Global health burden of ambient PM2.5 and the contribution of anthropogenic black carbon and organic aerosols

Assessing the spatiotemporal evolution and socioeconomic determinants of PM2.5-related premature deaths in China from 2000 to 2021

China's swift socioeconomic development has led to extremely severe ambient PM2.5 levels, the associated negative health outcomes of which include premature death. However, a comprehensive explanation of the socioeconomic mechanism contributing to PM2.5-related premature deaths has not yet to be fully elucidated through long-term spatial panel data. Here, we employed a global exposure mortality model (GEMM) and the system generalized method of moments (Sys-GMM) to examine the primary determinants contributing to premature deaths in Chinese provinces from 2000 to 2021. We found that in the research period, premature deaths in China increased by 46 %, reaching 1.87 million, a figure that decreased somewhat after the COVID-19 outbreak. 62 thousand premature deaths were avoided in 2020 and 2021 compared to 2019, primarily due to the decline in PM2.5 concentrations. Premature deaths have increased across all provinces, particularly in North China, and a discernible spatial agglomeration effect was observed, highlighting effects on nearby provinces. The findings also underscored the significance of determinants such as urbanization, import and export trade, and energy consumption in exacerbating premature deaths, while energy intensity exerted a mitigating influence. Importantly, a U-shaped relationship between premature deaths and economic development was unveiled for the first time, implying the need for vigilance regarding potential health impact deterioration and the implementation of countermeasures as the per capita GDP increases in China. Our findings deserve attention from policymakers as they shed fresh insights into atmospheric control and Health China action.

In-depth characterization of exhaust particles performed on-board a modern cruise ship applying a scrubber

To comply with environmental regulations, ship operators may adopt exhaust after-treatment devices such as scrubbers or selective catalytic reduction (SCR). Beyond gaseous emission control, these technologies impact the exhaust particles emitted from marine engines to the atmosphere. This study characterizes comprehensively the chemical composition and physical properties of exhaust aerosol particles upstream and downstream a hybrid scrubber operating in open loop mode on-board a modern cruise ship. The study considers two engines, one equipped with SCR and both with scrubber, during engine load conditions of 75 % and 40 %, and the influence of marine gas oil (MGO) use in addition to heavy fuel oil (HFO). At least 4 different particle types were observed in the exhaust based on transmission electron microscopy (TEM) studies both upstream and downstream scrubber, and both scrubber and SCR affected the particle number size distribution (PSD). The geometric mean diameter (GMD) of the particles increased over scrubber both due to removal of nucleation mode particles and particle growth in the scrubber. The scrubber effectively decreased particle number (PN) and, also, non-volatile particles, but the effect depended on particle size and no significant decrease was observed in number of particles above 50 nm, typically comprising black carbon (BC) and in the case of HFO combustion, also asymmetrical metal containing particles. In addition to PN, concentrations of PAH compounds were reduced in the scrubber. The results may be further utilized when including the exhaust aerosol characteristics from ships applying scrubbers to emission inventories, as well as climate and air quality models.

Spatiotemporal variations and source on black carbon over Chongqing, China: Long-term changes and observational experiments

Black carbon (BC), as a critical light-absorbing constituent within aerosols, exerts profound effects on atmospheric radiation balance, climate, air quality and human health, etc. And it is also a long-standing focus in rapidly developing megacities. So, this study primarily focuses on investigating the variation characteristics and underlying causes of BC in Chongqing (31,914,300 population), which is one of the municipalities directly under the central government of China, serving as a pivotal economic hub in southwest China. Utilizing MERRA-2 reanalysis data, we examined the long-term changes of atmospheric BC over Chongqing 20 years (from 2002 to 2021). Moreover, BC mass concentration observations were conducted using an Aethalometer (AE-33) from March 15 to June 14, 2021 in Liangping District, Chongqing. The statistical analysis over the last 20 years reveals an annual mean BC concentration in Chongqing of 3.42 ± 0.20 μg/m3, exhibiting growth from 2002 to 2008, followed by a decline from 2008 to 2021. Monthly concentration displays a "U-shaped" trend, with the lowest values occurring in summer and the highest in winter. Due to topographical and meteorological influences, local emissions primarily contribute to BC pollution, characterized by a spatial distribution pattern of high in the west and low in the east. Ground observation indicates a distinct dual-peaked pattern in the diurnal variation of BC, with peak concentrations aligning with periods of high traffic emissions. The variation in BC is significantly influenced by meteorological conditions (wind, temperature, atmospheric boundary layer) and local pollution sources (predominantly traffic). Furthermore, extreme events analysis suggests that local emissions and regional transport (with higher contributions from Chongqing and the Sichuan Basin) predominantly contributed to BC pollution. This study effectively makes up for the deficiency in analyzing the distribution and sources of BC pollution in Chongqing, providing valuable scientific insights for the atmospheric environment of megacities.

Characterizing the distribution pattern of traffic-related air pollutants in near-road neighborhoods

In near-road neighborhoods, residents are more frequently exposed to traffic-related air pollution (TRAP), and they are increasingly aware of pollution levels. Given this consideration, this study adopted portable air pollutant sensors to conduct a mobile monitoring campaign in two near-road neighborhoods, one in an urban area and one in a suburban area of Shanghai, China. The campaign characterized spatiotemporal distributions of fine particulate matter (PM2.5) and black carbon (BC) to help identify appropriate mitigation measures in these near-road micro-environments. The study identified higher mean TRAP concentrations (up to 4.7-fold and 1.7-fold higher for PM2.5 and BC, respectively), lower spatial variability, and a stronger inter-pollutant correlation in winter compared to summer. The temporal variations of TRAP between peak hour and off-peak hour were also investigated. It was identified that district-level PM2.5 increments occurred from off-peak to peak hours, with BC concentrations attributed more to traffic emissions. In addition, the spatiotemporal distribution of TRAP inside neighborhoods revealed that PM2.5 concentrations presented great temporal variability but almost remained invariant in space, while the BC concentrations showed notable spatiotemporal variability. These findings provide valuable insights into the unique spatiotemporal distributions of TRAP in different near-road neighborhoods, highlighting the important role of hyperlocal monitoring in urban micro-environments to support tailored designing and implementing appropriate mitigation measures.

Effects of burning and photochemical degradation of Macondo surrogate oil on its composition and toxicity

Petroleum products in the environment can produce significant toxicity through photochemically driven processes. Burning surface oil and photochemical degradation were two mechanisms for oil removal after the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico. After burning, residual oil remains in the environment and may undergo further weathering, a poorly understood fate. Although photochemistry was a major degradation pathway of the DWH oil, its effect on burned oil residue in the environment is under studied. Here, we ignited Macondo surrogate crude oil and allowed it to burn to exhaustion. Water-accommodated fractions (WAFs) of the burn residue were created in full sunlight to determine the effects of photochemical weathering on the burned oil residue. Our findings show that increased dissolved organic carbon concentrations (DOC) for the light unburned and light burned after sunlight exposure positively correlated to decreased microbial growth and production inhibition (i.e. more toxic) when compared to the dark controls. Optical and molecular analytical techniques were used to identify the classes of compounds contributing to the toxicity in the dark and light burned and dark and light unburned WAFs. After light exposure, the optical composition between the light unburned and light burned differed significantly (p < 0.05), revealing key fluorescence signatures commonly identified as crude oil degradation products. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis showed more condensed aromatic, reduced oxygenated compounds present in the light burned than in the light unburned. FT-ICR MS also showed an increase in the percent relative abundance of carboxyl-rich alicyclic molecules (CRAM) like compounds in the light burned compared to light unburned. The increase in CRAM suggests that the composition of the light burned is more photorefractory, i.e., reduced, explaining the residual toxicity observed in microbial activity. Overall, these data indicate burning removes some but not all toxic compounds, leaving behind compounds which retain considerable toxicity. This study shows that burn oil residues are photolabile breaking down further into complex reduced compounds.

