Ambient VOCs in residential areas near a large-scale petrochemical complex: Spatiotemporal variation, source apportionment and health risk

Establishment and verification of anthropogenic speciated VOCs emission inventory of Central China

Improving the accuracy of anthropogenic volatile organic compounds (VOCs) emission inventory is crucial for reducing atmospheric pollution and formulating control policy of air pollution. In this study, an anthropogenic speciated VOCs emission inventory was established for Central China represented by Henan Province at a 3 km × 3 km spatial resolution based on the emission factor method. The 2019 VOCs emission in Henan Province was 1003.5 Gg, while industrial process source (33.7%) was the highest emission source, Zhengzhou (17.9%) was the city with highest emission and April and August were the months with the more emissions. High VOCs emission regions were concentrated in downtown areas and industrial parks. Alkanes and aromatic hydrocarbons were the main VOCs contribution groups. The species composition, source contribution and spatial distribution were verified and evaluated through tracer ratio method (TR), Positive Matrix Factorization Model (PMF) and remote sensing inversion (RSI). Results show that both the emission results by emission inventory (EI) (15.7 Gg) and by TR method (13.6 Gg) and source contribution by EI and PMF are familiar. The spatial distribution of HCHO primary emission based on RSI is basically consistent with that of HCHO emission based on EI with a R-value of 0.73. The verification results show that the VOCs emission inventory and speciated emission inventory established in this study are relatively reliable.

Anthropogenic-driven changes in concentrations and sources of winter volatile organic compounds in an urban environment in the Yangtze River Delta of China between 2013 and 2021

Volatile organic compounds (VOCs) serve as crucial precursors to surface ozone and secondary organic aerosols (SOA). In response to severe air pollution challenges, China has implemented key air quality control policies from 2013 to 2021. Despite these efforts, a comprehensive understanding of the chemical composition and sources of urban atmospheric VOCs and their responses to emission reduction measures remains limited. Our study focuses on analyzing VOCs composition and concentrations during the winters of 2013 and 2021 through online field observations in urban Nanjing, a typical city in the Yangtze River Delta region of China. Using a machine learning approach, we found a notable reduction in total VOCs concentration from 52.4 ± 30.4 ppb to 33.9 ± 21.6 ppb between the two years, with dominant contributions (approximately 94.3 %) associated with anthropogenic emission control. Furthermore, alkanes emerged as the major contributors (48.6 %) to such anthropogenic-driven decline. The total SOA formation potential decreased by approximately 27.4 %, with aromatics identified as the major contributing species. Positive matrix factorization analysis identified six sources. In 2013, prominent contributors were solid fuel combustion (43.6 %), vehicle emission (16.7 %), and paint and solvent use (12.8 %). By 2021, major sources shifted to solid fuel combustion (31.9 %), liquefied petroleum gas and natural gas (26.8 %), and vehicle emission (25.5 %). Solid fuel combustion emerged as the primary driver for total VOCs reduction. The lifetime carcinogenic risk in 2021 decreased by 72.6 % relative to 2013, emphasizing the need to address liquefied petroleum gas and natural gas source, and vehicle emissions for improved human health. Our findings contribute critical insights for policymakers working on effective air quality management.

Estimates of the global burden of cancer-related deaths attributable to residential exposure to petrochemical industrial complexes from 2020 to 2040

The petrochemical industry is a major industrial emitter of greenhouse gas (CO2) and environmental pollution, posing health risks to nearby communities. Although previous studies have indicated that residents living near petrochemical industrial complexes are at a higher risk of cancer, they have focused on local or regional burdens. This study aimed to estimate the global cancer burden attributable to residential exposure to petrochemical industrial complexes. The geographical coordinates of petrochemical plants and oil refineries were retrieved and verified from published sources. The ArcGIS software and global population data were used to estimate the number of people living within specific distances (exposed population). The exposure time window was framed as ranging from 1992 to 2035, extending to the latest period of the exposure time window for all cancer types to estimate the attributable deaths between 2020 and 2040. The relative risk of cancer was estimated from 15 published studies. Population attributable fraction (PAF) method was used to estimate the risk of cancer attributable to residential exposure and calculate the number of cancer-related deaths. Our findings indicate that >300 million people worldwide will be estimated to live near petrochemical industrial complexes by 2040. The overall global burden of cancer-related deaths was 19,083 in 2020, and it is estimated to increase to 27,366 deaths by 2040. The region with the highest attributable cancer deaths due to exposure is the high-income region, which had 10,584 deaths in 2020 and is expected to reach 13,414 deaths by 2040. Residential exposure to petrochemical industrial complexes could contribute to global cancer deaths, even if the proportion is relatively small, and proactive measures are required to mitigate the cancer burdens among these residents. Enforcing emissions regulations, improving monitoring, educating communities, and fostering collaboration are vital to protecting residents' health.

Chemical structure of hydrocarbons significantly affects removal performance and microbial responses in gas biotrickling filters

The control of emissions of short-chain hydrocarbons with different structures is critical for the petrochemical industry. Herein, three two-carbon-containing (C2) hydrocarbons, ethane, ethylene, and acetylene, were chosen as pollutants to study the effects of chemical structure of hydrocarbons on removal performance and microbial responses in biotrickling filters. Results showed that the removal efficiency (RE) of C2 hydrocarbons followed the sequence of acetylene > ethane > ethylene. When the inlet loading rate was 30 g/(m3·h) and the empty bed residence time was 60 s, the RE of ethane, ethylene, and acetylene was 57 ± 4.0 %, 49 ± 1.0 %, and 84 ± 2.7 %, respectively. The high water solubility resulted in the high removal of C2 hydrocarbons, while a low surface tension enhanced the removal of C2 hydrocarbons. Additionally, the microbial community, enzyme activity, and extracellular properties of microorganisms also contributed to the difference in C2 hydrocarbon removal. These results could be referred for the effective control of light hydrocarbon emissions.

Characteristics and source apportionment of ambient volatile organic compounds and ozone generation sensitivity in urban Jiaozuo, China

In recent years, many cities have taken measures to reduce volatile organic compounds (VOCs), an important precursor of ozone (O3), to alleviate O3 pollution in China. 116 VOC species were measured by online and offline methods in the urban area of Jiaozuo from May to October in 2021 to analyze the compositional characteristics. VOC sources were analyzed by a positive matrix factorization (PMF) model, and the sensitivity of ozone generation was determined by ozone isopleth plotting research (OZIPR) simulation. The results showed that the average volume concentration of total VOCs was 30.54 ppbv and showed a bimodal feature due to the rush-hour traffic in the morning and at nightfall. The most dominant VOC groups were oxygenated VOCs (OVOCs, 29.3%) and alkanes (26.7%), and the most abundant VOC species were acetone and acetylene. However, based on the maximum incremental reactivity (MIR) method, the major VOC groups in terms of ozone formation potential (OFP) contribution were OVOCs (68.09 µg/m3, 31.5%), aromatics (62.90 µg/m3, 29.1%) and alkene/alkynes (54.90 µg/m3, 25.4%). This indicates that the control of OVOCs, aromatics and alkene/alkynes should take priority. Five sources of VOCs were quantified by PMF, including fixed sources of fossil fuel combustion (27.8%), industrial processes (25.9%), vehicle exhaust (19.7%), natural and secondary formation (13.9%) and solvent usage (12.7%). The empirical kinetic modeling approach (EKMA) curve obtained by OZIPR on O3 exceedance days indicated that the O3 sensitivity varied in different months. The results provide theoretical support for O3 pollution prevention and control in Jiaozuo.

Atmospheric VOCs in an industrial coking facility and the surrounding area: Characteristics, spatial distribution and source apportionment

Industrial coking facilities are an important emission source for volatile organic compounds (VOCs). This study analyzed the atmospheric VOC characteristics within an industrial coking facility and its surrounding environment. Average concentrations of total VOCs (TVOCs) in the surrounding residential activity areas (R1 and R2), the coking facility (CF) and the control area (CA) were determined to be 138.5, 47.8, 550.0, and 15.0 µg/m3, respectively. The cold drum process and coking and quenching areas within the coking facility were identified as the main polluting processes. The spatial variation in VOCs composition was analyzed, showing that VOCs in the coking facility and surrounding areas were mainly dominated by aromatic compounds such as BTX (benzene, toluene, and xylenes) and naphthalene, with concentrations being negatively correlated with the distance from the coking facility (p < 0.01). The sources of VOCs in different functional areas across the monitoring area were analyzed, finding that coking emissions accounted for 73.5%, 33.3% and 27.7% of TVOCs in CF, R1 and R2, respectively. These results demonstrated that coking emissions had a significant impact on VOC concentrations in the areas surrounding coking facility. This study evaluates the spatial variation in exposure to VOCs, providing important information for the influence of VOCs concentration posed by coking facility to surrounding residents and the development of strategies for VOC abatement.

