Volatile Organic Compounds In Ambient Air Research Articles

Investigation of the spatial variation of ambient air VOCs and their effects on the health risk caused by long-term exposure in urban area

ABSTRACT Long-term exposure to Volatile Organic Compounds (VOCs) is a health risk for citizens. In this study, the cumulative health risk of exposure to VOCs in Tehran was assessed by investigating the concentration of these pollutants in ambient air in a five-year period. Health risk assessment was calculated by the quantitative method and the carcinogenic risk level was determined using the lifetime carcinogenic risk (LCR) method. The average concentration of benzene, toluene, ortho-xylene, and ethylbenzene was 1.4–1.8, 4.8–5.4, 5–6.5, and 3.6–4 ppb, respectively. Although HQ was not greater than 1, but it was very close in the case of benzene, ortho-xylene, meta-xylene, and para-xylene. Benzene and ethylbenzene had the largest effect in the assessed health risk. So the long-term exposure of Tehran citizens to VOCs has serious health consequences for them, which could be different according to the exposure time and spatial variations.

Short-term impact of exposure to ambient air volatile organic compounds on daily clinic visits for urticaria in Kaohsiung, Taiwan.

Air volatile organic compounds (VOCs) cause allergic reaction mainly via the respiratory tract or skin. This study aimed to investigate the association between daily visits by patients with urticaria and short-term changes in exposure to ambient air VOCs. The dependent variable was information from patients with urticaria at a medical center in Kaohsiung, Taiwan, from 2014/01/01 to 2018/07/31. The multivariable model included one-day average 75th percentile values of air VOCs and meteorologic data retrieved from Taiwan Air Quality Monitoring Network database, and was analyzed using a case-crossover study design and conditional logistic regression. Total daily clinic visits for urticaria were significantly positively associated with higher levels of 4 VOCs (ethylbenzene, toluene, m-/p-xylene, and o-xylene (adjusted odds ratio (AOR: 1.03-1.28)) on the visit days, and 10 VOC levels on the fourth lag day (benzene, ethylbenzene, toluene, m-/p-xylene, o-xylene, 1,3,5-trimethylbenzene, n-hexane, methylcyclohexane, cyclohexane, and ethylene (AOR: 1.02-3.02)). Analyses of age and gender subgroups revealed that men showed resistance on the visit day, and women, older, and younger patients were more vulnerable. Men were influenced by higher benzene levels (AOR = 1.24) on the fourth lag day. Higher values of more than 6 VOCs on the fourth lag day significantly affected women, younger and older patients (AOR: 1.04-6.5). The most notable VOCs were methylcyclohexane (women AOR = 3.28, younger AOR = 3.82) and 1,3,5-trimethylbenzene (women AOR = 2.77, older AOR = 6.5) on the fourth lag day, which had the lowest concentrations but highest influence. The concentration of certain air VOCs significantly affected daily visits for urticaria.

Positive effect of exposure to ambient air volatile organic compounds on clinic visits for atopic dermatitis

Positive effect of exposure to ambient air volatile organic compounds on clinic visits for atopic dermatitis

Obtaining accurate non-methane hydrocarbon data for ambient air in urban areas: comparison of non-methane hydrocarbon data between indirect and direct methods

Abstract. Since non-methane hydrocarbons (NMHCs) include numerous species of volatile organic compounds (VOCs), they are the only indicators that can characterize the total amount of VOCs in ambient air. More than 90 % of NMHC instruments in the market use the indirect method for NMHC determination, utilizing a gas chromatograph to determine the concentrations of total hydrocarbons (THCs) and methane in air. However, we found indirect NMHC measurements incorrectly characterized the low NMHC concentrations in the urban air. These measurements were hindered by the uncertain changes in the errors associated with low THC concentrations, humidity and macroscopic substances (oxygen) in the atmosphere. In this study, we conducted intercomparisons between 10 instruments in the market using different operation principles; among these, two used the direct method, and eight used the indirect method. For the indirect method, experiments showed that when the NMHC concentration was 50 ppb C, the errors in the measurement results were 32 % (CH4) and 98 % (THC) when compared to theoretical values. The oxygen content in the sample gas directly affected the response of the THC. The effect of increased oxygen content on the analysis of oxygen-containing substances was more significant than that of the increase in hydrocarbon substances. The response of dry zero was blank, and the response value increased non-linearly with relative humidity (RH). RH had a great impact on low NMHC concentrations of nearly 50 %. For the direct method, although various flow designs were applied for different instruments, the results indicated that they generally showed lower interference and higher accuracy for the ambient NMHC measurements. With the online direct methods, we obtained more reliable data and characteristics for low-concentration NMHCs in downtown Shanghai. The median of hourly data was 163.1 ppb C, and the highest ratio of the maximum and minimum concentrations of NMHCs reached 9.56 in a single day.