Indoor air quality in subway microenvironments: Pollutant characteristics, adverse health impacts, and population inequity

Rapidly increasing urbanization in recent decades has elevated the subway as the primary public transportation mode in metropolitan areas. Indoor air quality (IAQ) inside subways is an important factor that influences the health of commuters and subway workers. This review discusses the subway IAQ in different cities worldwide by comparing the sources and abundance of particulate matter (PM2.5 and PM10) in these environments. Factors that affect PM concentration and chemical composition were found to be associated with the subway internal structure, train frequency, passenger volume, and geographical location. Special attention was paid to air pollutants, such as transition metals, volatile/semi-volatile organic compounds (VOCs and SVOCs), and bioaerosols, due to their potential roles in indoor chemistry and causing adverse health impacts. In addition, given that the IAQ of subway systems is a public health issue worldwide, we calculated the Gini coefficient of urban subway exposure via meta-analysis. A value of 0.56 showed a significant inequity among different cities. Developed regions with higher per capita income tend to have higher exposure. By reviewing the current advances and challenges in subway IAQ with a focus on indoor chemistry and health impacts, future research is proposed toward a sustainable urban transportation systems.

Spatiotemporal joint analysis of PM2.5 and Ozone in California with INLA approach

The substantial threat of concurrent air pollutants to public health is increasingly severe under climate change. To identify the common drivers and extent of spatiotemporal similarity of PM2.5 and ozone (O3), this paper proposed a log Gaussian-Gumbel Bayesian hierarchical model allowing for sharing a stochastic partial differential equation and autoregressive model of order one (SPDE-AR(1)) spatiotemporal interaction structure. The proposed model, implemented by the approach of integrated nested Laplace approximation (INLA), outperforms in terms of estimation accuracy and prediction capacity for its increased parsimony and reduced uncertainty, especially for the shared O3 sub-model. Besides the consistently significant influence of temperature (positive), extreme drought (positive), fire burnt area (positive), gross domestic product (GDP) per capita (positive), and wind speed (negative) on both PM2.5 and O3, surface pressure and precipitation demonstrate positive associations with PM2.5 and O3, respectively. While population density relates to neither. In addition, our results demonstrate similar spatiotemporal interactions between PM2.5 and O3, indicating that the spatial and temporal variations of these pollutants show relatively considerable consistency in California. Finally, with the aid of the excursion function, we see that the areas around the intersection of San Luis Obispo and Santa Barbara counties are likely to exceed the unhealthy O3 level for USG simultaneously with other areas throughout the year. Our findings provide new insights for regional and seasonal strategies in the co-control of PM2.5 and O3. Our methodology is expected to be utilized when interest lies in multiple interrelated processes in the fields of environment and epidemiology.

Dual isotopic evidence of δ15N and δ18O for priority control of vehicle emissions in a megacity of East China: Insight from measurements in summer and winter

The source apportionment and main formation pathway of nitrate aerosols in China are not yet fully understood. In this study, PM2.5 samples were collected in Shanghai in the summer and winter of 2019. Water-soluble inorganic ions and isotopic signatures of stable nitrogen (δ15N-NO3-) and stable oxygen (δ18O-NO3-) in PM2.5 were determined. The results showed that NO3- was less important in summer (NO3-/SO42- = 0.4 ± 0.8), while it became the dominant species in winter (52.1 %). The average values of δ15N-NO3- and δ18O-NO3- in summer were + 2.0 ± 6.1 ‰ and 63.3 ± 9.4 ‰ respectively, which were significantly lower than those in winter (+7.2 ± 3.4 ‰ and 88.3 ± 12.1 ‰), indicating discrepancies between NOx sources and nitrate formation pathways. Both δ15N-NO3- and δ18O-NO3- were elevated at night, demonstrating that N2O5 hydrolysis contributed to the nocturnal nitrate increase even in summer. The contribution of the OH oxidation pathway to nitrate aerosols averaged at 70.5 ± 17.0 % in summer and N2O5 hydrolysis dominated the nitrate production in winter (approximately 80 %). On average, vehicle exhaust, coal combustion, natural gas burning, and soil emission contributed 50.7 %, 21.5 %, 15.9 %, and 11.9 %, respectively, to nitrate aerosols in summer, and contributed 56.8 %, 23.9 %, 13.6 %, and 5.7 %, respectively, to nitrate production in winter. Notably, natural gas burning is a non-negligible source of nitrate aerosols in Shanghai. In contrast to an inverse correlation between δ15N-NO3- and PM2.5, the value of δ18O-NO3- was positively correlated with nitrate concentration and aerosol liquid water content (ALWC) in winter, suggesting that explosive growth of nitrate was driven by continuous accumulation of N-depleted NOx and rapid N2O5 hydrolysis under calm and humid conditions. To continuously improve air quality, priority control should be given to vehicle emissions as the dominant source of NOx and volatile organic compounds (VOCs) in Shanghai.

New insight into air pollution-related cardiovascular disease: an adverse outcome pathway framework of PM2.5-associated vascular calcification

Despite the air quality has been generally improved in recent years, ambient fine particulate matter (PM2.5), a major contributor to air pollution, remains one of the major threats to public health. Vascular calcification is a systematic pathology associated with an increased risk of cardiovascular disease. Although the epidemiological evidence has uncovered the association between PM2.5 exposure and vascular calcification, little is known about the underlying mechanisms. The adverse outcome pathway (AOP) concept offers a comprehensive interpretation of all of the findings obtained by toxicological and epidemiological studies. In this review, reactive oxygen species generation was identified as the molecular initiating event (MIE), which targeted subsequent key events (KEs) such as oxidative stress, inflammation, endoplasmic reticulum stress, and autophagy, from the cellular to the tissue/organ level. These KEs eventually led to the adverse outcome, namely increased incidence of vascular calcification and atherosclerosis morbidity. To the best of our knowledge, this is the first AOP framework devoted to PM2.5-associated vascular calcification, which benefits future investigations by identifying current limitations and latent biomarkers.

Can the aerosol pollution extreme events be revealed by global reanalysis products?