Source apportionment and suitability evaluation of seasonal VOCs contaminants in the soil around a typical refining-chemical integration park in China

Accurate source apportionment of volatile organic compounds (VOCs) in soil nearby petrochemical industries prevailing globally, is critical for preventing pollution. However, in the process, seasonal effect on contamination pathways and accumulation of soil VOCs is often neglected. Herein, Yanshan Refining-Chemical Integration Park, including a carpet, refining, synthetic rubber, and two synthetic resin zones, was selected for traceability. Season variations resulted in a gradual decrease of 31 VOCs in soil from winter to summer. A method of dry deposition resistance model coupling partitioning coefficient model was created, revealing that dry deposition by gas phase was the primary pathway for VOCs to enter soil in winter and spring, with 100 times higher flux than by particle phase. Source profiles for five zones were built by gas sampling with distinct substance indicators screened, which were used for positive matrix factorization factors determination. Contributions of the five zones were 14.9%, 20.8%, 13.6%, 22.1%, and 28.6% in winter and 33.4%, 12.5%, 10.7%, 24.9%, and 18.5% in spring, respectively. The variation in the soil sorption capacity of VOCs causes inter-seasonal differences in contribution. The better correlation between dry deposition capacity and soil storage of VOCs made root mean square and mean absolute errors decrease averagely by 8.8% and 5.5% in winter compared to spring. This study provides new perspectives and methods for the source apportionment of soil VOCs contamination in industrial sites.

Characteristics and sources of oxygenated VOCs in Hong Kong: Implications for ozone formation

To investigate the characteristics of oxygenated volatile organic compounds (OVOCs) and their potential contribution to ozone (O3) generation, we conducted 3-h high-resolution observations during the summertime of 2022 and the wintertime of 2021. This study focused on a total of 28 OVOCs in five different chemical classes, which were encompassed at two representative sites in Hong Kong, including a roadside and an urban area. During the summertime, the total concentrations of quantified OVOCs (∑OVOCs) were 45 ± 12 and 63 ± 20 μg m-3 at the roadside and urban sites, respectively, whereas the ∑OVOCs decreased by 31 ± 11 % and 38 ± 13 %, respectively, during the wintertime. Among the classes of OVOCs, carbonyls and alcohols were the two predominant at both sites, with relatively higher concentration levels of acetone, methanol, butanaldehyde, and acrolein. The sources of OVOCs have significant spatial and temporal characteristics. Spatially, OVOCs were predominately attributed to primary emission and background at the roadside site, whereas they were a combination of primary emission, secondary formation, and background at the urban site. Temporally, background sources dominated the summertime OVOCs, while the contribution of primary emissions increased for the wintertime OVOCs. The O3 formation potential (OFP) for the OVOCs was calculated. The OFPs were 67 ± 16 and 119 ± 31 μg m-3 at the roadside and urban sites during the summertime, whereas the winter OFPs declined 30 % at the roadside and 38 % at the urban site. The background sources of carbonyls and alcohols at the roadside and of carbonyls and acrylates in the urban area were the major contributors to the summer OFP. Controlling the OVOC sources from local non-combustion sources such as gasoline-fuel evaporation and volatile chemical-containing products could lead to a reduction of OVOCs in the background and subsequently mitigate the OFP. This is beneficial for local O3 reduction in Hong Kong and surrounding regions.

The underappreciated role of fugitive VOCs in ozone formation and health risk assessment emitted from seven typical industries in China

Fugitive emission from industrial sources may result in ozone formation and health risk, while the exact contribution of this source remains incompletely understood. In this study, emission characteristics, ozone formation potential (OFP) and health risk of fugitive VOCs in 7 representative industries were investigated. Chemical material industry was the dominant contributor to VOCs of fugitive emission in comparison with other industries. The OFP of VOCs from fugitive emission was in the range of 1.45 × 103-3.98 × 105 µg/m3, with a higher value than that of organized emission in seven industries except for the coking industry and the chemical material industry, suggesting that fugitive VOCs should be taken into account while developing control strategies. Acetaldehyde, m,p-xylene, n-nonane, ethylene, vinyl chloridethe and other high OFP-contributing species were the major reactive species that should be targeted. Health risk assessment investigated non-cancer and cancer risks of fugitive VOCs in 7 industries were all above safe level (HR > 1 and LCR > 1 × 10-4), posing remarkable health threats to human health. OVOCs were the main contributor to non-cancer risk, while halohydrocarbons and aromatics contributed most to cancer risks, posing remarkable health threat on human health. Our findings highlighted the contribution of fugitive VOCs on ozone formation and health risk was underestimated, indicating which should be considered in emission control strategies of industrial sources.

Passive air sampling of VOCs, O3, NO2, and SO2 in the large industrial city of Ulsan, South Korea: spatial-temporal variations, source identification, and ozone formation potential

Concerns about volatile organic compounds (VOCs) have increased due to their toxicity and secondary reaction with nitrogen oxides (NOX) to form ozone (O3). In this study, passive air sampling of VOCs, O3, NO2, and SO2 was conducted in summer, fall, winter, and spring from 2019 to 2020 at six industrial and ten urban sites in Ulsan, the largest industrial city in South Korea. Over the entire sampling period, the concentration of toluene (mean: 8.75 μg/m3) was the highest of the 50 target VOCs, followed by m,p-xylenes (4.52 μg/m3), ethylbenzene (4.48 μg/m3), 3-methylpentane (4.40 μg/m3), and n-octane (4.26 μg/m3). Total (Σ50) VOC levels did not statistically differ between seasons, indicating that large amounts of VOCs are emitted into the atmosphere throughout the year. On the other hand, O3, NO2, and SO2 exhibited strong seasonal variation depending on the meteorological conditions and emission sources. The spatial distribution of Σ50 VOCs, NO2, and SO2 indicated that industrial complexes were major sources in Ulsan, while O3 had the opposite spatial distribution. Using a positive matrix factorization model, five major sources were identified, with industrial effects dominant. Aromatic compounds, such as m,p,o-xylenes, toluene, and 1,2,4-trimethylbenzene, significantly contributed to O3 formation. The VOC/NO2 ratio and O3 concentrations suggested that reducing VOC emissions is more effective than reducing NO2 emissions in terms of preventing the secondary formation of O3. The findings of this study allow for a better understanding of the relationship between VOCs, O3, NO2, and SO2 in industrial cities.

Molecular mechanisms of 1,2-dichloroethane-induced neurotoxicity

The production of industrial solvents and adhesives often utilizes 1,2-dichloroethane (1,2-DCE), a highly toxic halogenated hydrocarbon compound. Occupational 1,2-DCE poisoning occurs frequently and is a public health concern. Exposure to 1,2-DCE can damage the brain, liver, and kidneys. The main and most severe damage caused by exposure to 1,2-DCE is to the nervous system, especially the central nervous system. Current research on 1,2-DCE mainly focuses on the mechanism of brain edema. Several possible mechanisms of 1,2-DCE neurotoxicity have been proposed, including oxidative stress, calcium overload, blood-brain barrier damage, and neurotransmitter changes. This article reviews the research progress on 1,2-DCE neurotoxicity and the mechanism behind it to provide a scientific basis for the prevention and treatment of 1,2-DCE poisoning.

Source-apportionment and spatial distribution analysis of VOCs and their role in ozone formation using machine learning in central-west Taiwan

This study assessed the machine learning based sensitivity analysis coupled with source-apportionment of volatile organic carbons (VOCs) to look into new insights of O₃ pollution in Yunlin County located in central-west region of Taiwan. One-year (Jan 1 to Dec 31, 2021) hourly mass concentrations data of 54 VOCs, NO_X, and O₃ from 10 photochemical assessment monitoring stations (PAMs) in and around the Yunlin County were analyzed. The novelty of the study lies in the utilization of artificial neural network (ANN) to evaluate the contribution of VOCs sources in O₃ pollution in the region. Firstly, the station specific source-apportionment of VOCs were carried out using positive matrix factorization (PMF)-resolving six sources viz. AAM: aged air mass, CM: chemical manufacturing, IC: Industrial combustion, PP: petrochemical plants, SU: solvent use and VE: vehicular emissions. AAM, SU, and VE constituted cumulatively more than 65% of the total emission of VOCs across all 10 PAMs. Diurnal and spatial variability of source-segregated VOCs showed large variations across 10 PAMs, suggesting for distinctly different impact of contributing sources, photo-chemical reactivity, and/or dispersion due to land-sea breezes at the monitoring stations. Secondly, to understand the contribution of controllable factors governing the O₃ pollution, the output of VOCs source-contributions from PMF model along with mass concentrations of NO_X were standardized and first time used as input variables to ANN, a supervised machine learning algorithm. ANN analysis revealed following order of sensitivity in factors governing the O₃ pollution: VOCs from IC > AAM > VE ≈ CM ≈ SU > PP ≈ NO_X. The results indicated that VOCs associated with IC (VOCs-IC) being the most sensitive factor which need to be regulated more efficiently to quickly mitigate the O₃ pollution across the Yunlin County.

