Estimation of the Leukemia Risk in Human Populations Exposed to Benzene from Tobacco Smoke Using Epidemiological Data

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

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

Performance and Mechanism of Chlorine Dioxide on BTEX Removal in Liquid and Indoor Air

With the development of the chemical industry, benzene, toluene, ethylbenzene, and xylene (BTEX) have gradually become the major indoor air pollutants. Various gas treatment techniques are widely used to prevent the physical and mental health hazards of BTEX in semi-enclosed spaces. Chlorine dioxide (ClO₂) is an alternative to chlorine as a secondary disinfectant with a strong oxidation ability, a wide range of action, and no carcinogenic effects. In addition, ClO₂ has a unique permeability which allows it to eliminate volatile contaminants from the source. However, little attention has been paid to the removal of BTEX by ClO₂, due to the difficulty of removing BTEX in semi-enclosed areas and the lack of testing methods for the reaction intermediates. Therefore, this study explored the performance of ClO₂ advanced oxidation technology on both liquid and gaseous benzene, toluene, o-xylene, and m-xylene. The results showed that ClO₂ was efficient in the removal of BTEX. The byproducts were detected by gas chromatography-mass spectrometry (GC-MS) and the reaction mechanism was speculated using the ab initio molecular orbital calculations method. The results demonstrated that ClO₂ could remove the BTEX from the water and the air without causing secondary pollution.

Effects of regional transport from different potential pollution areas on volatile organic compounds (VOCs) in Northern Beijing during non-heating and heating periods

Despite the adoption of air quality control measures, the influence of regional transport on volatile organic compounds (VOCs) pollution has gradually increased in Beijing. In this study, the whole observation period (September 24 to December 12, 2020) was divided into heating period and non-heating period to explore the impact of changing VOCs sources in different observation periods, and also classified into "Type-N" and "Type-S" periods both in non-heating period and heating period to explore the impact of regional transport from the northern and southern regions of sampling site, respectively. The average VOCs concentrations in northern Beijing during observation period were 22.6 ± 12.6 ppbv, which showed a decrease trend in recent years compared with other studies. And higher VOCs concentrations were observed in Type-S than in Type-N period. The positive matrix factorization results showed that vehicular exhaust dominated VOCs (26.1%-33.7%), but coal combustion could not be ignored in heating period, when it was twice that in non-heating period. In particular, coal combustion dominated VOCs in southern trajectories (30.9%) in heating period. The analysis of concentration weighted trajectory showed that coal combustion was affected by regional transport from the southeast regions of Beijing, while vehicular exhaust was affected by urban and the southeast regions of Beijing. Regarding human health risks, the carcinogenic risks of benzene and ethylbenzene exceeded the acceptable cancer risk value (1 × 10^-6), and were higher in Type-S than in Type-N period. The results indicated that regional transport from urban areas and the areas south of Beijing had a significant impact on VOCs in northern Beijing. Thus, targeted control measures for different potential pollution regions are important for controlling VOCs pollution in Beijing.

Multiple air pollutants exposure and leukaemia incidence in Tehran, Iran from 2010 to 2016: a retrospective cohort study

OBJECTIVE

Leukaemia is one of the most common cancers and may be associated with exposure to environmental carcinogens, especially outdoor air pollutants. The objective of this study was to investigate the association of ambient air pollution and leukaemia in Tehran, Iran.

DESIGN

In this retrospective cohort study, data about the residential district of leukaemia cases diagnosed from 2010 to 2016 were inquired from the Ministry of Health cancer database. Data from a previous study were used to determine long-term average exposure to different air pollutants in 22 districts of Tehran. Latent profile analysis (LPA) was used to classify pollutants in two exposure profiles. The association between air pollutants and leukaemia incidence was analysed by negative binomial regression.

SETTING

Twenty-two districts of Tehran megacity.

PARTICIPANTS

Patients with leukaemia.

OUTCOME MEASURES

The outcome variables were incidence rate ratios (IRR) of acute myeloid and lymphoid leukaemia across the districts of Tehran.

RESULTS

The districts with higher concentrations for all pollutants were near the city centre. The IRR was positive but non-significant for most of the air pollutants. However, annual mean NOx was directly and significantly associated with total leukaemia incidence in the fully adjusted model (IRR (95% CI): 1.03 (1.003 to 1.06) per 10 ppb increase). Based on LPA, districts with a higher multiple air-pollutants profile were also associated with higher leukaemia incidence (IRR (95% CI): 1.003 (0.99 to 1.007) per 1 ppb increase).

