Traffic-Related Airborne VOC Profiles Variation on Road Sites and Residential Area within a Microscale in Urban Area in Southern Taiwan

Elucidating contributions of volatile organic compounds to ozone formation using random forest during COVID-19 pandemic: A case study in China

Ozone has been reported to increase despite nitrogen oxides reductions during the COVID-19 pandemic, and ozone formation needs to be revisited using volatile organic compounds (VOCs), which are rarely measured during the pandemic. Here, a total of 98 VOCs species were monitored in an economy-active city in China from January 2021 to August 2022 to assess contributions to ozone formation during the pandemic. Total VOCs concentrations were 35.55 ± 21.47 ppb during the entire period, among which alkanes account for the largest fraction (13.78 ppb, 38.0%), followed by aromatics (6.16 ppb, 16.8%) and oxygenated VOCs (OVOCs, 5.69 ppb, 15.7%). Most VOCs groups (e.g., alkenes, OVOCs) and individual species (e.g., isoprene, methyl vinyl ketone) display obvious seasonal and diurnal variations, which are related to their sources and reactivities. No weekend effects of VOCs suggest limited influences from traffic emissions during pandemic. Aromatics and alkenes are the major contributors (39% and 33%) to ozone formation potential, largely driven by o/m/p-xylene (21%), ethylene (15%), toluene (9%). Secondary organic aerosol formation potential is dominated by toluene (>50%) despite its low proportion (5%). Further inclusion of VOCs and meteorology in the Random Forest model shows good ozone prediction performance (R2 = 0.77-0.86, RMSE = 11.95-19.91 μg/m3, MAE = 8.89-14.58 μg/m3). VOCs and NO2 contribute >50% of total importance with the largest difference in importance ratio of VOCs/NO2 in the summer and winter, implying ozone formation regime may vary. No seasonal variations in importance of meteorology are observed, while importance of other variables (e.g., PM2.5) is highest in the summer. This work identifies critical VOCs groups and species for ozone formation during the pandemic, and demonstrates the feasibility of machine learning algorithms in elucidation of ozone formation mechanisms.

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

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

Identify Primary Air Pollution Sources of BTEX by Using Positive Matrix Factorization (PMF): A Case Study of Ho Chi Minh City, Vietnam

Ho Chi Minh City (HCMC) is one of the main socioeconomic and financial centers of Vietnam. The city also faces serious air pollution. However, the city polluted with benzene, toluene, ethylbenzene, and xylene (BTEX) has rarely been studied. We used positive matrix factorization (PMF) to analyze BTEX concentrations measured at two sampling locations to identify the main sources of BTEX in HCMC. The locations represented residential area (i.e., To Hien Thanh) and industrial area (i.e., Tan Binh Industrial Park). At the To Hien Thanh location, the average concentrations of benzene, ethylbenzene, toluene, and xylene were 6.9, 14.4, 4.9, and 12.7 µg/m3, respectively. At the Tan Binh location, the average concentrations of benzene, ethylbenzene, toluene, and xylene were 9.8, 22.6, 2.4, and 9.2 µg/m3, respectively. The results showed that PMF was a reliable model for source apportionment in HCMC. Traffic activities were the main sources of BTEX. Besides, industrial activities also contributed to BTEX emissions, especially the location near the industrial park. The majority of BTEXs at the To Hien Thanh sampling site come from traffic sources accounting for 56.2%. Activities from traffic and photochemical reactions (42.7%) and industrial sources (40.5%) were the main sources affecting BTEX emissions at the sampling site of Tan Binh Industrial Park. This study can be used as a reference for mitigation solutions to reduce the BTEX emission in HCMC.

Impact of shipping emissions regulation on urban aerosol composition changes revealed by receptor and numerical modelling

Various shipping emissions controls have recently been implemented at both local and national scales. However, it is difficult to track the effect of these on PM2.5 levels, owing to the non-linear relationship that exists between changes in precursor emissions and PM components. Positive Matrix Factorisation (PMF) identifies that a switch to cleaner fuels since January 2020 results in considerable reductions in shipping-source-related PM2.5, especially sulphate aerosols and metals (V and Ni), not only at a port site but also at an urban background site. CMAQ sensitivity analysis reveals that the reduction of secondary inorganic aerosols (SIA) further extends to inland areas downwind from ports. In addition, mitigation of secondary organic aerosols (SOA) in coastal urban areas can be anticipated either from the results of receptor modelling or from CMAQ simulations. The results in this study show the possibility of obtaining human health benefits in coastal cities through shipping emission controls.

Ambient levels of BTEX at roadside in northern Iraq and its relationship with traffic volume

Among the mono-aromatic volatile organic compounds, benzene, toluene, ethylbenzene and xylene (BTEX) have occupied a large area in air pollution studies due to their carcinogenic and non-carcinogenic effect. In this study, a station was used to monitor BTEX concentrations at roadside in urban area at Mosul city along a year, with traffic volume and meteorological factors measurement. The annual mean of benzene was 12 µg/m³, which is more than twofolds of the standard European Union level of 5 µg/m³. In addition, 87.4% of the measured values in summer was higher than the standard level at roadside. Benzene was dominant in spring and summer among BTEX species, while the dominance changed to ethylbenzene in autumn and winter. Besides, benzene, toluene, ethylbenzene and o-xylene showed significant seasonal variation. BTEX and benzene concentrations increased as the number of vehicles on gasoline and diesel increased. In contrast, toluene and ethylbenzene were more affected with number of vehicles on diesel. On the other hand, the weak significant correlations among BTEX species and high T/B ratio indicate the difference in fuel types used and the existence of additional sources of BTEX emission with the vehicular exhausts. These results can be utilized in determining the control strategy in air quality management in Mosul city.

Spatial modeling of ambient concentrations of volatile organic compounds in Montreal, Canada

Volatile organic compounds (VOCs) are components of the complex mixture of air pollutants within cities and can cause various adverse health effects. Therefore, it is necessary to understand their spatial distribution for exposure assessment in epidemiological studies.

The concentration of BTEX in selected urban areas of Malaysia during the COVID-19 pandemic lockdown

Volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene and xylene (BTEX) are air pollutants that harm human health. This study aims to identify BTEX concentrations before the lockdown known as the Movement Control Order was imposed (BMCO), during the implementation of the Movement Control Order (MCO), and then during the Conditional Movement Control Order (CMCO). These orders were introduced during the COVID-19 pandemic in Malaysia. The study utilised data measured by the continuous monitoring of BTEX using online gas chromatography instruments located at three urban area stations. The results showed that the BTEX concentrations reduced by between -38% and -46% during the MCO compared to the BMCO period. The reduction of human mobility during the MCO and CMCO influenced the lower BTEX concentrations recorded at a station within the Kuala Lumpur area. The results of the BTEX diagnostic ratios and principal component analysis showed that the major source of BTEX, especially during the BMCO and CMCO periods, was motor vehicle emissions. Further investigation, using correlation analysis and polar plots, showed that the BTEX concentrations were also influenced by meteorological variables such as wind speed, air temperature and relative humidity.