A comprehensive investigation on source apportionment and multi-directional regional transport of volatile organic compounds and ozone in urban Zhengzhou

To understand the characteristics, source apportionment, and regional transport of volatile organic compounds (VOCs) and ozone (O₃) in a typical city with severe air pollution in central China, we observed and analyzed 115 VOC species at an urban site in Zhengzhou from 29 July to 26 September 2021. During this period, observation- and emission-based approaches revealed that Zhengzhou was in a VOC-limited regime. The average concentration of total VOCs (TVOCs) was 162.25 ± 71.42 μg/m³, dominated by oxygenated VOCs (OVOCs, 34.49%), alkanes (24.29%), and aromatics (19.49%). Six VOC sources were identified using positive matrix factorization (PMF) model, including paint solvent usage (25.32%), secondary production (24.11%), industrial production (19.22%), vehicle exhaust (16.18%), biogenic emission (8.87%), and combustion (6.30%). To assess the regional contribution and source apportionment of VOCs and O₃, Comprehensive Air Quality Model with Extensions (CAMx) with the Ozone Source Apportionment Technology (OSAT) was used for simulation. Results showed that the VOCs were significantly affected by local emissions (about 70%), while O₃ was mainly attributed to regional and super-regional transport. Regarding multi-directional regional transport of VOCs and O₃, dominant contributions were from the northeast and east-northeast directions, and O₃ contributions were also predominantly from the east and east-southeast directions. In terms of source apportionment, the transportation and industrial sectors (including solvent usage) were the major contributors to O₃ and VOCs. To alleviate VOCs and O₃ pollution, transportation and industrial emission reduction should be strengthened, and regional coordination, especially from the northeast to east-southeast directions, should be emphasized in addition to local management.

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.

Study on the Fingerprint and Atmospheric Activity of Volatile Organic Compounds from Typical Industrial Emissions

China is prone to severe surface ozone pollution in summer, so it is very important to understand the source of volatile organic compounds (VOCs) to control ozone formation. In this work, the emission characteristics of 91 VOC components from the plastic products industry, packaging and printing industries, printing ink industry, furniture manufacturing and vehicle manufacturing industries were studied. The results show that there are significant differences between these sources, and for the plastic products industry, alkanes (48%) are the most abundant VOCs. The main emission species in the packaging and printing industry are OVOCs (36%) and alkanes (34%). The proportion of OVOCs in the printing ink (73%) and furniture manufacturing industries (49%) is dominated by VOC emissions; aromatic hydrocarbons (33%), alkanes (33%), and OVOCs (17%) are the main emission species in the vehicle manufacturing industry. At the same time, the ozone generation potential (OFP) and secondary organic aerosol formation potential (SOA) of anthropogenic VOC emissions were evaluated, and the top 10 contributors to OFP and SOA were identified. Toluene, o-xylene, and m-xylene had a significant tendency to form OFP or SOA. Then, a health risk assessment of VOC components was carried out. These data can supplement the existing VOC emission characteristics of anthropogenic emissions, thus enriching the research progress of VOC emission sources.

Low-temperature degradation of toluene over Ag-MnOx-ACF composite catalyst

Volatile organic compounds (VOCs) have caused a serious threat to the atmosphere and human health. Therefore, it is of great significance to exploit effective catalytic materials for the safe and effective catalytic elimination of VOCs. Herein, Ag-MnO_x-ACF composite catalysts were constructed via a two-step impregnation strategy and used for catalytic toluene degradation. A remarkable low-temperature catalytic activity (T₁₀₀= 50℃), excellent stability, as well as CO₂ selectivity (80%) were achieved over the Ag-MnO_x-ACF catalyst. A series of characterizations indicated that the unique manganese defects structure of birnessite phase manganese oxide played an essential role for toluene oxidation, which was conducive to generating surface adsorbed oxygen. The higher ratio of Mn³⁺/Mn⁴⁺, abundant surface adsorbed oxygen and highly dispersed Ag species were determined to significantly facilitate toluene degradation. The mechanism of efficient degradation of toluene at low temperature was proposed. O₃ and H₂O molecules were activated via surface hydroxyl and Mn defects on Ag-MnO_x-ACF to produce sufficient •OH, enhancing the degradation performance of toluene. We provide a new idea for the catalytic oxidation of benzene VOCs at low even room temperatures.

Ambient volatile organic compounds in urban and industrial regions in Beijing: Characteristics, source apportionment, secondary transformation and health risk assessment

Field measurements of volatile organic compounds (VOCs) were conducted simultaneously at an urban site and one industrial park site in Beijing in summer. The VOCs concentrations were 94.3 ± 157.8 ppbv and 20.7 ± 8.9 ppbv for industrial and urban sites, respectively. Alkanes and aromatics were the major contributors to VOCs in industrial site, while oxygenated volatile organic compounds (OVOCs) contributed most in urban site. The most abundant VOC species were n-pentane and formaldehyde for industrial site and urban site, respectively. The calculated ozone formation potential (OFP) and OH loss rates (L_OH) were 621.1 ± 1491.9 ppbv (industrial site), 102.9 ± 37.3 ppbv (urban site), 22.0 ± 39.0 s^-1 (industrial site) and 5.3 ± 2.2 s^-1 (urban site), respectively. Based on the positive matrix factorization (PMF) model, solvent utilization I (34.1 %), solvent utilization II (27.9 %), mixture combustion source (19.3 %), OVOCs related source (9.6 %) and biogenic source (9.1 %) were identified in the industrial site, while OVOCs related source (27.8 %), vehicle exhaust (22.1 %), solvent utilization (19.3 %), coal combustion (16.0 %) and biogenic source (14.8 %) were identified in the urban site. The results of O₃-VOCs-NOx sensitivity indicated that O₃ formation were respectively under the VOC-limited and NOx-limited conditions in Beijing urban and industrial regions. Additionally, aromatics accounted remarkable SOA formation ability both in the two sites, and SOA potentials of xylene, toluene and ethylbenzene as the indicator species for the solvent utilization in industrial site were remarkable higher than those obtained in urban regions. The hazard index values in the industrial and urban sites were 1.72 and 3.39, respectively, suggesting a high non-carcinogenic risks to the exposed population. Formaldehyde had the highest carcinogenic risks in the two sites, and the cumulative carcinogenic risks in the industrial site and urban site were 1.95 × 10^-5 and 1.21 × 10^-5, respectively.

How a winding-down oil refinery park impacts air quality nearby?

It is always difficult to compare, let alone estimate, the difference of air pollutant concentrations before and after closure of a major source because the pollutants cannot be traced or predicted after entering the ambient. Indeed, we are not aware of any studies specifically related to the air pollutants impacted by a winding-down source. In this work, we applied nine years (2010-2018) online measurement of air pollutants (including PM₁₀, PM_2.5, NO₂, SO₂, O₃ and VOCs) to investigate (i) the temporal behavior of air pollutants before and after closure of an oil refinery park by using pair-wise statistics and correlations between wind speed and direction, and (ii) the source impacts on O₃ concentrations using PMF coupled with multiple linear regression (MLR) analysis (PMF-MLR). Example applications are presented at two monitoring sites (A and B) close to the Kaohsiung Oil Refinery (KOR), located in the southern industrial city of Taiwan. The results show that the KOR shutdown changed air pollutant concentrations to a certain extent in these study areas. We also conclude that, instead of using propylene-equivalent and ozone formation potential (OFP) concentrations, it is better to estimate the formation of O₃ based on PMF-MLR analysis as developed in this study. The PMF analysis has identified various VOCs sources at both sites including solvent usage, petrochemical industrial sources, industrial emissions, vehicle-related sources, vegetation emissions and aged air-masses. Also, the MLR model shows that both the background sources and petrochemical industrial sources may significantly change O₃ concentrations.

Characteristics of volatile organic compounds in the metropolitan city of Seoul, South Korea: Diurnal variation, source identification, secondary formation of organic aerosol, and health risk

Atmospheric volatile organic compounds (VOCs) in Seoul, the capital of South Korea, have attracted increased attention owing to their emission, secondary formation, and human health risk. In this study, we collected 24 hourly samples once a month at an urban site in Seoul for a year (a total of 288 samples) using a sequential tube sampler. Analysis results revealed that toluene (9.08 ± 8.99 μg/m³) exhibited the highest annual mean concentration, followed by ethyl acetate (5.55 ± 9.09 μg/m³), m,p-xylenes (2.79 ± 4.57 μg/m³), benzene (2.37 ± 1.55 μg/m³), ethylbenzene (1.81 ± 2.27 μg/m³), and o-xylene (0.91 ± 1.47 μg/m³), indicating that these compounds accounted for 77.8-85.6% of the seasonal mean concentrations of the total (Σ₅₉) VOCs. The concentrations of the Σ₅₉ VOCs were statistically higher in spring and winter than in summer and fall because of meteorological conditions, and the concentrations of individual VOCs were higher during the daytime than nighttime owing to higher human activities during the daytime. The conditional bivariate probability function and concentration weighted trajectory analysis results suggested that domestic effects (e.g., vehicular exhaust and solvents) exhibited a dominant effect on the presence of VOCs in Seoul, as well as long-range atmospheric transport of VOCs. Further, the most important secondary organic aerosol formation potential (SOAFP) compounds included benzene, toluene, ethylbenzene, and m,p,o-xylenes, and the total SOAFP of nine VOCs accounted for 5-29% of the seasonal mean PM_2.5 concentrations. The cancer and non-cancer risks of the selected VOCs were below the tolerable (1 × 10^-4) and acceptable (Hazard quotient: HQ < 1) levels, respectively. Overall, this study highlighted the feasibility of the sequential sampling of VOCs and hybrid receptor modeling to further understand the source-receptor relationship of VOCs.