Extreme aerosol pollution poses significant risks to the climate, environment, and human health. To investigate the formation and impacts of aerosol pollution extreme events (APEE), the reanalysis product presents meticulous spatiotemporal information on the three-dimensional distribution of aerosols. However, there is a lack of comprehensive evaluation and information regarding the data quality of reanalysis products employed in APEE research, as well as limited understanding of their spatial and temporal distribution, variation, and long-term trends. To address this scientific gap, we conducted a global study for distribution and variation patterns of APEE using two widely-used reanalysis products, MERRA-2 (Modern-Era Retrospective Analysis for Research-2) and CAMS (Copernicus Atmospheric Monitoring Service). The APEE was defined here as a day when the daily aerosol optical depth (AOD) exceeding its 90th percentile for a given station and month. Eleven distinct land regions worldwide were selected for evaluation by comparing both reanalysis products with MODIS satellite products and ground-based observations in terms of frequency, intensity, and temporal trends of APEE. The analysis indicates that MERRA-2 and CAMS exhibit high matching rates (70 % and 80 %, respectively) in terms of occurrence timeline for APEE at monthly and seasonal scales, while also exhibiting strong monthly correlation coefficients (>0.65) with ground-based observations over selected regions. The total AOD (-0.002 ∼ -0.123 decade-1), APEE AOD (-0.004 ∼ -0.293 decade-1), and APEE frequency (-0.264 ∼ -1.769 day month-1 decade-1) of both observations and reanalysis products in most regions showed a decreasing trend with various magnitude, except for some regions such as South Asia where the trend is increasing. Based on the aforementioned evaluation, it is evident that reanalysis products are effective and useful in identifying the temporal trends associated with APEE.

Biomass fuels related-PM2.5 promotes lung fibroblast-myofibroblast transition through PI3K/AKT/TRPC1 pathway

Emerging evidence has suggested that exposure to PM2.5 is a significant contributing factor to the development of chronic obstructive pulmonary disease (COPD). However, the underlying biological effects and mechanisms of PM2.5 in COPD pathology remain elusive. In this study, we aimed to investigate the implication and regulatory effect of biomass fuels related-PM2.5 (BRPM2.5) concerning the pathological process of fibroblast-to-myofibroblast transition (FMT) in the context of COPD. In vivo experimentation revealed that exposure to biofuel smoke was associated with airway inflammation in rats. After 4 weeks of exposure, there was inflammation in the small airways, but no significant structural changes in the airway walls. However, after 24 weeks, airway remodeling occurred due to increased collagen deposition, myofibroblast proliferation, and tracheal wall thickness. In vitro, cellular immunofluorescence results showed that with stimulation of BRPM2.5 for 72 h, the cell morphology of fibroblasts changed significantly, most of the cells changed from spindle-shaped to star-shaped irregular, α-SMA stress fibers appeared in the cytoplasm and the synthesis of type I collagen increased. The collagen gel contraction experiment showed that the contractility of fibroblasts was enhanced. The expression level of TRPC1 in fibroblasts was increased. Specific siRNA-TRPC1 blocked BRPM2.5-induced FMT and reduced cell contractility. Additionally, specific siRNA-TRPC1 resulted in a decrease in the augment of intracellular Ca2+ concentration ([Ca2+]i) induced by BRPM2.5. Notably, it was found that the PI3K inhibitor, LY294002, inhibited enhancement of AKT phosphorylation level, FMT occurrence, and elevation of TRPC1 protein expression induced by BRPM2.5. The findings indicated that BRPM2.5 is capable of inducing the FMT, with the possibility of mediation by PI3K/AKT/TRPC1. These results hold potential implications for the understanding of the molecular mechanisms involved in BRPM2.5-induced COPD and may aid in the development of novel therapeutic strategies for pathological conditions characterized by fibrosis.

Fires as a source of annual ambient PM2.5 exposure and chronic health impacts in Europe

Chronic exposure to ambient PM2.5 is the largest environmental health risk in Europe. We used a chemical transport model and recent exposure response functions to simulate ambient PM2.5, contribution from fires and related health impacts over Europe from 1990 to 2019. Our estimation indicates that the excess death burden from exposure to ambient PM2.5 declined across Europe at a rate of 10,000 deaths per year, from 0.57 million (95 % confidence intervals: 0.44-0.75 million) in 1990 to 0.28 million (0.19-0.42 million) in the specified period. Among these excess deaths, approximately 99 % were among adults, while only around 1 % occurred among children. Our findings reveal a steady increase in fire mortality fractions (excess deaths from fires per 1000 deaths from ambient PM2.5) from 2 in 1990 to 13 in 2019. Notably, countries in Eastern Europe exhibited significantly higher fire mortality fractions and experienced more pronounced increases compared to those in Western and Central Europe. We performed sensitivity analyses by considering fire PM2.5 to be more toxic as compared to other sources, as indicated by recent studies. By considering fire PM2.5 to be more toxic than other PM2.5 sources results in an increased relative contribution of fires to excess deaths, reaching 2.5-13 % in 2019. Our results indicate the requirement of larger mitigation and adaptation efforts and more sustainable forest management policies to avert the rising health burden from fires.

Exploring the association between long-term MODIS aerosol and air pollutants data across the Northern Great Plains through machine learning analysis

Aerosol optical depth (AOD) and Ångström exponent (AE) are the major environmental indicators to perceive air quality and the impact of aerosol on climate change and health as well as the global atmospheric conditions. In the present study, an average of AOD and AE data from Tera and Aqua satellites of MODIS sensors has been investigated over 7 years i.e., from 2016 to 2022, at four locations over Northern Great Plains. Both temporal and seasonal variations over the study periods have been investigated to understand the behavior of AOD and AE. Over the years, the highest AOD and AE were observed in winter season, varying from 0.75 to 1.17 and 1.30 to 1.63, respectively. During pre-monsoon season, increasing trend of AOD varying from 0.65 to 0.95 was observed from upper (New Delhi) to lower (Kolkata) Gangetic plain, however, during monsoon and post-monsoon a reverse trend varying from 0.85 to 0.65 has been observed. Seasonal and temporal aerosol characteristics have also been analyzed and it has been assessed that biomass burning was found to be the major contributor, followed by desert dust at all the locations except in Lucknow, where the second largest contributor was dust instead of desert dust. During season-wise analysis, biomass burning was also found to be as the major contributor at all the places in all the seasons except New Delhi and Lucknow, where dust was the major contributor during pre-monsoon. A boosting regression algorithm was done using machine learning to explore the relative influence of different atmospheric parameters and pollutants with PM2.5. Water vapor was assessed to have the maximum relative influence i.e., 51.66 % followed by CO (21.81 %). This study aims to help policy makers and decision makers better understand the correlation between different atmospheric components and pollutants and the contribution of different types of aerosols.

The Associations of Prenatal Exposure to Fine Particulate Matter and Its Chemical Components with Allergic Rhinitis in Children and the Modification Effect of Polyunsaturated Fatty Acids: A Birth Cohort Study

BACKGROUND

Polyunsaturated fatty acids (PUFAs) have been shown to protect against fine particulate matter < 2.5 μ m in aerodynamic diameter (PM 2.5 )-induced hazards. However, limited evidence is available for respiratory health, particularly in pregnant women and their offspring.

OBJECTIVES

We aimed to investigate the association of prenatal exposure to PM 2.5 and its chemical components with allergic rhinitis (AR) in children and explore effect modification by maternal erythrocyte PUFAs.

METHODS

This prospective birth cohort study involved 657 mother-child pairs from Guangzhou, China. Prenatal exposure to residential PM 2.5 mass and its components [black carbon (BC), organic matter (OM), sulfate (SO 4 2 - ), nitrate (NO 3 - ), and ammonium (NH 4 + )] were estimated by an established spatiotemporal model. Maternal erythrocyte PUFAs during pregnancy were measured using gas chromatography. The diagnosis of AR and report of AR symptoms in children were assessed up to 2 years of age. We used Cox regression with the quantile-based g-computation approach to assess the individual and joint effects of PM 2.5 components and examine the modification effects of maternal PUFA levels.

