval that would be caused by a specified change in exposure, as predicted by a fully specified causal model. We define the closely related concept of causal assigned share (CAS) as the predicted fraction of disease risk that would be removed or prevented by a specified reduction in exposure, holding other variables fixed. Traditional approaches used to evaluate the preventable risk implications of epidemiological associations, including population attributable fraction (PAF) and the Bradford Hill considerations, cannot reveal whether removing a risk factor would reduce disease incidence. We argue that modern formal causal models coupled with causal artificial intelligence (CAI) and realistically partial and imperfect knowledge of underlying disease mechanisms, show great promise for determining and quantifying IPoC and CAS for exposures and diseases of practical interest.

METHODS

We briefly review key CAI concepts and terms and then apply them to define IPoC and CAS. We present steps to quantify IPoC using a fully specified causal Bayesian network (BN) model. Useful bounds for quantitative IPoC and CAS calculations are derived for a two-stage clonal expansion (TSCE) model for carcinogenesis and illustrated by applying them to benzene and formaldehyde based on available epidemiological and partial mechanistic evidence.

RESULTS

Causal BN models for benzene and risk of acute myeloid leukemia (AML) incorporating mechanistic, toxicological and epidemiological findings show that prolonged high-intensity exposure to benzene can increase risk of AML (IPoC of up to 7e-5, CAS of up to 54%). By contrast, no causal pathway leading from formaldehyde exposure to increased risk of AML was identified, consistent with much previous mechanistic, toxicological and epidemiological evidence; therefore, the IPoC and CAS for formaldehyde-induced AML are likely to be zero.

CONCLUSION

We conclude that the IPoC approach can differentiate between likely and unlikely causal factors and can provide useful upper bounds for IPoC and CAS for some exposures and diseases of practical importance. For causal factors, IPoC can help to estimate the quantitative impacts on health risks of reducing exposures, even in situations where mechanistic evidence is realistically incomplete and individual-level exposure-response parameters are uncertain. This illustrates the strength that can be gained for causal inference by using causal models to generate testable hypotheses and then obtaining toxicological data to test the hypotheses implied by the models-and, where necessary, refine the models. This virtuous cycle provides additional insight into causal determinations that may not be available from weight-of-evidence considerations alone.

Unlocking the secrets: Volatile Organic Compounds (VOCs) and their devastating effects on lung cancer

Lung cancer (LCs) is still a serious health problem globally, with many incidences attributed to environmental triggers such as Volatile Organic Compounds (VOCs). VOCs are a broad class of compounds that can be released via various sources, including industrial operations, automobile emissions, and indoor air pollution. VOC exposure has been linked to an elevated risk of lung cancer via multiple routes. These chemicals can be chemically converted into hazardous intermediate molecules, resulting in DNA damage and genetic alterations. VOCs can also cause oxidative stress, inflammation, and a breakdown in the cellular protective antioxidant framework, all of which contribute to the growth of lung cancer. Moreover, VOCs have been reported to alter critical biological reactions such as cell growth, apoptosis, and angiogenesis, leading to tumor development and metastasis. Epidemiological investigations have found a link between certain VOCs and a higher probability of LCs. Benzene, formaldehyde, and polycyclic aromatic hydrocarbons (PAHs) are some of the most well-researched VOCs, with comprehensive data confirming their cancer-causing potential. Nevertheless, the possible health concerns linked with many more VOCs and their combined use remain unknown, necessitating further research. Identifying the toxicological consequences of VOCs in LCs is critical for establishing focused preventative tactics and therapeutic strategies. Better legislation and monitoring mechanisms can limit VOC contamination in occupational and environmental contexts, possibly reducing the prevalence of LCs. Developing VOC exposure indicators and analyzing their associations with genetic susceptibility characteristics may also aid in early identification and targeted therapies.

Leukemia Mortality among Benzene-Exposed Workers in Brazil (2006-2011)

BACKGROUND

In this study, the annual leukemia mortality rate is estimated by occupational groups potentially exposed to benzene in Brazil and compared to non-exposed workers by sex.

METHODS

Data were extracted from the Mortality Information System and the National Institute of Geography and Statistics from 2006 to 2011. Occupational groups exposed to benzene were defined by using the Finnish Job-Exposure Matrix, FINJEM.

RESULTS

We found 21,049 leukemia deaths in 1917 in occupational groups potentially exposed to benzene, corresponding to an annual average mortality rate of 4.5/100,000, higher than the estimate for non-exposed workers: 2.6/100,000, corresponding to a Mortality rate ratio MRR = 1.7. Each benzene-exposed occupational group had increased leukemia mortality, and printers and occupations in graphics presented the highest MRR (2.7), followed by laboratory assistants (MRR = 2.6), laundry workers, chemists, and upholsterers, each of these occupational groups presenting MRR = 2.3.

CONCLUSIONS

Benzene shows the need for better enforcement of protective norms against this known carcinogen. Our results support the need for better enforcement of protective norms to reduce benzene exposure.

The epidemic of acute lymphoid leukemia in China: current trends and future prediction

Background

China has experienced one of the fastest increases in the incidence of acute lymphoid leukemia (ALL). The aim of this study was to assess the long-term trends of the incidence and mortality of ALL in mainland China between 1990 and 2019 and to project these trends through 2028.

Methods

Data on ALL were extracted from the Global Burden of Disease Study 2019; population data were extracted from World Population Prospects 2019. An age-period-cohort framework was used in the analysis.

Results

The net drift for the incidence of ALL was 7.5% (95% confidence interval [CI]: 7.1%, 7.8%) per year in women and 7.1% (95% CI: 6.7%, 7.6%) in men, and local drift was found to be higher than 0 in every studied age group (p<0.05). The net drift for mortality was 1.2% (95% CI: 1.0%, 1.5%) in women and 2.0% (95% CI: 1.7%, 2.3%) in men. Local drift was lower than 0 in boys aged 0-4 years and girls aged 0-9 years and higher than 0 in men aged 10-84 years and women aged 15-84 years. The estimated period relative risks (RRs) for both incidence and mortality showed increasing trends in the recent period. The cohort RRs for incidence showed increasing trends in both sexes; however, the cohort RR for mortality was decreased in the recent birth cohort (women born after 1988-1992 and men born after 2003-2007). Compared with that in 2019, the incidence of ALL in 2028 is projected to increase by 64.1% in men and 75.0% in women, and the mortality is predicted to decrease by 11.1% in men and 14.3% in women. The proportion of older adult/adults individuals with incident ALL and ALL-related death was projected to increase.

Conclusions

Over the last three decades, the incidence and mortality rates of ALL have generally increased. It is projected that the incidence rate of ALL in mainland China will continue to increase in the future, but the associated mortality rate will decline. The proportion of older adult/adults individuals with incident ALL and ALL-related death was projected to increase gradually among both sexes. More efforts are needed, especially for older adult/adults individuals.

Network Analysis of Biomarkers Associated with Occupational Exposure to Benzene and Malathion

Complex diseases are associated with the effects of multiple genes, proteins, and biological pathways. In this context, the tools of Network Medicine are compatible as a platform to systematically explore not only the molecular complexity of a specific disease but may also lead to the identification of disease modules and pathways. Such an approach enables us to gain a better understanding of how environmental chemical exposures affect the function of human cells, providing better perceptions about the mechanisms involved and helping to monitor/prevent exposure and disease to chemicals such as benzene and malathion. We selected differentially expressed genes for exposure to benzene and malathion. The construction of interaction networks was carried out using GeneMANIA and STRING. Topological properties were calculated using MCODE, BiNGO, and CentiScaPe, and a Benzene network composed of 114 genes and 2415 interactions was obtained. After topological analysis, five networks were identified. In these subnets, the most interconnected nodes were identified as: IL-8, KLF6, KLF4, JUN, SERTAD1, and MT1H. In the Malathion network, composed of 67 proteins and 134 interactions, HRAS and STAT3 were the most interconnected nodes. Path analysis, combined with various types of high-throughput data, reflects biological processes more clearly and comprehensively than analyses involving the evaluation of individual genes. We emphasize the central roles played by several important hub genes obtained by exposure to benzene and malathion.

