Use of partial order in environmental pollution studies demonstrated by urban BTEX air pollution in 20 major cities worldwide

Outdoor Pollution Comparison Between Bucharest and Its Outskirts Using Mobile Laboratory

This study presents a modern mobile laboratory to monitor outdoor air quality in Bucharest, Romania, with a focus on pollutants associated with transportation. Particulate matter (PM2.5, PM10), carbon monoxide (CO), ozone (O3), sulfur dioxide (SO2), nitrogen oxides (NO, NO2), and BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) were among the significant pollutants that were examined in the lab. Meteorological variables such wind direction and speed, temperature, humidity, and solar radiation were also routinely observed in order to assess their influence on pollution levels. The study looked at two locations-a bustling city road in Bucharest and a remote community 40 kmawayin Snagov-under a range of weather conditions, including sunny, rainy, warm, and chilly days. The findings showed that the primary source of pollution in the urban area, which had significantly higher pollution levels than the rural site, was transportation. Particularly in the city, alarming concentrations of harmful particulate matter and carcinogens like benzene were found, underscoring the need for continuous air quality monitoring. The weather has a major impact on the dispersal of contaminants. Because of washout effects, rainy days decreased airborne pollutants, but sunny days showed higher pollution deposition. This study highlights the importance of outdoor air quality monitoring, particularly in urban environments, where traffic and weather have a significant impact on pollution levels. These findings provide crucial data that policymakers can utilize to implement targeted pollution control measures that protect human health.

Risk assessment of Benzene, Toluene, Ethyl benzene, and Xylene (BTEX) in the atmospheric air around the world: A review

Volatile organic compounds, such as BTEX, have been the subject of numerous debates due to their detrimental effects on the environment and human health. Human beings have had a significant role in the emergence of this situation. Even though US EPA, WHO, and other health-related organizations have set standard limits as unhazardous levels, it has been observed that within or even below these limits, constant exposure to these toxic chemicals results in negative consequences as well. According to these facts, various studies have been carried out all over the world - 160 of which are collected within this review article, so that experts and governors may come up with effective solutions to manage and control these toxic chemicals. The outcome of this study will serve the society to evaluate and handle the risks of being exposed to BTEX. In this review article, the attempt was to collect the most accessible studies relevant to risk assessment of BTEX in the atmosphere, and for the article to contain least bias, it was reviewed and re-evaluated by all authors, who are from different institutions and backgrounds, so that the insights of the article remain unbiased. There may be some limitations to consistency or precision in some points due to the original sources, however the attempt was to minimize them as much as possible.

A Three-Year Analysis of Toxic Benzene Levels and Associated Impact in Ploieşti City, Romania

