Gasoline: A complex chemical mixture, or a dangerous vehicle for benzene exposure?

The Influence of Blood Titanium Levels on DNA Damage in Brazilian Workers Occupationally Exposed to Different Chemical Agents

Occupational exposure to pollutants may cause health-damaging effects in humans. Genotoxicity assays can be used to detect the toxic effects of pollutants. In the present study, we evaluated genetic damage in three populations occupationally exposed to benzene, pyrenes, and agrochemicals and assessed the possible influence of titanium (Ti) co-exposure. A total of 275 subjects were enrolled in this study. The occupationally exposed population was composed of 201 male individuals, divided into three different groups: gas station attendants (GSA group) (n = 76), taxi drivers (TD group) (n = 97), farmers (farmers group) (n = 28), and control (n = 74). Biomarkers of exposure and effect were investigated such as AChe, BuChE, t,t-muconic acid (t,t-MA), and 1-hydroxypyrene (1-OHP). Ti levels in blood were higher in all the workers compared with the control group. DNA damage evaluated by comet assay was higher in the taxi drivers and farmers than in the controls, and the frequency of micronucleate buccal cells was higher in the gas station attendants and taxi drivers than in the controls. Correlations were found among occupational exposure time and biomarkers of exposure, genotoxicity biomarkers, and blood Ti levels. Our results demonstrated Ti co-exposure in the gas station attendants, taxi drivers, and farmers, and blood Ti levels were linked with the respective biomarkers of exposure. Additionally, tools through machine learning corroborated these findings, and Ti was the factor that contributed to DNA damage. Thus, the present study indicates the role of Ti in occupational settings and interactions with already known major xenobiotics present in the occupational environment contributing to genotoxicity.

Assessment of urinary 6-hydroxy-2,4-cyclohexadienyl mercapturic acid as a novel biomarker of benzene exposure

Assessing benzene exposure is a public health priority due to its deleterious health effects and ubiquitous industrial and environmental sources of exposure. Phenyl mercapturic acid (PhMA) is a commonly used urinary biomarker to assess benzene exposure. However, recent work has identified significant interlaboratory variation in urinary PhMA concentrations related to methodological differences. In this study, we present urinary 6-hydroxy-2,4-cyclohexadienyl mercapturic acid (pre-PhMA), a metabolite that undergoes acid-catalyzed dehydration to form PhMA, as a novel and specific urinary biomarker for assessing benzene exposure. We developed and validated the first quantitative liquid chromatography-tandem mass spectrometry assay for measuring urinary concentrations of pre-PhMA. The pH effect on the method of ruggedness testing determined that pre-PhMA is stable across the normal human urine pH range and that neutral conditions must be maintained throughout quantification for robust and accurate measurement of urinary pre-PhMA concentrations. The method exhibited below 2 ng/mL sensitivity for pre-PhMA, linearity over three orders of magnitude, and precision and accuracy within 10%. Urinary pre-PhMA concentrations were assessed in 369 human urine samples. Smoking individuals exhibited elevated levels of pre-PhMA compared to non-smoking individuals. Furthermore, the relationship between benzene exposure and urinary pre-PhMA levels was explored by examining the correlation of pre-PhMA with 2-cyanoethyl mercapturic acid, a smoke exposure biomarker. The urinary biomarkers exhibited a positive correlation (r = 0.720), indicating that pre-PhMA levels increased with benzene exposure. The results of this study demonstrate that urinary pre-PhMA is a rugged and effective novel biomarker of benzene exposure that can be widely implemented for future biomonitoring studies.

The impact of stay-home policies during Coronavirus-19 pandemic on the chemical and toxicological characteristics of ambient PM2.5 in the metropolitan area of Milan, Italy

The goal of this study was to characterize changes in components and toxicological properties of PM2.5 during the nationwide 2019-Coronavirus (COVID-19) lockdown restrictions in Milan, Italy. Time-integrated PM2.5 filters were collected at a residential site in Milan metropolitan area from April 11th to June 3rd at 2020, encompassing full-lockdown (FL), the followed partial-lockdown (PL2), and full-relaxation (FR) periods of COVID-19 restrictions. The collected filters were analyzed for elemental and organic carbon (EC/OC), water-soluble organic carbon (WSOC), individual organic species (e.g., polycyclic aromatic hydrocarbons (PAHs), and levoglucosan), and metals. According to online data, nitrogen dioxide (NO2) and benzene (C6H6) levels significantly decreased during the entire COVID-19 period compared to the same time span in 2019, mainly due to the government-backed shutdowns and curtailed road traffic. Similarly, with a few exceptions, surrogates of tailpipe emissions (e.g., traffic-associated PAHs) as well as re-suspended road dust (e.g., Fe, Mn, Cu, Cr, and Ti) were relatively lower during FL and PL2 periods in comparison with year 2019, whereas an increasing trend in mass concentration of mentioned species was observed from FL to PL2 and FR phases due to the gradual lifting of lockdown restrictions. In contrast, comparable concentrations of ambient PM2.5 and black carbon (BC) between lockdown period and the same time span in 2019 were attributed to the interplay between decreased road traffic and elevated domestic biomass burning as a result of adopted stay-home strategies. Finally, the curtailed road traffic during FL and PL2 periods led to ~25% drop in the PM2.5 oxidative potential (measured via 2',7'-dichlorodihydrofluorescein (DCFH) and dithiothreitol (DTT) assays) with respect to the FR period as well as the same time span in 2019. The results of this study provide insights into the changes in components and oxidative potential of PM2.5 in the absence of road traffic during COVID-19 restrictions.