Preliminary Assessment of Occurrence, Potential Origin, and Human Health Risk of Volatile Organic Compounds in Uncontrolled Springs, North Morocco

In recent years, with the drastic increase in worldwide pollution rates, considerable attention has been paid to the volatile organic compounds (VOCs) that might lead to serious health problems, e.g., cancer. As there appears to be a notable lack of research on the pollution (specifically, VOCs) of water bodies in Morocco, we aimed to assess the occurrence of VOCs in some uncontrolled springs in the north of Morocco that have not been previously investigated. We also discuss the estimation of health risks posed by ingestion and dermal contact as well as the different potential origins of these pollutants. For this purpose, water samples were collected from twenty-six sampling sites and were analyzed via headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Out of the 60 suspected VOCs, a total of 15 compounds belonging to five distinct groups were identified and quantified. Among them, fumigants, solvents, and gasoline hydrocarbons were the most abundant groups, with proportions of 40%, 26.7%, and 20%, respectively. A heatmap clustered the provinces based on their degree of pollution, while a dendrogram was used to classify the studied springs into six main groups. Regarding carcinogenic risk, all the samples were safe for consumption as well as for dermal contact, except for S17, S18, and S8, and S19, which might present a severe threat to inhabitants due to their contents of, respectively, naphthalene (2.1 × 10-3), chloroform (2.5 × 10-4), and cis and trans-dichlropropene (1.61 × 10-4 and 1.11 × 10-4). Our investigation revealed several anthropogenic sources of water contamination, which could aid authorities in limiting contamination spread in water bodies.

Effects of Benzene: Hematological and Hypersensitivity Manifestations in Resident Living in Oil Refinery Areas

Literature is teeming with publications on industrial pollution. Over the decades, the main industrial pollutants and their effects on human health have been widely framed. Among the various compounds involved, benzene plays a leading role in the onset of specific diseases. Two systems are mainly affected by the adverse health effects of benzene exposure, both acute and chronic: the respiratory and hematopoietic systems. The most suitable population targets for a proper damage assessment on these systems are oil refinery workers and residents near refining plants. Our work fits into this area of interest with the aim of reviewing the most relevant cases published in the literature related to the impairment of the aforementioned systems following benzene exposure. We perform an initial debate between the two clinical branches that see a high epidemiological expression in this slice of the population examined: residents near petroleum refinery areas worldwide. In addition, the discussion expands on highlighting the main immunological implications of benzene exposure, finding a common pathophysiological denominator in inflammation, oxidative stress, and DNA damage, thus helping to set the basis for an increasingly detailed characterization aimed at identifying common molecular patterns between the two clinical fields discussed.

Occupational Exposures and Health Risks of Benzene, Toluene, and Xylenes (BTX) in Automobile Repair Industry in Beijing City, China

This study aimed to evaluate the occupational health risks of benzene, toluene, and xylenes (BTX) exposure in the automobile repair industry in Beijing city in China. The concentrations of BTX were monitored at 140 operating positions of 51 randomly selected automobile repair enterprises in 2018. Samples analysis showed that all monitoring concentrations were not higher than the occupational exposure limits. The long-term exposure concentration ranges of benzene, toluene, and xylenes were 0.1 to 0.3, 0.1 to 49.7, and 0.2 to 49.5 mg/m³, respectively. The short-term exposure concentration ranges of benzene, toluene, and xylenes were 0.1 to 0.3, 0.1 to 98.7, and 0.2 to 100.0 mg/m³, respectively. But assessment results revealed unneglectable occupational health risks, especially the combined health risks of BTX exposure. Thereafter, effective control and improvement measures were put forward, including strengthening the management of the production, sale, and use of vehicle paints and coatings; improving ventilation; and implementing hierarchical management measures for occupational health risks.

Let-7e-5p, a promising novel biomarker for benzene toxicity, is involved in benzene-induced hematopoietic toxicity through targeting caspase-3 and p21

Benzene is a common industrial chemical and environmental pollutant. However, the mechanism of hematotoxicity caused by exposure to low doses of benzene is unknown. Let-7e-5p pathway regulatory networks were constructed by bioinformatics analysis using a benzene-induced aplastic anemia (BIAA) mouse model. The MTT assay, EdU staining, flow cytometric analysis, dual luciferase reporter gene assay, and RIP assay were utilized to evaluate the effects of benzoquinone (1,4-BQ) on let-7e-5p pathway. This study consisted of 159 workers with a history of low-level benzene exposure and 159 workers with no history of benzene exposure. After the confounding factors were identified, the associations between let-7e-5p expression and hematotoxicity were assessed by multiple linear regression. Furthermore, we used four machine learning algorithms (decision trees, neural network, Bayesian network, and support vector machines) to construct a predictive model for detecting benzene-causing hematotoxicity in workers. In this study, compared with respective controls, let-7e-5p expression was decreased in BIAA mice and benzene-exposed workers. After 1,4-BQ exposure, let-7e-5p overexpression negatively regulated caspase-3 and p21 expression, protected cells from apoptosis, and facilitated cell proliferation. RIP assays, and dual luciferase reporter gene assays confirmed that let-7e-5p could target p21 and caspase-3 and regulate the cell cycle and apoptosis. The support vector machines classifier achieved the best prediction of benzene-induced hematotoxicity (prediction accuracy = 88.27, AUC = 0.83) by statistically characterizing the internal dose of benzene exposure and the oxidative stress index, as well as the expression levels of let-7e-5p pathway-related genes in benzene-exposed workers. Let-7e-5p may be a potential therapeutic target of benzene-induced hematotoxicity, provide a basis for evaluating the health hazards of long-term and low-dose benzene exposure in workers, and supply a reference for revising occupational health standards.

Benzene Exposure From Selected Work Tasks on Offshore Petroleum Installations on the Norwegian Continental Shelf, 2002-2018

OBJECTIVES

Work on offshore petroleum installations may cause exposure to benzene. Benzene is a carcinogenic agent, and exposure among workers should be as low as reasonably practicable. We aimed to assess short-term (less than 60 min) benzene exposure from the most frequent work tasks on offshore installations on the Norwegian continental shelf and identify determinants of exposure. In addition, we aimed to assess the time trend in task-based benzene measurements from 2002 to 2018.

METHODS

The study included 763 task-based measurements with a sampling duration of less than 60 min, collected on 28 offshore installations from 2002 to 2018. The measurements were categorized into 10 different tasks. Multilevel mixed-effect Tobit regression models were developed for two tasks: sampling and disassembling/assembling equipment. Benzene source, season, indoors or outdoors, design of process area, year of production start, sampling method, and work operation were considered as potential determinants for benzene exposure in the models.

RESULTS

The overall geometric mean (GM) benzene exposure was 0.02 ppm (95% confidence intervals 95%(CI: 0.01-0.04). The pipeline inspection gauge (PIG) operation task was associated with the highest exposure, with a GM of 0.33 ppm, followed by work on flotation cells, disassembling/assembling, and sampling, with GMs of 0.16, 0.04, and 0.01 ppm, respectively. Significant determinants for the disassembling/assembling task were work operation (changing or recertifying valves, changing or cleaning filters, and breaking pipes) and benzene source. For sampling, the benzene source was a significant determinant. Overall, the task-based benzene exposure declined annually by 10.2% (CI 95%: -17.4 to -2.4%) from 2002 to 2018.

CONCLUSIONS

The PIG operation task was associated with the highest exposure out of the ten tasks, followed by work on flotation cells and when performing disassembling/assembling of equipment. The exposure was associated with the type of benzene source that was worked on. Despite the decline in task-based exposure in 2002-2018, technical measures should still be considered in order to reduce the exposure.