This study examines the levels of benzene and the potential health impact during three years of continuous monitoring (2019-2021), including the COVID-lockdown period from 2020 in a city that is an important Romanian center for petroleum refining and associated product manufacturing. The dataset contains benzene, toluene, NOx, PM10 concentrations, and meteorological factors monitored by six automatic stations from the national network of which four are in the city and two outside. Special attention was given to the benzene dynamics to establish patterns related to the health impact and leukemia. An assessment of the exposure was performed using EPA's ExpoFIRST v. 2.0 for computing the inhalation Average Daily Dose (ADD) and Lifetime Average Daily Dose (LADD). The health impact was estimated based on several indicators such as lifetime cancer risk (LCR), Hazard Quotient (HQ), Disability-Adjusted Life Years (DALY), and Environmental burden of disease (EBD). Overall, the annual average of all stations was almost similar between years i.e., 3.46 in 2019, 3.41 in 2020, and 3.63 µg/m3 in 2021, respectively. The average of all stations during the lockdown period was 2.67 µg/m3, which was lower than the multiannual average of the 2019-2021 period, i.e., 3.5 µg/m3. Significant correlations were present between benzene and other pollutants such as NOx (r = 0.57), PM10 fraction (r = 0.70), and toluene (r = 0.69), and benzene and temperature (r = -0.46), humidity (r = 0.28), and wind speed (r = -0.34). Regarding the ADD, in all scenarios, the most affected age categories are small children, despite a lower outdoor exposure time. From birth to <70 years, the ADD varied depending on the exposure scenario resulting in 3.27 × 10-4, 5.6 × 10-4, and 4.04 × 104 mg/kg-day, and 3.95 × 10-4, 10.6 × 10-4, and 6.76 × 10-4 mg/kg-day for the LADD, respectively. The Integrated Lifetime Cancer Risk (ILTCR) values were 14.1 × 10-5 in winter, 9.04 × 10-5 in spring, 8.74 × 10-5 in summer, and 10.6 × 10-4 in autumn. The ILTCR annual averages were 1.08 × 10-4 (2019), 1.07 × 10-4 (2020), 1.04 × 10-4 (2021), and 1.06 × 10-4 for the entire period. The resulting ILTCR values point out very risky conditions, with the annual averages reaching the definite cancer risk category. The corresponding burden based on the DALY's loss due to leukemia in Ploieşti was estimated at 0.291 (2 μg/m3 benzene), 0.509 (3.5 μg/m3 benzene), 0.582 (4 μg/m3 benzene), and 0.873 DALYs per 100,000 inhabitants (6 μg/m3 benzene), respectively. The current study provides useful insights for a better understanding of the exposure levels to benzene and associated health impact in Ploieşti despite the limitations determined by the data hiatus and incomplete or missing information regarding the health impact.

BTEX in Ambient Air of Zarand, the Industrial City in Southeast of Iran: Concentration, Spatio-temporal Variation and Health Risk Assessment

The existence of several industries in Zarand, a city in Southeastern Iran, caused challenges for the residents about air pollutants and associated health effects. In the present study, the concentration of benzene, toluene, ethylbenzene, and xylene (BTEX), spatio-temporal distribution and related health risks were evaluated. Passive samplers were used to collect 30 samples in the over the hot and cold periods in 2020. The ordinary Kriging method was used to predict the spatio-temporal distribution of BTEXs. Also, the Monte Carlo simulation was used to evaluate the related carcinogenic and non-carcinogenic risks of BTEX for adults. The ranking of mean concentration of overall toluene, xylene, ethylbenzene, and benzene followed as 82.49 ± 26.86, 30.91 ± 14.04, 4.75 ± 3.28, and 0.91 ± 0.18 µg/m3, respectively. The mean value of lifetime carcinogenic risk (LTCR) for residents related to benzene was 7.52 × 10- 6, indicating a negligible carcinogenic risk for them. Furthermore, the ranking of non-carcinogenic risk calculated through hazard quotient (HQ) for investigated BTEX compounds followed as xylene > benzene > toluene > ethylbenzene over the hot period and xylene > toluene > ethylbenzene over the cold period which all points had HQ < 1. Additionally, according to the findings of the sensitivity analysis, the concentration of benzene was the main contributor in increasing the carcinogenic risk. According to our results, it can be stated that the existence of several industries in the study area could not possibly occur the significant carcinogenic and non-carcinogenic risks to the adults residents in the study period. Human studies are recommended to determine definite results.

A novel preclinical model of environment-like combined benzene, toluene, ethylbenzene, and xylenes (BTEX) exposure: Behavioral and neurochemical findings

Environmental exposure to toxicants is a major health issue and a leading risk factor for premature mortality worldwide, including environmental exposures to volatile organic compounds (VOCs), specifically Benzene, Toluene, Ethylbenzene, and Xylene (BTEX). While exposure to these compounds individually has shown behavioral and neurochemical effects, this investigation examined the impact of exposure to combined BTEX using a preclinical model. Male Swiss Webster mice were exposed to BTEX vapors designed to approximate environmental levels in urban communities. Animals were exposed to one of four treatment conditions: a 0-ppm (air control), two BTEX groups representing levels of environmental-like exposure, and a fourth group modeling occupational-like exposure. These exposures were conducted in 1.5-h sessions, 2 sessions/day, 5 days/week, for 3 weeks. Effects on coordination (i.e., rotarod and inverted screen test), learning and memory (i.e., Y-maze), and locomotor behavior (i.e., movement during exposure) were assessed during and after exposure. Monoamine levels in the medial prefrontal cortex and nucleus accumbens were assessed immediately following exposure. Effects of BTEX exposure were found on the variance of locomotor activity but not in other behavioral or neurochemical assessments. These results indicate that the combination of inhaled BTEX at environmentally representative concentrations has demonstrable, albeit subtle, effects on behavior.