Health risk assessment from exposure to ambient VOCs and particulate matter in different functional zones in Dhanbad, India

This study evaluates the non-cancer risks (NCR) and cancer risks (CR) in outdoor working personnel in Dhanbad city, exposed to volatile organic compounds (VOCs) and particulate matter (PM) present in the ambient air. Dhanbad is known for its coal mines and is one of the most polluted cities in India and the world. Sampling was conducted in different functional zones; namely, traffic intersections, industrial, and institutional areas, to estimate the concentration of different PM-bound heavy metals and VOCs in the ambient air using Inductively coupled plasma-optical emission spectrometry (ICP-OES) and gas chromatography (GC) respectively. Our results show that the concentration levels (of VOCs and PM) and health risks were maximum at the traffic intersection area, followed by the industrial and institutional areas. The major contribution to CR came from chloroform, naphthalene, and PM-bound chromium, while the contribution to NCR mainly came from naphthalene, trichloroethylene, xylenes, and PM-bound chromium, nickel, and cadmium. It was observed that CR and NCR from VOCs are quite comparable (average CRvoc 8.92E-05 and NCRvoc 6.82) to that from the PM-bound heavy metals (average CRPM 9.93E-05 and NCRPM 3.52). According to the sensitivity analysis performed using Monte-Carlo Simulation, it was also found that the output risk is most significantly influenced by the pollutant concentration followed by exposure duration and exposure time. The study reveals that Dhanbad city is not only a critically polluted area but also a highly hazardous and cancer-prone area due to the pollution arising from incessant coal mining activities and heavy vehicular movement. Given the paucity of data on exposure to VOCs in ambient air and their risk assessment pertaining to coal mining cities of India, our study provides useful information and insight for the regulatory and enforcing authorities to devise appropriate strategies for air pollution and health risk management in such cities.

Characteristics and Secondary Organic Aerosol Formation of Volatile Organic Compounds from Vehicle and Cooking Emissions

In the present work, volatile organic compounds (VOCs) from vehicle exhaust and cooking fumes were investigated via simulation experiments, which covered engine emissions produced during gasoline direct injection (GDI) using two kinds of fuels and cooking emissions produced by preparing three domestic dishes. The distinct characteristics of VOCs emitted during the two processes were identified. Alkanes (73% mass fraction on average) and aromatics (15% on average) dominated the vehicle VOCs, while oxygenated VOCs (49%) and alkanes (29%) dominated the cooking VOCs. Isopentane (22%) was the most abundant species among the vehicle VOCs. N-hexanal (20%) dominated the cooking VOCs. The n-hexanal-to-n-pentanal ratio (3.68 ± 0.64) was utilized to identify cooking VOCs in ambient air. The ozone formation potential produced by cooking VOCs was from 1.39 to 1.93 times higher than that produced by vehicle VOCs, which indicates the significant potential contribution of cooking VOCs to atmospheric ozone. With the equivalent photochemical age increasing from 0 h to 72 h, the secondary organic aerosol formation by vehicle VOCs was from 3% to 38% higher than that of cooking VOCs. Controlling cooking emissions can reduce SOA pollution in a short time due to its higher SOA formation rate than that of vehicle VOCs within the first 30 h. However, after 30 h of oxidation, the amount of SOAs formed by vehicle exhaust emissions exceeded the amount of SOAs produced by cooking activities, implying that reducing vehicle emissions will benefit particle pollution for a longer time. Our results highlight the importance of VOCs produced by cooking fumes, which has not been given much attention before. Further, our study suggested that more research on semi-volatile organic compounds produced by cooking emissions should be conducted in the future.

