Urinary benzene metabolite and insulin resistance in elderly adults

Distribution of volatile organic compounds by distance from industrial complexes and potential health impact on the residents

Volatile organic compounds (VOCs) are the air pollutants emitted from the petrochemical industry known to pose adverse health effects on workers. The database based on the third phase of The Environmental Health Study in the Korean National Industrial Complexes (EHSNIC) in Ulsan conducted from 2018 to 2021 was used. Subjects were divided into the exposed and control group according to the estimated pollution level and distances from the industrial complexes. Ambient benzene, ethylbenzene, and xylene were significantly higher in the exposed group compared to the controls, as well as their metabolites. Risk of chronic disease and atopic dermatitis was higher in the exposed group which was supported by higher serum inflammatory markers and high hazard index of the exposed region. These results can draw attention to people engaged with environmental plans and used as primary data when making policies to reduce pollutant levels around industrial complexes.

Effects of Various Heavy Metal Exposures on Insulin Resistance in Non-diabetic Populations: Interpretability Analysis from Machine Learning Modeling Perspective

Increasing and compelling evidence has been proved that heavy metal exposure is involved in the development of insulin resistance (IR). We trained an interpretable predictive machine learning (ML) model for IR in the non-diabetic populations based on levels of heavy metal exposure. A total of 4354 participants from the NHANES (2003-2020) with complete information were randomly divided into a training set and a test set. Twelve ML algorithms, including random forest (RF), XGBoost (XGB), logistic regression (LR), GaussianNB (GNB), ridge regression (RR), support vector machine (SVM), multilayer perceptron (MLP), decision tree (DT), AdaBoost (AB), Gradient Boosting Decision Tree (GBDT), Voting Classifier (VC), and K-Nearest Neighbour (KNN), were constructed for IR prediction using the training set. Among these models, the RF algorithm had the best predictive performance, showing an accuracy of 80.14%, an AUC of 0.856, and an F1 score of 0.74 in the test set. We embedded three interpretable methods, the permutation feature importance analysis, partial dependence plot (PDP), and Shapley additive explanations (SHAP) in RF model for model interpretation. Urinary Ba, urinary Mo, blood Pb, and blood Cd levels were identified as the main influencers of IR. Within a specific range, urinary Ba (0.56-3.56 µg/L) and urinary Mo (1.06-20.25 µg/L) levels exhibited the most pronounced upwards trend with the risk of IR, while blood Pb (0.05-2.81 µg/dL) and blood Cd (0.24-0.65 µg/L) levels showed a declining trend with IR. The findings on the synergistic effects demonstrated that controlling urinary Ba levels might be more crucial for the management of IR. The SHAP decision plot offered personalized care for IR based on heavy metal control. In conclusion, by utilizing interpretable ML approaches, we emphasize the predictive value of heavy metals for IR, especially Ba, Mo, Pb, and Cd.

Association of Urinary Benzene Metabolite and the Ratio of Triglycerides to High-Density Lipoprotein Cholesterol: A Cross-Sectional Study Using the Korean National Environmental Health Survey (2018-2020)

The aim of this study was to investigate the association between benzene and toluene, and the ratio of triglycerides to high-density lipoprotein cholesterol (TG/HDL-C). This cross-sectional study analyzed 1928 adults using nationally representative data from the Korean National Environmental Health Survey (KoNEHS) Cycle 4 (2018-2020). Urinary trans, trans-muconic acid (t,t-MA) and benzylmercapturic acid (BMA) were measured by high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS), and high-density lipoprotein cholesterol (HDL-C) and triglycerides (TGs) were analyzed by colorimetry. Survey logistic regression analysis was applied to examine the association between urinary t,t-MA and BMA and the TG/HDL-C ratio. Urinary t,t-MA is significantly associated with an elevated TG/HDL-C ratio in both men and women (for men, OR [95% (CI)]: 2nd quartile: 2.10 [1.04, 4.22]; 3rd quartile: 2.13 [0.98, 4.62]; 4th quartile: 2.39 [1.05, 5.45]; for women, OR [95% (CI)]: 2nd quartile: 1.21 [0.71, 2.06]; 3rd quartile: 1.65 [0.94, 2.90]; 4th quartile: 1.78 [1.01, 3.11]), with significant dose-response relationships (P for trend: for men, 0.029; women, 0.024). This study shows that environmental exposure to benzene is associated with the TG/HDL-C ratio in the Korean general population. This suggests that more stringent environmental health policies are needed to reduce benzene exposure.