Neurotoxicity induced by toluene: In silico and in vivo evidences of mitochondrial dysfunction and dopaminergic neurodegeneration

Toluene is an air pollutant widely used as an organic solvent in industrial production and emitted by fossil fuel combustion, in addition to being used as a drug of abuse. Its toxic effects in the central nervous system have not been well established, and how and which neurons are affected remains unknown. Hence, this study aimed to fill this gap by investigating three central questions: 1) How does toluene induce neurotoxicity? 2) Which neurons are affected? And 3) What are the long-term effects induced by airborne exposure to toluene? To this end, a Caenorhabditis elegans model was employed, in which worms at the fourth larval stage were exposed to toluene in the air for 24 h in a vapor chamber to simulate four exposure scenarios. After the concentration-response curve analysis, we chose scenarios 3 (E3: 792 ppm) and 4 (E4: 1094 ppm) for the following experiments. The assays were performed 1, 48, or 96 h after removal from the exposure environments, and an irreversible reduction in neuron fluorescence and morphologic alterations were observed in different neurons of exposed worms, particularly in the dopaminergic neurons. Moreover, a significant impairment in a dopaminergic-dependent behavior was also associated with negative effects in healthspan endpoints, and we also noted that mitochondria may be involved in toluene-induced neurotoxicity since lower adenosine 5'-triphosphate (ATP) levels and mitochondrial viability were observed. In addition, a reduction of electron transport chain activity was evidenced using ex vivo protocols, which were reinforced by in silico and in vitro analysis, demonstrating toluene action in the mitochondrial complexes. Based on these findings model, it is plausible that toluene neurotoxicity can be initiated by complex I inhibition, triggering a mitochondrial dysfunction that may lead to irreversible dopaminergic neuronal death, thus impairing neurobehavioral signaling.

External Exposure to BTEX, Internal Biomarker Response, and Health Risk Assessment of Nonoccupational Populations near a Coking Plant in Southwest China

Benzene, toluene, ethylbenzene and xylene isomers (BTEX) have raised increasing concern due to their adverse effects on human health. In this study, a coking factory and four communities nearby were selected as the research area. Atmospheric BTEX samples were collected and determined by a preconcentrator GC-MS method. Four biomarkers in the morning urine samples of 174 participants from the communities were measured by LC-MS. The health risks of BTEX exposure via inhalation were estimated. This study aimed to investigate the influence of external BTEX exposure on the internal biomarker levels and quantitatively evaluate the health risk of populations near the coking industry. The results showed that the average total BTEX concentration in residential area was 7.17 ± 7.24 μg m^-3. Trans,trans-muconic acid (T,T-MA) was the urinary biomarker with the greatest average level (127 ± 285 μg g^-1 crt). Similar spatial trends can be observed between atmospheric benzene concentration and internal biomarker levels. The mean values of the LCR for male and female residents were 2.15 × 10^-5 and 2.05 × 10^-5, respectively. The results of the risk assessment indicated that special attention was required for the non-occupational residents around the area.