CONCLUSIONS

Our study shows that districts with higher air pollution (nitrogen oxides and multipollutants) have higher incidence rates of leukaemia in Tehran, Iran. This study warrants conducting further research with individual human data and better control of confounding.

Actividades económicas, laborales, ambientales y aditivas con exposición a benceno y el desarrollo de leucemia mieloide aguda

Introducción: el benceno es un hidrocarburo aromático obtenido por destilación del alquitrán utilizado en gasolineras y como solvente industrial, clasificado como cancerígeno por exposición ocupacional o ambiental. Está relacionado con el desarrollo de leucemia mieloide aguda (LMA) por su absorción principal por vía inhalatoria, y su metabolismo hepático con producción de benzoquinona de alta liposolubilidad que le permite depositarse en la médula ósea y tejido graso. Objetivo: analizar la asociación de las formas de exposición por actividades económicas, oficios, cargos, exposición ambiental y aditiva con el desarrollo de   LMA. Materiales y métodos: revisión sistemática de la literatura en las bases de datos Medline, Embase, Lilacs, Cochrane Library, Toxnet y OpenGrey, en inglés y español con los términos benzene, cancer, leukemia, occupational and enviromental exposition. Resultados: la mayoría de los estudios muestran una relación causal entre la exposición a benceno y el desarrollo de LMA, con predominio en ambientes laborales, seguidos de factores ambientales y aditivos como el humo del cigarrillo. Conclusiones: se encontró evidencia de asociación entre la exposición a benceno ocupacional y/o ambiental con el desarrollo de leucemia mieloide aguda, debido a que altera el estrés oxidativo y la desregulación del aryl hidrocarburo generando efectos citogenéticos, mutación genética y alteraciones epigenéticas que se expresan en hematotoxicidad y desarrollo de leucemia.

Handheld Device for Selective Benzene Sensing over Toluene and Xylene

More than 1 million workers are exposed routinely to carcinogenic benzene, contained in various consumer products (e.g., gasoline, rubbers, and dyes) and released from combustion of organics (e.g., tobacco). Despite strict limits (e.g., 50 parts per billion (ppb) in the European Union), routine monitoring of benzene is rarely done since low-cost sensors lack accuracy. This work presents a compact, battery-driven device that detects benzene in gas mixtures with unprecedented selectivity (>200) over inorganics, ketones, aldehydes, alcohols, and even challenging toluene and xylene. This can be attributed to strong Lewis acid sites on a packed bed of catalytic WO₃ nanoparticles that prescreen a chemoresistive Pd/SnO₂ sensor. That way, benzene is detected down to 13 ppb with superior robustness to relative humidity (RH, 10-80%), fulfilling the strictest legal limits. As proof of concept, benzene is quantified in indoor air in good agreement (R² ≥ 0.94) with mass spectrometry. This device is readily applicable for personal exposure assessment and can assist the implementation of low-emission zones for sustainable environments.

Chitosan as possible inhibitory agents and delivery systems in leukemia

Leukemia is a lethal cancer in which white blood cells undergo proliferation and immature white blood cells are seen in the bloodstream. Without diagnosis and management in early stages, this type of cancer can be fatal. Changes in protooncogenic genes and microRNA genes are the most important factors involved in development of leukemia. At present, leukemia risk factors are not accurately identified, but some studies have pointed out factors that predispose to leukemia. Studies show that in the absence of genetic risk factors, leukemia can be prevented by reducing the exposure to risk factors of leukemia, including smoking, exposure to benzene compounds and high-dose radioactive or ionizing radiation. One of the most important treatments for leukemia is chemotherapy which has devastating side effects. Chemotherapy and medications used during treatment do not have a specific effect and destroy healthy cells besides leukemia cells. Despite the suppressing effect of chemotherapy against leukemia, patients undergoing chemotherapy have poor quality of life. So today, researchers are focusing on finding more safe and effective natural compounds and treatments for cancer, especially leukemia. Chitosan is a valuable natural compound that is biocompatible and non-toxic to healthy cells. Anticancer, antibacterial, antifungal and antioxidant effects are examples of chitosan biopolymer properties. The US Food and Drug Administration has approved the use of this compound in medical treatments and the pharmaceutical industry. In this article, we take a look at the latest advances in the use of chitosan in the treatment and improvement of leukemia.

The effects of genetic polymorphisms on benzene-exposed workers: A systematic review

BACKGROUND AND AIMS

Benzene is a group I carcinogen, which has been associated with leukemia and myelodysplastic syndrome. Moreover, it has been proposed that polymorphisms in benzene metabolizing genes influence the outcomes of benzene exposure in the human body. This systematic review aims to elucidate the existent relationship between genetic polymorphisms and the risk of developing adverse health effects in benzene-exposed workers.

