Exposure to BTEX in buses: The influence of vehicle fuel type.

Diesel-fueled buses have been replaced by Compressed Natural Gas (CNG) to minimize the high level of emissions in urban areas. However, differences in indoor exposure levels to Benzene, Toluene, Ethylbenzene and Xylene (BTEX) in those vehicles have not been investigated so far. The primary aim of this study was to determine if passengers are exposed to different BTEX levels when using buses powered by CNG or by diesel, and further explore if indoor levels are influenced by external air quality. For this purpose, BTEX air concentrations were measured in bus cabins (CNG and diesel), parking stations and in a background urban area using passive air samplers. Results showed that BTEX concentrations inside vehicles were higher than outside, but no significant differences were found between buses powered by CNG or by diesel. In CNG vehicles, high and significant positive correlation was found between benzene and the number of journeys in the same route (rs = 0.786, p < 0.05), vehicle operating time (rs = 0.738, p < 0.05), exposure time (rs = 0.714, p < 0.05) and exposure index (rs = 0.738, p < 0.05), but this was not observed for diesel vehicles. Benzene in bus cabins was found to be significantly below reference value for human health protection. However, excepting p-xylene, all other aromatic pollutants have a mean concentration significantly above the lowest effect level (p ≤ 0.002 for all comparisons). Additionally, higher BTEX levels in cabin buses than in outdoor air suggest the presence of other emission sources in indoor cabins. These findings emphasize the need for further studies to fully characterize indoor emission sources in order to minimize the negative impact of BTEX exposure to human health.

The association between natural gas well activity and specific congenital anomalies in Oklahoma, 1997-2009.

BACKGROUND: Natural gas drilling may pose multiple health risks, including congenital anomalies, through air pollutant emissions and contaminated water. Two recent studies have evaluated the relationship between natural gas activity and congenital anomalies, with both observing a positive relationship. OBJECTIVES: We aimed to evaluate whether residence near natural gas wells is associated with critical congenital heart defects (CCHD), neural tube defects (NTD), and oral clefts in Oklahoma, the third highest natural gas producing state in the US. METHODS: We conducted a retrospective cohort study among singleton births in Oklahoma (n = 476,600) to evaluate natural gas activity and congenital anomalies. We calculated an inverse distance-squared weighted (IDW) score based on the number of actively producing wells within a two-mile radius of the maternal residence during the month of delivery. We used modified Poisson regression with robust error variance to estimate prevalence proportion ratios (PPR) and 95% confidence intervals (CI) for the association between tertiles of natural gas activity (compared to no wells) and CCHD, NTD, and oral clefts adjusted for maternal education. RESULTS: We observed an increased, though imprecise, prevalence of NTDs among children with natural gas activity compared to children with no wells (2nd tertile PPR: 1.34, 95% CI: 0.93, 1.93; 3rd tertile PPR: 1.20, 95% CI: 0.82, 1.75). We observed no association with CCHD or oral clefts overall. Specific CCHDs of common truncus, transposition of the great arteries, pulmonary valve atresia and stenosis, tricuspid valve atresia and stenosis, interrupted aortic arch, and total anomalous pulmonary venous connection were increased among those living in areas with natural gas activity compared to those living in areas without activity, though not statistically significant. DISCUSSION: Our results were similar to previous studies for NTDs and specific CCHDs. Future directions include evaluating the association between specific phases of the drilling process and congenital anomalies to better refine the relevant exposure period.

Toxicity and mutagenicity of exhaust from compressed natural gas: Could this be a clean solution for megacities with mixed-traffic conditions?

Despite intensive research carried out on particulates, correlation between engine-out particulate emissions and adverse health effects is not well understood yet. Particulate emissions hold enormous significance for mega-cities like Delhi that have immense traffic diversity. Entire public transportation system involving taxis, three-wheelers, and buses has been switched from conventional liquid fuels to compressed natural gas (CNG) in the Mega-city of Delhi. In this study, the particulate characterization was carried out on variety of engines including three diesel engines complying with Euro-II, Euro-III and Euro-IV emission norms, one Euro-II gasoline engine and one Euro-IV CNG engine. Physical, chemical and biological characterizations of particulates were performed to assess the particulate toxicity. The mutagenic potential of particulate samples was investigated at different concentrations using two different Salmonella strains, TA98 and TA100 in presence and absence of liver S9 metabolic enzyme fraction. Particulates emitted from diesel and gasoline engines showed higher mutagenicity, while those from CNG engine showed negligible mutagenicity compared to other test fuels and engine configurations. Polycyclic aromatic hydrocarbons (PAHs) adsorbed onto CNG engine particulates were also relatively fewer compared to those from equivalent diesel and gasoline engines. Taken together, our findings indicate that CNG is comparatively safer fuel compared to diesel and gasoline and can offer a cleaner transport energy solution for mega-cities with mixed-traffic conditions, especially in developing countries.