Separation of Volatile Organic Compounds in TAMOF-1

Separation of volatile organic compounds is one of the most studied processes in industry. TAMOF-1 is a homochiral metal-organic framework with a crystalline network of interconnected ≈1 nm channels and has high thermal and chemical stability. Thanks to these features, it can resolve racemic mixtures of chiral drugs as a chiral stationary phase in chromatography. Interestingly, the particular shape and size of its channels, along with the presence of metallic centers and functional groups, allow establishing weak but significant interactions with guest molecules. This opens interesting possibilities not only to resolve racemates but also to separate other organic mixtures, such as saturated/unsaturated and/or linear/branched molecules. In search of these applications, we have studied the separation of volatile organic compounds in TAMOF-1. Monte Carlo simulations in the grand-canonical ensemble have been carried out to evaluate the separation of the selected molecules. Our results predict that TAMOF-1 is able to separate xylene isomers, hexane isomers, and benzene-cyclohexane mixtures. Experimental breakthrough analysis in the gas phase and also in the liquid phase confirms these predictions. Beds of TAMOF-1 are able to recognize the substitution in xylenes and the branching in hexanes, yielding excellent separation and reproducibility, thanks to the chemical and mechanical features of this material.

Volatile Organic Compounds Released During the Fast Pyrolysis of Peanut Shells and Environmental Implications

The biomass conversion technologies, especially different types of pyrolysis, have been intensively studied to improve biomass energy transformation suggesting a low impact on the environment. In particular, fast pyrolysis of biomass is considered to be a thermal process in which the starting material is converted to bio-oil, char and gas products. In this work, volatile organic compounds (VOCs) of the gaseous fraction of peanut shells fast pyrolysis were collected and identified at atmospheric pressure. Aromatic compounds, hydrocarbons, furans and other oxygenated compounds were identified using solid phase microextraction (SPME) and gas chromatography coupled to mass spectrometry (CG-MS) as a detection system. The composition of volatiles was analyzed and compared with the constituents of liquid fraction for comparative purposes. Atmospheric implications of the main compounds identified in the gases fraction were assessed by determining tropospheric lifetimes of the VOCs identified and its impact on environment at the local, regional or global scale.

Designing oxide chemiresistors for detecting volatile aromatic compounds: recent progresses and future perspectives

Oxide chemiresistors have mostly been used to detect reactive gases such as ethanol, acetone, formaldehyde, nitric dioxide, and carbon monoxide. However, the selective and sensitive detection of volatile aromatic compounds such as benzene, toluene, and xylene, which are extremely toxic and harmful, using oxide chemiresistors remains challenging because of the molecular stability of benzene rings containing chemicals. Moreover, the performance of the sensing materials is insufficient to detect trace concentration levels of volatile aromatic compounds, which lead to harmful effects on human beings. Here, the strategies for designing highly selective and sensitive volatile aromatic compound gas sensors using oxide chemiresistors were suggested and reviewed. Key approaches include the use of thermal activation, design of sensing materials with high catalytic activity, the utilization of catalytic microreactors and bilayer structures with catalytic overlayer, and the pretreatment of analyte gases or post analysis of sensing signals. In addition, future perspectives from the viewpoint of designing sensing materials and sensor structures for high-performance and robust volatile aromatic compounds gas sensors are provided. Finally, we discuss possible applications of the sensors and sensor arrays.

Mortality of 196,826 Men and Women Working in U.S.-Based Petrochemical and Refinery Operations: Update 1979 to 2010

OBJECTIVE

To describe mortality trends of men and women working in various petrochemical and refinery operations of a U.S.-based company.

METHODS

The cohort consists of full-time employees with at least 1 day of service during 1979 through 2010. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) were calculated for 111 possible causes of death studied.

RESULTS

SMRs for malignant mesothelioma and asbestosis were highest for the 1940s decade of hire. Increased SMRs were observed for malignant melanoma and motor neuron disease with no obvious work patterns. Decreasing mortality patterns were observed for aplastic anemia and acute nonlymphocytic leukemia.

CONCLUSIONS

Mortality surveillance of this large established cohort aids in assessing the chronic health status of the workforce. Identifying methods for incorporating job-exposure matrices and nonoccupational risk factors could further enhance interpretations for some findings such as motor neuron disease.

Research development and trends of benzene-induced leukemia from 1990 to 2019-A bibliometric analysis

Benzene is an occupational and environmental toxicant, causing hematopoietic damage. Our study is aimed to extract the trend of benzene-induced leukemia (BIL) and qualitatively and quantitatively estimate research on it. Publications on BIL were identified from the Web of Science Core Collection (WoSCC). Microsoft Excel 2019 (Redmond, WA) and The CiteSpace 5.6.R5 software (Drexel University, Philadelphia, PA) were used to analyze the publication outcomes, countries, institutions, authors, keywords, and research frontiers. The overall 1152 publications were collected from 1990 to 2019 until November 6, 2020. Environ Health Persp had the highest number of articles published. The USA were the top country in terms of BIL. The Smith MT, Yin SN, Lan Q, and Hayes RB are both listed in the top 10 of co-cited authors, high contribution authors, and the authors of co-cited references. High IF articles account for a considerable proportion, among all the publications. Chinese institutions engaged in BIL and contributed a large part of articles. Exposure population, exposure dose, and exposure risk are the research hotspots in this field. The risk of benzene exposure on childhood leukemia is at issue, and the studies on attributable risk of benzene-induced leukemia are few. More early, sensitive, and specific epigenetic biomarkers of benzolism may be the leading research fields of benzene-induced leukemia in the next few years.

OUP accepted manuscript

Purpose

Workers on offshore petroleum installations are at risk of being exposed to benzene which is carcinogenic to humans. The present study aimed to assess the time trend of full-shift benzene exposure from 2002 to 2018 in order to characterize benzene exposure among laboratory technicians, mechanics, process operators, and industrial cleaners, and to examine the possible determinants of benzene exposure.

Methods

A total of 924 measurements of benzene exposure from the Norwegian petroleum offshore industry were included. The median sampling duration was 680 min, ranging from 60 to 940 min. The overall geometric mean (GM) and 95% confidence interval, time trends, and determinants of exposure were estimated using multilevel mixed-effects tobit regression analyses. Time trends were estimated for sampling duration below and above 8 h, both overall and for job groups. The variability of exposure between installation and workers was investigated in a subset of data containing worker identification.

Results

The overall GM of benzene exposure was 0.004 ppm. When adjusting for job group, design of process area, season, wind speed, and sampling duration, industrial cleaners had the highest exposure (GM = 0.012). Laboratory technicians, mechanics, and process operators had a GM exposure of 0.004, 0.003, and 0.004 ppm, respectively. Overall, the measured benzene exposure increased by 7.6% per year from 2002 to 2018. Mechanics had an annual increase of 8.6% and laboratory technicians had an annual decrease of 12.6% when including all measurements. When including only measurements above 8 h, mechanics had an increase of 16.8%. No statistically significant time trend was found for process operators. Open process area, high wind speed, and wintertime were associated with reduced exposure level.

Conclusions

An overall increase in measured exposure was observed from 2002 to 2018. The increase may reflect changes in measurement strategy from mainly measuring on random days to days with expected exposure. However, the time trend varied between job groups and was different for sampling duration above or below 8 h. Industrial cleaners had the highest exposure of the four job groups while no differences in exposure were observed between laboratory technicians, mechanics, and process operators. The design of the process area, job group, wind speed, and season were all significant determinants of benzene exposure.