METHODS

Three databases were systematically searched until April 2020. The preferred reporting items for systematic reviews and meta-analyses method was used to select articles published between 2005 and 2020. Quality assessment and risk of bias were evaluated by the Newcastle-Ottawa scale.

RESULTS

After full-text evaluation, 36 articles remained out of 645 initially screened. The most studied health effects within the reviewed papers were chronic benzene poisoning, hematotoxicity, altered urinary biomarkers of exposure, micronucleus/chromosomal aberrations, and gene methylation. Furthermore, some polymorphisms on NQO1, GSTT1, GSTM1, MPO, and CYP2E1, among other genes, showed a statistically significant relationship with an increased risk of developing at least one of these effects on benzene-exposed workers. However, there was no consensus among the reviewed papers on which specific polymorphisms were the ones associated with the adverse health-related outcomes, except for the NQO1 rs1800566 and the GSTT1 null genotypes. Additionally, the smoking habit was identified as a confounder, demonstrating worse health outcomes in exposed workers that smoked.

CONCLUSION

Though there is a positive relationship between genetic polymorphisms and detrimental health outcomes for benzene-exposed workers, broader benzene-exposed cohorts that take into account the genetic diversity of the population are needed in order to determine which specific polymorphisms incur in health risks.

Large Differences in Urinary Benzene Metabolite S-Phenylmercapturic Acid Quantitation: A Comparison of Five LC-MS-MS Methods

Benzene is a known genotoxic carcinogen linked to many hematological abnormalities. S-phenylmercapturic acid (PHMA, N-acetyl-S-(phenyl)-L-cysteine, CAS# 4775-80-8) is a urinary metabolite of benzene and is used as a biomarker to assess benzene exposure. Pre-S-phenylmercapturic acid (pre-PHMA) is a PHMA precursor that dehydrates to PHMA at acidic pH. Published analytical methods that measure urinary PHMA adjust urine samples to a wide range of pH values using several types of acid, potentially leading to highly variable results depending on the concentration of pre-PHMA in a sample. Information is lacking on the variation in sample preparation among laboratories regularly measuring PHMA and the effect of those differences on PHMA quantitation in human urine samples. To investigate the differences in PHMA quantitation, we conducted an inter-laboratory comparison that included the analysis of 50 anonymous human urine samples (25 self-identified smokers and 25 self-identified non-smokers), quality control samples and commercially available reference samples in five laboratories using different analytical methods. Observed urinary PHMA concentrations were proportionally higher at lower pH, and results for anonymous urine samples varied widely among the methods. The method with the neutral preparation pH yielded results about 60% lower than the method using the most acidic conditions. Samples spiked with PHMA showed little variation, suggesting that the variability in results in human urine samples across methods is driven by the acid-mediated conversion of pre-PHMA to PHMA.

Production of Gasolines and Monocyclic Aromatic Hydrocarbons: From Fossil Raw Materials to Green Processes

The properties and the applications of the main monocyclic aromatic hydrocarbons (benzene, toluene, ethylbenzene, styrene, and the three xylene isomers) and the industrial processes for their manufacture from fossil raw materials are summarized. Potential ways for their production from renewable sources with thermo-catalytic processes are described and discussed in detail. The perspectives of the future industrial organic chemistry in relation to the production of high-octane bio-gasolines and monocyclic aromatic hydrocarbons as renewable chemical intermediates are discussed.

Mitigation of indoor air pollution: A review of recent advances in adsorption materials and catalytic oxidation

Indoor air pollution with toxic volatile organic compounds (VOCs) and fine particulate matter (PM2.5) is a threat to human health, causing cancer, leukemia, fetal malformation, and abortion. Therefore, the development of technologies to mitigate indoor air pollution is important to avoid adverse effects. Adsorption and photocatalytic oxidation are the current approaches for the removal of VOCs and PM2.5 with high efficiency. In this review we focus on the recent development of indoor air pollution mitigation materials based on adsorption and photocatalytic decomposition. First, we review on the primary indoor air pollutants including formaldehyde, benzene compounds, PM2.5, flame retardants, and plasticizer: Next, the recent advances in the use of adsorption materials including traditional biochar and MOF (metal-organic frameworks) as the new emerging porous materials for VOCs absorption is reviewed. We review the mechanism for mitigation of VOCs using biochar (noncarbonized organic matter partition and adsorption) and MOF together with parameters that affect indoor air pollution removal efficiency based on current mitigation approaches including the mitigation of VOCs using photocatalytic oxidation. Finally, we bring forward perspectives and directions for the development of indoor air mitigation technologies.