Drilling and Production Activity Related to Unconventional Gas Development and Severity of Preterm Birth.

BACKGROUND: Studies of unconventional gas development (UGD) and preterm birth (PTB) have not presented risk estimates by well development phase or trimester. OBJECTIVE: We examined phase and trimester-specific associations between UGD activity and PTB. METHODS: We conducted a case-control study of women with singleton births in the Barnett Shale area, Texas, from 30 November 2010 to 29 November 2012. We individually age- and race/ethnicity-matched five controls to each PTB case (n=13,328) and truncated controls' time at risk according to the matched case's gestational age. We created phase-specific UGD-activity metrics: a) inverse squared distance-weighted (IDW) count of wells in the drilling phase ≤0.5 mi (804.7 meters) of the residence and b) IDW sum of natural gas produced ≤0.5 mi of the residence. We also constructed trimester- and gestation-specific metrics. Metrics were categorized as follows: zero wells (reference), first, second, third tertiles of UGD activity. Analyses were repeated by PTB severity: extreme, very, and moderate (<28, 28 to<32, and 32 to<37 completed weeks). Data were analyzed using conditional logistic regression. RESULTS: We found increased odds of PTB in the third tertile of the UGD drilling {odds ratio (OR)=1.20 [95% confidence interval (CI): 1.06, 1.37]} and UGD-production [OR=1.15 (1.05, 1.26)] metrics. Among women in the third tertile of UGD-production, associations were strongest in trimesters one [OR=1.18 (1.02, 1.37)] and two [OR=1.14 (0.99, 1.31). The greatest risk was observed for extremely PTB [third tertile ORs: UGD drilling, 2.00 (1.23, 3.24); UGD production, 1.53 (1.03-2.27)]. CONCLUSIONS: We found evidence of differences in phase- and trimester-specific associations of UGD and PTB and indication of particular risk associated with extremely preterm birth. Future studies should focus on quantifying specific chemical and nonchemical stressors associated with UGD. https://doi.org/10.1289/EHP2622.

Assessment of DNA damage in blood lymphocytes of bakery workers by comet assay.

The comet assay is widely used in screening and identification of genotoxic effects of different substances on people in either their working or living environment. Exposure to fuel smoke leads to DNA damage and ultimately different types of cancer. Using a comet assay, the present study aimed to assess peripheral blood lymphocyte DNA damage in people working in bakeries using natural gas, kerosene, diesel, or firewood for fuel compared to those in the control group. The subjects of this study were 55 people in total who were divided into four experimental groups, each of which comprised of 11 members (based on the type of fuel used), and one control group comprised of 11 members. Using CometScore, the subjects' peripheral blood lymphocytes were examined for DNA damage. All bakers, that is, experimental subjects, showed significantly greater peripheral blood lymphocyte DNA damage compared to the individuals in the control group. There was greater peripheral blood lymphocyte DNA damage in bakers who had been using firewood for fuel compared to those using other types of fuel to such an extent that tail moments (µm) for firewood-burning bakers was 4.40 ± 1.98 versus 1.35 ± 0.84 for natural gas, 1.85 ± 1.33 for diesel, and 2.19 ± 2.20 for kerosene. The results indicated that burning firewood is the greatest inducer of peripheral blood lymphocytes DNA damage in bakers. Nonetheless, there was no significant difference in peripheral blood lymphocyte DNA damage among diesel and kerosene burning bakers.

[The functional activity of lymphocytes in the spleen and peripheral blood in association with the toxic effect of household gas].