The effects of glucose-6-phosphate dehydrogenase deficiency on benzene-induced hematotoxicity in mice

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme deficiency. Our previous study revealed the level of G6PD changed in wild type (WT) mice after benzene exposure. In this study, the pentose phosphate pathway (PPP) in regulation of benzene-induced hematotoxicity was investigated and other potential pathways were discovered in a G6PD deficiency mouse model. WT and G6PD mutation (G6PD^mut) mice were exposed to benzene (diluted in corn oil) at doses of 0 and 160 mg/kg by subcutaneous injection for 5 days/week, 4 weeks. Peripheral blood samples and bone marrow cells (BMCs) were obtained and measured. The levels of nicotinamide adenine dinucleotide phosphate (NADPH),reduced glutathione (GSH) and malondialdehyde (MDA) were detected and comet assay was analyzed for DNA damage in BMCs. Finally, RNA sequencing (RNA-seq) of BMCs was performed. The results showed that white blood cells decreased significantly in G6PD^mut mice compared with WT mice after benzene treatment. The ratio of hematopoietic stem/progenitor cells significantly decreased in G6PD^mut mice exposed to benzene. The reduction of NADPH and GSH revealed the effect on PPP with G6PD deficiency, which then caused the increase of MDA and DNA damage. Finally, RNA-seq results suggested potential genes including SHROOM4, CAMK2B and REN1 played potential roles of G6PD deficiency on benzene-induced hematotoxicity. Renin-angiotensin system and cAMP signaling pathway were potentially involved in the process. Our study provides a better understanding for the effects of G6PD deficiency on benzene-induced hematotoxicity.

Benzene exposure and non-Hodgkin lymphoma: a systematic review and meta-analysis of human studies

BACKGROUND

Non-Hodgkin lymphoma comprises a heterogeneous group of cancers with unresolved aetiology, although risk factors include environmental exposures to toxic chemicals. Although the ubiquitous pollutant benzene is an established leukemogen, its potential to cause non-Hodgkin lymphoma has been widely debated. We aimed to examine the potential link between benzene exposure and risk of non-Hodgkin lymphoma in humans by evaluating a wide array of cohort and case-control studies using electronic systematic review.

METHODS

We did a comprehensive systematic review and meta-analysis of all qualified human epidemiological studies that assessed the relationship between benzene exposure and non-Hodgkin lymphoma. We queried the PubMed and Embase databases for relevant articles published before June 5, 2019, and applied the SysRev platform for study selection. All peer-reviewed human cohort and case-control studies that reported non-Hodgkin lymphoma risk estimates specifically for benzene exposure were eligible for inclusion. Studies that calculated relative risks (RRs) for industries or job types without identifying those specifically exposed to benzene, that combined non-Hodgkin lymphoma with other cancer types, or that reported many different solvent exposures together were excluded. From each study, two investigators independently extracted information on the study design, location, years, sample size, participation rates, age, sex, sources of cases and controls, diagnosis, histological verification, exposure assessment, results, adjustment, and statistical analysis, and subsequently assessed study quality. We calculated the meta-analysis relative risk (meta-RR) and CIs using the fixed effect and random effect models, as well as assessing publication bias.

FINDINGS

Our search yielded 2481 articles. After screening and removal of duplicates, 20 case-control studies and eight cohort studies were included in our meta-analysis, which included a total of 9587 patients with non-Hodgkin lymphoma. We reported an increased meta-relative risk (meta-RR) of 33% in highly exposed groups, when data were available (meta-RR 1·33 [95% CI 1·13-1·57], n=28). The meta-RR rose to 1·51 (1·22-1·87, n=18) in the studies that provided results specifically for highly exposed individuals. In particular, we reported a doubling of this risk for diffuse large B-cell lymphoma, a major non-Hodgkin lymphoma subtype (1·67 [1·01-2·77]). We also detected increased risks for follicular lymphoma (1·47 [0·95-2·27]) and hairy cell leukaemia (1·77 [0·99-3·16]), though they were not statistically significant. Funnel plot, Egger's test (p=0·77) and Begg's test (p=0·98) did not show evidence of publication bias. We evaluated the major aspects of causal inference and found evidence to support all the Hill considerations for assigning causation.

INTERPRETATION

Our findings suggest a causal link between benzene exposure and non-Hodgkin lymphoma, especially for diffuse large B-cell lymphoma.

FUNDING

National Institute of Environmental Health Sciences.

Linalool reverses benzene-induced cytotoxicity, oxidative stress and lysosomal/mitochondrial damages in human lymphocytes

Benzene exposure results in bone marrow suppression, leading to a decrease in the number of circulating white blood cells, an increased risk of chronic lymphocytic leukemia, acute myeloid leukemia and aplastic anemia. Since the mechanism of induction of benzene toxicity is due to active metabolites through cytochrome p450 enzymes and production of reactive oxygen species (ROS), we hypothesized that natural compound such linalool with anti-inflammatory/antioxidant properties could be effective in reducing its toxicity. Lymphocytes isolated from healthy individuals were simultaneously cotreated with different concentrations of LIN (10, 25 and 50 µM) and benzene (50 µM) for 4 h at 37 °C. After incubation, the toxicity parameters such cytotoxicity, ROS formation, lysosomal membrane integrity, mitochondria membrane potential (ΔΨm) collapse, oxidized/reduced glutathione (GSH/GSSG) and malondialdehyde (MDA) were analyzed using biochemical and flow cytometry evaluations. Our data showed that benzene (50 µM) induced a significant increase in cytotoxicity, ROS formation, mitochondrial membrane potential (MMP) collapse, lipid peroxidation and oxidative stress while LIN with antioxidant potential reversed the toxic effects of benzene on isolated human lymphocytes. Our results suggest that LIN reduces and reverses benzene-induced cytotoxicity, oxidative stress and lysosomal/mitochondrial damages in human lymphocyte. This study demonstrated that cotreatment of LIN with benzene can reduce several parameters indicative of oxidative stress. As such, LIN could represent a potential therapeutic agent in reducing certain aspects of benzene-induced toxicity.

Characterizing methane and total non-methane hydrocarbon levels in Los Angeles communities with oil and gas facilities using air quality monitors

Over the past decade, sensor networks have been proven valuable to assess air quality on highly localized scales. Here we leverage innovative sensors to characterize gaseous pollutants in a complex urban environment and evaluate differences in air quality in three different Los Angeles neighborhoods where oil and gas activity is present. We deployed monitors across urban neighborhoods in South Los Angles adjacent to oil and gas facilities with varying levels of production. Using low-cost sensors built in-house, we measured methane, total non-methane hydrocarbons (TNMHCs), carbon monoxide, and carbon dioxide during three deployment campaigns over four years. The multi-sensor linear regression calibration model developed to quantify methane and TNMHCs offers up to 16% improvement in coefficient of determination and up to a 22% reduction in root mean square error for the most recent dataset as compared to previous models. The deployment results demonstrate that airborne methane concentrations are higher within a 500 m radius of three urban oil and gas facilities, as well as near a natural gas distribution pipeline, likely a result of proximity to sources. While there are numerous additional sources of TNMHCs in complex urban environments, some sites appear to be larger emitters than others. Significant methane emissions were also measured at an idle site, suggesting that fugitive emissions may still occur even if production is ceased. Episodic spikes of both compounds suggested an association with oil and gas activities, demonstrating how sensor networks can be used to elucidate community-scale sources and differences in air quality moving forward.

An Assessment on Ethanol-Blended Gasoline/Diesel Fuels on Cancer Risk and Mortality

Although cancer is traditionally considered a genetic disease, the epigenetic abnormalities, including DNA hypermethylation, histone deacetylation, and/or microRNA dysregulation, have been demonstrated as a hallmark of cancer. Compared with gene mutations, aberrant epigenetic changes occur more frequently, and cellular epigenome is more susceptible to change by environmental factors. Excess cancer risks are positively associated with exposure to occupational and environmental chemical carcinogens, including those from gasoline combustion exhausted in vehicles. Of note, previous studies proposed particulate matter index (PMI) as a measure for gasoline sooting tendency, and showed that, compared with the other molecules in gasoline, 1,2,4-Trimethylbenzene, 2-methylnaphthalene and toluene significantly contribute to PMI of the gasoline blends. Mechanistically, both epigenome and genome are important in carcinogenicity, and the genotoxicity of chemical agents has been thoroughly studied. However, less effort has been put into studying the epigenotoxicity. Moreover, as the blending of ethanol into gasoline substitutes for carcinogens, like benzene, toluene, xylene, butadiene, and polycyclic aromatic hydrocarbons, etc., a reduction of secondary aromatics has been achieved in the atmosphere. This may lead to diminished cancer initiation and progression through altered cellular epigenetic landscape. The present review summarizes the most important findings in the literature on the association between exposures to carcinogens from gasoline combustion, cancer epigenetics and the potential epigenetic impacts of biofuels.