The Current Situation and Future Trend of Leukemia Mortality by Sex and Area in China

Leukemia is one of the most common cancers. We conducted this study to comprehensively analyze the temporal trends of leukemia mortality during 2003–2017 and project the trends until 2030. We extracted national-level data on annual leukemia mortality from China Health Statistics Yearbooks (2003–2017). We applied the Joinpoint regression model to assess leukemia mortality trends in urban and rural China by sex during 2003–2017. We also produced sex-specific leukemia mortality using the adjusted Global Burden Disease (GBD) 2016 projection model. In urban areas, age-standardized leukemia mortality decreased significantly among females during 2003–2017 (APC = −0.9%; 95% CI: −1.7, −0.1%). In rural areas, significant decreases of age-standardized leukemia mortality were both found among males (APC = −1.7%; 95% CI: −2.9, −0.5%) and females (APC = −1.6%; 95% CI: −2.6, −0.7%) from 2008 to 2017. Rural-urban and sex disparities of leukemia mortality will continue to exist until the year 2030. According to projection, the leukemia mortality rates of males and rural populations are higher than that of females and urban populations. In 2030, leukemia mortality is projected to decrease to 3.03/100,000 and 3.33/100,000 among the males in urban and rural areas, respectively. In females, leukemia mortality will decrease to 1.87/100,000 and 2.26/100,000 among urban and rural areas, respectively. Our study suggests that more precautionary measures to reduce leukemia mortality are need, and more attention should be paid to rural residents and males in primary prevention of leukemia in China.

Impact of Filter on the Estimation of Quantitative Mixture Risk Caused by Some Chemical Constituents Generated from Popular Cigarette Brands in Iran

Background

This study was conducted to evaluate the impact of filter on the eventual carcinogenic and non-carcinogenic risks caused by the main toxic constituents of popular cigarette brands in Iran.

Methods

At this laboratory study, the concentration of benzene, formaldehyde, arsenic, and cadmium in the mainstream smoke of 11 popular cigarette brands in Iran, on the without and with-filter modes was determined based on an established method. The hazard quotient (HQ), incremental lifetime cancer risk (ILCR), and mixture quantitative risk assessments (QRAs) were performed based on the QRA method recommended by United States Environmental Protection Agency (USEPA).

Findings

The mean of HQ due to benzene, formaldehyde, arsenic, and cadmium in without-filter cigarette smoke was from 3.96 to 3505. The findings indicated that the HQs related to benzene, formaldehyde, arsenic, and cadmium in cigarette smoke were decreased with filter by 48.3%, 25.3%, 37.6%, and 49.1%, respectively. The filter of cigarette decreased ILCR of benzene, formaldehyde, arsenic, and cadmium in cigarette smoke by 53.02%, 25.31%, 37.70%, and 61.01%, respectively. The mixture of non-carcinogenic and carcinogenic estimated risks due to inhalation of studied cigarettes smoke was very high and unacceptable.

Conclusion

The cigarette filter plays an essential role in reducing inhalation exposure to hazardous compounds in mainstream cigarette smoke; nevertheless, the average of overall mixture HQs and ILCRs estimated caused by studied compounds was higher than the acceptable value. It is recommended that future empirical studies investigate the impact of the type of fiber used in cigarette filter on reducing carcinogenic and non-carcinogenic risks caused by cigarette smoke.

The association between air pollution and cancers: controversial evidence of a systematic review

There are inconsistent reports on the association between air pollution and cancers. This systematic review was, therefore, conducted to ascertain the relationship between air pollution and some cancers. This is a systematic review study, which all articles published in this area were extracted from January 1, 1950 to December 31, 2018 from Web of Science, PubMed, Scopus, Cochrane Library, MEDLINE, EMBASE, Science Direct, Google scholar. Searching was performed independently by two search-method experts. The required data were extracted from the articles by an author-made questionnaire. Forty-eight articles were investigated. Evidence linking air pollution to some cancers is limited. Leukemia had the highest association with exposure to various air pollutants and bladder cancer had the lowest association. It is noteworthy that the specific type of pollutants in all studies was not specified. Based on the findings, the results are contradictory, and the role of air pollution in some cancers cannot be supported. Accordingly, studies are recommended to be performed at the individual level or multifactorial studies to specifically investigate the relationship between air pollution and these types of cancers. In this way, the role of air pollution in the incidence of these cancers can be determined more accurately.