Microplastics in the Environment: Intake through the Food Web, Human Exposure and Toxicological Effects

Recently, studies on microplastics (MPs) have increased rapidly due to the growing awareness of the potential health risks related to their occurrence. The first part of this review is devoted to MP occurrence, distribution, and quantification. MPs can be transferred from the environment to humans mainly through inhalation, secondly from ingestion, and, to a lesser extent, through dermal contact. As regards food web contamination, we discuss the microplastic presence not only in the most investigated sources, such as seafood, drinking water, and salts, but also in other foods such as honey, sugar, milk, fruit, and meat (chickens, cows, and pigs). All literature data suggest not-negligible human exposure to MPs through the above-mentioned routes. Consequently, several research efforts have been devoted to assessing potential human health risks. Initially, toxicological studies were conducted with aquatic organisms and then with experimental mammal animal models and human cell cultures. In the latter case, toxicological effects were observed at high concentrations of MPs (polystyrene is the most common MP benchmark) for a short time. Further studies must be performed to assess the real consequences of MP contamination at low concentrations and prolonged exposure.

Spatial distribution and health risk of exposure to BTEX in urban area: a comparison study of different land-use types and traffic volumes

Many previous studies have investigated BTEX concentrations in urban areas; however, the available evidence on the association of different land-use types and BTEX concentrations is still scarce. In this study, the BTEX concentrations were measured and compared in different land-use types and traffic volumes of Mashhad metropolis, Iran. Sampling was conducted in summer and winter of 2018 based on NIOSH 1501 method in six land-use types, including Residential, Commercial/official, Industrial, Greenspace, Transportation, and Tourism. The spatial autocorrelation model was used to investigate the emission pattern. The Monte Carlo simulation technique and sensitivity analysis were used to assess the health risk of exposure to BTEX compounds. The median [interquartile range (IQR)] of benzene, toluene, ethylbenzene m-xylene, o-xylene and total BTEX concentrations based on overall mean were 4 (2.23), 8.37 (4.48), 1.2 (1.46), 0.89 (2.59), 0.8 (1.73) and 17.7 (8.19) µg/m³, respectively. Benzene and toluene had clustered emission patterns (z-score > 1.96). Exposure to benzene in the study area had a carcinogenic risk for inhabitants. The concentration of BTEX compounds was significantly different based on land-use type. The maximum and minimum concentrations of BTEX were observed in Transportation and Greenspace land uses, respectively. The BTEX concentrations in summer were significantly higher than in winter, and traffic had a significant effect on BTEX concentrations. Overall, our results supported a significant relationship between land-use type and BTEX concentrations in the urban area. Moreover, ambient benzene concentration had a carcinogenic risk potential for inhabitants of study area.

Air Quality and Industrial Emissions in the Cities of Kazakhstan

Industrial emissions are of major concern, especially in developing countries. Hence, there is a need for studies that investigate the trends in industrial emissions in these countries. The purpose of this study is to discuss trends in industrial emissions in Kazakhstan and the air pollution level in its industrial cities. Data on emission limit values from the permitting documents of twenty-one power plants and nine metallurgical enterprises of Kazakhstan were analyzed. Eight cities (out of fourteen) had a “high” level of atmospheric air pollution according to the Air Pollution Index in 2019. Most of the considered enterprises increased their emission limit values compared to the previous permitting period. In some cities there is a lack of monitoring stations, indicating the need for improving the spatial coverage of the air quality monitoring network in the industrial cities of Kazakhstan. The location of industrial plants far outside the cities could reduce the exposure of the urban population to air pollution. Kazakhstan urgently needs to adopt stringent emissions standards for coal-fired power plants and heavy industrial plants. The national air quality standards and definitions of air pollutants need to be updated based on the latest scientific knowledge.

Effects of inhaled combined Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX): Toward an environmental exposure model

Combined environmental exposures to the volatile organic compounds (VOCs) Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) pose clear risks to public health. Research into these risks is under-studied even as BTEX levels in the atmosphere are predicted to rise. This review focuses on the available literature using single- and combined-BTEX component inhaled solvent exposures in animal models, necessarily also drawing on findings from models of inhalant abuse and occupational exposures. Health effects of these exposures are discussed for multiple organ systems, but with particular attention on neurobehavioral outcomes such as locomotor activity, impulsivity, learning, and psychopharmacological responses. It is clear that animal models have significant differences in the concentrations, durations and patterns of exposure. Experimental evidence of the deleterious health and neurobehavioral consequences of exposures to the individual components of BTEX were found, but these effects were typically assessed using concentrations and exposure patterns not characteristic of environmental exposure. Future studies with animal models designed appropriately to explore combined BTEX will be necessary and advantageous to discovering health outcomes and more subtle neurobehavioral impacts of long-term environmental exposures.