RESULTS

Approximately 5.33 % and 8.07% of children had AR and related symptoms, respectively. The average concentration of prenatal PM 2.5 was 35.50 ± 5.31   μ g / m 3 . PM 2.5 was positively associated with the risk of developing AR [hazard ratio ( HR ) = 1.85 ; 95% confidence interval (CI): 1.16, 2.96 per 5   μ g / m 3 ] and its symptoms (HR = 1.79 ; 95% CI: 1.22, 2.62 per 5   μ g / m 3 ) after adjustment for confounders. Similar associations were observed between individual PM 2.5 components and AR outcomes. Each quintile change in a mixture of components was associated with an adjusted HR of 3.73 (95% CI: 1.80, 7.73) and 2.69 (95% CI: 1.55, 4.67) for AR and AR symptoms, with BC accounting for the largest contribution. Higher levels of n-3 docosapentaenoic acid and lower levels of n-6 linoleic acid showed alleviating effects on AR symptoms risk associated with exposure to PM 2.5 and its components.

CONCLUSION

Prenatal exposure to PM 2.5 and its chemical components, particularly BC, was associated with AR/symptoms in early childhood. We highlight that PUFA biomarkers could modify the adverse effects of PM 2.5 on respiratory allergy. https://doi.org/10.1289/EHP13524.

METTL3-m6A-SIRT1 axis affects autophagic flux contributing to PM2.5-induced inhibition of testosterone production in Leydig cells

Epidemiological studies have found that long-term inhalation of PM2.5 is closely related to spermatogenesis disorders and infertility, but the underlying molecular mechanism is still unidentified. Testosterone, an essential reproductive hormone produced by Leydig cells, whose synthesis is disrupted by multiple environmental pollutants. In the current study, we explored the role of METTL3-m6A-SIRT1 axis-mediated abnormal autophagy in PM2.5-induced inhibition of testosterone production in in vivo and in vitro models. Our in vivo findings shown that long-term inhalation of PM2.5 decreased sperm count, increased sperm deformity rates, and altered testicular interstitial morphology accompanied by reduced testosterone in serum and testes. Further, data from the in vitro model displayed that exposure to PM2.5 caused an increase in m6A modification and METTL3 levels, followed by a decrease in testosterone levels and autophagy dysfunction in Leydig cells. The knockdown of METTL3 promotes autophagy flux and testosterone production in Leydig cells. Mechanistically, PM2.5 increased METTL3-induced m6A modification of SIRT1 mRNA in Leydig cells, bringing about abnormal autophagy. Subsequently, administration of SRT1720 (a SIRT1 activator) enhanced autophagy and further promoted testosterone biosynthesis. Collectively, our discoveries indicate that METTL3-m6A-SIRT1 axis-mediated autophagic flux contributes to PM2.5-induced inhibition of testosterone biosynthesis. This research offers a novel viewpoint on the mechanism of male reproductive injury following PM2.5 exposure.

Insights into the source contributions to the elevated fine particulate matter in Nigeria using a source-oriented chemical transport model

In 2021, Nigeria was ranked by the World Health Organization (WHO) as one of the top countries with highly deteriorating air quality in the world. To date, no study has elucidated the sources of elevated fine particulate matter (PM2.5) concentrations over the entire Nigeria. In this study, the Community Multiscale Air Quality (CMAQ) model was applied to quantify the contributions of seven emissions sectors to PM2.5 and its components in Nigeria in 2021. Residential, industry, and agriculture were the major sources of primary PM (PPM) during the four seasons, elemental carbon (EC) and primary organic carbon (POC) were dominated by residential and industry, while residential, industry, transportation, and agriculture were the important sources of secondary inorganic aerosols (SIA) and its components in most regions. PM2.5 was up to 150 μg/m3 in the north in all the seasons, while it reached ∼80 μg/m3 in the south in January. Residential contributed most to PM2.5 (∼80 μg/m3), followed by industry (∼40 μg/m3), transportation (∼20 μg/m3), and agriculture (∼15 μg/m3). The large variation in the sources of PM2.5 and its components across Nigeria suggests that emissions control strategies should be separately designed for different regions. The results imply that urgent control of PM2.5 pollution in Nigeria is highly necessitated.

Reassessing the role of urban green space in air pollution control

The assumption that vegetation improves air quality is prevalent in scientific, popular, and political discourse. However, experimental and modeling studies show the effect of green space on air pollutant concentrations in urban settings is highly variable and context specific. We revisited the link between vegetation and air quality using satellite-derived changes of urban green space and air pollutant concentrations from 2,615 established monitoring stations over Europe and the United States. Between 2010 and 2019, stations recorded declines in ambient NO2, (particulate matter) PM10, and PM2.5 (average of -3.14% y-1), but not O3 (+0.5% y-1), pointing to the general success of recent policy interventions to restrict anthropogenic emissions. The effect size of total green space on air pollution was weak and highly variable, particularly at the street scale (15 to 60 m radius) where vegetation can restrict ventilation. However, when isolating changes in tree cover, we found a negative association with air pollution at borough to city scales (120 to 16,000 m) particularly for O3 and PM. The effect of green space was smaller than the pollutant deposition and dispersion effects of meteorological drivers including precipitation, humidity, and wind speed. When averaged across spatial scales, a one SD increase in green space resulted in a 0.8% (95% CI: -3.5 to 2%) decline in air pollution. Our findings suggest that while urban greening may improve air quality at the borough-to-city scale, the impact is moderate and may have detrimental street-level effects depending on aerodynamic factors like vegetation type and urban form.

Atmospheric pollutant black carbon induces ocular surface damage in mice

The threats of air pollution to human health have been gradually discovered, including its effects on eyes. The purpose of the study is to investigate the potential correlation between ocular surface exposure to black carbon and ocular surface structural damage as well as tear film dysfunction. To achieve this goal, 60 6-8-week-aged male BALB/C mice were randomly divided into 4 groups (n = 15). 0.5 mg/ml (group A), 1 mg/ml (group B), 5 mg/ml (group C) black carbon suspension droplets and PBS solution (group D) were used in the right eyes, 4 μl per time of three times per day. Tear break-up time, corneal fluorescein staining scores, and tear volume were assessed before treatment (day 0) and on days 4, 7, 10, and 14 after treatment. On day 14, the mice were sacrificed, and corneal and conjunctival tissues were collected for histological analysis. As the exposure time increased, there were no significant changes in the measured parameters from PBS-treated group of mice (P > 0.05). However, in the black carbon-treated group, there were significant decreases in tear film break-up time, significant increases in corneal fluorescein staining scores, and significant reductions in tear secretion (all P < 0.05). After 14 days, H&E staining of the corneal epithelium showed that in the PBS-treated group of mice, the corneal epithelial cells were neatly arranged, with no inflammatory cell infiltration, while in the black carbon-treated group, the corneal epithelium was significantly thickened, the basal cell arrangement was disrupted, the number of cell layers increased, and there was evidence of inflammatory cell infiltration. In the ultrastructure of the corneal epithelium, it could be observed that the black carbon-treated group had an increased amount of corneal epithelial cell detachment compared to the PBS-treated group, at the same time, the intercellular connections were looser, and there was a decrease in the number of microvilli and desmosomes in the black carbon-treated group. The results indicate that the ocular surface exposure to black carbon can result in a decrease in tear film stability and tear secretion in mice. Moreover, it can induce alterations in the corneal structure.