Microglial NF-κB Signaling Deficiency Protects Against Metabolic Disruptions Caused by Volatile Organic Compound via Modulating the Hypothalamic Transcriptome

Prolonged exposure to benzene, a prevalent volatile organic compound (VOC), at concentrations found in smoke, triggers hyperglycemia, and inflammation in mice. Corroborating this with existing epidemiological data, we show a strong correlation between environmental benzene exposure and metabolic impairments in humans. To uncover the underlying mechanisms, we employed a controlled exposure system and continuous glucose monitoring (CGM), revealing rapid blood glucose surges and disturbances in energy homeostasis in mice. These effects were attributed to alterations in the hypothalamic transcriptome, specifically impacting insulin and immune response genes, leading to hypothalamic insulin resistance and neuroinflammation. Moreover, benzene exposure activated microglial transcription characterized by heightened expression of IKKβ/NF-κB-related genes. Remarkably, selective removal of IKKβ in immune cells or adult microglia in mice alleviated benzene-induced hypothalamic gliosis, and protected against hyperglycemia. In summary, our study uncovers a crucial pathophysiological mechanism, establishing a clear link between airborne toxicant exposure and the onset of metabolic diseases.

Adult-Onset Transcriptomic Effects of Developmental Exposure to Benzene in Zebrafish (Danio rerio): Evaluating a Volatile Organic Compound of Concern

Urban environments are afflicted by mixtures of anthropogenic volatile organic compounds (VOCs). VOC sources that drive human exposure include vehicle exhaust, industrial emissions, and oil spillage. The highly volatile VOC benzene has been linked to adverse health outcomes. However, few studies have focused on the later-in-life effects of low-level benzene exposure during the susceptible window of early development. Transcriptomic responses during embryogenesis have potential long-term consequences at levels equal to or lower than 1 ppm, therefore justifying the analysis of adult zebrafish that were exposed during early development. Previously, we identified transcriptomic alteration following controlled VOC exposures to 0.1 or 1 ppm benzene during the first five days of embryogenesis using a zebrafish model. In this study, we evaluated the adult-onset transcriptomic responses to this low-level benzene embryogenesis exposure (n = 20/treatment). We identified key genes, including col1a2 and evi5b, that were differentially expressed in adult zebrafish in both concentrations. Some DEGs overlapped at the larval and adult stages, specifically nfkbiaa, mecr, and reep1. The observed transcriptomic results suggest dose- and sex-dependent changes, with the highest impact of benzene exposure to be on cancer outcomes, endocrine system disorders, reproductive success, neurodevelopment, neurological disease, and associated pathways. Due to molecular pathways being highly conserved between zebrafish and mammals, developmentally exposed adult zebrafish transcriptomics is an important endpoint for providing insight into the long term-effects of VOCs on human health and disease.

Association of metabolites of benzene and toluene with lipid profiles in Korean adults: Korean National Environmental Health Survey (2015-2017)

Background

Environmental exposure to benzene and toluene is a suspected risk factor for metabolic disorders among the general adult population. However, the effects of benzene and toluene on blood lipid profiles remain unclear. In this study, we investigated the association between urinary blood lipid profiles and metabolites of benzene and toluene in Korean adults.

Methods

We analyzed the data of 3,423 adults from the Korean National Environmental Health Survey Cycle 3 (2015–2017). We used urinary trans,trans-muconic acid (ttMA) as a biomarker of benzene exposure, and urinary benzylmercapturic acid (BMA) as an indicator of toluene exposure. Multivariate logistic regression analyses were performed to explore the association between blood lipid profiles and urinary metabolites of benzene and toluene. Additionally, we examined the linear relationship and urinary metabolites of benzene and toluene between lipoprotein ratios using multivariate regression analyses.