Epigenetic Effects of Benzene in Hematologic Neoplasms: The Altered Gene Expression

Simple Summary

Benzene is produced by diverse petroleum transformation processes and it is widely employed in industry despite its oncogenic effects. In fact, occupational exposure to benzene may cause hematopoietic malignancy. The leukemogenic action of benzene is particularly complex. Possible processes of onset of hematological malignancies have been recognized as a genotoxic action and the provocation of immunosuppression. However, benzene can induce modifications that do not involve alterations in the DNA sequence, the so-called epigenetics changes. Acquired epigenetic modification may also induce leukemogenesis, as benzene may alter nuclear receptors, and cause changes at the protein level, thereby modifying the function of regulatory proteins, including oncoproteins and tumor suppressor proteins.

Abstract

Benzene carcinogenic ability has been reported, and chronic exposure to benzene can be one of the risk elements for solid cancers and hematological neoplasms. Benzene is acknowledged as a myelotoxin, and it is able to augment the risk for the onset of acute myeloid leukemia, myelodysplastic syndromes, aplastic anemia, and lymphomas. Possible mechanisms of benzene initiation of hematological tumors have been identified, as a genotoxic effect, an action on oxidative stress and inflammation and the provocation of immunosuppression. However, it is becoming evident that genetic alterations and the other causes are insufficient to fully justify several phenomena that influence the onset of hematologic malignancies. Acquired epigenetic alterations may participate with benzene leukemogenesis, as benzene may affect nuclear receptors, and provoke post-translational alterations at the protein level, thereby touching the function of regulatory proteins, comprising oncoproteins and tumor suppressor proteins. DNA hypomethylation correlates with stimulation of oncogenes, while the hypermethylation of CpG islands in promoter regions of specific tumor suppressor genes inhibits their transcription and stimulates the onset of tumors. The discovery of the systems of epigenetic induction of benzene-caused hematological tumors has allowed the possibility to operate with pharmacological interventions able of stopping or overturning the negative effects of benzene.

Etiology of Acute Leukemia: A Review

Simple Summary

Acute leukemias are some of the most common cancers affecting all age groups. Despite a significant improvement made in the treatment of acute leukemias, their cause remains unknown. A number of genetic and environmental factors for the development of acute leukemias have been proposed, but none have been proven. Undoubtedly, genetics have a major role in the development of these diseases. The effects of a variety of environmental factors, occupations and hobbies have been explored. A recent “two-hit” theory” for the development of acute lymphoblastic leukemia has been proposed. This combines genetic factors and exposure to infections for the development of this disease. Several genetic factors are suggested. Most recently, for the infection portion, exposure to a virus containing Aspergillus Flavus has been proposed. This review summarizes what is currently known about the factors that are proposed for the development of acute leukemias.

Abstract

Acute leukemias constitute some of the most common malignant disorders. Despite significant progress made in the treatment of these disorders, their etiology remains unknown. A large and diverse group of genetic and environmental variables have been proposed. The role of a variety of factors, including pre-existing and acquired genetic mutations, exposure to radiation and various chemicals during preconception, pregnancy and throughout life, have been explored. The effects of inherited genetic variations and disorders, pre-existing diseases, infectious agents, hobbies, occupations, prior treatments, and a host of other factors have been proposed, but none is universally applicable to all cases. Variation in the incidence and prognosis based on the age, sex, race, type of the disease, geographic area of residence and other factors are intriguing but remain unexplained. Advances in genomic profiling, including genome-wide gene expression, DNA copy number and single nucleotide polymorphism (SNP) genotype, may shed some light on the role of genetics in these disparities. Separate two-hit hypotheses for the development of acute myeloblastic and lymphoblastic leukemia have been proposed. The latter combines genetics and infection factors resulting in leukemogenesis. A number of pre- and post-natal environmental conditions and exposure to infections, including a mycovirus infected Aspergillus flavus, have been suggested. The exact nature, timing, sequence of the events and mechanisms resulting in the occurrence of leukemia requires further investigations. This review summarizes some of the above factors in acute lymphoblastic and myeloblastic leukemias and the direction for future research on the etiology of these disorders.

The shape of low-concentration dose-response functions for benzene: implications for human health risk assessment

Are dose-response relationships for benzene and health effects such as myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) supra-linear, with disproportionately high risks at low concentrations, e.g. below 1 ppm? To investigate this hypothesis, we apply recent mode of action (MoA) and mechanistic information and modern data science techniques to quantify air benzene-urinary metabolite relationships in a previously studied data set for Tianjin, China factory workers. We find that physiologically based pharmacokinetics (PBPK) models and data for Tianjin workers show approximately linear production of benzene metabolites for air benzene (AB) concentrations below about 15 ppm, with modest sublinearity at low concentrations (e.g. below 5 ppm). Analysis of the Tianjin worker data using partial dependence plots reveals that production of metabolites increases disproportionately with increases in air benzene (AB) concentrations above 10 ppm, exhibiting steep sublinearity (J shape) before becoming saturated. As a consequence, estimated cumulative exposure is not an adequate basis for predicting risk. Risk assessments must consider the variability of exposure concentrations around estimated exposure concentrations to avoid over-estimating risks at low concentrations. The same average concentration for a specified duration is disproportionately risky if it has higher variance. Conversely, if chronic inflammation via activation of inflammasomes is a critical event for induction of MDS and other health effects, then sufficiently low concentrations of benzene are predicted not to cause increased risks of inflammasome-mediated diseases, no matter how long the duration of exposure. Thus, we find no evidence that the dose-response relationship is supra-linear at low doses; instead sublinear or zero excess risk at low concentrations is more consistent with the data. A combination of physiologically based pharmacokinetic (PBPK) modeling, Bayesian network (BN) analysis and inference, and partial dependence plots appears a promising and practical approach for applying current data science methods to advance benzene risk assessment.

Key event-informed risk models for benzene-induced acute myeloid leukaemia

Occupational exposure to benzene at levels of 10 ppm or more has been associated with increased risk of acute myeloid leukaemia (AML). The mode of action (MOA) for AML development leading to mortality is anticipated to include multiple earlier key events, which can be observed in hematotoxicity and genetic toxicity in peripheral blood of exposed workers. Prevention of these early events would lead to prevention of the apical, adverse outcomes, the morbidity and mortality caused by the myelodysplastic syndromes (MDS) and AML. Incorporation of key event information should modify the risk model, but few modification approaches have been suggested. To that end, two approaches to risk model modification are described that use sub-linear and segmented linear increases in risk below key events, while maintaining a linear increase in AML mortality risk beginning at 2 ppm, the lowest observed adverse effect concentration (LOAEC) identified for hemato- and geno- toxicity in high quality studies of human occupational exposure. Below 2 ppm two different modification approaches to quantitative risk models were applied: a continuously decreasing slope model and a segmented modification in slope. These two approaches provide greater flexibility to incorporate MOA information in risk model development and selection.