A Long-Term Comparison between the AethLabs MA350 and Aerosol Magee Scientific AE33 Black Carbon Monitors in the Greater Salt Lake City Metropolitan Area

Black carbon (BC) or soot contains ultrafine combustion particles that are associated with a wide range of health impacts, leading to respiratory and cardiovascular diseases. Both long-term and short-term health impacts of BC have been documented, with even low-level exposures to BC resulting in negative health outcomes for vulnerable groups. Two aethalometers-AethLabs MA350 and Aerosol Magee Scientific AE33-were co-located at a Utah Division of Air Quality site in Bountiful, Utah for just under a year. The aethalometer comparison showed a close relationship between instruments for IR BC, Blue BC, and fossil fuel source-specific BC estimates. The biomass source-specific BC estimates were markedly different between instruments at the minute and hour scale but became more similar and perhaps less-affected by high-leverage outliers at the daily time scale. The greater inter-device difference for biomass BC may have been confounded by very low biomass-specific BC concentrations during the study period. These findings at a mountainous, high-elevation, Greater Salt Lake City Area site support previous study results and broaden the body of evidence validating the performance of the MA350.

Oligomerization Mechanism of Methylglyoxal Regulated by the Methyl Groups in Reduced Nitrogen Species: Implications for Brown Carbon Formation

Uncertain chemical mechanisms leading to brown carbon (BrC) formation affect the drivers of the radiative effects of aerosols in current climate predictions. Herein, the aqueous-phase reactions of methylglyoxal (MG) and typical reduced nitrogen species (RNSs) are systematically investigated by using combined quantum chemical calculations and laboratory experiments. Imines and diimines are identified from the mixtures of methylamine (MA) and ammonia (AM) with MG, but not from dimethylamine (DA) with the MG mixture under acidic conditions, because deprotonation of DA cationic intermediates is hindered by the amino groups occupied by two methyl groups. It leads to N-heterocycle (NHC) formation in the MG + MA (MGM) and MG + AM (MGA) reaction systems but to N-containing chain oligomer formation in the MG + DA (MGD) reaction system. Distinct product formation is attributed to electrostatic attraction and steric hindrance, which are regulated by the methyl groups of RNSs. The light absorption and adverse effects of NHCs are also strongly related to the methyl groups of RNSs. Our finding reveals that BrC formation is mainly contributed from MG reaction with RNSs with less methyl groups, which have more abundant and broad sources in the urban environments.

Health effects of carbonaceous PM2.5 compounds from residential fuel combustion and road transport in Europe

Exposure to fine particulate matter (PM2.5) is associated with an increased risk of morbidity and mortality. In Europe, residential fuel combustion and road transport emissions contribute significantly to PM2.5. Toxicological studies indicate that PM2.5 from these sources is relatively more hazardous, owing to its high content of black and organic carbon. Here, we study the contribution of the emissions from these sectors to long-term exposure and excess mortality in Europe. We quantified the impact of anthropogenic carbonaceous aerosols on excess mortality and performed a sensitivity analysis assuming that they are twice as toxic as inorganic particles. We find that total PM2.5 from residential combustion leads to 72,000 (95% confidence interval: 48,000-99,000) excess deaths per year, with about 40% attributed to carbonaceous aerosols. Similarly, road transport leads to about 35,000 (CI 23,000-47,000) excess deaths per year, with 6000 (CI 4000-9000) due to carbonaceous particles. Assuming that carbonaceous aerosols are twice as toxic as other PM2.5 components, they contribute 80% and 37%, respectively, to residential fuel combustion and road transport-related deaths. We uncover robust national variations in the contribution of each sector to excess mortality and emphasize the importance of country-specific emission reduction policies based on national characteristics and sectoral shares.

Air pollution deaths attributable to fossil fuels: observational and modelling study

OBJECTIVES

To estimate all cause and cause specific deaths that are attributable to fossil fuel related air pollution and to assess potential health benefits from policies that replace fossil fuels with clean, renewable energy sources.

DESIGN

Observational and modelling study.

METHODS

An updated atmospheric composition model, a newly developed relative risk model, and satellite based data were used to determine exposure to ambient air pollution, estimate all cause and disease specific mortality, and attribute them to emission categories.

DATA SOURCES

Data from the global burden of disease 2019 study, observational fine particulate matter and population data from National Aeronautics and Space Administration (NASA) satellites, and atmospheric chemistry, aerosol, and relative risk modelling for 2019.

RESULTS

Globally, all cause excess deaths due to fine particulate and ozone air pollution are estimated at 8.34 million (95% confidence interval 5.63 to 11.19) deaths per year. Most (52%) of the mortality burden is related to cardiometabolic conditions, particularly ischaemic heart disease (30%). Stroke and chronic obstructive pulmonary disease both account for 16% of mortality burden. About 20% of all cause mortality is undefined, with arterial hypertension and neurodegenerative diseases possibly implicated. An estimated 5.13 million (3.63 to 6.32) excess deaths per year globally are attributable to ambient air pollution from fossil fuel use and therefore could potentially be avoided by phasing out fossil fuels. This figure corresponds to 82% of the maximum number of air pollution deaths that could be averted by controlling all anthropogenic emissions. Smaller reductions, rather than a complete phase-out, indicate that the responses are not strongly non-linear. Reductions in emission related to fossil fuels at all levels of air pollution can decrease the number of attributable deaths substantially. Estimates of avoidable excess deaths are markedly higher in this study than most previous studies for these reasons: the new relative risk model has implications for high income (largely fossil fuel intensive) countries and for low and middle income countries where the use of fossil fuels is increasing; this study accounts for all cause mortality in addition to disease specific mortality; and the large reduction in air pollution from a fossil fuel phase-out can greatly reduce exposure.

CONCLUSION

Phasing out fossil fuels is deemed to be an effective intervention to improve health and save lives as part the United Nations' goal of climate neutrality by 2050. Ambient air pollution would no longer be a leading, environmental health risk factor if the use of fossil fuels were superseded by equitable access to clean sources of renewable energy.

Chemical and oxidative properties of fine particulate matter from near-road traffic sources

The toxicity associated with the fine particulate matter (PM2.5) has not been well studied, particularly in relation to the emissions from on-road vehicles and other sources in low- and middle-income countries such as India. Thus, a study was conducted to examine the oxidative potential (OP) of PM2.5 at a roadside (RS) site with heavy vehicular traffic and an urban background (BG) site in Mumbai using the dithiothreitol (DTT) assay. Simultaneous gravimetric PM2.5 was measured at both sites and characterized for carbonaceous constituents and water-soluble trace elements and metals. Results depicted higher PM2.5, elemental carbon (EC), and organic carbon (OC) concentrations on the RS than BG (by a factor of 1.7, 4.6, and 1.2, respectively), while BG had higher water-soluble organic carbon (WSOC) levels (by a factor of 1.4) and a higher WSOC to OC ratio (86%), likely due to the dominance of secondary aerosol formation. In contrast, the measured OPDTTv at RS (8.9 ± 5.5 nmol/min/m3) and BG (8.1 ± 6.4 nmol/min/m3) sites were similar. However, OPDTTv at BG was higher during the afternoon, suggesting the influence of photochemical transformation on measured OPDTTv at BG. At RS, OC and redox-active metals (Cu, Zn, Mn, and Fe) were significantly associated with measured OP (p < 0.05), while at BG, WSOC was most strongly associated (p < 0.05). The coefficient of divergence (COD) for PM2.5, its chemical species, and OPDTTv was >0.2, indicating spatial heterogeneity between the sites, and differences in emission sources and toxicity. The estimated hazard index (HI) was not associated with OPDTTv, indicating that current PM2.5 mass regulations may not adequately capture the health effects of PM2.5. The study highlights the need for further studies examining PM2.5 toxicity and developing toxicity-based air quality regulations.