Results

After adjusting for covariates, the fourth quartile (Q4) of ttMA [odds ratio (OR) (95% confidence interval, CI = 1.599 (1.231, 2.077)] and Q3 of BMA [OR (95% CI) = 1.579 (1.129, 2.208)] were associated with an increased risk of hypertriglyceridemia. However, the Q4 of urinary ttMA [OR (95% CI) = 0.654 (0.446, 0.961)] and Q3 of urinary BMA [OR (95% CI) = 0.619 (0.430, 0.889)] decreased the risk of a high level of low-density lipoprotein cholesterol (LDL-C). Higher urinary ttMA levels were positively associated with the ratio of triglycerides to high-density lipoproteins [Q4 compared to Q1: β = 0.11, 95% CI: (0.02, 0.20)]. Higher urinary metabolite levels were negatively associated with the ratio of low-density lipoprotein to high-density lipoprotein [Q4 of ttMA compared to reference: β = -0.06, 95% CI: (-0.11, -0.01); Q4 of BMA compared to reference: β = -0.13, 95% CI: (-0.19, -0.08)].

Conclusion

Benzene and toluene metabolites were significantly and positively associated with hypertriglyceridemia. However, urinary ttMA and BMA levels were negatively associated with high LDL-C levels. These findings suggest that environmental exposure to benzene and toluene disrupts lipid metabolism in humans.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-14319-x.

The association between oil spill cleanup-related total hydrocarbon exposure and diabetes

BACKGROUND

Although evidence suggests relationships between some crude oil components and glycemic dysregulation, no studies have examined oil spill-related chemical exposures in relation to type 2 diabetes mellitus (DM) risk. This study examined the relationship between total hydrocarbon (THC) exposure among workers involved in the 2010 Deepwater Horizon (DWH) oil spill and risk of DM up to 6 years afterward.

METHODS

Participants comprised 2660 oil-spill cleanup or response workers in the prospective GuLF Study who completed a clinical exam and had no self-reported DM diagnosis prior to the spill. Maximum THC exposure was estimated with a job-exposure matrix based on interview data and personal measurements taken during cleanup operations. We defined incident DM by self-reported physician diagnosis of DM, antidiabetic medication use, or a measured hemoglobin A1c value ≥ 6.5%. We used log binomial regression to estimate risk ratios (RRs) for DM across ordinal categories of THC exposure. The fully adjusted model controlled for age, sex, race/ethnicity, education, employment status, and health insurance status. We also stratified on clinical body mass index categories.

RESULTS

We observed an exposure-response relationship between maximum daily ordinal THC exposure level and incident DM, especially among overweight participants. RRs among overweight participants were 0.99 (95% CI: 0.37, 2.69), 1.46 (95% CI: 0.54, 3.92), and 2.11 (95% CI: 0.78, 5.74) for exposure categories 0.30-0.99 ppm, 1.00-2.99 ppm, and ≥3.00 ppm, respectively (ptrend = 0.03).

CONCLUSION

We observed suggestively increasing DM risk with increasing THC exposure level among overweight participants, but not among normal weight or obese participants.

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

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

Sex Difference and Benzene Exposure: Does It Matter?

Sex-related biological differences might lead to different effects in women and men when they are exposed to risk factors. A scoping review was carried out to understand if sex could be a discriminant in health outcomes due to benzene. Studies on both animals and humans were collected. In vivo surveys, focusing on genotoxicity, hematotoxicity and effects on metabolism suggested a higher involvement of male animals (mice or rats) in adverse health effects. Conversely, the studies on humans, focused on the alteration of blood parameters, myeloid leukemia incidence and biomarker rates, highlighted that, overall, women had significantly higher risk for blood system effects and a metabolization of benzene 23-26% higher than men, considering a similar exposure situation. This opposite trend highlights that the extrapolation of in vivo findings to human risk assessment should be taken with caution. However, it is clear that sex is a physiological parameter to consider in benzene exposure and its health effects. The topic of sex difference linked to benzene in human exposure needs further research, with more numerous samples, to obtain a higher strength of data and more indicative findings. Sex factor, and gender, could have significant impacts on occupational exposures and their health effects, even if there are still uncertainties and gaps that need to be filled.