Improving VOC control strategies in industrial parks based on emission behavior, environmental effects, and health risks: A case study through atmospheric measurement and emission inventory

Industrial parks have a very important impact on regional economic development, but the extremely complex and relatively concentrated volatile organic compound (VOC) emissions from industrial parks also result in it being difficult to control VOCs. In this study, we took a large integrated industrial park in the upper reaches of the Yangtze River as an example, conducted a 1-year monitoring campaign of ambient air VOCs, and established a speciated VOC emission inventory based on the measured chemical profiles of the key industries. The comprehensive control index (CCI) of 125 VOCs was evaluated using the entropy weighting method based on comprehensive consideration of three aspects, namely, emission behavior, environmental effects, and health risks of VOCs, to identify priority VOC species and their key sources for VOC control in industrial parks. The total estimated VOC emissions in the industrial park in 2019 were 6446.96 t. Steel production, sewage treatment, natural gas chemical industry, pharmaceuticals, and industrial boilers were the main sources of VOC emissions. In terms of VOC components, halocarbons, aromatics, and OVOCs were the largest groups of VOCs emitted from the industrial park, accounting for 73.75 % of the total VOC emissions. Using the entropy weighting method, we evaluated the index weights of five parameters: emissions, ozone formation potential, secondary organic aerosol formation potential, hazard quotient, and lifetime cancer risk. Based on the CCI, five control levels for VOC species were further established. The VOC species in Level I and Level II, which contain species such as naphthalene, 2-chlorotoluene, benzene, acrolein, and chloroform, should be considered as extremely important priority control species. These results serve as a reference for the development of precise control strategies for VOCs in industrial parks.

Photocatalytic potential of a titanium dioxide–supported platinum catalyst against VOCs with complicated composition under varying humidity conditions

It is more important to assess the performance of photocatalysts against volatile organic compounds (VOCs) as a mixture rather than as single-component systems to understand the factors and processes governing photocatalytic (PC) destruction of VOCs under real-world operation condition. It is often critical because VOCs in ambient air generally exist in the form of complicated mixtures. In this context, the PC destruction of 14 VOCs as a mixture was studied using a reduced titanium dioxide (TiO2)-supported platinum (1 wt%) catalyst under varying humidity conditions (room temperature (RT) and ultraviolet irradiation (λmax: 254 nm)). The removal efficiencies for aromatic hydrocarbons (e.g., benzene, toluene, m-xylene, and styrene), when examined in the relative humidity (RH) range of 0 to 100%, were in four distinctive ranges of 8.93% and 13.3%, 29.1% and 39.4%, 61.9% and 75.6%, and 92.9% and 96.6%, respectively. In contrast, the removal of ketones increased with RH between 0% and 20%, such as 30.7%–73.8% for methyl ethyl ketone and 68.7%–95.9% for methyl isobutyl ketone. Aldehydes were removed efficiently in the dark through a synergy between thermal oxidation and adsorption at RT. Overall, RH had positive and/or negative effects on photocatalysis depending on the VOC type. The overall results of this study are expected to offer a theoretical framework and practical insights into the PC processes occurring toward complex VOC systems.

Sources and Seasonal Variance of Ambient Volatile Organic Compounds in the Typical Industrial City of Changzhi, Northern China

Volatile organic compounds (VOCs) emitted from industrial processes, which are major emission sources of air pollutants, could cause significant impacts on air quality. However, studies on the comprehensive analysis from sources contributing to the health risk perspective regarding ambient VOCs in industrial cities are limited. In this study, VOC samples were collected from 15 April 2018 to 19 October 2018 in Changzhi, a typical industrial city in northern China, and a total of 57 VOCs were measured for analysis. The average VOC concentrations were 54.4 µg·m−3, with the highest concentrations in autumn (58.4 µg·m−3). Ambient VOCs in spring, summer and autumn were all dominated by alkanes (66.8%), with contributions of 70.3%, 66.3% and 63.8%, respectively. The top five concentrations of total VOCs were isopentane (19.0%), ethane (9.5%), n-butane (8.1%), benzene (7.9%) and propane (5.2%), indicating that vehicle exhaust and coal combustion are the main sources of VOCs. Source apportionment by principal component analysis showed that vehicle exhaust (27.5%) and coal combustion (23.5%) were the main sources of VOCs in Changzhi, followed by industrial production (17.4%), solvent evaporation (13.5%), liquefied petroleum gas/natural gas leaking (9.5%), and biogenic emissions (8.7%). Sources of coal combustion and vehicle exhaust contributed more VOCs than industrial production. The carcinogenic risks of benzene (3.4 × 10−5) and ethylbenzene (2.2 × 10−6) were higher than the limit levels (1 × 10−6). Coal combustion contributed most (25.3%) to the carcinogenic risks because of its high VOC emissions. In an industrial city such as Changzhi, vehicle exhaust and coal combustion have become major sources of ambient air VOCs owing to the increasingly stringent industrial standards. Therefore, VOCs from vehicle exhaust and coal combustion also need to take into account mitigation measures for VOCs from the perspective of source contribution to health risk.