Elegant Nematodes Improve Our Understanding of Human Neuronal Diseases, the Role of Pollutants and Strategies of Resilience

The prevalence of neurodegenerative disorders such as Alzheimer's and Parkinson's disease are rising globally. The role of environmental pollution in neurodegeneration is largely unknown. Thus, this perspective advocates exposome research in C. elegans models of human diseases. The models express amyloid proteins such as Aβ, recapitulate the degeneration of specifically vulnerable neurons and allow for correlated neurobehavioral phenotyping throughout the entire life span of the nematode. Neurobehavioral traits like locomotion gaits, rigidity, or cognitive decline are quantifiable and carefully mimic key aspects of the human diseases. Underlying molecular pathways of neurodegeneration are elucidated in pollutant-exposed C. elegans Alzheimer's or Parkinson's models by transcriptomics (RNA-seq), mass spectrometry-based proteomics and omics addressing other biochemical traits. Validation of the identified disease pathways can be achieved by genome-wide association studies in matching human cohorts. A consistent One Health approach includes isolation of nematodes from contaminated sites and their comparative investigation by imaging, neurobehavioral profiling and single worm proteomics. C. elegans models of neurodegenerative diseases are likewise well-suited for high throughput methods that provide a promising strategy to identify resilience pathways of neurosafety and keep up with the number of pollutants, nonchemical exposome factors, and their interactions.

Transcriptomics profile of human bronchial epithelial cells exposed to ambient fine particles and influenza virus (H3N2)

Fine particulate matter (PM2.5) pollution remains a major threat to public health. As the physical barrier against inhaled air pollutants, airway epithelium is a primary target for PM2.5 and influenza viruses, two major environmental insults. Recent studies have shown that PM2.5 and influenza viruses may interact to aggravate airway inflammation, an essential event in the pathogenesis of diverse pulmonary diseases. Airway epithelium plays a critical role in lung health and disorders. Thus far, the mechanisms for the interactive effect of PM2.5 and the influenza virus on gene transcription of airway epithelial cells have not been fully uncovered. In this present pilot study, the transcriptome sequencing approach was introduced to identify responsive genes following individual and co-exposure to PM2.5 and influenza A (H3N2) viruses in a human bronchial epithelial cell line (BEAS-2B). Enrichment analysis revealed the function of differentially expressed genes (DEGs). Specifically, the DEGs enriched in the xenobiotic metabolism by the cytochrome P450 pathway were linked to PM2.5 exposure. In contrast, the DEGs enriched in environmental information processing and human diseases, such as viral protein interaction with cytokines and cytokine receptors and epithelial cell signaling in bacterial infection, were significantly related to H3N2 exposure. Meanwhile, co-exposure to PM2.5 and H3N2 affected G protein-coupled receptors on the cell surface. Thus, the results from this study provides insights into PM2.5- and influenza virus-induced airway inflammation and potential mechanisms.

Deposition of secondary organic aerosol in human lung model: Effect of photochemically aged aerosol on human respiratory system

Ultrafine particles (UFP) of Secondary Organic Aerosol (SOA) penetrate deep into the human respiratory system and exert fatal effects on human health. However, there is little data on the potential deposited doses of UFP-generated SOA in the human respiratory tract. This study is to estimate the fraction of aerosol deposition using a multiple-path-particle-dosimetry (MPPD) model. For relevancy of real life, the model employed measured concentrations of toluene-derived fresh and aged SOA produced within serially connected smog chamber and PAM-OFR (Potential Aerosol Mass-Oxidation Flow Reactor) under atmospheric environmental conditions (NOx and relative humidity). The number concentrations and chemical composition of fresh and aged aerosols produced within the chambers were measured using Scanning Mobility Particle Sizer (SMPS) and High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), while the morphology of individual particles was analyzed using Scanning Electron Microscopy (SEM). The number concentration of aged SOA-w/s was more than double compared to that of fresh SOA-w/s (maximum reached after 10 h) with its size less than 100 nm. The O:C ratio for aged SOA-w/s were 0.96 and 1.15 depending on RH (0.96 at 3% RH and 1.15 at 50% RH), and individual spherical particles containing water were present in agglomerates with its size of less than 1 µm. In all inhalable fresh and aged SOA produced in the two chambers, 5-22% of aerosol is deposited in the Head airways, 4-8% in the tracheobronchial, and 8-34% in the alveolar regions. The predominant deposition of the aged aerosol occurred in the alveoli (in the generation 20th lobe), and the deposition faction in the alveoli was 2-3 times higher in the children group than the adults group. This study presented a quantitative exposure assessment of SOA generated under a realistic simulation and suggested the possibility of evaluating long-term exposure to SOA and potential health effects by determining the potential inhalable aerosol doses and the fraction of deposition in the human respiratory system.

Prenatal and childhood exposure to ambient air pollution and cognitive function in school-age children: Examining sensitive windows and sex-specific associations

BACKGROUND

Combined effect of both prenatal and early postnatal exposure to ambient air pollution on child cognition has rarely been investigated and periods of sensitivity are unknown. This study explores the temporal relationship between pre- and postnatal exposure to PM10, PM2.5, NO2 and child cognitive function.

METHODS

Using validated spatiotemporally resolved exposure models, pre- and postnatal daily PM2.5, PM10 (satellite based, 1 km resolution) and NO2 (chemistry-transport model, 4 km resolution) concentrations at the mother's residence were estimated for 1271 mother-child pairs from the French EDEN and PELAGIE cohorts. Scores representative of children's General, Verbal and Non-Verbal abilities at 5-6 years were constructed based on subscale scores from the WPPSI-III, WISC-IV or NEPSY-II batteries, using confirmatory factor analysis (CFA). Associations of both prenatal (first 35 gestational weeks) and postnatal (60 months after birth) exposure to air pollutants with child cognition were explored using Distributed Lag Non-linear Models adjusted for confounders.

RESULTS

Increased maternal exposure to PM10, PM2.5 and NO2, during sensitive windows comprised between the 15th and the 33rd gestational weeks, was associated with lower males' General and Non-verbal abilities. Higher postnatal exposure to PM2.5 between the 35th and 52nd month of life was associated with lower males' General, Verbal and Non-verbal abilities. Some protective associations were punctually observed for the very first gestational weeks or months of life for both males and females and the different pollutants and cognitive scores.

DISCUSSION

These results suggest poorer cognitive function at 5-6 years among males following increased maternal exposure to PM10, PM2.5 and NO2 during mid-pregnancy and child exposure to PM2.5 around 3-4 years. Apparent protective associations observed are unlikely to be causal and might be due to live birth selection bias, chance finding or residual confounding.