Benzene metabolite SPMA and acrylamide metabolites AAMA and GAMA in urine of children and adolescents in Germany - human biomonitoring results of the German Environmental Survey 2014-2017 (GerES V)

Benzene and acrylamide are carcinogenic substances contained inter alia in tobacco smoke. The mercapturic acid metabolites of benzene, N-acetyl-S-phenyl-L-cysteine (SPMA), and of acrylamide, N-acetyl-S-(3-amino-3-oxopropyl)-cysteine (AAMA) and N-acetyl-S-(3-amino-2-hydroxy-3-oxopropyl)-cysteine (GAMA), were analysed in 2260 first-morning void urine samples from children and adolescents aged 3-17 years, participating in the population-representative German Environmental Survey on Children and Adolescents, GerES V 2014-2017. SPMA was detected in 98% of the participants with a geometric mean (GM) of 0.097 μg/L urine. Smokers had about 10-fold higher levels of the benzene metabolite SPMA than non-smokers. The sample comprises of 48 self-reported smokers, mainly in the oldest age group (14-17-year-olds). Second-hand smoke exposure, living near busy or very busy roads, and using domestic fuels for heating were additionally associated with higher benzene metabolite levels. SPMA levels in GerES V were lower compared to levels found in other countries, which in part however may reflect different proportions of smokers. The acrylamide metabolites AAMA and GAMA were detected in 100% of the participants with a GM of 72.6 μg/L urine for AAMA and 15.0 μg/L urine for GAMA. Smoking children and adolescents had about 2.5-fold higher AAMA levels than non-smoking ones. The frequency of consumption of french-fried potatoes and potato crisps consumption was also positively associated with urinary AAMA and GAMA levels. Compared to the urinary AAMA and GAMA levels in Germany and other countries, levels in GerES V tended to be higher than in the few studies reported. The urinary levels of the benzene biomarker SPMA, and the acrylamide biomarkers AAMA and GAMA build the basis to derive reference values for the exposure of children and adolescents in Germany. The results reveal options for exposure reduction mainly in personal choices regarding smoking and diet, but also requiring policy to maintain efforts in non-smoking regulations and improving ambient air quality. Providing these results also to the European HBM Initiative HBM4EU will contribute to gain knowledge on the exposure of the European population, the health impact of carcinogens and thus providing support for substantiated exposure assessment.

Association between leukemia incidence and mortality and residential petrochemical exposure: A systematic review and meta-analysis

BACKGROUND

The global burden of leukemia, which grew by 19% from 2007 to 2017, poses a threat to human development and global cancer control. Factors contributing to this growth include massive industrial pollution, especially from large-scale petrochemical industry complexes (PICs). Globally, around 700 PICs are continuously operating. Data on the impact of PICs on leukemia incidence and mortality in residents are sparse and inconsistent.

OBJECTIVE

To determine the association between residential exposure to PICs and leukemia incidence and mortality using systematic review and meta-analysis.

METHODS

The studies were identified through seven databases (Clinical Key, Cochrane Library, EBSCOhost, Embase, PubMed, ScienceDirect, and Web of Science). We screened the eligibility of studies using following criteria: (1) observational studies that focused on residential exposure to PICs; (2) exposure group that was defined as residents living close to PICs; (3) outcome that was defined as all leukemia incidence and mortality; and (4) available population data. We applied the Grading of Recommendations Assessment, Development, and Evaluation to assess the certainty of evidence. The random-effects model used to estimate the pooled effects in the meta-analysis.

RESULTS

We identified thirteen epidemiologic studies (including eleven for leukemia incidence, one for leukemia mortality, and one for both), covering 125,580 individuals from Croatia, Finland, Italy, Serbia, Spain, Sweden, Taiwan, the United Kingdom, and the United States. We found moderate certainty of evidence indicated the risk of leukemia incidence (relative risk [RR] = 1.18; 95% CI = 1.03-1.35) and mortality (RR = 1.26; 95% CI = 1.10-1.45) in residents living close to PICs. Our subgroup analysis found increased RRs for leukemia incidence in studies using distance-based exposure indicator (RR = 1.11; 95% CI = 1.00-1.23), and with longer follow-up periods (RR = 1.24; 95% CI = 1.06-1.45).

CONCLUSION

Our analysis provides low-certainty evidence of increased leukemia incidence and moderate-certainty evidence of increased leukemia mortality among residents living close to PICs. While the global petrochemicals sector is growing, our findings suggest the need to consider disease prevention and pollution control measures during the development of PICs.

The association between residential proximity to brownfield sites and high-traffic areas and measures of immunity

The mechanisms by which neighborhood environmental exposures influence health are poorly understood, although immune system dysregulation represents a potential biological pathway. While many neighborhood exposures have been investigated, there is little research on residential proximity to brownfield waste. Using biomarker data from 262 participants in the Detroit Neighborhood Health Study, we estimated the association between proximity to brownfields and heavy traffic and signal joint T-cell receptor excision circles (sjTRECs, a measure of naive T-cell production), C-reactive protein (CRP, a measure of systemic inflammation), and interleukin-6 (IL-6, a pro-inflammatory cytokine). We assessed residential proximity ≤200 m from brownfields and highways on all three biomarkers using multivariate regression. We demonstrated that living ≤200 m from a brownfield site was associated with a 0.30 (95% CI = 0.59, 0.02, p = 0.04) log_e-unit decrease in sjTRECs per million whole blood cells, as well as non-significantly elevated levels of CRP and IL-6. Heavy traffic was not associated with any biomarker. Persons living in close proximity to brownfield sites had significantly lower naive T-cell production, suggesting accelerated immune aging. Decreased T-cell production associated with brownfield proximity may be caused by toxicant exposure in brownfield sites, or may serve as a marker of other neighborhood stressors.

A clandestine culprit with critical consequences: Benzene and acute myeloid leukemia

While most clinicians recognize adult therapy-related leukemias following cytotoxic chemotherapy and radiation, environmental regulatory agencies evaluate exposure to "safe levels" of leukemogenic compounds. Benzene represents the most notorious leukemogenic chemical. Used in the production of ubiquitous items such as plastics, lubricants, rubbers, dyes, and pesticides, benzene may be responsible for the higher risk of acute myeloid leukemia (AML) among automobile, janitorial, construction, and agricultural workers. It is possible that ambient benzene may contribute to many cases of "de novo" AML not arising out of germline predispositions. In this appraisal of the available literature, we evaluate and discuss the association between chronic, low-dose and ambient exposure to environmental benzene and the development of adult AML.

A systematic review and meta-analysis of haematological malignancies in residents living near petrochemical facilities

BACKGROUND

The petrochemical industry is a major source of hazardous and toxic air pollutants that are recognised to have mutagenic and carcinogenic properties. A wealth of occupational epidemiology literature exists around the petrochemical industry, with adverse haematological effects identified in employees exposed to 'low' concentrations of aromatic hydrocarbons (benzene, toluene, ethylbenzene, and xylene). Releases from the petrochemical industry are also thought to increase the risk of cancer incidence in fenceline communities. However, this emerging and at times inconclusive evidence base remains fragmented. The present study's aim was to conduct a systematic review and meta-analysis of epidemiological studies investigating the association between incidences of haematological malignancy and residential exposure to the petrochemical industry.

METHODS

Epidemiological studies reporting the risk of haematological malignancies (Leukaemia, Hodgkin's lymphoma, Non-Hodgkin's lymphoma, and Multiple myeloma) were included where the following criteria were met: (i) Cancer incidence is diagnosed by a medical professional and coded in accordance to the International Classification of Diseases; (ii) A clear definition of fenceline communities is provided, indicating the proximity between exposed residents and petrochemical activities; and (iii) Exposure is representative of normal operating conditions, not emergency events. Two investigators independently extracted information on study characteristics and outcomes in accordance with PRISMA and MOOSE guidelines. Relative risks and their 95% confidence intervals were pooled across studies for the four categories of haematological malignancy, using a random effects meta-analysis.

RESULTS

The systematic review identified 16 unique studies, which collectively record the incidence of haematological malignancies across 187,585 residents living close to a petrochemical operation. Residents from fenceline communities, less than 5 km from a petrochemical facility (refinery or manufacturer of commercial chemicals), had a 30% higher risk of developing Leukaemia than residents from communities with no petrochemical activity. Meanwhile, the association between exposure and rarer forms of haematological malignancy remains uncertain, with further research required.

CONCLUSIONS

The risk of developing Leukaemia appears higher in individuals living near a petrochemical facility. This highlights the need for further policy to regulate the release of carcinogens by industry.