Insight into the environmental monitoring and source apportionment of volatile organic compounds (VOCs) in various functional areas

Atmospheric aerosol contamination has caused widespread concern about human and environmental health. However, research about VOCs as an important precursor of secondary aerosols in ambient air is still limited. In this study, VOCs at sites from three typical functional areas in Hefei, China, were monitored using GC–MS/FID. The VOCs in ambient air from different functional areas showed significantly different characteristics. The highest concentrations and the biggest diurnal difference of VOCs were found in the High-tech Zone (industrial area) with serried emission sources. Additionally, lower VOC concentration was observed in Changjiang West Road, the center area of studied city. The VOC concentration in this area is strongly related to other pollutants. The composition of VOCs at all sampling sites showed certain common characteristics, i.e., alkanes, OVOCs, and halogenated hydrocarbons account for more than 75% of the total VOCs’ quality. The High-tech Zone with the highest concentration of VOCs also has the highest proportion of alkanes. Besides, the positive matrix factorization analysis results revealed that vehicle exhaust, LPG volatilization sources, and chemical solvents were the most important VOC emission sources in Hefei. In terms of the contribution of VOC components to the OFP at the three sites, the olefins and alkynes at the Changjiang West Road site and the Science Island site contribute the most significant proportion. In contrast, the OVOCs at the High-tech Zone site contribute the largest proportion.

One-year monitoring of aromatic volatile organic compounds (VOCs) in urban areas of Malaysia

VOCs have been one of the important limiting factors of O3 photochemical production in the urban tropical region. This study aims to determine the variation and composition of aromatic VOCs as well as their contribution to the O3 formation. The hourly data of benzene, toluene, ethylbenzene and xylenes (BTEX) and ozone (O3) were retrieved from January until December 2019 at three continuous air quality monitoring stations (S1, S2 and S3) operated by the Malaysian Department of Environment (DOE). Aromatic VOCs is detected by using an online gas chromatography analyser (GC 5000BTX). The annual average ΣBTEX concentrations ranged from 14.53 ± 12.43 μg m-3 to 25.04 ± 24.04 μg m-3 during the observation period, with toluene as the most dominant species with an average concentration of 10.65 ± 12.12 μg m-3. The O3 formation potential (OFP) was calculated and the results indicated that toluene is the highest contributor of O3-forming potential, followed by m, p-xylene, o-xylene, ethylbenzene and benzene with the value of 127.8 μg m-3 (40.90 %), 103.0 μg m-3 (32.97 %), 48.66 μg m-3 (15.58 %), 26.17 μg m-3 (8.38 %) and 6.74 μg m-3 (2.15 %), respectively. Since the study of VOCs in Malaysia is quite limited, a more comprehensive study is currently underway to integrate the research on variation of VOCs in ambient air and its impact on the environment and human health.

Exposure of heat-not-burn tobacco effect on the quality of air and expiratory plume