Assessment of persistent indoor VOCs inside public transport during winter season

The present work intends to analyze the pollution level at the indoor environments of the public transport units of León Guanajuato, Mexico during winter season. An identification and quantification of persistent organic pollutants were carried out within three of the principal bus lines of the city in order to determine their possible origin, the differences in the levels of contamination between routes, and the potential risk to the health of the users, these analyses were carried out with different statistical techniques (ANOVA, PCA, and correlation network maps). Fourteen different organic compounds were identified as persistent pollutants. Although toluene and hexane were the compounds that were detected at the highest concentrations (average of 86.52 ± 56.1 μg m^-3 and 183.33 ± 10.7 μg m^-3, respectively), the correlation analysis showed that xylene, styrene, and ethylbenzene were the compounds that were mostly related to the other compounds identified as persistent. Otherwise, the statistical analysis of the concentration of these pollutants allowed to establish the fuel combustion vapors as the main source of these compounds. In the same way, the potential exposition health risk to the users were calculated in accordance to the Environmental Protection Agency of United States on those commuters grouped as students and workers. This analysis shown that the xylenes are the most representative organic pollutant in this particulate indoor spaces, and is the one with potential to generate a greater risk to the health of the bus-users, this without demising the potential danger of other pollutants.

Assessing air quality changes in large cities during COVID-19 lockdowns: The impacts of traffic-free urban conditions in Almaty, Kazakhstan

Number of cities worlwide experienced air quality improvements during COVID-19 lockdowns; however, such changes may have been different in places with major contributions from nontraffic related sources. In Almaty, a city-scale quarantine came into force on March 19, 2020, which was a week after the first COVID-19 case was registered in Kazakhstan. This study aims to analyze the effect of the lockdown from March 19 to April 14, 2020 (27 days), on the concentrations of air pollutants in Almaty. Daily concentrations of PM_2.5, NO₂, SO₂, CO, O₃, and BTEX were compared between the periods before and during the lockdown. During the lockdown, the PM_2.5 concentration was reduced by 21% with spatial variations of 6-34% compared to the average on the same days in 2018-2019, and still, it exceeded WHO daily limit values for 18 days. There were also substantial reductions in CO and NO₂ concentrations by 49% and 35%, respectively, but an increase in O₃ levels by 15% compared to the prior 17 days before the lockdown. The concentrations of benzene and toluene were 2-3 times higher than those during in the same seasons of 2015-2019. The temporal reductions may not be directly attributed to the lockdown due to favorable meteorological variations during the period, but the spatial effects of the quarantine on the pollution levels are evidenced. The results demonstrate the impact of traffic on the complex nature of air pollution in Almaty, which is substantially contributed by various nontraffic related sources, mainly coal-fired combined heat and power plants and household heating systems, as well as possible small irregular sources such as garbage burning and bathhouses.

Application of spatial analysis to investigate contribution of VOCs to photochemical ozone creation

This study was concerned with the temporal analysis of benzene, toluene, ethylbenzene, xylenes (BTEXs), and ozone in Rochester, New York, between 2012 and 2018. Additionally, the influence of ozone precursors (e.g., BTEXs and NO₂) and meteorological variables (e.g., relative humidity (RH), temperature along with wind speed) on ozone dispersion was investigated in the eastern half of the USA using the integrated nested Laplace approximation and stochastic partial differential equation (INLA-SPDE). The benzene variability at seasonal scale was characterized by higher values during the cold seasons. On the contrary, the long-term temporal trend of ozone depicted a repetitive cyclic behavior while an episode, with values exceeding 5 μg/m³, was detected associated with benzene in 2015. The spatial analysis by INLA-SPDE indicated that 1,3,5-trimethylbenzene and benzene were the key ozone precursors influencing ozone formation. It was demonstrated that increase of temperature had a considerable impact on ozone build-up whereas the increment of RH leads to decrease in ambient values of ozone. The amounts of root mean squared error (RMSE), mean absolute error (MAE), and bias for the validation data (e.g., 32 samples) were 0.005, 0.004, and 0.0008, exhibiting a reasonable out-of-sample forecasting by the INLA-SPDE model. The distribution map of ozone highlighted a hot spot in the state of Florida.