A mixed spatial prediction model in estimating spatiotemporal variations in benzene concentrations in Taiwan

It is well known benzene negatively impacts human health. This study is the first to predict spatial-temporal variations in benzene concentrations for the entirety of Taiwan by using a mixed spatial prediction model integrating multiple machine learning algorithms and predictor variables selected by Land-use Regression (LUR). Monthly benzene concentrations from 2003 to 2019 were utilized for model development, and monthly benzene concentration data from 2020, as well as mobile monitoring vehicle data from 2009 to 2019, served as external data for verifying model reliability. Benzene concentrations were estimated by running six LUR-based machine learning algorithms; these algorithms, which include random forest (RF), deep neural network (DNN), gradient boosting (GBoost), light gradient boosting (LightGBM), CatBoost, extreme gradient boosting (XGBoost), and ensemble algorithms (a combination of the three best performing models), can capture how nonlinear observations and predictions are related. The results indicated conventional LUR captured 79% of the variability in benzene concentrations. Notably, the LUR with ensemble algorithm (GBoost, CatBoost, and XGBoost) surpassed all other integrated methods, increasing the explanatory power to 92%. This study establishes the value of the proposed ensemble-based model for estimating spatiotemporal variation in benzene exposure.

An integrated strategy by using long-term monitoring data to identify volatile organic compounds of high concern near petrochemical industrial parks

Exposure to ambient volatile organic compounds (VOCs) is associated with a risk of cancer in the residents living near petrochemical facilities. However, research on the contribution of different VOCs to the lifetime cancer risk remains inconclusive. The variability in source emissions, geographical locations, seasons, and meteorological conditions can be assessed through long-term measurement of ambient VOCs with a wide spatial distribution, thus reducing the uncertainty of health risk assessment from source emissions. This study analyzed comprehensive measurement data of 109 VOCs at 17 monitoring stations around petrochemical industrial parks, collected once every six days during 2015-2018 by the Taiwan Environmental Protection Agency. We calculated the annual mean concentration of selected VOCs and then integrated the probability risk assessment (PRA) and positive matrix factorization (PMF) models to identify the sources of VOCs of high concern. First, we prioritized 12 out of 23 carcinogenic VOCs based on the PRA results. Further, the results obtained from the PMF model revealed that petrochemical industrial parks contributed to more than 50% of the emissions of six VOCs, namely 1,3-butadiene, benzene, 1,2-dichloroethane, chloroform, vinyl chloride, and acrylonitrile, measured at a few monitoring stations. This integrated approach can help regulatory agencies to efficiently propose control strategies on the emissions of VOCs of high concern, thereby reducing the population's health risk.

Characterization of VOCs during Nonheating and Heating Periods in the Typical Suburban Area of Beijing, China: Sources and Health Assessment

In recent years, the “coal to electricity” project (CTEP) using clean energy instead of coal for heating has been implemented by Beijing government to cope with air pollution. However, VOC pollution after CTEP was rarely studied in suburbs of Beijing. To fill this exigency, 116 volatile organic compounds (VOCs) were observed during nonheating (P1) and heating (P2) periods in suburban Beijing. The results showed that the total of VOCs (TVOCs) was positively correlated with PM2.5, PM10, NO2, CO, and SO2 but negatively correlated with O3 and wind speed. The average TVOCs concentration was 19.43 ± 12.41 ppbv in P1 and 16.25 ± 8.01 ppbv in P2. Aromatics and oxygenated VOCs (OVOCs) were the main contributors to ozone formation potential (OFP). Seven sources of VOCs identified by the positive matrix factorization (PMF) model were industrial source, coal combustion, fuel evaporation, gasoline vehicle exhaust, diesel vehicle exhaust, background and biogenic sources, and solvent usage. The contribution of coal combustion to VOCs increased significantly during P2, whereas industrial sources, fuel evaporation, and solvent usage exhibited opposite trends. The potential source contribution function (PSCF) and concentration weighted trajectory (CWT) were used to analyze the source distributions. The results showed that VOC pollution was caused mainly by air mass from southern Hebei during P1 but by local emissions during P2. Therefore, although the contribution of coal combustion after heating increased, TVOCs concentration during P2 was lower than that during P1. Chronic noncarcinogenic risks of all selected VOC species were below the safe level, while the carcinogenic risks of most selected VOC species were above the acceptable risk level, especially for tetrachloromethane and 1,2-dichloroethane. The cancer risks posed by gasoline vehicle emissions, industrial enterprises, and coal combustion should be paid more attention.

Exploration of O3-precursor relationship and observation-oriented O3 control strategies in a non-provincial capital city, southwestern China

To investigate photochemical ozone (O₃) formation and provide localized control strategies, an intensive sampling of O₃ and its precursors (i.e. volatile organic compounds (VOCs) and nitrogen oxides (NO_x = NO + NO₂)) were conducted at an urban site in Leshan, Sichuan province during 4-13 August 2019. The mixing ratios of O₃, total VOCs (TVOCs) and NO_x were 40.0 ± 5.3, 22.5 ± 2.6 and 14.6 ± 3.8 ppbv, respectively (±95% confidence intervals). O₃ and its precursors existed a well negative correlation, indicating intensive local O₃ formation. To further explore the O₃-precursors relationship and observation-oriented O₃ control strategies, a photochemical box model coupled with master chemical mechanism (PBM-MCM) was adapted. The relative incremental reactivity (RIR) calculated by model results showed that Leshan was in the VOCs-limited and O₃ production was most sensitive to alkenes. Moreover, O₃ isopleth diagram was drawn using the PBM-MCM simulation results and seven reduction scenarios were evaluated in Leshan. The reduction ratio of VOCs/NO_x on 3:1 was proposed to be the best solution, which can be achieved effective reduction on local O₃ formation. At last, since VOCs were the key precursors of O₃ in Leshan, VOC sources and their potential contributions to O₃ formation were investigated by using the positive matrix factorization (PMF) model. Seven sources were identified, and traffic related emissions (including vehicle exhaust and gasoline evaporation, 29.9%) and fixed combustion (27.7%) had the large contribution to ambient VOCs. Among anthropogenic sources, fixed combustion and solvent usage in painting were the large contributors to O₃ formation, accounting for 30.9% and 18.3%, respectively, which should have high priorities on source reduction. This study provides scientific advices for future O₃ pollution control strategies in Leshan, which can be extended to other cities.

Characteristics and health risks of benzene series and halocarbons near a typical chemical industrial park

Health risks of typical benzene series and halocarbons (BSHs) in a densely populated area near a large-scale chemical industrial park were investigated. Ambient and indoor air and tap water samples were collected in summer and winter; and the concentration characteristics, sources, and exposure risks of typical BSH species, including five benzene series (benzene, toluene, ethylbenzene, o-xylene, m,p-xylene) and five halocarbons (dichloromethane, trichloromethane, trichloroethylene, tetrachloromethane, and tetrachloroethylene), were analysed. The total mean concentrations of BSHs were 53.32 μg m^-3, 36.29 μg m^-3, and 26.88 μg L^-1 in indoor air, ambient air, and tap water, respectively. Halocarbons dominated the total BSHs with concentrations relatively higher than those in many other industrial areas. Industrial solvent use, industrial processes, and vehicle exhaust emissions were the principal sources of BSHs in ambient air. The use of household products (e.g., detergents and pesticides) was the principal source of indoor BSHs. Inhalation is the primary human exposure route. Ingestion of drinking water was also an important exposure route but had less impact than inhalation. Lifetime non-cancer risks of individual and cumulative BSHs were below the threshold (HQ = 1), indicating no significant lifetime non-cancer risks in the study area. However, tetrachloromethane, benzene, trichloromethane, ethylbenzene, and trichloroethylene showed potential lifetime cancer risk. The cumulative lifetime cancer risks exceeded the tolerable benchmark (1 × 10^-4), indicating a lifetime cancer risk of BSHs to residents near the chemical industry park. This study provides valuable information for the management of public health in chemical industrial parks.