The objective of the present work was to study the population composition and functional activity of lymphocytes in the spleen and peripheral blood of the rats exposed experimentally to the toxic effect of household gas. The study included the morphofunctional examination of the state of the immune organs and the immunological investigation of the population composition and functional activity of lymphocytes from the peripheral blood of the experimental animals. We also evaluated the activity of nucleic acids, NADH2-dehydrogenase, and 5'-nucleotidase. The study revealed the relationship between the pathological and histochemical changes and the shifts in the population composition and functional activity of lymphocytes in the spleen and peripheral blood of the rats. Specifically, the action of household gas induced by the profound inhibition of the proliferative activity of the lymphocytes, enhanced the suppressive activity of the immunoregulatory cells (T-suppressors), and altered the population composition of the effector cells in the spleen and peripheral blood. It is concluded that the impairment of the functional activity of T-lymphocytes under the influence of household gas should be attributed not only to its direct toxic action but also to the increased activity of T-suppressors.

Hazard Ranking Methodology for Assessing Health Impacts of Unconventional Natural Gas Development and Production: The Maryland Case Study.

The recent growth of unconventional natural gas development and production (UNGDP) has outpaced research on the potential health impacts associated with the process. The Maryland Marcellus Shale Public Health Study was conducted to inform the Maryland Marcellus Shale Safe Drilling Initiative Advisory Commission, State legislators and the Governor about potential public health impacts associated with UNGDP so they could make an informed decision that considers the health and well-being of Marylanders. In this paper, we describe an impact assessment and hazard ranking methodology we used to assess the potential public health impacts for eight hazards associated with the UNGDP process. The hazard ranking included seven metrics: 1) presence of vulnerable populations (e.g. children under the age of 5, individuals over the age of 65, surface owners), 2) duration of exposure, 3) frequency of exposure, 4) likelihood of health effects, 5) magnitude/severity of health effects, 6) geographic extent, and 7) effectiveness of setbacks. Overall public health concern was determined by a color-coded ranking system (low, moderately high, and high) that was generated based on the overall sum of the scores for each hazard. We provide three illustrative examples of applying our methodology for air quality and health care infrastructure which were ranked as high concern and for water quality which was ranked moderately high concern. The hazard ranking was a valuable tool that allowed us to systematically evaluate each of the hazards and provide recommendations to minimize the hazards.

In situ and laboratory toxicity of coalbed natural gas produced waters with elevated sodium bicarbonate.

Some tributaries in the Powder River Structural Basin, USA, were historically ephemeral, but now contain water year round as a result of discharge of coalbed natural gas (CBNG)-produced waters. This presented the opportunity to study field sites with 100% effluent water with elevated concentrations of sodium bicarbonate. In situ experiments, static renewal experiments performed simultaneously with in situ experiments, and static renewal experiments performed with site water in the laboratory demonstrated that CBNG-produced water reduces survival of fathead minnow (Pimephales promelas) and pallid sturgeon (Scaphirhynchus albus). Age affected survival of fathead minnow, where fish 2 d posthatch (dph) were more sensitive than 6 dph fish, but pallid sturgeon survival was adversely affected at both 4 and 6 dph. This may have implications for acute assays that allow for the use of fish up to 14 dph. The survival of early lifestage fish is reduced significantly in the field when concentrations of NaHCO(3) rise to more than 1500 mg/L (also expressed as >1245 mg HCO(3) (-) /L). Treatment with the Higgin's Loop technology and dilution of untreated water increased survival in the laboratory. The mixing zones of the 3 outfalls studied ranged from approximately 800 m to 1200 m below the confluence. These experiments addressed the acute toxicity of effluent waters but did not address issues related to the volumes of water that may be added to the watershed.

Environmental public health dimensions of shale and tight gas development.

BACKGROUND: The United States has experienced a boom in natural gas production due to recent technological innovations that have enabled this resource to be produced from shale formations. OBJECTIVES: We reviewed the body of evidence related to exposure pathways in order to evaluate the potential environmental public health impacts of shale gas development. We highlight what is currently known and identify data gaps and research limitations by addressing matters of toxicity, exposure pathways, air quality, and water quality. DISCUSSION: There is evidence of potential environmental public health risks associated with shale gas development. Several studies suggest that shale gas development contributes to ambient air concentrations of pollutants known to be associated with increased risk of morbidity and mortality. Similarly, an increasing body of studies suggest that water contamination risks exist through a variety of environmental pathways, most notably during wastewater transport and disposal, and via poor zonal isolation of gases and fluids due to structural integrity impairment of cement in gas wells. CONCLUSION: Despite a growing body of evidence, data gaps persist. Most important, there is a need for more epidemiological studies to assess associations between risk factors, such as air and water pollution, and health outcomes among populations living in close proximity to shale gas operations.