Effects of microclimate and human parameters on outdoor thermal sensation in the high-density tropical context of Dhaka

A thermal comfort questionnaire survey was carried out in the high-density, tropical city Dhaka. Comfort responses from over 1300 subjects were collected at six different sites, alongside meteorological parameters. The effect of personal and psychological parameters was examined in order to develop predictive models. Personal parameters included gender, age, activity, profession-type (indoor or outdoor-based), exposure to air-conditioned space and sweat-levels. Psychological parameters, such as 'the reason for visiting the place' and 'next destination is air-conditioned', had statistically significant effects on thermal sensation. Other parameters, such as 'body type', 'body exposure to sun', 'time living in Dhaka', 'travelling in last_30 min', and 'hot food' did not have any significant impact. Respondents' humidity, wind speed and solar radiation sensation had profound impacts and people were found willing to adjust to the thermal situations with adaptive behaviour. Based on actual sensation votes from the survey, empirical models are developed to predict outdoor thermal sensation in the case study areas. Ordinal linear regression techniques are applied for predicting thermal sensation by considering meteorological and personal conditions of the field survey. The inclusion of personal and weather opinion factors produced an improvement in models based on meteorological factors. The models were compared with the actual thermal sensation using the cross-tabulation technique. The predictivity of the three models (meteorological, thermos-physiological and combined parameter) as expressed by the gamma coefficient were 0.575, 0.636 and 0.727, respectively. In all three models, better predictability was observed in the 'Slightly Warm' (71% in meteorological model) and 'Hot' (64.9% in combined parameter model) categories-the most important ones in a hot-humid climate.

Monitoring of volatile organic compounds in ambient air of Taldykorgan, Kazakhstan

The pollution of ambient air is one of the main sources of risk to human health in the world. There is a direct relationship between the level of air pollution and risk of the development of cancer, cardiovascular, respiratory and other diseases. Benzene, toluene, ethylbenzene and o-xylene (BTEX) are one of the most toxic volatile organic compounds. The aim of this study was to quantify BTEX in air of Taldykorgan, Kazakhstan using solid-phase microextraction followed by gas chromatography with mass-spectrometric detection. In different sampling seasons, average concentrations of four BTEX analytes varied from 7.5 to 27 µg/m3, from 15 to 250 µg/m3, from 2.4 to 12.8 µg/m3 and from 2.6 to 21 µg/m3, respectively. The highest concentrations of TEX were detected in autumn, while the highest concentrations of benzene were observed in winter. Toluene-to-benzene ratios in almost all measurements were above 1 indicating that the traffic emissions are the main source of air pollution with BTEX.

An overview of the development of vertical sampling technologies for ambient volatile organic compounds (VOCs)

Atmospheric volatile organic compounds (VOCs) are harmful to human health and the environment, and are precursors of other toxic air pollutants, e.g. ozone (O₃) and secondary organic aerosols (SOAs). In recent years, due to scientific and technological advancements, vertical VOC profile in the atmosphere has been increasingly studied since it plays an essential role in the atmospheric research by providing multilevel three-dimensional data. Such information will improve the predictive ability of existing air quality models. This review summarizes the latest development of vertical VOC sampling technologies, highlighting the technical and non-technical challenges with possible solutions and future applications of vertical VOC sampling technologies. Further, other important issues concerning ambient VOCs have also been discussed, e.g. emission sources, VOC air samplers, VOC monitoring strategies, factors influencing airborne VOC measurement, the use of VOC data in air quality models and future smart city air quality management. Since ambient VOC levels can fluctuate significantly with altitude, technologies for vertical VOC profiling have been developed from building/tower-based measurements and tethered balloons to aircrafts, unmanned aerial vehicles (UAVs) and satellites in order to improve the temporal-spatial capacity and accuracy. Between the existing sampling methods, so far, UAVs are capable of providing more reliable VOC measurements and better temporal-spatial capacities. Heretofore, their disadvantages and challenges, e.g. sampling height, sampling time, sensitivity of the sensors and interferences from other chemical species, have limited the application of UAV for vertical VOC profiling.