Genetic, epigenetic, and lineage-directed mechanisms in benzene-induced malignancies and hematotoxicity targeting hematopoietic stem cells niche

Benzene is a known hematotoxic and leukemogenic agent with hematopoietic stem cells (HSCs) niche being the potential target. Occupational and environmental exposure to benzene has been linked to the incidences of hematological disorders and malignancies. Previous studies have shown that benzene may act via multiple modes of action targeting HSCs niche, which include induction of chromosomal and micro RNA aberrations, leading to genetic and epigenetic modification of stem cells and probable carcinogenesis. However, understanding the mechanism linking benzene to the HSCs niche dysregulation is challenging due to complexity of its microenvironment. The niche is known to comprise of cell populations accounted for HSCs and their committed progenitors of lymphoid, erythroid, and myeloid lineages. Thus, it is fundamental to address novel approaches via lineage-directed strategy to elucidate precise mechanism involved in benzene-induced toxicity targeting HSCs and progenitors of different lineages. Here, we review the key genetic and epigenetic factors that mediate hematotoxicological effects by benzene and its metabolites in targeting HSCs niche. Overall, the use of combined genetic, epigenetic, and lineage-directed strategies targeting the HSCs niche is fundamental to uncover the key mechanisms in benzene-induced hematological disorders and malignancies.

Distribution of volatile organic compounds over Indian subcontinent during winter: WRF-chem simulation versus observations

We investigate the distribution of volatile organic compounds (VOCs) over Indian subcontinent during a winter month of January 2011 combining the regional model WRF-Chem (Weather Research and Forecasting model coupled with Chemistry) with ground- and space-based observations and chemical reanalysis. WRF-Chem simulated VOCs are found to be comparable with ground-based observations over contrasting environments of the Indian subcontinent. WRF-Chem results reveal the elevated levels of VOCs (e. g. propane) over the Indo-Gangetic Plain (16 ppbv), followed by the Northeast region (9.1 ppbv) in comparison with other parts of the Indian subcontinent (1.3-8.2 ppbv). Higher relative abundances of propane (27-31%) and ethane (13-17%) are simulated across the Indian subcontinent. WRF-Chem simulated formaldehyde and glyoxal show the western coast, Eastern India and the Indo-Gangetic Plain as the regional hotspots, in a qualitative agreement with the MACC (Monitoring Atmospheric Composition and Climate) reanalysis and satellite-based observations. Lower values of R_GF (ratio of glyoxal to formaldehyde <0.04) suggest dominant influences of the anthropogenic emissions on the distribution of VOCs over Indian subcontinent, except the northeastern region where higher R_GF (∼0.06) indicates the role of biogenic emissions, in addition to anthropogenic emissions. Analysis of HCHO/NO₂ ratio shows a NO_x-limited ozone production over India, with a NO_x-to-VOC transition regime over central India and IGP. The study highlights a need to initiate in situ observations of VOCs over regional hotspots (Northeast, Central India, and the western coast) based on WRF-Chem results, where different satellite-based observations differ significantly.

Developing Large-Scale Research in Response to an Oil Spill Disaster: a Case Study

Research conducted in the wake of a disaster can provide information to help mitigate health consequences, support future recovery efforts, and improve resilience. However, a number of barriers have prevented time-sensitive research responses following previous disasters. Furthermore, large-scale disasters present their own special challenges due to the number of people exposed to disaster conditions, the number of groups engaged in disaster response, and the logistical challenges of rapidly planning and implementing a large study. In this case study, we illustrate the challenges in planning and conducting a large-scale post-disaster research study by drawing on our experience in establishing the Gulf Long-term Follow-up (GuLF) Study following the 2010 Deepwater Horizon disaster. We describe considerations in identifying at-risk populations and appropriate comparison groups, garnering support for the study from different stakeholders, obtaining timely scientific and ethics review, measuring and characterizing complex exposures, and addressing evolving community health concerns and unmet medical needs. We also describe the NIH Disaster Research Response (DR2) Program, which provides a suite of resources, including data collection tools, research protocols, institutional review board guidance, and training materials to enable the development and implementation of time-critical studies following disasters and public health emergencies. In describing our experiences related to the GuLF Study and the ongoing efforts through the NIH DR2 Program, we aim to help improve the timeliness, quality, and value of future disaster-related data collection and research studies.

Land Use Regression models for 60 volatile organic compounds: Comparing Google Point of Interest (POI) and city permit data

Land Use Regression (LUR) models of Volatile Organic Compounds (VOC) normally focus on land use (e.g., industrial area) or transportation facilities (e.g., roadway); here, we incorporate area sources (e.g., gas stations) from city permitting data and Google Point of Interest (POI) data to compare model performance. We used measurements from 50 community-based sampling locations (2013-2015) in Minneapolis, MN, USA to develop LUR models for 60 VOCs. We used three sets of independent variables: (1) base-case models with land use and transportation variables, (2) models that add area source variables from local business permit data, and (3) models that use Google POI data for area sources. The models with Google POI data performed best; for example, the total VOC (TVOC) model has better goodness-of-fit (adj-R²: 0.56; Root Mean Square Error [RMSE]: 0.32 μg/m³) as compared to the permit data model (0.42; 0.37) and the base-case model (0.26; 0.41). Area source variables were selected in over two thirds of models among the 60 VOCs at small-scale buffer sizes (e.g., 25 m-500 m). Our work suggests that VOC LUR models can be developed using community-based sampling and that models improve by including area sources as measured by business permit and Google POI data.

The prevalence and persistence of aberrant promoter DNA methylation in benzene-exposed Chinese workers

Aberrant DNA methylation patterns are common in cancers and environmental pollutant exposed subjects. Up to date, few studies have examined the aberrant DNA methylation patterns in benzene exposed workers. We recruited 141 benzene-exposed workers, including 83 benzene-exposed workers from a shoe factory in Wenzhou and 58 workers from a painting workshop in Wuhu, 35 workers in Wuhu were followed from 2009 to 2013, and 48 indoor workers as controls from Wenzhou. We used high-resolution melting (HRM) to quantitate human samples of DNA methylation in long interspersed nuclear element-1 (LINE-1), (6)-methylguanine-DNA methyltransferase (MGMT), and DNA mismatch repair gene human mutator L homologue 1 (hMLH1). AML-5 cells were treated with benzoquinone (BQ) and hydroquinone (HQ), and the promoter methylation of MGMT and hMLH1 was detected using the bisulfite sequencing PCR method. The degree of LINE-1 methylation in benzene-exposed workers was significantly lower than that of the controls (p<0.001), and the degree of MGMT (p<0.001) and hMLH1 (p = 0.01) methylation was significantly higher than that of the controls. The in vitro study validated the aberrant hypermethylation of hMLH1 after treatment with BQ. Among the cohort workers who were followed from 2009 to 2013, the LINE1 methylation elevated in 2013 than 2009 (p = 0.004), and premotor methylation in hMLH1 reduced in 2013 than 2009 (p = 0.045) with the reduction of the benzene exposure. This study provides evidence that benzene exposure can induce LINE-1 hypomethylation and DNA repair gene hypermethylation.

Air Emissions from Natural Gas Facilities in New York State

While New York has banned fracking, new and expanded natural gas pipelines are being constructed across the state. Our previous studies have reported that compressor stations are a major source of air pollution at fracking sites. We have used two federal datasets, the U.S. Environmental Protection Agency's (EPA) National Emissions Inventory and Greenhouse Gas Inventory, to determine what is known concerning emissions from the compressor stations along natural gas pipelines in the state. From a total of 74 compressor stations only 18 report to EPA on emissions. In the seven year period between 2008 and 2014 they released a total of 36.99 million pounds of air pollutants, not including CO₂ and methane. This included emissions of 39 chemicals known to be human carcinogens. There was in addition 6.1 billion pounds of greenhouse gases release from ten stations in a single year. These data clearly underestimate the total releases from the state's natural gas transportation and distribution system. However, they demonstrate significant releases of air pollutants, some of which are known to cause human disease. In addition, they release large amounts of greenhouse gases that contribute to climate change.