The increasing interest to avoid the consumption of regular tobacco has lead in the development of several types of devices to decrease the effects of this practice on active and bystanders. In this work, the impact of the use of new heat-not-burn (HnB) devices has been evaluated and compared with that of regular cigarettes and electronic cigarettes (e-cigs). Portable monitoring devices were employed for CO, CO2, particulate matter (PM) and volatile organic compounds (VOCs) to evaluate the quality of indoor air and expiratory plume of both, active and passive, users during these practices. It can be noticed that the levels of VOCs in active HnB smokers expiratory air are five times lower in particular cases than those provided by regular tobacco and three times lower than those obtained for e-cigs, while the contribution of particulate matter to air pollution decreases between 200 and 600 times regarding the values obtained for e-cig vaping and regular tobacco smoking. The level of contaminants as CO decreases significantly in both, active and passive HnB smokers, in comparison with active and passive regular tobacco smokers, due to the absence of organic material combustion.Regarding passive HnB smokers, the exposure to HnB smoke do not increases the level of VOCs in ambient air nor in expiratory plume, remaining at the basal levels, being three times lower than values obtained to an exposure to regular tobacco smoke and two times lower than exposure to e-cigs vapours. On the other hand, the use of HnB devices decreases the concentration of PM in bystanders around thirty five times in relation with values obtained for passive regular tobacco smokers. Concerning the nicotine content delivered by HnB tobacco, data shown that HnB tobacco provides values from 0.5 to 1.7 mg of nicotine to the mainstream, being these values similar to those found in conventional tobacco.

Rapid Determination of Ethylene Oxide and 75 VOCs in Ambient Air with Canister Sampling and Associated Growth Issues

A canister-based sampling method along with preconcentrator-Gas chromatography-Mass Spectrometry (GC-MS) analysis was applied to ethylene oxide (EtO or EO) and 75 other volatile organic compounds (VOCs) in ambient air. Ambient air can contain a large variety of VOCs, and thorough analysis requires non-discriminatory sampling and a chromatographic method capable of resolving a complex mixture. Canister collection of whole air samples allows for the collection of a wide range of volatile compounds, while the simultaneous analysis of ethylene oxide and other VOCs allows for faster throughput than separate methods. The method presented is based on US EPA Method TO-15A and allows for the detection of EtO from 18 to 2500 pptv. The method has an average accuracy of 104% and precision of 13% relative standard deviation (RSD), with an instrument run time of 32 min. In addition, a link between canister cleanliness and ethylene oxide growth is observed, and potential mechanisms and cleaning strategies are addressed.

Microsecond pulsed glow discharge in copper hollow cathode reveals a new approach to ionization and determination of volatile organic compounds

Recently glow discharge (GD) mass spectrometry, which is conventionally used to analyze solid samples, was successfully applied for ionization and the subsequent determination of volatile organic compounds (VOCs). In the present study, the possibility of direct determination of VOCs in ambient air using time-of-flight mass spectrometry with microsecond pulsed discharge in a copper hollow cathode was considered for the first time. The discharge cell of the mass spectrometer was modified for the direct analysis of gaseous samples by the introduction of a quartz capillary into the argon input channel. Various classes of compounds (aromatic and aliphatic hydrocarbons and derivatives of carboxylic acids) were studied. Particular attention was paid to the ionization mechanisms of VOCs. New mechanisms of chemical and electron ionization, resulting in the formation of associate ions with cathode material (copper) – CuM+, were demonstrated and implemented. Alternative mechanisms of organic compounds ionization in GD may be related to Penning process and proton transfer reactions. These processes are mainly responsible for the formation of molecular and protonated molecular ions. The relative contribution of all these mechanisms can be adjusted by operating parameters. In general, an extremely low degree of fragmentation of molecular ions or associates was observed. Due to its isotopic structure (only two isotopes 63Cu and 65Cu with comparable abundances), the use of copper as cathode material additionally increases the reliability of VOC identification in the form of their CuM+ associates. Such association shifts the detected ions to the region of large masses with fewer interferences and noise related to scattered ions.

Concomitant exposure to area-level poverty, ambient air volatile organic compounds, and cardiometabolic dysfunction: a cross-sectional study of U.S. adolescents