1,2-Dichloroethane induces apoptosis in the cerebral cortexes of NIH Swiss mice through microRNA-182-5p targeting phospholipase D1 via a mitochondria-dependent pathway

1,2-Dichloroethane (1,2-DCE) is a pervasive environmental pollutant found in ambient and residential air, as well as ground and drinking water. Overexposure to it results in cortex edema, in both animals and humans. 1,2-DCE induces apoptosis in the cerebellum, liver and testes. This promotes the hypothesis that 1,2-DCE may induce apoptosis in the cortex as brain edema progresses. To validate our hypothesis, 40 NIH male mice were exposed to 0, 100, 350, 700 mg/m³ 1,2-DCE by whole-body dynamic inhalation for 28 consecutive days. MicroRNA (miRNA) and mRNA microarray combined with TdT-mediated dUTP nick-end labeling, flow cytometry, and mitochondrial membrane potential (mtΔΨ) measurement were applied to identify the cortex apoptosis pathways' specific responses to 1,2-DCE, in vitro and in vivo. The results showed that 1,2-DCE caused brain edema and increased apoptosis in the mouse cortexes. We confirmed that 1,2-DCE induced increased apoptosis via mitochondrial pathway, both in vitro and in vivo, as evidenced by increased Caspase-3, cleaved Caspase-3, Cytochrome c and Bax expression, and decreased Bcl-2 expression. Additionally, mtΔΨ decreased after 1,2-DCE treatment in vitro. 1,2-DCE exposure increased miR-182-5p and decreased phospholipase D1 (PLD1) in the cerebral cortex of mice. MiR-182-5p overexpression and PLD1 inhibition reduced mtΔΨ and increased astrocyte apoptosis, yet miR-182-5p inhibition alleviated the 1,2-DCE-induced PLD1 down-regulation and the increased apoptosis. Finally, PLD1 was confirmed to be a target of miR-182-5p by luciferase assay. Taken together, our findings indicate that 1,2-DCE exposure induces apoptosis in the cortex via a mitochondria-dependent pathway. This pathway is regulated by a miR-182-5p⊣PLD1 axie.

Compositions, sources, and potential health risks of volatile organic compounds in the heavily polluted rural North China Plain during the heating season

Severe volatile organic compound (VOC) pollution has become an urgent problem during the heating season in the North China Plain (NCP), as exposure to hazardous VOCs can lead to chronic or acute diseases. A campaign with online VOC measurements was conducted at a rural site in Wangdu, NCP during the 2018 heating season to characterize the compositions and associated sources of VOCs and to assess their potential health risks. The total concentration of VOCs with 94 identified species was 77.21 ± 54.39 ppb. Seven source factors were identified by non-negative matrix factorization, including coal combustion (36.1%), LPG usage (21.1%), solvent usage (13.9%), biomass burning and secondary formation (14.2%), background (7.0%), industrial emissions (4.5%), and vehicle emissions (3.3%). The point estimate approach and Monte Carlo simulation were used to estimate the carcinogenic and non-carcinogenic risks of harzadous VOCs. The results showed that the cumulative health risk of VOCs was above the safety level. Acrolein, 1.2-dichloroethane, 1,2-dichloropropane, chloroform, 1,3-butadiene, and benzene were identified as the key hazardous VOCs in Wangdu. Benzene had the highest average carcinogenic risk. Solvent usage and secondary formation were the dominant sources of adverse health effects. During the Spring Festival, most sources were sharply reduced; and VOC concentration declined by 49%. However, coal and biomass consumptions remained relatively large, probably due to heating demand. This study provides important references for the control strategies of VOCs during the heating season in heavily polluted rural areas in the NCP.

An integrated geospatial correlation analysis and human health risk assessment approach for investigating abandoned industrial sites

An integrated geospatial correlation analysis (GCA)-human health risk assessment (HHRA) approach was developed to investigate abandoned industrial sites featured by heterogeneous contamination data. Critical areas of high health risk concerns can be prioritized for remediation using the integrated approach. An abandoned chemical complex site in Hubei, China was investigated as a case study. GCA and HHRA were performed using soil and groundwater sampling data collected in 2016 and 2019. Benzene, chlorobenzene, dichlorobenzenes, 2-nitrochlorobenzene, and α-hexachlorocyclohexane were determined to be critical contaminants in soil. The 2019 sampling data revealed new contaminated locations that were not found in the 2016 sampling campaign. High concentrations (89.81-386.55 mg/L) of vinyl chloride were also found in groundwater samples. Several critical location clusters of high concentrations of dichlorobenzenes, chlorobenzene, and α-hexachlorocyclohexane were found within the site according to the GCA outcomes. These contaminants could pose significant cancer and non-cancer risks to onsite workers. The critical areas were ranked according to cancer and non-cancer risks estimated by HHRA, respectively, for informed remediation planning. Among the critical contaminants, α-hexachlorocyclohexane, 2-nitrochlorobenzene, and 1,4-dichlorobenzene in soil, as well as vinyl chloride in groundwater, contributed a predominant part to the total health risk. The integrated approach can be used to assess the contamination of other similar abandoned industrial complex sites.

Cancer risk assessment for exposure to hazardous volatile organic compounds in Calgary, Canada

Oil and natural gas (O&G) extraction operations emit hazardous volatile organic compounds (VOCs) in quantities that have adverse effects on human health. Our current understanding of the exposure risks associated with upstream O&G exploitations remains limited, and very few quantitative on-site remediation strategies have been proposed. To this end, we assessed the health risks associated with the emission of hazardous VOCs and presented a set of remediation goals for the city of Calgary, which is a major center of the Canadian oil industry. Results from probabilistic risk assessment (PRA) suggested that although VOCs had a negligible impact on chronic non-cancer-associated risk, inhalation-associated cancer risk remained a significant concern. Carbon tetrachloride, benzene, and 1,3-butadiene were the dominant VOCs, representing 88% of the integrated inhalation cancer risk (= 7.8 × 10^-5); background, solid fuel combustion, and O&G extraction were among the primary sources that posed the greatest threat to human health. Results of a Monte Carlo simulation revealed that the probability of developing cancer due to inhalation of hazardous VOCs was ∼13.1% on clean air days and 45.9% on days with significant levels of air pollution. Preliminary remediation goals (PRGs) included reductions of 24.2-65.1% and 11.4-50.9% targeting priority VOCs and their sources, respectively. Taken together, our findings suggest that stringent control of the sources of VOCs, particularly fossil fuel combustion, is an urgent priority. PRA coupled with PRGs provides informative risk assessments and suggests quantitative remediation strategies that can be applied toward improved management of hazardous pollutants.

Source profiles, emission factors and associated contributions to secondary pollution of volatile organic compounds (VOCs) emitted from a local petroleum refinery in Shandong

An in-depth study was conducted to quantify and characterize VOC emissions from a petroleum refinery located in Shandong, China. The VOC emission inventory established in this study showed that storage tanks were the largest emission source, accounting for 56.4% of total emissions, followed by loading operations, wastewater collection and treatment system, process vents, and equipment leaks. Meanwhile, the localization factors for refining, storage tanks and loading operations were calculated, which were 1.33, 0.75 and 0.31g VOCs/kg crude oil refined. Furthermore, the characteristics of fugitive and organized emissions were determined for various processes and emission sources using a gas chromatography-mass spectrometry/flame ionization detection (GC-MS/FID) system. Most samples contained mainly alkanes, but the total VOC concentrations and key species varied greatly among processes. The source profile of the refinery, synthesized using the weighted average method, indicated that cis-2-butene (14.5%), n-pentane (10.2%), n-butane (7.4%), isopentane (6.5%) and MTBE (5.9%) were the major species released by this refinery. Assessment of O₃ and secondary organic aerosol formation potentials were completed, and the results indicated that cis-2-butene, m/p-xylene, toluene, n-pentane, isopentane, benzene, o-xylene and ethylbenzene were the active species for which treatment should be prioritized.

Predicting carbonaceous aerosols and identifying their source contribution with advanced approaches

Organic carbon (OC) and elemental carbon (EC) play important roles in various atmospheric processes and health effects. Predicting carbonaceous aerosols and identifying source contributions are important steps for further epidemiological study and formulating effective emission control policies. However, we are not aware of any study that examined predictions of OC and EC, and this work is also the first study that attempted to use machine learning and hyperparameter optimization method to predict concentrations of specific aerosol contaminants. This paper describes an investigation of the characteristics and sources of OC and EC in fine particulate matter (PM_2.5) from 2005 to 2010 in the City of Taipei. Respective hourly average concentrations of OC and EC were 5.2 μg/m³ and 1.6 μg/m³. We observed obvious seasonal variation in OC but not in EC. Hourly and daily OC and EC concentrations were predicted using generalized additive model and grey wolf optimized multilayer perceptron model, which could explain up to about 80% of the total variation. Subsequent clustering suggests that traffic emission was the major contribution to OC, accounting for about 80% in the spring, 65% in the summer, and 90% in the fall and winter. In the Taipei area, local emissions were the dominant sources of OC and EC in all seasons, and long-range transport had a significant contribution to OC and in PM_2.5 in spring.