Molecular Self-Organization in Surfactant Atmospheric Aerosol Proxies

ConspectusAerosols are ubiquitous in the atmosphere. Outdoors, they take part in the climate system via cloud droplet formation, and they contribute to indoor and outdoor air pollution, impacting human health and man-made environmental change. In the indoor environment, aerosols are formed by common activities such as cooking and cleaning. People can spend up to ca. 90% of their time indoors, especially in the western world. Therefore, there is a need to understand how indoor aerosols are processed in addition to outdoor aerosols.Surfactants make significant contributions to aerosol emissions, with sources ranging from cooking to sea spray. These molecules alter the cloud droplet formation potential by changing the surface tension of aqueous droplets and thus increasing their ability to grow. They can also coat solid surfaces such as windows ("window grime") and dust particles. Such surface films are more important indoors due to the higher surface-to-volume ratio compared to the outdoor environment, increasing the likelihood of surface film-pollutant interactions.A common cooking and marine emission, oleic acid, is known to self-organize into a range of 3-D nanostructures. These nanostructures are highly viscous and as such can impact the kinetics of aerosol and film aging (i.e., water uptake and oxidation). There is still a discrepancy between the longer atmospheric lifetime of oleic acid compared with laboratory experiment-based predictions.We have created a body of experimental and modeling work focusing on the novel proposition of surfactant self-organization in the atmosphere. Self-organized proxies were studied as nanometer-to-micrometer films, levitated droplets, and bulk mixtures. This access to a wide range of geometries and scales has resulted in the following main conclusions: (i) an atmospherically abundant surfactant can self-organize into a range of viscous nanostructures in the presence of other compounds commonly encountered in atmospheric aerosols; (ii) surfactant self-organization significantly reduces the reactivity of the organic phase, increasing the chemical lifetime of these surfactant molecules and other particle constituents; (iii) while self-assembly was found over a wide range of conditions and compositions, the specific, observed nanostructure is highly sensitive to mixture composition; and (iv) a "crust" of product material forms on the surface of reacting particles and films, limiting the diffusion of reactive gases to the particle or film bulk and subsequent reactivity. These findings suggest that hazardous, reactive materials may be protected in aerosol matrixes underneath a highly viscous shell, thus extending the atmospheric residence times of otherwise short-lived species.

Understanding the time-activity pattern to improve the measurement of personal exposure: An exploratory and experimental research

Although ambient fine particulate matter (PM2.5) concentrations and their components are commonly used as proxies for personal exposure monitoring, developing an accurate and cost-effective method to use these proxies for personal exposure measurement continues to pose a significant challenge. Herein, we propose a scenario-based exposure model to precisely estimate personal exposure level of heavy metal(loid)s (HMs) using scenario HMs concentrations and time-activity patterns. Personal exposure levels and ambient pollution levels for PM2.5 and HMs differed significantly with corresponding personal/ambient ratios of approximately 2, and exposure scenarios could narrow the assessment error gap by 26.1-45.4%. Using a scenario-based exposure model, we assessed the associated health risks of a large sample population and identified that the carcinogenic risk of As exceeded 1 × 10-6, while we observed non-carcinogenic risks from As, Cd, Ni, and Mn in personal exposure to PM2.5. We conclude that the scenario-based exposure model is a preferential alternative for monitoring personal exposure compared to ambient concentrations. This method ensures the feasibility of personal exposure monitoring and health risk assessments in large-scale studies.

Per- and polyfluoroalkyl substances in ambient fine particulate matter in the Pearl River Delta, China: Levels, distribution and health implications

Per- and polyfluoroalkyl substances (PFAS) have attracted worldwide attention as one of persistent organic pollutants; however, there is limited knowledge about the exposure concentrations of PFAS-contained ambient particulate matter and the related health risks. This study investigated the abundance and distribution of 32 PFAS in fine particulate matter (PM2.5) collected from 93 primary or secondary schools across the Pearl River Delta region (PRD), China. These chemicals comprise four PFAS categories which includes perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs), perfluoroalkyl acid (PFAA) precursors and PFAS alternatives. In general, concentrations of target PFAS ranged from 11.52 to 419.72 pg/m3 (median: 57.29 pg/m3) across sites. By categories, concentrations of PFSAs (median: 26.05 pg/m3) were the dominant PFAS categories, followed by PFCAs (14.25 pg/m3), PFAS alternatives (2.75 pg/m3) and PFAA precursors (1.10 pg/m3). By individual PFAS, PFOS and PFOA were the dominant PFAS, which average concentration were 24.18 pg/m3 and 6.05 pg/m3, respectively. Seasonal variation showed that the concentrations of PFCAs and PFSAs were higher in winter than in summer, whereas opposite seasonal trends were observed in PFAA precursors and PFAS alternatives. Estimated daily intake (EDI) and hazard quotient (HQ) were used to assess human inhalation-based exposure risks to PFAS. Although the health risks of PFAS via inhalation were insignificant (HQ far less than one), sufficient attention should be levied to ascertain the human exposure risks through inhalation, given that exposure to PFAS through air inhalation is a long term and cumulative process.

Global Health and Climate Effects of Organic Aerosols from Different Sources

The impact of aerosols on human health and climate is well-recognized, yet many studies have only focused on total PM2.5 or changes from anthropogenic activities. This study quantifies the health and climate effects of organic aerosols (OA) from anthropogenic, biomass burning, and biogenic sources. Using two atmospheric chemistry models, CAM-chem and GEOS-Chem, our findings reveal that anthropogenic primary OA (POA) has the highest efficiency for health effects but the lowest for direct radiative effects due to spatial and temporal variations associated with population and surface albedo. The treatment of POA as nonvolatile or semivolatile also influences these efficiencies through different chemical processes. Biogenic OA shows moderate efficiency for health effects and the highest for direct radiative effects but has the lowest efficiency for indirect effects due to the reduced high cloud, caused by stabilized temperature profiles from aerosol-radiation interactions in biogenic OA-rich regions. Biomass burning OA is important for cloud radiative effect changes in remote atmospheres due to its ability to be transported further than other OAs. This study highlights the importance of not only OA characteristics such as toxicity and refractive index but also atmospheric processes such as transport and chemistry in determining health and climate impact efficiencies.