PurposeA key to better understanding the influence of the place of residence on cardiometabolic function is the effect of concomitant exposure to both air pollution and residence in economically marginalized areas. We hypothesized that, among adolescents, the association between air pollution and cardiometabolic function is exacerbated among residents of economically marginalized areas. MethodsIn this cross-sectional study, individual-level data on cardiometabolic function collected from a representative sample of U.S. adolescents in the National Health and Nutrition Examination Survey (n = 10,415) were merged with data on area-level poverty (U.S. decennial survey and American Community Survey) and air pollution levels (National-Scale Air Toxics Assessment ) using contemporary census-tract identifiers. We excluded respondents who were pregnant, had hypertension or diabetes or using medication for hypertension or diabetes, or with missing data on outcome variables. ResultsWe observed a significant interaction between area-level poverty and air pollution. Among residents of high-poverty areas, exposure to high levels of air pollution predicted a 30% elevated odds of cardiometabolic dysfunction (OR = 1.30; 95% CI: 1.04, 1.61), whereas in low-poverty areas, exposure to high levels of air pollution was not associated with elevated odds of cardiometabolic dysfunction (OR = 1.04; 95% CI: 0.85, 1.28). ConclusionsOur findings suggest that the cardiometabolic consequences of air pollution are more readily realized among residents of economically marginalized areas. Structural remedies are discussed.

Hazardous volatile organic compounds in ambient air of China.

Volatile organic compounds (VOCs) are ubiquitous in the atmosphere and the majority of them have been proved to be detrimental to human health. The hazardous VOCs were studied very insufficiently in China, despite the enormous emissions of VOCs. In this study, the concentrations and sources of 17 hazardous VOCs reported in literature were reviewed, based on which the health effects were assessed. In-depth survey indicated that benzene and toluene had the highest concentrations in eastern China (confined to the study regions reviewed, same for the other geographic generalization), which however showed significant declines. The southern China featured high levels of trichloroethylene. Dichloromethane and chloroform were observed to be concentrated in northern China. The distributions of 1,2-dichloropropane and tetrachloroethylene were homogeneous across the country. Basically consistent with the spatial patterns of ozone, the summertime formaldehyde exhibited higher levels in eastern and northern China, and increased continuously. While transportation served as the largest source of benzene and toluene, industrial emissions and secondary formation were the predominant contributors of halogenated hydrocarbons and aldehydes (formaldehyde and acetaldehyde), respectively. The chronic non-cancer effects of inhalation exposure to the hazardous VOCs were insignificant, however the probabilities of developing cancers by inhaling the hazardous VOCs in ambient air of China were quite high. Formaldehyde was identified as the primary carcinogenic VOC in the atmosphere of most regions. The striking results, especially the high inhalation cancer risks, alerted us that the emission controls of hazardous VOCs were urgent in China, which must be grounded upon full understanding of their occurrence, presence and health effects.

National secular trends in ambient air volatile organic compound levels and biomarkers of exposure in the United States

BackgroundExposure to air pollution is a leading cause of global mortality. Volatile organic compounds (VOCs) are constituents of ambient air that could exert adverse health effects. ObjectiveTo examine the relationship between VOC levels in ambient air and individual-level exposure to VOCs, as assessed by urinary VOC metabolites. MethodsSecular trends in 11 ambient air VOCs (2005–2013) and individual-level metabolites of 14 VOCs (2005–2014) were assessed using National Monitoring Programs (NMP) and National Health and Nutrition Examination Survey (NHANES) data, respectively. To isolate environmental exposure, individuals reporting exposure to tobacco smoke were excluded. Quantile regression models were used to assess secular trends in VOC exposure, and survey-weighted regression models were built to identify factors associated with VOC exposure. ResultsAll annual levels of ambient VOCs decreased from 2005 to 2013 (Range: 12.5%–77.2%). However, 11 of the corresponding VOC metabolites increased during the same time (Range: 0.3%–53.6%). There was a proportional change in patterns of VOC exposure across NHANES waves, with the middle quantiles of exposure showing the largest increase. VOC exposures were significantly associated with age, sex, race, education, and physical inactivity, but not with secular VOC trends. DiscussionIn the United States, individual-level exposure to several VOCs increased between 2005 and 2014 despite a decline in ambient air VOC levels. This inverse relationship suggests that ambient VOCs are not the primary source of VOC exposure, therefore, decreasing ambient VOCs alone may not be sufficient to protect against the adverse health effects associated with VOC exposure.