Association between urinary trans,trans-muconic acid and diabetes: a cross-sectional analysis of data from Korean National Environmental Health Survey (KoNEHS) cycle 3 (2015-2017)

BACKGROUND

Benzene is a ubiquitous air pollutant that is well known to cause hematopoietic effects in humans including leukemia. Recently, several studies have discussed its non-carcinogenic effects such as diabetes. This study aimed to investigate the association between diabetes and urinary trans,trans-muconic acid (t,t-MA), one of benzene metabolite, using adult data from Korean National Environmental Health Survey (KoNEHS) cycle 3 (2015-2017).

METHODS

This study analyzed 3,777 adults (1,645 men and 2,132 women) from the KoNEHS cycle 3 (2015-2017). The distribution and fraction of each independent variable were presented separately according to the urinary benzene metabolite levels (t,t-MA quartiles) and diabetes to determine the general characteristics of the subjects. Odds ratios (ORs) were calculated using logistic regression after stratification by gender and smoking status to identify the association between urinary t,t-MA and diabetes.

RESULTS

Compared with the first quartile (reference), the risk of diabetes significantly increased above the 4th (1.834 [1.107-3.039]) quartile in men and above the 3rd (1.826 [1.095-3.044]) and 4th (2.243 [1.332-3.776]) quartiles in women after adjustment. Stratified analysis based on smoking revealed that the ORs for the 3rd (1.847 [1.146-2.976]) and 4th (1.862 [1.136-3.052]) quartiles in non-smokers and those for the 2nd (1.721 [1.046-2.832]), 3rd (1.797 [1.059-3.050]), and 4th (2.546 [1.509-4.293]) quartiles in smokers were significantly higher.

CONCLUSIONS

We confirmed that urinary t,t-MA is significantly associated with diabetes regardless of gender and smoking status. And further studies are necessary to access the clinical impacts of this findings.

Exposure to polycyclic aromatic hydrocarbons and volatile organic compounds is associated with a risk of obesity and diabetes mellitus among Korean adults: Korean National Environmental Health Survey (KoNEHS) 2015-2017

Environmental pollutants have been known to increase the risks of not only respiratory and cardiovascular disease but also metabolic diseases such as obesity and diabetes mellitus (DM). Polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) such as benzene and toluene are major constituents of environmental pollution. In the present study, we employed the population of the Korean National Environmental Health Survey (KoNEHS) Cycle 3 conducted between 2015 and 2017, and assessed the associations of urinary biomarkers for PAHs and VOCs exposure with obesity and DM. A total of 3787 adult participants were included and the urinary concentrations of four PAH metabolites and two VOC metabolites were measured. For correcting urine dilution, a covariate-adjusted standardization method was used. The highest quartiles of urinary 2-hydroxynaphthalene (2-NAP) [OR (95% confidence interval (CI)) = 1.46 (1.13, 1.87)] and sum of PAH metabolites [OR (95% CI) = 1.45 (1.13, 1.87)] concentrations were associated with a higher risk of obesity [body mass index (BMI)≥25 kg/m²]. BMI was positively associated with urinary 2-NAP [β (95% CI) = 0.25 (0.09, 0.41), p = 0.003] and sum of PAH metabolites [β (95% CI) = 0.29 (0.08, 0.49), p = 0.006] concentrations. The risk of DM was increased with increasing quartile of 2-hydroxyfluorene (2-OHFlu) and trans, trans-muconic acid (t,t-MA) (p for trend<0.05 and < 0.001, respectively). The highest quartile of t,t-MA showed a significantly higher risk of DM [OR (95% CI) = 2.77 (1.74, 4.42)] and obesity [OR (95% CI) = 1.42 (1.06, 1.90)]. Urinary t,t,-MA level was positively associated with BMI [(β (95% CI) = 0.51 (0.31, 0.71), p < 0.001] and non-alcoholic fatty liver disease index [(β (95% CI) = 0.09 (0.06, 0.12), p < 0.001]. In conclusion, the benzene metabolites t,t-MA and PAH metabolite 2-OHFlu were associated with an increased risk of DM. Urinary biomarkers for PAHs and VOCs were positively associated with BMI in the Korean adult population. Further studies to validate these observations in other populations are warranted.