The impact of chronic environmental metal and benzene exposure on human urinary metabolome among Chinese children and the elderly population

The health effects of metals and benzene exposure have been extensively investigated; however, information on the impact of chronic environmental metal and benzene exposure on human urinary metabolome is limited. In this study, a total of 566 participants, including 352 elderly and 214 children, were split into the "exposed" and "control" groups. The urine samples of all the participants were collected and stored at - 80 °C until analysis. The urinary levels of 17 metals and S-phenylmercapturic acid (S-PMA) were determined by the ICP-MS and LC-MS/MS methods to comprehensively assess the personal metal and benzene exposure levels, respectively. Then, the individual levels of metal and benzene exposure were correlated to the metabolic consequences of ambient pollutant exposure, which were previously observed in our metabolomics study. As a result, multiple metals, including Cd, Co, Cr, Cu, Fe, Hg, Li, Mo, Ni, Pb, Se, and Zn, exhibited a significant linear dose-dependent association with one or more urinary metabolites, including two amino acids (pyroglutamic acid and 3-methylhistidine), three organic acids (azelaic acid, decenedioic acid, and hydroxytetradecanedioic acid), ten medium-chainacylcarnitines (heptenedioylcarnitine, octenedioylcarnitine, nonenedioylcarnitine, decenedioylglucuronide, 3-hydroxydecanoylcarnitine, dodecanedioylcarnitine, nonanoylcarnitine, decadienylcarnitine, hydroxydodecenoylcarnitine, dodecadienylcarnitine, and dodecenoylcarnitine), and one glucuronide conjugate (decenedioylglucuronide). These observations indicate that the increased environmental metal exposure has caused various oxidative stress-related effects, including the depletion of antioxidants, accelerated muscle proteolysis, elevated activity of UGTs, increased lipid peroxidation, and the disorder of mitochondrial lipid metabolism among exposed children and the elderly. The current study provides new insights into the biological effects induced by metal exposure in the environment.

Determinants of airborne benzene evaporating from fresh crude oils released into seawater

Benzene, toluene, ethylbenzene, xylenes, naphthalene and n-hexane evaporating from a thin oil film was measured for 30 min in a small-scale test system at 2 and 13 °C and the impact of physicochemical properties on airborne benzene with time after bulk oil release was studied. Linear mixed-effects models for airborne benzene in three time periods; first 5, first 15 and last 15 min of sampling, indicated that benzene content in fresh oil, oil group (condensate/light crude oil) and pour point were significant determinants explaining 63-73% of the total variance in the outcome variables. Oils with a high pour point evaporated considerably slower than oils with a low pour point. The mean air concentration of total volatile organic compounds was significatly higher at 13 °C (735 ppm) compared to 2 °C (386 ppm) immediately after release of oil, but at both temperatures the concentration rapidly declined.

Alcohol consumption and risk of multiple myeloma in the NIH-AARP Diet and Health Study

The epidemiologic evidence regarding the relationship between alcohol consumption and multiple myeloma (MM) risk remains limited and inconsistent, although recent studies suggest a potential protective effect. We prospectively investigated the risk of MM in relation to alcohol consumption frequency among 499,292 participants enrolled in the National Institutes of Health (NIH)-AARP Diet and Health Study in 1995-1996. A total of 1,312 MM cases were identified during follow-up through December 2011. Hazard ratios (HR) and 95% confidence intervals (CI) for categories of alcohol consumption relative to those defined as light drinkers (<1 drink/week) were estimated using multivariate Cox proportional hazard models. Overall, increasing frequency of alcohol consumption was inversely associated with MM (p-trend = 0.01), with a statistically significant association among those who consumed 2 drinks per day (HR = 0.70, 95% CI: 0.50, 0.98); similar but not statistically significant associations were observed for greater frequency of alcohol consumption. Among women, risk of MM was reduced among those who consumed less than one drink per day (HR = 0.73, 95% CI: 0.56, 0.97) and associations with greater frequency of alcohol consumption were inverse although not statistically significant. The findings of this large prospective investigation suggest that moderate alcohol consumption may be associated with reduced future risk of MM.

Excess lung cancer occurrence in poultry plants. Occupational risk factors: Findings for oncogenic viruses exposure and other occupational exposures

Certain viruses naturally infect and cause cancer in chickens and turkeys. Humans are widely exposed. The viruses cause cancer in primates, and transform human cells in vitro, but it is not known if they cause cancer in humans, mainly because of the lack of epidemiologic evidence. We conducted cohort mortality studies of workers in poultry slaughtering/processing plants across the United States, because they have the highest human exposures. An excess of lung cancer and other deaths was recorded in the poultry workers. Here, we report on a case-cohort study of the lung cancer deaths nested within these cohorts, that was conducted to provide epidemiologic evidence linking these viruses with human cancer occurrence, while adjusting for possible confounders, including workplace chemical carcinogens. We obtained interviews for 339 lung cancer deaths and 457 controls, selected from our combined cohorts of 30,411 poultry plant workers and 16,405 non-poultry workers, belonging to United Food & Commercial Workers unions. Data was analyzed by both logistic regression and Cox regression, adjusting for smoking and other confounders. Lung cancer risk was independently associated with tasks or work areas indicative of exposure to both poultry oncogenic viruses and to workplace chemical carcinogens. The study provides an incremental piece of evidence (epidemiologic), indirectly linking the oncogenic viruses of poultry with the occurrence of cancer in humans, and thus may have public health implications, but the limitations highlighted must be considered. Confirmatory studies, particularly molecular studies providing definitive proof of poultry oncogenic retrovirus integration in human DNA are needed, before the findings observed in this study can be put into proper perspective.

Global Gene Expression Response in Peripheral Blood Cells of Petroleum Workers Exposed to Sub-Ppm Benzene Levels

Altered gene expression in pathways relevant to leukaemogenesis, as well as reduced levels of circulating lymphocytes, have been reported in workers that were exposed to benzene concentrations below 1 ppm. In this study, we analysed whole blood global gene expression patterns in a worker cohort with altered levels of T cells and immunoglobulins IgM and IgA at three time points; pre-shift, post-shift (after three days), and post-recovery (12 hours later). Eight benzene exposed tank workers performing maintenance work in crude oil cargo tanks with a mean benzene exposure of 0.3 ppm (range 0.1–0.5 ppm) and five referents considered to be unexposed were examined by gene expression arrays. By using our data as independent validation, we reanalysed selected genes that were reported to be altered from previous studies of workers being exposed to sub-ppm benzene levels Four out of six genes previously proposed as marker genes in chronically exposed workers separated benzene exposed workers from unexposed referents (CLEC5, ACSL1, PRG2, IFNB1). Even better separation of benzene exposed workers and referents was observed for short-term exposure for genes in the Jak-STAT pathway, particularly elevated expression of IL6 and reduced expression of IL19.

Rethink potential risks of toxic emissions from natural gas and oil mining

Studies have showed the increasing environmental and public health risks of toxic emissions from natural gas and oil mining, which have become even worse as fracking is becoming a dominant approach in current natural gas extraction. However, governments and communities often overlook the serious air pollutants from oil and gas mining, which are often quantified lower than the significant levels of adverse health effects. Therefore, we are facing a challenging dilemma: how could we clearly understand the potential risks of air toxics from natural gas and oil mining. This short study aims at the design and application of simple and robust methods to enhance and improve current understanding of the becoming worse toxic air emissions from natural gas and oil mining as fracking is becoming the major approach. Two simple ratios, the min-to-national-average and the max-to-national-average, are designed and applied to each type of air pollutants in a natural gas and oil mining region. The two ratios directly indicate how significantly high a type of air pollutant could be due to natural gas and oil mining by comparing it to the national average records, although it may not reach the significant risks of adverse health effects according to current risk screening methods. The min-to-national-average and the max-to-national-average ratios can be used as a direct and powerful method to describe the significance of air pollution by comparing it to the national average. The two ratios are easy to use for governments, stakeholders, and the public to pay enough attention on the air pollutants from natural gas and oil mining. The two ratios can also be thematically mapped at sampled sites for spatial monitoring, but spatial mitigation and analysis of environmental and health risks need other measurements of environmental and demographic characteristics across a natural gas and oil mining area.