Evaluation of immunological, inflammatory, and oxidative stress biomarkers in gasoline station attendants

Background

Gasoline is a complex mixture of saturated and unsaturated hydrocarbons, in which aromatic compounds, such as BTX (benzene, toluene, and xylene) feature as the main constituents. Simultaneous exposure to these aromatic hydrocarbons causes a significant impact on benzene toxicity. In order to detect early alterations caused in gasoline station attendants exposed to BTX compounds, immunological, inflammatory, and oxidative stress biomarkers were evaluated.

Methods

A total of 66 male subjects participated in this study. The gasoline station attendants (GSA) group consisted of 38 gasoline station attendants from Rio Grande do Sul, Brazil. The non-exposed group consisted of 28 subjects who were non-smokers and who had no history of occupational exposure. Environmental and biological monitoring of BTX exposure was performed using blood and urine.

Results

The GSA group showed increased BTX concentrations in relation to the non-exposed group (p < 0.001). The GSA group showed elevated protein carbonyl (PCO) levels and pro-inflammatory cytokines, decreased expression of CD80 and CD86 in monocytes, and reduced glutathione S-transferase (GST) activity compared to the non-exposed group (p < 0.05). BTX levels and trans,trans-muconic acid levels were positively correlated with pro-inflammatory cytokines and negatively correlated with interleukin-10 contents (p < 0.001). Increased levels of pro-inflammatory cytokines were accompanied by increased PCO contents and decreased GST activity (p < 0.001). Furthermore, according to the multiple linear regression analysis, benzene exposure was the only factor that significantly contributed to the increased pro-inflammatory cytokines (p < 0.05).

Conclusions

Taken together, these findings show the influence of exposure to BTX compounds, especially benzene, on the immunological, inflammatory, and oxidative stress biomarkers evaluated. Furthermore, the data suggest the relationship among the evaluated biomarkers of effect, which could contribute to providing early signs of damage to biomolecules in subjects occupationally exposed to BTX compounds.

Exposição ao benzeno em postos de combustíveis: estratégia de ações integradas de Vigilância em Saúde do Trabalhador na região dos Vales/RS

Resumo Introdução: O benzeno é uma importante fonte de contaminação ambiental e está presente na composição da gasolina, expondo trabalhadores de Postos de Revenda de Combustíveis (PRC) a intoxicações. Objetivo: relatar experiências de vigilância da exposição ao benzeno do Centro de Referência em Saúde do Trabalhador da região dos Vales/RS. Métodos: a vigilância no território incluiu o mapeamento regional dos PRC, ações intrasetoriais, intersetoriais e interinstitucionais, inspeção nos locais de trabalho, desenvolvimento de instrumento de intervenção específico para esse ramo produtivo - Notificação Recomendatória, avaliações individuais dos trabalhadores - e outras abordagens visando intervir nos ambientes com exposição ao benzeno. Resultados: foram observadas alterações em biomarcadores de efeito e de exposição, além de inadequações dos PRC no monitoramento clínico e laboratorial dos trabalhadores. Nos ambientes e processos de trabalho ficaram evidentes situações que ampliam a exposição: inadequações nas pistas de abastecimento, uso de “flanela”, inexistência ou insuficiência de medidas de proteção coletivas, ausência de medição eletrônica dos tanques e de higienização dos uniformes por parte das empresas, dentre outras. Conclusão: as experiências desencadeadas por meio de ações integradas no setor saúde demonstraram a potencialidade benéfica da vigilância da exposição ao benzeno em PRC.