In Utero Maternal Benzene Exposure Predisposes to the Metabolic Imbalance in the Offspring

Environmental chemicals play a significant role in the development of metabolic disorders, especially when exposure occurs early in life. We have recently demonstrated that benzene exposure, at concentrations relevant to cigarette smoke, induces a severe metabolic imbalance in a sex-specific manner affecting male but not female mice. However, the roles of benzene in the development of aberrant metabolic outcomes following gestational exposure, remain largely unexplored. In this study, we exposed pregnant C57BL/6JB dams to benzene at 50 ppm or filtered air for 6 h/day from gestational day 0.5 (GD0.5) through GD21 and studied male and female offspring metabolic phenotypes in their adult life. While no changes in body weight or body composition were observed between groups, 4-month-old male and female offspring exhibited reduced parameters of energy homeostasis (VO2, VCO2, and heat production). However, only male offspring from benzene-exposed dams were glucose intolerant and insulin resistant at this age. By 6 months of age, both male and female offspring exhibited marked glucose intolerance however, only male offspring developed severe insulin resistance. This effect was accompanied by elevated insulin secretion and increased beta-cell mass only in male offspring. In support, Homeostatic Model Assessment for Insulin Resistance, the index of insulin resistance was elevated only in male but not in female offspring. Regardless, both male and female offspring exhibited a considerable increase in hepatic gene expression associated with inflammation and endoplasmic reticulum stress. Thus, gestational benzene exposure can predispose offspring to increased susceptibility to the metabolic imbalance in adulthood with differential sensitivity between sexes.

Acarbose protects from central and peripheral metabolic imbalance induced by benzene exposure

Benzene is a well-known human carcinogen that is one of the major components of air pollution. Sources of benzene in ambient air include cigarette smoke, e-cigarettes vaping, and evaporation of benzene containing petrol processes. While the carcinogenic effects of benzene exposure have been well studied, less is known about the metabolic effects of benzene exposure. We show that chronic exposure to benzene at low levels induces a severe metabolic imbalance in a sex-specific manner, and is associated with hypothalamic inflammation and endoplasmic reticulum (ER) stress. Benzene exposure rapidly activates hypothalamic ER stress and neuroinflammatory responses in male mice, while pharmacological inhibition of ER stress response by inhibiting IRE1α-XBP1 pathway significantly alleviates benzene-induced glial inflammatory responses. Additionally, feeding mice with Acarbose, a clinically available anti-diabetes drug, protected against benzene induced central and peripheral metabolic imbalance. Acarbose imitates the slowing of dietary carbohydrate digestion, suggesting that choosing a diet with a low glycemic index might be a potential strategy for reducing the negative metabolic effect of chronic exposure to benzene for smokers or people living/working in urban environments with high concentrations of exposure to automobile exhausts.