Relationship of leukaemias with long-term ambient air pollution exposures in the adult Danish population

Background

Few population-based epidemiological studies of adults have examined the relationship between air pollution and leukaemias.

Methods

Using Danish National Cancer Registry data and Danish DEHM-UBM-AirGIS system-modelled air pollution exposures, we examined whether particulate matter (PM_2.5), black carbon (BC), nitrogen dioxide (NO₂) and ozone (O₃) averaged over 1, 5 or 10 years were associated with adult leukaemia in general or by subtype. In all, 14,986 adult cases diagnosed 1989–2014 and 51,624 age, sex and time-matched controls were included. Separate conditional logistic regression models, adjusted for socio-demographic factors, assessed exposure to each pollutant with leukaemias.

Results

Fully adjusted models showed a higher risk of leukaemia with higher 1-, 5- and 10-year-average exposures to PM_2.5 prior to diagnosis (e.g. OR per 10 µg/m³ for 10-year average: 1.17, 95% CI: 1.03, 1.32), and a positive relationship with 1-year average BC. Results were driven by participants 70 years and older (OR per 10 µg/m³ for 10-year average: 1.35, 95% CI: 1.15–1.58). Null findings for younger participants. Higher 1-year average PM_2.5 exposures were associated with higher risks for acute myeloid and chronic lymphoblastic leukaemia.

Conclusion

Among older adults, higher risk for leukaemia was associated with higher residential PM_2.5 concentrations averaged over 1, 5 and 10 years prior to diagnosis.

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.

The global burden and attributable risk factor analysis of acute myeloid leukemia in 195 countries and territories from 1990 to 2017: estimates based on the global burden of disease study 2017

BACKGROUND

Acute myeloid leukemia (AML) is a common leukemia subtype and has a poor prognosis. The risk of AML is highly related to age. In the context of population aging, a comprehensive report presenting epidemiological trends of AML is evaluable for policy-marker to allocate healthy resources.

METHODS

This study was based on the Global Burden of Disease 2017 database. We analyzed the change trends of incidence rate, death rate, and disability-adjusted life year (DALY) rate by calculating the corresponding estimated annual percentage change (EAPC) values. Besides, we investigated the influence of social development degree on AML's epidemiological trends and potential risk factors for AML-related mortality.

RESULTS

From 1990 to 2017, the incidence of AML gradually increased in the globe. Males and elder people had a higher possibility to develop AML. Developed countries tended to have higher age-standardized incidence rate and death rate than developing regions. Smoking, high body mass index, occupational exposure to benzene, and formaldehyde were the main risk factors for AML-related mortality. Notably, the contribution ratio of exposure to carcinogens was significantly increased in the low social-demographic index (SDI) region than in the high SDI region.

CONCLUSION

Generally, the burden of AML became heavier during the past 28 years which might need more health resources to resolve this population aging-associated problem. In the present stage, developed countries with high SDI had the most AML incidences and deaths. At the same time, developing countries with middle- or low-middle SDI also need to take actions to relieve rapidly increased AML burden.

Vulnerability of small-scale fishers to benzene exposure and the current knowledge gap on benzene-exposure in Brazilian fishers

Fishers are a particularly vulnerable population, chronically exposed to many stresses, injuries and health conditions directly linked to their fishing activities. This includes benzene exposure through gasoline and diesel exhaust fumes. Benzene is a known carcinogen, and has been assessed in many worker groups, but reports on fisher benzene exposure are extremely scarce in the literature. This paper discusses benzene exposure in small-scale fishers and reflects on the current knowledge gap on benzene-exposure in Brazilian fishers.

Epidemiology of acute myeloid leukemia: Recent progress and enduring challenges

Acute myeloid leukemia (AML) is a malignant disorder of the bone marrow which is characterized by the clonal expansion and differentiation arrest of myeloid progenitor cells. The age-adjusted incidence of AML is 4.3 per 100,000 annually in the United States (US). Incidence increases with age with a median age at diagnosis of 68 years in the US. The etiology of AML is heterogeneous. In some patients, prior exposure to therapeutic, occupational or environmental DNA-damaging agents is implicated, but most cases of AML remain without a clear etiology. AML is the most common form of acute leukemia in adults and has the shortest survival (5-year survival = 24%). Curative therapies, including intensive chemotherapy and allogeneic stem cell transplantation, are generally applicable to a minority of patients who are younger and fit, while most older individuals exhibit poor prognosis and survival. Differences in patient outcomes are influenced by disease characteristics, access to care including active therapies and supportive care, and other factors. After many years without therapeutic advances, several new therapies have been approved and are expected to impact patient outcomes, especially for older patients and those with refractory disease.