Air pollution diffusion simulation and seasonal spatial risk analysis for industrial areas

The petrochemical industry produces many air pollutants during production, such as airborne particulate matters (PM₁₀ and PM_2.5), sulfur oxides, nitrogen oxides, volatile organic compounds, carbon oxides, etc. Petrochemical industrial accidents are more likely to cause major air pollution hazards in a short period. Therefore this study simulated diffusion and performed air pollution spatial risk analysis for potential air pollutants generated by the petrochemical industry using meteorological observation data from 2017 to 2019. The study targets were No. 6 Naphtha Cracker Complex Petrochemical Industrial Park (6NCC) of Formosa Petrochemical Corporation and Taichung Thermal Power Plant (TTPP) in central Taiwan. We used the industrial source complex model short term (ISCST3) air simulation model developed by the US Environmental Protection Agency to simulate pollutant diffusion under different weather conditions and seasons. Air pollution spatial risk was investigated for neighboring hospitals and schools for pollutant emission and diffusion to provide feedback to petrochemical related industry's risk management. Emission areas (6NCC and TTPP) were all in the southwest since the main air pollution accumulation and diffusion is to the northeast during monsoon season (October through March). Air pollution April through September each year is more evenly distributed, with pollutant concentrations low in all directions, approximately half the concentration in winter. Simulated air pollutant concentrations often overlapped with high risk population clusters (schools and hospitals). 6NCC posed little impact on nearby schools throughout the year; whereas TTPP posed relatively low risks to nearby schools and hospitals in summer, with slightly higher risk for Shenren Elementary School in Shengang township, Changhua County in winter. Overall 6NCC posed higher risk for Mailiao and Taixi townships in Yunlin County; whereas the TTPP posed higher risk on Longjing District of Taichung City, Shengang and Xianxi townships in Changhua County, particularly during winter. The results of this study will help the petrochemical industry and public health authority to wider manage air pollution risks.

Variations in Levels and Sources of Atmospheric VOCs during the Continuous Haze and Non-Haze Episodes in the Urban Area of Beijing: A Case Study in Spring of 2019

To better evaluate the variations in concentration characteristics and source contributions of atmospheric volatile organic compounds (VOCs) during continuous haze days and non-haze days, hourly observations of atmospheric VOCs were conducted using a continuous on-line GC-FID (Airmo VOC GC-866) monitoring system during 1–15 March 2019, in urban areas of Beijing, China. The results showed that the total VOC concentrations during haze days and non-haze days were 59.13 ± 31.08 μg/m3 and 16.91 ± 7.19 μg/m3, respectively. However, the average O3 concentrations during the two haze days were lower than those of non-haze days due to the extremely low concentrations at night instead of the reported lower photochemical reaction in daytime. The ratio of OH radical concentration during haze and non-haze days indicating that the rate of photochemical reaction during haze days was higher than those of non-haze days from 13:00–19:00. The stable air conditions and the local diesel emission at night were the main reasons for the decreased O3 concentrations during haze days. Six major sources were identified by positive matrix factorization (PMF), namely, diesel exhaust, combustion, gasoline evaporation, solvent usage, gasoline exhaust, and the petrochemical industry, contributing 9.93%, 25.29%, 3.90%, 16.88%, 35.59% and 8.41%, respectively, during the whole observation period. The contributions of diesel exhaust and the petrochemical industry emissions decreased from 26.14% and 6.43% during non-haze days to 13.70% and 2.57%, respectively, during haze days. These reductions were mainly ascribed to the emergency measures that the government implemented during haze days. In contrast, the contributions of gasoline exhaust increased from 34.92% during non-haze days to 48.77% during haze days. The ratio of specific VOC species and PMF both showed that the contributions of gasoline exhaust emission increased during haze days. The backward trajectories, potential source contribution function (PSCF) and concentration weighted trajectory (CWT) showed that the air mass of VOCs during haze days was mainly affected by the short-distance transportation from the southwestern of Hebei province. However, the air mass of VOCs during non-haze days was mainly affected by the long-distance transportation from the northwest.

Process-based VOCs source profiles and contributions to ozone formation and carcinogenic risk in a typical chemical synthesis pharmaceutical industry in China

The chemical synthesis pharmaceutical industry plays an important role in VOCs emissions from industrial sources, which has caused increasing concern. In this study, the process-based pollution characteristics of VOCs from the chemical synthesis pharmaceutical industry were investigated in the Yangtze River Delta, China. A total of 16 samples were collected from 12 process units (including 5 production lines and 2 postprocessing units) and 2 factory boundary sites. 116 VOCs species were analyzed and sorted into 6 classes, including alkanes, alkenes, acetylene, aromatics, halocarbons and oxygenated VOCs (OVOCs). The concentration of stack VOCs was 3.37 × 10⁴ μg·m^-3, while the concentration of fugitive VOCs from other process units ranged from 827 μg·m^-3 to 2.11 × 10⁴ μg·m^-3. Aromatics, halocarbons and OVOCs accounted for a relatively high proportion in all process units. Process-based source profiles of each process unit were compiled. Generally, toluene, dichloromethane, ethanol, methanol and acetone were the most abundant species in all process units. Furthermore, the process-based ozone formation potentials (OFPs) and carcinogenic risk potentials (CRPs) were calculated, suggesting that toluene, methanol, ethanol and m/p-xylene should be preferentially controlled to reduce the OFPs, while acetaldehyde and chloroform were the priority control species to reduce the CRPs. Further discussion showed that ambient VOCs pollution at the factory boundary was affected by both stack and fugitive sources from the production process. The source profiles built in this study are necessary addition to the current profiles and are a good reference to study VOCs emission characteristics from the perspective of the process procedure. The results obtained from this work provide a guidance for effective VOCs abatement strategies and further lay a foundation for related research on VOCs in the chemical synthesis pharmaceutical industry.

A Review of Volatile Organic Compound Contamination in Post-Industrial Urban Centers: Reproductive Health Implications Using a Detroit Lens

Volatile organic compounds (VOCs) are a group of aromatic or chlorinated organic chemicals commonly found in manufactured products that have high vapor pressure, and thus vaporize readily at room temperature. While airshed VOCs are well studied and have provided insights into public health issues, we suggest that belowground VOCs and the related vapor intrusion process could be equally or even more relevant to public health. The persistence, movement, remediation, and human health implications of subsurface VOCs in urban landscapes remain relatively understudied despite evidence of widespread contamination. This review explores the state of the science of subsurface movement and remediation of VOCs through groundwater and soils, the linkages between these poorly understood contaminant exposure pathways and health outcomes based on research in various animal models, and describes the role of these contaminants in human health, focusing on birth outcomes, notably low birth weight and preterm birth. Finally, this review provides recommendations for future research to address knowledge gaps that are essential for not only tackling health disparities and environmental injustice in post-industrial cities, but also protecting and preserving critical freshwater resources.

Temporal variations and source apportionment of volatile organic compounds at an urban site in Shijiazhuang, China

Shijiazhuang, the city with the worst air quality in China, is suffering from severe ozone pollution in summer. As the key precursors of ozone generation, it is necessary to control the Volatile Organic Compounds (VOCs) pollution. To have a better understanding of the pollution status and source contribution, the concentrations of 117 ambient VOCs were analyzed from April to August 2018 in an urban site in Shijiazhuang. Results showed that the monthly average concentration of total VOCs was 66.27 ppbv, in which, the oxygenated VOCs (37.89%), alkanes (33.89%), and halogenated hydrocarbons (13.31%) were the main composite on. Eight major sources were identified using Positive Matrix Factorization modeling with an accurate VOCs emission inventory as inter-complementary methods revealed that the petrochemical industry (26.24%), other industrial sources (15.19%), and traffic source (12.24%) were the major sources for ambient VOCs in Shijiazhuang. The spatial distributions of major industrial activities emissions were identified by using geographic information statistics system, which illustrated the VOCs was mainly from the north and southeast of Shijiazhuang. The inverse trajectory analysis using Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) and Potential Source Contribution Function (PSCF) clearly demonstrated the features of pollutant transport to Shijiazhuang. These findings can provide references for local governments regarding control strategies to reduce VOCs emissions.