Benzene Exposure Induces Insulin Resistance in Mice

Benzene is a ubiquitous pollutant associated with hematotoxicity but its metabolic effects are unknown. We sought to determine if and how exposure to volatile benzene impacted glucose handling. We exposed wild type C57BL/6 mice to volatile benzene (50 ppm × 6 h/day) or HEPA-filtered air for 2 or 6 weeks and measured indices of oxidative stress, inflammation, and insulin signaling. Compared with air controls, we found that mice inhaling benzene demonstrated increased plasma glucose (p = .05), insulin (p = .03), and HOMA-IR (p = .05), establishing a state of insulin and glucose intolerance. Moreover, insulin-stimulated Akt phosphorylation was diminished in the liver (p = .001) and skeletal muscle (p = .001) of benzene-exposed mice, accompanied by increases in oxidative stress and Nf-κb phosphorylation (p = .025). Benzene-exposed mice also demonstrated elevated levels of Mip1-α transcripts and Socs1 (p = .001), but lower levels of Irs-2 tyrosine phosphorylation (p = .0001). Treatment with the superoxide dismutase mimetic, TEMPOL, reversed benzene-induced effects on oxidative stress, Nf-κb phosphorylation, Socs1 expression, Irs-2 tyrosine phosphorylation, and systemic glucose intolerance. These findings suggest that exposure to benzene induces insulin resistance and that this may be a sensitive indicator of inhaled benzene toxicity. Persistent ambient benzene exposure may be a heretofore unrecognized contributor to the global human epidemics of diabetes and cardiovascular disease.

Association between Heavy Metals, Bisphenol A, Volatile Organic Compounds and Phthalates and Metabolic Syndrome

The incidence of metabolic syndrome (MetS), which causes heart disease and stroke, has increased significantly worldwide. Although many studies have revealed the relationship between heavy metals (cadmium, mercury, and lead), the sum of metabolites of di(2-ethylhexyl) phthalate (DEHP), and MetS, the results remain inconsistent. No study has reported the association between various volatile organic compounds (VOCs) and phthalate metabolites with MetS. This cross-sectional study of a representative sample of adult South Koreans aimed to evaluate the relationship between heavy metals, VOC metabolites, phthalate metabolites, bisphenol A and MetS after adjusting for demographic variables. Data from the Korean National Environmental Health Survey II (2012–2014) (n = 5251) were used in the analysis. Multiple logistic regression analysis was performed for MetS with log-transformed hazardous material quartiles after covariate adjustment. Urine muconic acid (MuA) and mono- (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) levels were significantly associated with MetS after adjusting for confounders (odds ratio: 1.34 and 1.39, respectively). Urine MuA and MEHHP levels were significantly associated with MetS. Because of the rarity of this study, which investigated the relationship between each VOC and phthalate metabolite with MetS and the strict definition of all indirect measures of MetS components, further research is needed.

Association of benzene exposure with insulin resistance, SOD, and MDA as markers of oxidative stress in children and adolescents

Benzene is a ubiquitous environmental pollutant with various health effects. It is reported that benzene exposure might be associated with insulin resistance in elderly adults. The aim of this study is to investigate the association between urinary benzene metabolite, trans, trans-muconic acid (t,t-ma) and markers of oxidative stress and insulin resistance in children and adolescents. This cross-sectional study was conducted in 2017 among 86 children and adolescents, aged 6-18 years, living in Isfahan, Iran. t,t-ma was measured as urinary benzene metabolite and homeostasis model assessment (HOMA-IR) was determined as an index of insulin resistance. Moreover, malondialdehyde (MDA) and superoxide dismutase (SOD) were assessed as oxidative stress markers. We found significant association between insulin resistance, fasting blood glucose, and fasting blood insulin with t,t-ma (p values = 0.002, 0.03, and 0.001, respectively). Results of this study indicate that benzene metabolite in higher concentrations in comparison with lower concentrations is associated with increased risk of insulin resistance. Moreover, after adjustment for age, sex, and household passive smoking, statistically significant increase were documented in SOD and MDA (4.49- and 3.54-fold, respectively) in intermediate levels of t,t-ma vs. low levels of t,t-ma (p values = 0.01 and 0.034, respectively). To the best of our knowledge, this is the first study in its kind in the pediatric age group. It showed that benzene exposures, even in environmental levels, might be associated with insulin resistance and oxidative stress in children and adolescents. Further longitudinal studies are necessary to assess the clinical impacts of this finding.