Sources of volatile organic compounds in suburban homes in Shanghai, China, and the impact of air filtration on compound concentrations

Air pollution in China is an ongoing concern, with subsets of the population (e.g., asthmatic children) especially susceptible to the associated health effects. In addition, people spend the majority of their time indoors, where pollutant composition may differ from the better characterized ambient environment. Although volatile organic compounds (VOCs) present health risks and have high concentrations indoors, their sources have not been thoroughly quantified in typical homes in suburban China. Similarly lacking is an understanding of how well a purifier with high efficiency particulate air and activated carbon filters can remove VOCs in a real-world setting in China. In this study, we a) quantified total VOCs (TVOC) and 900 + individual VOCs in 20 homes in China, b) identified potential sources of VOCs, and c) evaluated impacts of filtration. We used non-negative matrix factorization, a variable reduction technique, to identify sources. TVOC and individual compounds had higher concentrations indoors than outdoors (mean [range] indoors, filtration with pre-filter only: 302 [56-793] μg m-3; outdoors, entire study: 92 [26-629] μg m-3), indicating prevalent sources indoors. Many compounds detected have not, to our knowledge, been measured in homes in China. Some compounds (e.g., octanal, heptanal, ⍺-cedrene) were specific to the indoor environment, a few were ubiquitous (e.g., acetaldehyde, formaldehyde), and others were detected infrequently. These compounds may originate from consumer products, solvents, vehicle emissions, a hexane source, wooden products, and cooking. Filtration may improve air quality indoors by lowering concentrations of some VOCs, and, specifically, contributions related to solvents and consumer products.

Unexplored aspects of unipolar ionizer characteristics in context of indoor air cleaning

Indoor air pollution affects human health via acute and chronic exposure. Traditionally, filter systems have been used for indoor air cleaning; however, issues like filter life and routine maintenance remain associated with their operation. Ionizers are emerging as a potential candidate for indoor air cleaning. A major part of previous studies intended to "project ionizers as air cleaners" focus on particle removal in different conditions. But indices representing charge effects have not been given due attention. This study focuses on the measurement of spatial profile of ion concentration and aerosol current around a single ionizer and a circular array of five ionizers. The distribution of ion concentration around the system/array was found to be isotropic in the absence of ventilation. Aerosol current values under ionizer action have been measured for the first time. Results obtained from this work could be instrumental for the design of future ionizer systems with improved efficacy.

Characterizing petroleum hydrocarbons deposited on road surfaces in urban environments

Petroleum hydrocarbons are a toxic pollutant group, primarily including volatile organic compounds (VOC), semi-volatile organic compounds (SVOC) and non-volatile organic compounds (NVOC). These pollutants can be accumulated on urban roads during dry periods and then washed-off by stormwater runoff in rainy days. Unlike heavy metals and polycyclic aromatic hydrocarbons, petroleum hydrocarbons have not received an equal attention in the field of stormwater pollutant processes. This paper investigated characteristics of VOC, SVOC and NVOC pollutant loads deposited on urban roads and their influential factors using a forward stepwise regression and PROMETHEE-GAIA analysis techniques. The results indicate that the loads deposited on urban roads were NVOC > SVOC > VOC. It is also noted that the degrees of factors in influencing petroleum hydrocarbons deposited on urban roads did not equal and their order was total solids > land use type > vehicular traffic > roughness of road surfaces. The research results also showed that petroleum hydrocarbons on urban road surfaces tend to be source limiting rather than transport limiting. These outcomes can contribute to petroleum hydrocarbons polluted stormwater management, such as treatment system design and stormwater modelling approach improvement.