A Systematic Review of Air Quality Sensors, Guidelines, and Measurement Studies for Indoor Air Quality Management

The existence of indoor air pollutants—such as ozone, carbon monoxide, carbon dioxide, sulfur dioxide, nitrogen dioxide, particulate matter, and total volatile organic compounds—is evidently a critical issue for human health. Over the past decade, various international agencies have continually refined and updated the quantitative air quality guidelines and standards in order to meet the requirements for indoor air quality management. This paper first provides a systematic review of the existing air quality guidelines and standards implemented by different agencies, which include the Ambient Air Quality Standards (NAAQS); the World Health Organization (WHO); the Occupational Safety and Health Administration (OSHA); the American Conference of Governmental Industrial Hygienists (ACGIH); the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE); the National Institute for Occupational Safety and Health (NIOSH); and the California ambient air quality standards (CAAQS). It then adds to this by providing a state-of-art review of the existing low-cost air quality sensor (LCAQS) technologies, and analyzes the corresponding specifications, such as the typical detection range, measurement tolerance or repeatability, data resolution, response time, supply current, and market price. Finally, it briefly reviews a sequence (array) of field measurement studies, which focuses on the technical measurement characteristics and their data analysis approaches.

Emission characteristics and associated assessment of volatile organic compounds from process units in a refinery

The accuracy and reliability of volatile organic compound (VOC) emission data are essential for assessing emission characteristics and their potential impact on air quality and human health. This paper describes a new method for determining VOC emission data by multipoint sampling from various process units inside a large-scale refinery. We found that the emission characteristics of various production units were related to the raw materials, products, and production processes. Saturated alkanes accounted for the largest fraction in the continuous catalytic reforming and wastewater treatment units (48.0% and 59.2%, respectively). In the propene recovery unit and catalytic cracking unit, alkenes were the most dominant compounds, and propene provided the largest contributions (57.8% and 23.0%, respectively). In addition, n-decane (12.6%), m,p-xylene (12.4%), and n-nonane (8.9%) were the main species in the normal production process of the delayed coking unit. Assessments of photochemical reactivity and carcinogenic risk were carried out, and the results indicate that VOC emissions from the propene recovery unit and catalytic cracking unit should be controlled to reduce the ozone formation potential; in addition, alkenes are precedent-controlled pollutants. The cancer risk assessments reveal that 1,2-dibromoethane, benzene, 1,2-dichloroethane, and chloroform were the dominant risk contributors, and their values were much higher than the standard threshold value of 1.0 × 10^-6 but lower than the significant risk value defined by the US Supreme Court. Based on the VOC composition and a classification algorithm, the samples were classified into eight main groups that corresponded to different process units in the petroleum refinery. In conclusion, this work provides valuable data for investigating process-specific emission characteristics of VOCs and performing associated assessments of photochemical reactivity and carcinogenic risk in petrochemical refineries.

Kriging-Based Land-Use Regression Models That Use Machine Learning Algorithms to Estimate the Monthly BTEX Concentration

This paper uses machine learning to refine a Land-use Regression (LUR) model and to estimate the spatial–temporal variation in BTEX concentrations in Kaohsiung, Taiwan. Using the Taiwanese Environmental Protection Agency (EPA) data of BTEX (benzene, toluene, ethylbenzene, and xylenes) concentrations from 2015 to 2018, which includes local emission sources as a result of Asian cultural characteristics, a new LUR model is developed. The 2019 data was then used as external data to verify the reliability of the model. We used hybrid Kriging-land-use regression (Hybrid Kriging-LUR) models, geographically weighted regression (GWR), and two machine learning algorithms—random forest (RF) and extreme gradient boosting (XGBoost)—for model development. Initially, the proposed Hybrid Kriging-LUR models explained each variation in BTEX from 37% to 52%. Using machine learning algorithms (XGBoost) increased the explanatory power of the models for each BTEX, between 61% and 79%. This study compared each combination of the Hybrid Kriging-LUR model and (i) GWR, (ii) RF, and (iii) XGBoost algorithm to estimate the spatiotemporal variation in BTEX concentration. It is shown that a combination of Hybrid Kriging-LUR and the XGBoost algorithm gives better performance than other integrated methods.

Formaldehyde and VOC emissions from plywood panels bonded with bio-oil phenolic resins

Pyrolysis bio-oil was used to partially substitute for phenol in reacting with formaldehyde for the production of bio-oil phenol formaldehyde plywood (BPFP) panels, with the phenol substitution ratio being 20%, 40%, or 60%. Emissions of formaldehyde and volatile organic compounds (VOCs) from the BPFP panels were studied using solid-phase micro-extraction (SPME) followed by headspace gas chromatography/mass spectrometry (GC/MS), and were compared to those from the phenol formaldehyde plywood (PFP) panels. The sources for VOCs were analyzed, and the health risks associated with the BPFP were examined. Results showed that at 80 °C: (1) Formaldehyde emissions from the BPFP panels were increased to about 4 times that of PFP; (2) VOCs emissions were significantly reduced by up to 84.9% mainly due to the greatly reduced phenol emissions, although the total number of VOCs was increased from 20 to 35; (3) BPFP presents greatly increased carcinogenic and non-carcinogenic health risks because of its much stronger emissions of formaldehyde, N,N-dimethylformamide, benzofuran, furfural, and many chemicals from the bio-oil. It is highly advisable that the health risks are properly taken care of before the wide application of BPFP, or similar bio-oil based engineered wood products.

Characteristics of atmospheric volatile organic compounds in urban area of Beijing: Variations, photochemical reactivity and source apportionment

Atmospheric volatile organic compounds (VOCs) were observed by an on-line gas chromatography-flame ionization detector monitoring system from November 2016 to August 2017 in Beijing. The average concentrations were winter (40.27 ± 25.25 μg/m³) > autumn (34.25 ± 19.90 µg/m³) > summer (32.53 ± 17.39 µg/m³) > spring (24.72 ± 17.22 µg/m³). Although benzene (15.70%), propane (11.02%), ethane (9.32%) and n-butane (6.77%) were the most abundant species, ethylene (14.07%) and propene (11.20%) were the key reactive species to ozone formation potential (OFP), and benzene, toluene, ethylbenzene, m-xylene + p-xylene and o-xylene (54.13%) were the most reactive species to secondary organic aerosol formation potential (SOAFP). The diurnal and seasonal variations indicated that diesel vehicle emission during early morning, gasoline vehicle emission at the traffic rush hours and coal burning during the heating period might be important sources. Five major sources were further identified by positive matrix factorization (PMF). The vehicle exhaust (gasoline exhaust and diesel exhaust) was found to be contributed most to atmospheric VOCs, with 43.59%, 41.91%, 50.45% and 43.91%, respectively in spring, summer, autumn and winter; while solvent usage contributed least, with 11.10%, 7.13%, 14.00% and 19.87%, respectively. Biogenic emission sources (13.11%) were only identified in summer. However, both vehicle exhaust and solvent usage were identified to be the key sources considering contributions to the OFP and SOAFP. Besides, the contributions of combustion during heating period and gasoline evaporation source during warm seasons to OFP and SOAFP should not be overlooked.

Effective removal of aromatic pollutants via adsorption and photocatalysis of porous organic frameworks

PAF-45 with a wholly aromatic framework, intrinsic microporosity and π-π conjugation system shows excellent performance in aromatic pollutant removal. It exhibits a high adsorption capacity for the benzene series and moderate photocatalytic performance. As an adsorbent, PAF-45 can adsorb 35 wt% benzene and 68 wt% chlorobenzene in static adsorption experiments at room temperature and pressure. In benzene simulation wastewater, PAF-45 also shows excellent adsorption capacity, without significant reduction after 10 cycles of the adsorption-desorption process. Moreover, PAF-45 exhibits an impressive photocatalytic degradability of aromatic compounds, like aniline and phenol, under visible light illumination.

Health risks for the population living near petrochemical industrial complexes. 1. Cancer risks: A review of the scientific literature

Petrochemical complexes and oil refineries are well known sources of a wide range of environmental pollutants. Consequently, the potential harmful health effects of living near these facilities is a topic of concern among the population living in the neighborhood. Anyhow, the number of studies carried out on this issue is rather limited and, in some cases, results are even slightly contradictory. The present Review was aimed at assessing whether living in the vicinity of petrochemical industries and oil refineries is associated with a higher incidence of cancer and cancer mortality. In this sense, up to 23 investigations were found in PubMed and Scopus databases. According to the type of cancer, leukemia and other hematological malignancies were reported as the main types of cancer for populations living in the neighborhood of petrochemical industries. This was concluded based on studies performed in Taiwan, Spain, United Kingdom, Italy and Nigeria. In contrast, no association was found in 4 different investigations conducted in Sweden, Finland and USA with the same purpose. Other scientific studies reported a high incidence of lung and bladder cancer in Taiwan, Italy and USA, as well as an excess mortality of bone, brain, liver, pleural, larynx and pancreas cancers in individuals living near petrochemical complexes from Taiwan, Spain, Italy, United Kingdom and USA. Thus, human exposure to certain carcinogenic pollutants emitted from petrochemical industries might increase the incidence of some cancers and cancer mortality. Anyway, since the limited number of investigations conducted until now, further studies are required in order to corroborate -in a more generalized way-this conclusion.