Exploring the endocrine activity of air pollutants associated with unconventional oil and gas extraction

BACKGROUND

In the last decade unconventional oil and gas (UOG) extraction has rapidly proliferated throughout the United States (US) and the world. This occurred largely because of the development of directional drilling and hydraulic fracturing which allows access to fossil fuels from geologic formations that were previously not cost effective to pursue. This process is known to use greater than 1,000 chemicals such as solvents, surfactants, detergents, and biocides. In addition, a complex mixture of chemicals, including heavy metals, naturally-occurring radioactive chemicals, and organic compounds are released from the formations and can enter air and water. Compounds associated with UOG activity have been linked to adverse reproductive and developmental outcomes in humans and laboratory animal models, which is possibly due to the presence of endocrine active chemicals.

METHODS

Using systematic methods, electronic searches of PubMed and Web of Science were conducted to identify studies that measured chemicals in air near sites of UOG activity. Records were screened by title and abstract, relevant articles then underwent full text review, and data were extracted from the studies. A list of chemicals detected near UOG sites was generated. Then, the potential endocrine activity of the most frequently detected chemicals was explored via searches of literature from PubMed.

RESULTS

Evaluation of 48 studies that sampled air near sites of UOG activity identified 106 chemicals detected in two or more studies. Ethane, benzene and n-pentane were the top three most frequently detected. Twenty-one chemicals have been shown to have endocrine activity including estrogenic and androgenic activity and the ability to alter steroidogenesis. Literature also suggested that some of the air pollutants may affect reproduction, development, and neurophysiological function, all endpoints which can be modulated by hormones. These chemicals included aromatics (i.e., benzene, toluene, ethylbenzene, and xylene), several polycyclic aromatic hydrocarbons, and mercury.

CONCLUSION

These results provide a basis for prioritizing future primary studies regarding the endocrine disrupting properties of UOG air pollutants, including exposure research in wildlife and humans. Further, we recommend systematic reviews of the health impacts of exposure to specific chemicals, and comprehensive environmental sampling of a broader array of chemicals.

Benzene exposure is associated with cardiovascular disease risk

Benzene is a ubiquitous, volatile pollutant present at high concentrations in toxins (e.g. tobacco smoke) known to increase cardiovascular disease (CVD) risk. Despite its prevalence, the cardiovascular effects of benzene have rarely been studied. Hence, we examined whether exposure to benzene is associated with increased CVD risk. The effects of benzene exposure in mice were assessed by direct inhalation, while the effects of benzene exposure in humans was assessed in 210 individuals with mild to high CVD risk by measuring urinary levels of the benzene metabolite trans,trans-muconic acid (t,t-MA). Generalized linear models were used to assess the association between benzene exposure and CVD risk. Mice inhaling volatile benzene had significantly reduced levels of circulating angiogenic cells (Flk-1⁺/Sca-1⁺) as well as an increased levels of plasma low-density lipoprotein (LDL) compared with control mice breathing filtered air. In the human cohort, urinary levels of t,t-MA were inversely associated several populations of circulating angiogenic cells (CD31⁺/34⁺/45⁺, CD31⁺/34⁺/45⁺/AC133^–, CD34⁺/45⁺/AC133⁺). Although t,t-MA was not associated with plasma markers of inflammation or thrombosis, t,t-MA levels were higher in smokers and in individuals with dyslipidemia. In smokers, t,t-MA levels were positively associated with urinary metabolites of nicotine (cotinine) and acrolein (3-hydroxymercapturic acid). Levels of t,t-MA were also associated with CVD risk as assessed using the Framingham Risk Score and this association was independent of smoking. Thus, benzene exposure is associated with increased CVD risk and deficits in circulating angiogenic cells in both smokers and non-smokers.