Birth outcomes and maternal residential proximity to natural gas development in rural Colorado.

BACKGROUND: Birth defects are a leading cause of neonatal mortality. Natural gas development (NGD) emits several potential teratogens, and U.S. production of natural gas is expanding. OBJECTIVES: We examined associations between maternal residential proximity to NGD and birth outcomes in a retrospective cohort study of 124,842 births between 1996 and 2009 in rural Colorado. METHODS: We calculated inverse distance weighted natural gas well counts within a 10-mile radius of maternal residence to estimate maternal exposure to NGD. Logistic regression, adjusted for maternal and infant covariates, was used to estimate associations with exposure tertiles for congenital heart defects (CHDs), neural tube defects (NTDs), oral clefts, preterm birth, and term low birth weight. The association with term birth weight was investigated using multiple linear regression. RESULTS: Prevalence of CHDs increased with exposure tertile, with an odds ratio (OR) of 1.3 for the highest tertile (95% CI: 1.2, 1.5); NTD prevalence was associated with the highest tertile of exposure (OR = 2.0; 95% CI: 1.0, 3.9, based on 59 cases), compared with the absence of any gas wells within a 10-mile radius. Exposure was negatively associated with preterm birth and positively associated with fetal growth, although the magnitude of association was small. No association was found between exposure and oral clefts. CONCLUSIONS: In this large cohort, we observed an association between density and proximity of natural gas wells within a 10-mile radius of maternal residence and prevalence of CHDs and possibly NTDs. Greater specificity in exposure estimates is needed to further explore these associations.

Prenatal exposure to cooking gas and respiratory health in infants is modified by tobacco smoke exposure and diet in the INMA birth cohort study.

BACKGROUND: Studies that have evaluated the association between exposure to gas appliances emissions at home with respiratory health in children obtained heterogeneous and limited results. The aim of this study is to analyze the association between the use of gas cooking at home during pregnancy and respiratory problems in children during their first year of life. METHODS: In the years 2003 through 2008 pregnant women were enrolled in 4 Spanish areas and visited in different age-points following a common protocol. Outcomes studied (from a questionnaire) were any episode of lower respiratory tract infection (LRTI), wheezing, persistent cough, chestiness and otitis. The association between exposure to gas cooking at home and respiratory outcomes was assessed using logistic regression and adjusting by confounding variables. Some potential effect modifiers (i.e. smoking, fruit and vegetables consumption) were examined. RESULTS: Among the 2003 children included in the study, a total of 731 (36.6%) had a LRTI episode, 693 (34.6%) experienced wheezing, 302 (15.5%) a persistent cough, 939 (47.4%) chestiness and 620 (31.2%) had an episode of otitis during their first year of life. Gas cookers were present in 45.5% of homes. Exposure to gas cooking in homes was not associated with respiratory outcomes Odds Ratios (OR) were close to 1 and not statistically significant. However, a positive association was found for otitis among infants whose mothers reported low intakes of fruit and vegetables during pregnancy [OR (95% CI) = 1.38 (1.01-1.9)] and also wheezing and chestiness were associated with gas cookers among those children whose mothers smoked during pregnancy. CONCLUSIONS: In susceptible subjects (those whose mothers smoke and consumed below average fruit and vegetables) we found an association between exposure to gas cooking during pregnancy and risk of wheezing, chestiness and otitis during the first year of life. But more research is needed regarding not only gas cooking and respiratory health but also the possible effect modifier role of diet and tobacco.

Toxicological properties of emission particles from heavy duty engines powered by conventional and bio-based diesel fuels and compressed natural gas.