National Secular Trends in Ambient Air Volatile Organic Compound Levels and Biomarkers of Exposure in the United States

Abstract Background Exposure to air pollution is a leading cause of global mortality. Volatile organic compounds (VOCs) are constituents of ambient air that could exert adverse health effects. Objective To examine the relationship between VOC levels in ambient air and individual-level exposure to VOCs, as assessed by urinary VOC metabolites. Methods Secular trends in 11 ambient air VOCs (2005–2013) and individual-level metabolites of 14 VOCs (2005–2014) were assessed using National Monitoring Programs (NMP) and National Health and Nutrition Examination Survey (NHANES) data, respectively. To isolate environmental exposure, individuals reporting exposure to tobacco smoke were excluded. Quantile regression models were used to assess secular trends in VOC exposure, and survey-weighted regression models were built to identify factors associated with VOC exposure. Results All annual levels of ambient VOCs decreased from 2005 to 2013 (Range: 12.5%–77.2%). However, 11 of the corresponding VOC metabolites increased during the same time (Range: 0.3%–53.6%). There was a proportional change in patterns of VOC exposure across NHANES waves, with the middle quantiles of exposure showing the largest increase. VOC exposures were significantly associated with age, sex, race, education, and physical inactivity, but not with secular VOC trends. Discussion In the United States, individual-level exposure to several VOCs increased between 2005 and 2014 despite a decline in ambient air VOC levels. This inverse relationship suggests that ambient VOCs are not the primary source of VOC exposure, therefore, decreasing ambient VOCs alone may not be sufficient to protect against the adverse health effects associated with VOC exposure.

Determination of 104 volatile organic compounds in air by double column gas chromatography-mass spectrometry/flame ionization detector coupled with electronically controlled cryo-focusing unit

A method for the determination of 104 volatile organic compounds (VOCs) in ambient air based on double column multi dean switching gas chromatography-mass spectrometry/flame ionization detector (GC-MS/FID) coupled with sorbent assisted electronically controlled cryo-focusing unit was developed and evaluated. The sorbent assisted electronically controlled cryo-focusing unit was used for trapping, dehydration and focusing of VOCs sampled in summa canisters. The VOCs were split into two parts by the multi dean switching unit in GC-MS/FID. The C2-C3 components were determined in a PLOT capillary column with an FID detector, while the C4-C12 components were determined in an Intercap-624 capillary column with a MS detector. The C2-C3 components were qualitatively confirmed from the retention time and quantified by the calibration curves, while the C4-C12 components were qualitatively confirmed from the retention time and the relative abundance ratio of characteristic ions, and quantified by the internal standard calibration curves. The major factors influencing the cryo-focusing performance including the type of sorbent tube, the pressure employed in assisted pressure control unit (APC), and the split point in multi dean switching unit were investigated. The chromatographic and MS parameters were optimized. Under optimum conditions, a linear relationship was observed with the content of VOCs ranging from 0.0446 to 0.892 μmol/m3, and correlation coefficients (r) no less than 0.9984. The average spiked recoveries of the six VOCs at two levels of 0.0446 μmol/m3 and 0.223 μmol/m3 were 86.4%-116.1%, with relative standard deviations in the range of 0.9%-11.3% The method detection limits (MDLs) and the limits of quantification (LOQs) were 0.145-1.90 μg/m3 and 0.435-5.70 μg/m3, respectively. The method is accurate, sensitive and simple, and is suitable for the determination of the 104 VOCs in ambient air.

Spatiotemporal variation, ozone formation potential and health risk assessment of ambient air VOCs in an industrialized city in Iran

Volatile organic compounds (VOCs) are common air pollutants that are primarily emitted by motor vehicles and through industrial activity and can have a significant impact on air quality and adversely affect human health. The aim of this study was to characterize benzene, toluene, xylenes and styrene (BTXS) in the ambient air of Tabriz, a city in northwestern Iran, and describe their spatiotemporal variations, ozone formation potential (OFP) and provide a health risk assessment. The measured concentrations of BTXS ranged from 0.46 to 69.32 μg/m3. Diurnal variation showed a significant difference between the morning and evening concentrations, in which the evening values were primarily higher. Spatial analysis showed that the maximum levels of BTXS occurred in the industrial zone. The estimated OFP values ranged from 26 to 418 and 16 to 725 in winter and summer, respectively. In addition, the mean T/B ratio was 1.84, indicating the combustion of fuel in motor vehicles as the main source of VOCs. The hazard ratio of target pollutants was lower than the limits recommended by the USEPA and WHO; however, the estimated lifetime cancer risk for benzene was 7.82 × 10−6, which exceeds the threshold of 1 × 10−6.