Benzoate and Sorbate Salts: A Systematic Review of the Potential Hazards of These Invaluable Preservatives and the Expanding Spectrum of Clinical Uses for Sodium Benzoate

Sodium benzoate and potassium sorbate are extremely useful agents for food and beverage preservation, yet concerns remain over their complete safety. Benzoate can react with the ascorbic acid in drinks to produce the carcinogen benzene. A few children develop allergy to this additive while, as a competitive inhibitor of D-amino acid oxidase, benzoate can also influence neurotransmission and cognitive functioning. Model organism and cell culture studies have raised some issues. Benzoate has been found to exert teratogenic and neurotoxic effects on zebrafish embryos. In addition, benzoate and sorbate are reported to cause chromosome aberrations in cultured human lymphocytes; also to be potently mutagenic toward the mitochondrial DNA in aerobic yeast cells. Whether the substantial human consumption of these compounds could significantly increase levels of such damages in man is still unclear. There is no firm evidence that it is a risk factor in type 2 diabetes. The clinical administration of sodium benzoate is of proven benefit for many patients with urea cycle disorders, while recent studies indicate it may also be advantageous in the treatment of multiple sclerosis, schizophrenia, early-stage Alzheimer's disease and Parkinson's disease. Nevertheless, exposure to high amounts of this agent should be approached with caution, especially since it has the potential to generate a shortage of glycine which, in turn, can negatively influence brain neurochemistry. We discuss here how a small fraction of the population might be rendered-either through their genes or a chronic medical condition-particularly susceptible to any adverse effects of sodium benzoate.

Sex-dependent and body weight-dependent associations between environmental PAHs exposure and insulin resistance: Korean urban elderly panel

BACKGROUND

The prevalence of metabolic diseases rises rapidly with an ageing population. Recent studies suggest the potential involvement of environmental chemicals in insulin resistance (IR) that plays a core role in the development of metabolic diseases. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous components of outdoor and indoor air pollution. The influence of PAHs on IR may differ depending on sex and weight.

OBJECTIVES

We examined the association between exposure to environmental PAHs and IR in Korean urban elderly adults controlling for major risk factors that contribute to an increase in IR.

METHODS

Between 2008 and 2010, PAH metabolite levels (urinary 1-hydroxypyrene (1-OHP)) and the homoeostatic model assessment index (HOMA-IR) were repeatedly measured in 502 adults aged ≥60 years. Linear mixed effect models were fit to evaluate the associations of 1-OHP concentration with HOMA-IR. Subgroups were modelled by sex and weight.

RESULTS

After adjusting for sociodemographics, air pollution and metabolic disease status, the highest (vs lowest) quartile of 1-OHP was associated with an 0.57 (95% CI 0.10 to 1.04) increase in the HOMA-IR score (p trend=0.037). When stratified by sex, women presented a significantly dose-dependent trend of 1-OHP with HOMA-IR (p trend=0.013), whereas no association was observed in men (p trend=0.904). When further stratified by weight (body mass index ≥25 vs <25 kg/m(2)), a significant association was found only in overweight women (p trend=0.023).

CONCLUSIONS

Our results suggest that environmental exposure to PAHs is associated with increased IR in elderly adults and that the association may be limited to overweight women.

New Look at BTEX: Are Ambient Levels a Problem?

Benzene, toluene, ethylbenzene, and xylene (BTEX) are retrieved during fossil fuel extraction and used as solvents in consumer and industrial products, as gasoline additives, and as intermediates in the synthesis of organic compounds for many consumer products. Emissions from the combustion of gasoline and diesel fuels are the largest contributors to atmospheric BTEX concentrations. However, levels indoors (where people spend greater than 83% of their time) can be many times greater than outdoors. In this review we identified epidemiological studies assessing the noncancer health impacts of ambient level BTEX exposure (i.e., nonoccupational) and discussed how the health conditions may be hormonally mediated. Health effects significantly associated with ambient level exposure included sperm abnormalities, reduced fetal growth, cardiovascular disease, respiratory dysfunction, asthma, sensitization to common antigens, and more. Several hormones including estrogens, androgens, glucocorticoids, insulin, and serotonin may be involved in these health outcomes. This analysis suggests that all four chemicals may have endocrine disrupting properties at exposure levels below reference concentrations (i.e., safe levels) issued by the U.S. Environmental Protection Agency. These data should be considered when evaluating the use of BTEX in consumer and industrial products and indicates a need to change how chemicals present at low concentrations are assessed and regulated.