Temporal and spatial distribution characteristics and source origins of volatile organic compounds in a megacity of Sichuan Basin, China

As important pollution gases and represented precursors of both ozone and second organic aerosol (SOA), the component characteristics, source origins, environmental health and emission control of volatile organic compounds (VOCs), are gaining more and more attention in Chinese megacities. In order to understand the concentration, composition and temporal and spatial distribution characteristics of VOCs in the atmosphere of Chengdu, a megacity located in Sichuan basin in southwest China, the offline sampling measurements of VOCs were carried out at 28 different field sites covering all the districts and counties of Chengdu during special periods from May 2016 to January 2017. Speciated VOCs measurement was performed by the GC-FID/MS, and 99 species were identified. The averaged total VOC mixing ratios of each sampling site were in the range from 35.03 to 180.57 ppbv. Based on these observational data, the distribution characteristics of VOCs in different months and different regions of Chengdu were clarified. The VOCs data were used to estimate the potential amount of ozone, secondary aerosol formation and health risk assessment in Chengdu. Furthermore, the positive matrix factorization (PMF) model was used to identify the dominant emission sources and evaluate their contribution to VOCs in the city. The two main sources of VOCs in Chengdu were motor vehicle exhaust and solvent utilization. These accounted for 43% of all emission sources. In the summertime, due to higher temperatures and stronger sunlight, the contribution of natural sources and secondary emissions were also relatively high, which were supported by the regional emission inventories. Finally, the controlling direction of VOCs and O₃ pollution in Chengdu was discussed, and the VOCs pollution control strategy was proposed for the near future.

Definition of an Emission Factor for VOC Emitted from Italian and European Refineries

Refineries are a major source of atmospheric emissions, which typically include CO, SO2, NOX, particulates, and volatile organic compounds (VOCs). There has been an increasing level of attention toward the emissions of VOCs related to their environmental impact as well as their potential to cause adverse effects on human health and the discomfort associated with their unpleasant odor. In general, an emission factor (EF) represents a model for a first order estimate of emissions, which correlates the quantity of pollutant released into the atmosphere with a so-called “activity index” related to the release of that pollutant. Based on the study of the scientific and technical literature regarding the Italian and European refining scenarios, an attempt was made to verify the existence of a correlation between the size of a refinery and the related total VOC emissions. Once this correlation was evaluated, it was possible to develop an emission factor for VOC emissions considering the plant capacity as the related activity index. After collecting and analyzing data concerning operative capacity and total VOCs emitted from 15 refineries in 2018, the resulting emission factor turned out to be equal to 188 ± 166 g per ton of crude oil processed. This value is in agreement with the range of 50–1000 g/ton reported in the European Best Available Techniques Reference Document for the Refining of Mineral Oil and Gas.

Volatile organic compounds in Shihezi, China, during the heating season: pollution characteristics, source apportionment, and health risk assessment

From November 2018 to March 2019, the mixing ratios of 57 types of volatile organic compounds (VOCs) were measured using gas chromatography-mass spectrometry in Shihezi. The results depicted that the average mixing ratios of VOCs were 58.48 ppbv and alkanes (34.15 ppbv) showed the largest contribution, followed by ethyne (20.16 ppbv), alkenes (2.62 ppbv), and aromatics (1.55 ppbv). Based on the positive matrix factorization (PMF) model result, coal burning (39.83%), traffic-related exhaust (26.87%), liquefied petroleum gas/natural gas usage (LPG/NG) (17.32%), fuel evaporation and paint usage (9.02%), and industrial emission (6.96%) were distinguished. Secondary formation potential was applied to demonstrate the probability of secondary pollution; the results indicated that alkanes (27.30 ppbv) and alkenes (21.42 ppbv) played leading roles in ozone formation potential (OFP) and the contributions of alkanes (1.05 μg/m³) and aromatics (0.99 μg/m³) were nearly equal for secondary organic aerosol formation potential (SOAFP) under high-NOx condition. However, under a low-NOx condition, aromatics (2.12 μg/m³) dominated, and the contribution of alkanes (1.05 μg/m³) was lower. Monte Carlo simulation results showed that exposure to 1,3-butadiene and benzene may contribute potential carcinogenic risks to local residents; PMF results showed that reducing traffic-related and industrial emissions as well as coal burning was more effective in controlling carcinogenic risks. This study provides a crucial theoretical basis for decision-makers to minimize local air pollution more effectively.

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.

Photocatalytic effect of addition of TiO2 to acrylic-based paint for passive toluene degradation

Volatile organic compounds (VOCs) are known to be hazardous and associated with several human health problems. Thus, many technologies have been developed in recent years for their removal, such as thermal catalysis, photocatalysis and ozonization. In this study, the main objective was to evaluate the effects of incorporating titanium dioxide into an acrylic-based paint for gaseous toluene abatement. Paints with photocatalytic properties were prepared by adding TiO₂ P25 powder to an acrylic-based paint, using the following proportions: 0, 10, 15, 20 and 50 wt% (dry basis). Toluene and CO₂ concentrations at the reactor input and output were determined using GC/MS, and GC/FID, respectively, and the toluene conversion and CO₂ formation were assessed. The compounds adsorbed onto photocatalytic paints were extracted and then identified by GC/MS. The results indicated that the addition of 50 wt% of TiO₂ P25 results in a paint of reduced quality. The addition of 20 wt% of TiO₂ P25 to the paint led to higher values for the photocatalytic conversion of toluene to CO₂. The occurrence of two simultaneous processes was observed: the photocatalytic oxidation of toluene to CO₂ and the self-degradation of the organic compounds, such as polymeric acrylic, in the paint. The adsorption of different compounds onto the photocatalytic paints was identified by GC/MS analysis. The use of photocatalytic paints is a promising technique for toluene abatement, but it requires further study and improvement particularly with regard to the effects of the self-degradation of the paint.

Incidence of Respiratory Symptoms for Residents Living Near a Petrochemical Industrial Complex: A Meta-Analysis

The air pollution emitted by petrochemical industrial complexes (PICs) may affect the respiratory health of surrounding residents. Previous meta-analyses have indicated a higher risk of lung cancer mortality and incidence among residents near a PIC. Therefore, in this study, a meta-analysis was conducted to estimate the degree to which PIC exposure increases the risk of the development of nonmalignant respiratory symptoms among residents. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to systematically identify, select, and critically appraise relevant research. Finally, we identified 16 study groups reporting 5 types of respiratory symptoms: asthma, bronchitis, cough, rhinitis, and wheezing. We estimated pooled odds ratios (ORs) using random-effect models and investigated the robustness of pooled estimates in subgroup analyses by location, observation period, and age group. We determined that residential exposure to a PIC was significantly associated with a higher incidence of cough (OR = 1.35), wheezing (OR = 1.28), bronchitis (OR = 1.26), rhinitis (OR = 1.17), and asthma (OR = 1.15), although the latter two associations did not reach statistical significance. Subgroup analyses suggested that the association remained robust across different groups for cough and bronchitis. We identified high heterogeneity for asthma, rhinitis, and wheezing, which could be due to higher ORs in South America. Our meta-analysis indicates that residential exposure to a PIC is associated with an increased risk of nonmalignant respiratory symptoms.

Ambient volatile organic compounds (VOCs) in two coastal cities in western Canada: Spatiotemporal variation, source apportionment, and health risk assessment

Ambient volatile organic compounds (VOCs) in urban areas is of great interest due to their important roles in the atmospheric photochemistry as well as their potential adverse effects on public health. Limited information is available on the spatiotemporal variation, sources, and health risks of VOCs in the coastal cities of Canada, where the population density is much higher than inland areas. In this study, we investigated ambient VOCs levels, their potential sources and associated health risks in two coastal cities in Metro Vancouver during 2012-2016. Levels of the total measured VOCs were relatively higher in an industrial region in Port Moody (56.7 μg/m³) than an urban area of Burnaby south (38.0 μg/m³). A clear seasonality was observed for VOCs species with significantly higher levels in winter than in summer except for isoprene. Alkanes were the most dominant compounds at both sites accounting for up to 59.4% of the total measured VOCs, followed by halocarbons, aromatics, and alkenes. Industrial-related emissions (30.5%) and traffic-related emissions (35.8%) were the major sources contributing to ambient VOCs in Port Moody and Burnaby south, respectively, as calculated by the positive matrix factorization (PMF) model. A hybrid health risk assessment strategy using deterministic and stochastic approaches revealed that non-cancer risks of ambient VOCs exposure were all below the safe level of 1 at both cities, while the cumulative cancer risks of toxic VOCs exposure in Port Moody (9.2 × 10^-5) and Burnaby south (7.6 × 10^-5) were significantly higher than the provincial acceptable risk level (1.0 × 10^-5). Surprisingly, the probabilities for cumulative cancer risks of VOCs exceeding the US EPA tolerable risk level (1.0 × 10^-4) were 33.7% and 18.6% in Port Moody and Burnaby south, respectively. From a risk management perspective, greater emphasis on the reduction of emissions of carbon tetrachloride, benzene, and 1,3-butadiene is highly recommended in both cities of Metro Vancouver.