Classificação clínico-laboratorial para manejo clínico de trabalhadores expostos ao benzeno em postos de revenda de combustíveis

Resumo Introdução: trabalhadores de postos de revenda de combustíveis estão expostos a compostos orgânicos voláteis, dos quais se destaca o benzeno. O manejo clínico do amplo espectro de sinais e sintomas desses trabalhadores ainda é um desafio para assistência em saúde. Objetivo: apresentar proposta de classificação clínico-laboratorial baseada na análise de hemograma e na avaliação clínica dos trabalhadores, para orientar a conduta dos profissionais de saúde. Métodos: a classificação clínico-laboratorial foi definida a partir de critérios de hierarquização dos resultados das avaliações clínicas e de vigilância à saúde de modo a possibilitar a organização dos procedimentos e fluxos de atenção à saúde. Resultados: a proposta define o manejo clínico com base na classificação dos expostos ao benzeno em quatro níveis de alterações clínico-laboratoriais que determinam os procedimentos compatíveis com o grau da exposição e de seus efeitos à saúde: 1) sem alterações significativas; 2) alterações inespecíficas ou incompletas, 3) alterações clínicas e/ou laboratoriais; 4) alterações sugestivas de benzenismo. Conclusão: a proposta de classificação dos achados clínico-laboratoriais é potencialmente capaz de orientar a conduta médica na avaliação das condições de saúde e dos riscos da exposição ao benzeno e de subsidiar o monitoramento sistemático e contínuo necessário para a definição de rotinas assistenciais para os coletivos de trabalhadores.

Cancer risk assessment: Optimizing human health through linear dose-response models

This paper proposes that generic cancer risk assessments be based on the integration of the Linear Non-Threshold (LNT) and hormetic dose-responses since optimal hormetic beneficial responses are estimated to occur at the dose associated with a 10(-4) risk level based on the use of a LNT model as applied to animal cancer studies. The adoption of the 10(-4) risk estimate provides a theoretical and practical integration of two competing risk assessment models whose predictions cannot be validated in human population studies or with standard chronic animal bioassay data. This model-integration reveals both substantial protection of the population from cancer effects (i.e. functional utility of the LNT model) while offering the possibility of significant reductions in cancer incidence should the hormetic dose-response model predictions be correct. The dose yielding the 10(-4) cancer risk therefore yields the optimized toxicologically based "regulatory sweet spot".

Early hematological and immunological alterations in gasoline station attendants exposed to benzene

INTRODUCTION

Elucidation of effective biomarkers may provide tools for the early detection of biological alterations caused by benzene exposure and may contribute to the reduction of occupational diseases. This study aimed to assess early alterations on hematological and immunological systems of workers exposed to benzene.

METHODS

Sixty gasoline station attendants (GSA group) and 28 control subjects were evaluated. Environmental and biological monitoring of benzene exposure was performed in blood and urine. The potential effect biomarkers evaluated were δ-aminolevulinate dehydratase (ALA-D) activity, CD80 and CD86 expression in lymphocytes and monocytes, and serum interleukin-8 (IL-8). The influence of confounding factors and toluene co-exposure were considered.

RESULTS

Although exposures were below ACGIH (American Conference of Governmental Industrial Hygienists) limits, reduced ALA-D activity, decreased CD80 and CD86 expression in monocytes and increased IL-8 levels were found in the GSA group compared to the control subjects. Furthermore, according to multiple linear regression analysis, benzene exposure was associated to a decrease in CD80 and CD86 expression in monocytes.

CONCLUSIONS

These findings suggest, for the first time, a potential effect of benzene exposure on ALA-D activity, CD80 and CD86 expression, IL-8 levels, which could be suggested as potential markers for the early detection of benzene-induced alterations.

Traffic-related air pollution and the onset of myocardial infarction: disclosing benzene as a trigger? A small-area case-crossover study

Background and Objectives

Exposure to traffic is an established risk factor for the triggering of myocardial infarction (MI). Particulate matter, mainly emitted by diesel vehicles, appears to be the most important stressor. However, the possible influence of benzene from gasoline-fueled cars has not been explored so far.

Methods and Results

We conducted a case-crossover study from 2,134 MI cases recorded by the local Coronary Heart Disease Registry (2000–2007) in the Strasbourg Metropolitan Area (France). Available individual data were age, gender, previous history of ischemic heart disease and address of residence at the time of the event. Nitrogen dioxide, particles of median aerodynamic diameter <10 µm (PM₁₀), ozone, carbon monoxide and benzene air concentrations were modeled on an hourly basis at the census block level over the study period using the deterministic ADMS-Urban air dispersion model. Model input data were emissions inventories, background pollution measurements, and meteorological data. We have found a positive, statistically significant association between concentrations of benzene and the onset of MI: per cent increase in risk for a 1 µg/m³ increase in benzene concentration in the previous 0, 0–1 and 1 day was 10.4 (95% confidence interval 3–18.2), 10.7 (2.7–19.2) and 7.2 (0.3–14.5), respectively. The associations between the other pollutants and outcome were much lower and in accordance with the literature.

Conclusion

We have observed that benzene in ambient air is strongly associated with the triggering of MI. This novel finding needs confirmation. If so, this would mean that not only diesel vehicles, the main particulate matter emitters, but also gasoline-fueled cars –main benzene emitters–, should be taken into account for public health action.