BACKGROUND: One of the major areas for increasing the use of renewable energy is in traffic fuels e.g. bio-based fuels in diesel engines especially in commuter traffic. Exhaust emissions from fossil diesel fuelled engines are known to cause adverse effects on human health, but there is very limited information available on how the new renewable fuels may change the harmfulness of the emissions, especially particles (PM). We evaluated the PM emissions from a heavy-duty EURO IV diesel engine powered by three different fuels; the toxicological properties of the emitted PM were investigated. Conventional diesel fuel (EN590) and two biodiesels were used - rapeseed methyl ester (RME, EN14214) and hydrotreated vegetable oil (HVO) either as such or as 30% blends with EN590. EN590 and 100% HVO were also operated with or without an oxidative catalyst (DOC + POC). A bus powered by compressed natural gas (CNG) was included for comparison with the liquid fuels. However, the results from CNG powered bus cannot be directly compared to the other situations in this study. RESULTS: High volume PM samples were collected on PTFE filters from a constant volume dilution tunnel. The PM mass emission with HVO was smaller and with RME larger than that with EN590, but both biofuels produced lower PAH contents in emission PM. The DOC + POC catalyst greatly reduced the PM emission and PAH content in PM with both HVO and EN590. Dose-dependent TNFα and MIP-2 responses to all PM samples were mostly at the low or moderate level after 24-hour exposure in a mouse macrophage cell line RAW 264.7. Emission PM from situations with the smallest mass emissions (HVO + cat and CNG) displayed the strongest potency in MIP-2 production. The catalyst slightly decreased the PM-induced TNFα responses and somewhat increased the MIP-2 responses with HVO fuel. Emission PM with EN590 and with 30% HVO blended in EN590 induced the strongest genotoxic responses, which were significantly greater than those with EN590 + cat or 100% HVO. The emission PM sample from the CNG bus possessed the weakest genotoxic potency but had the strongest oxidative potency of all the fuel and catalyst combinations. The use of 100% HVO fuel had slightly weaker and 100% RME somewhat stronger emission PM induced ROS production, when compared to EN590. CONCLUSIONS: The harmfulness of the exhaust emissions from vehicle engines cannot be determined merely on basis of the emitted PM mass. The study conditions and the engine type significantly affect the toxicity of the emitted particles. The selected fuels and DOC + POC catalyst affected the PM emission from the heavy EURO IV engine both qualitative and quantitative ways, which influenced their toxicological characteristics. The plain HVO fuel performed very well in emission reduction and in lowering the overall toxicity of emitted PM, but the 30% blend of HVO in EN590 was no better in this respect than the plain EN590. The HVO with a DOC + POC catalyst in the EURO IV engine, performed best with regard to changes in exhaust emissions. However some of the toxicological parameters were significantly increased even with these low emissions.

Human health risk assessment of air emissions from development of unconventional natural gas resources.

BACKGROUND: Technological advances (e.g. directional drilling, hydraulic fracturing), have led to increases in unconventional natural gas development (NGD), raising questions about health impacts. OBJECTIVES: We estimated health risks for exposures to air emissions from a NGD project in Garfield County, Colorado with the objective of supporting risk prevention recommendations in a health impact assessment (HIA). METHODS: We used EPA guidance to estimate chronic and subchronic non-cancer hazard indices and cancer risks from exposure to hydrocarbons for two populations: (1) residents living >½ mile from wells and (2) residents living ≤ ½ mile from wells. RESULTS: Residents living ≤ ½ mile from wells are at greater risk for health effects from NGD than are residents living >½ mile from wells. Subchronic exposures to air pollutants during well completion activities present the greatest potential for health effects. The subchronic non-cancer hazard index (HI) of 5 for residents ≤ ½ mile from wells was driven primarily by exposure to trimethylbenzenes, xylenes, and aliphatic hydrocarbons. Chronic HIs were 1 and 0.4. for residents ≤ ½ mile from wells and >½ mile from wells, respectively. Cumulative cancer risks were 10 in a million and 6 in a million for residents living ≤ ½ mile and >½ mile from wells, respectively, with benzene as the major contributor to the risk. CONCLUSIONS: Risk assessment can be used in HIAs to direct health risk prevention strategies. Risk management approaches should focus on reducing exposures to emissions during well completions. These preliminary results indicate that health effects resulting from air emissions during unconventional NGD warrant further study. Prospective studies should focus on health effects associated with air pollution.