Analysis of the diversity in emissions of selected gaseous and particulate pollutants in the European Union countries

The article presents the analysis results of the grouping of the European Union countries with regard to emission levels of gaseous pollutants (NH3, NMVOCs, SO_x, NO_x) and particulate air pollutants (PM10 and PM2.5) which are one of the most dangerous type of pollution for human health. Their long-lasting effects on the human body may negatively affect health and life expectancy. The analysis was based on the taxonomic method of grouping data using the K-means method which is a non-hierarchical method. The analysis used the data published by Eurostat. Organizing countries into categories of emissions of gaseous and dust pollutants to the atmosphere was conducted for four cases: the total level of emission, the level of emissions related to the GDP, the area, and per capita. The Euclidean distance was a measure of the distance between Member States. The obtained results indicate that, depending on the adopted criterion, there is a significant change in the composition of individual clusters. This confirms the assumptions of the Authors who claimed that in order to develop a more comprehensive analysis and assessment of the state of atmospheric pollution in EU countries it is necessary to include additional criteria, other than only the total emission of a given pollution. The objective of the research was to indicate that the analysis of emissions of selected type of pollution, and at the same time most threatening to human health, does not fully reflect the actual state of the problem when presented only in terms of the emitted amount. It is therefore appropriate for EU institutions to take more account of the differences between the individual countries in terms of the criteria presented in the paper, during the decision-making process concerning the sustainable development policy in the field of environmental protection.

Characterization of BTEX group of VOCs and inhalation risks in indoor microenvironments at small enterprises

Concentrations of BTEX group (benzene, toluene, ethylbenzene and xylene) were measured in indoor and outdoor environments at four printing shops and two photocopy centers in Sakaka city, KSA. Fifty four BTEX samples were collected using passive diffusion monitors (SKC VOC 575) and analyzed by GC-MS. The results showed that toluene was the most prevailing compound within the BTEX group and its indoor levels were much higher than outdoor. The average indoor concentrations (μg/m³) ranged from 2.45 to 14.66, 81.59 to 955.65, 11.19 to 97.35, 35.66 to 291.88 and 3.90 to 28.39 for benzene, toluene, ethylbenzene, m/p-xylene and o-xylene, respectively. The indoor/outdoor ratios of concentrations of BTEX species were more than one in most cases, indicating the effect of indoor emission sources. Based on (Toluene/Benzene) ratios, all sites were affected by the traffic emissions. Ventilation efficiency, ink type and outdoor pollutant concentration are responsible for results disparity. Cancer and non-cancer risks were assessed in the indoor environments by calculating the lifetime cancer risk (LCR) and hazard ratio (HR), respectively. For benzene and ethylbenzene measured concentrations, LCR values were more than the acceptable USEPA risk level of 1 × 10^-6. HR values for BTEX species were in general lower than the threshold limit of one.

Research and application of a novel hybrid air quality early-warning system: A case study in China

As one of the most serious meteorological disasters in modern society, air pollution has received extensive attention from both citizens and decision-makers. With the complexity of pollution components and the uncertainty of prediction, it is both critical and challenging to construct an effective and practical early-warning system. In this paper, a novel hybrid air quality early-warning system for pollution contaminant monitoring and analysis was proposed. To improve the efficiency of the system, an advanced attribute selection method based on fuzzy evaluation and rough set theory was developed to select the main pollution contaminants for cities. Moreover, a hybrid model composed of the theory of "decomposition and ensemble", an extreme learning machine and an advanced heuristic algorithm was developed for pollution contaminant prediction; it provides deterministic and interval forecasting for tackling the uncertainty of future air quality. Daily pollution contaminants of six major cities in China were selected as a dataset to evaluate the practicality and effectiveness of the developed air quality early-warning system. The superior experimental performance determined by the values of several error indexes illustrated that the proposed early-warning system was of great effectiveness and efficiency.