Impact of long-range transport on black carbon source contribution and optical aerosol properties in two urban environments

Urban areas, as major sources of aerosol black carbon emissions, contribute to increased pollution levels in surrounding regions by air mass long-range transport, which should be taken into account in implementation of emission-reduction strategies. Properties of light-absorbing aerosol particles and a novel approach to assess the impact of long-range transport on black carbon (BC) pollution in two under-investigated urban environments: Warsaw (Poland, Central Europe) and Vilnius (Lithuania, North-Eastern Europe) are presented. During the warm season of May-August 2022, BC mass concentration and aerosol optical properties: the scattering Ångström exponent (SAE), absorption Ångström exponent (AAE), and single scattering albedo (SSA) were investigated. Generally, the mean BC mass concentration was higher at the more polluted site in Warsaw (1.07 μg/m3) than in Vilnius (0.77 μg/m3). The BC source apportionment to biomass burning (BCBB) and fossil fuel combustion (BCFF) showed similar contributions for both sites with BCBB (13-19%) being significantly lower than BCFF (81-87%). A uniform flow of air masses transporting aerosol particles over long distances to both sites was observed for 42% of the days. It affected BC mass concentration as follows: BC decrease was found similar at both sites (42% in Warsaw, 50% in Vilnius) but increase was twice higher in Vilnius (64%) than in Warsaw (30%). Despite variations in BC mass concentration, both sites exhibited a comparable abundance (90%) of submicron (SAE<1.3), BC-dominated (AAE<1.5) particles. The mean SSA was very low (0.69 ± 0.1 in Warsaw, 0.72 ± 0.1 in Vilnius), which indicates a very strong contribution of light-absorbing aerosol particles in both environments. The local episodes of biomass burning due to celebrations of May Days on 1st - 3rd May in Warsaw and Midsummer on 24th June in Vilnius showed similar aerosol properties in both cities (1.5 Collapse

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Affiliation(s)

Agnė Minderytė SRI Center for Physical Sciences and Technology (FTMC), 10257 Vilnius, Lithuania
Emeka A. Ugboma Faculty of Physics, University of Warsaw (UW), 02-093 Warsaw, Poland
Fátima Francisca Mirza Montoro Faculty of Physics, University of Warsaw (UW), 02-093 Warsaw, Poland
Iwona S. Stachlewska Faculty of Physics, University of Warsaw (UW), 02-093 Warsaw, Poland
Steigvilė Byčenkienė SRI Center for Physical Sciences and Technology (FTMC), 10257 Vilnius, Lithuania

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Spatial and sector-specific contributions of emissions to ambient air pollution and mortality in European cities: a health impact assessment

BACKGROUND

Ambient air pollution is a major risk to health and wellbeing in European cities. We aimed to estimate spatial and sector-specific contributions of emissions to ambient air pollution and evaluate the effects of source-specific reductions in pollutants on mortality in European cities to support targeted source-specific actions to address air pollution and promote population health.

METHODS

We conducted a health impact assessment of data from 2015 for 857 European cities to estimate source contributions to annual PM_2·5 and NO₂ concentrations using the Screening for High Emission Reduction Potentials for Air quality tool. We evaluated contributions from transport, industry, energy, residential, agriculture, shipping, and aviation, other, natural, and external sources. For each city and sector, three spatial levels were considered: contributions from the same city, the rest of the country, and transboundary. Mortality effects were estimated for adult populations (ie, ≥20 years) following standard comparative risk assessment methods to calculate the annual mortality preventable on spatial and sector-specific reductions in PM_2·5 and NO₂.

FINDINGS

We observed strong variability in spatial and sectoral contributions among European cities. For PM_2·5, the main contributors to mortality were the residential (mean contribution of 22·7% [SD 10·2]) and agricultural (18·0% [7·7]) sectors, followed by industry (13·8% [6·0]), transport (13·5% [5·8]), energy (10·0% [6·4]), and shipping (5·5% [5·7]). For NO₂, the main contributor to mortality was transport (48·5% [SD 15·2]), with additional contributions from industry (15·0% [10·8]), energy (14·7% [12·9]), residential (10·3% [5·0]), and shipping (9·7% [12·7]). The mean city contribution to its own air pollution mortality was 13·5% (SD 9·9) for PM_2·5 and 34·4% (19·6) for NO₂, and contribution increased among cities of largest area (22·3% [12·2] for PM_2·5 and 52·2% [19·4] for NO₂) and among European capitals (29·9% [12·5] for PM_2·5 and 62·7% [14·7] for NO₂).

INTERPRETATION

We estimated source-specific air pollution health effects at the city level. Our results show strong variability, emphasising the need for local policies and coordinated actions that consider city-level specificities in source contributions.

FUNDING

Spanish Ministry of Science and Innovation, State Research Agency, Generalitat de Catalunya, Centro de Investigación Biomédica en red Epidemiología y Salud Pública, and Urban Burden of Disease Estimation for Policy Making 2023-2026 Horizon Europe project.

Whether cycling around the city is in fact healthy in the light of air quality - Results of black carbon

Studying the air quality and exposure of the inhabitants of urban agglomerations to pollution is the basis for the creation and development of more sustainable cities. Although research on black carbon (BC) has not yet reached the official acceptable levels and guidelines, the World Health Organization clearly indicates the need to measure and control the level of this pollutant. In Poland, monitoring of the level of BC concentration is not included in the air quality monitoring network. To estimate the extent of this pollutant to which pedestrians and cyclists are exposed, mobile measurements were carried out on over 26 km of bicycle paths in Wrocław. The obtained results indicate the influence of urban greenery next to the bicycle path (especially if the cyclist is separated from the street lane by hedges or other tall plants) and the 'breathability' (i.e., associated with surrounding infrastructure) of the area on the obtained concentrations; the average concentration of BC in such places ranged from 1.3 to 2.2 μg/m³, whereas a cyclist riding directly on bike paths adjacent to the main roads in the city center is exposed to concentrations in the range of 2.3-14 μg/m³. The results of the measurements, also related to stationary measurements made at a selected point of one of the routes, clearly indicate the importance of the infrastructure surrounding the bicycle paths, their location, and the impact of urban traffic on the obtained BC concentrations. The results presented in our study are based only on short-term-field campaigns preliminary studies. To determine the quantitative impact of the characteristics of the bicycle route on the concentration of pollutants, and thus the exposure of users, the systematized research should cover a greater part of the city and be representative in terms of various hours of the day.

Highly Time-Resolved Apportionment of Carbonaceous Aerosols from Wildfire Using the TC-BC Method: Camp Fire 2018 Case Study

The Camp Fire was one of California's deadliest and most destructive wildfires, and its widespread smoke threatened human health over a large area in Northern California in November 2018. To analyze the Camp Fire influence on air quality on a 200 km distant site in Berkeley, highly time-resolved total carbon (TC), black carbon (BC), and organic carbon (OC) were measured using the Carbonaceous Aerosol Speciation System (CASS, Aerosol Magee Scientific), comprising two instruments, a Total Carbon Analyzer TCA08 in tandem with an Aethalometer AE33. During the period when the air quality was affected by wildfire smoke, the BC concentrations increased four times above the typical air pollution level presented in Berkeley before and after the event, and the OC increased approximately ten times. High-time-resolution measurements allow us to study the aging of OC and investigate how the characteristics of carbonaceous aerosols evolve over the course of the fire event. A higher fraction of secondary carbonaceous aerosols was observed in the later phase of the fire. At the same time, the amount of light-absorbing organic aerosol (brown carbon) declined with time.

Potential mechanisms mediating PM2.5-induced alterations of H3N2 influenza virus infection and cytokine production in human bronchial epithelial cells

Exposure to particulate matter (PM) has been associated with increased hospital admissions for influenza. Airway epithelial cells are a primary target for inhaled environmental insults including fine PM (PM_2.5) and influenza viruses. The potentiation of PM_2.5 exposure on the effects of influenza virus on airway epithelial cells has not been adequately elucidated. In this study, the effects of PM_2.5 exposure on influenza virus (H3N2) infection and downstream modulation of inflammation and antiviral immune response were investigated using a human bronchial epithelial cell line, BEAS-2B. The results showed that PM_2.5 exposure alone increased the production of pro-inflammatory cytokines including interleukin-6 (IL-6) and IL-8 but decreased the production of the antiviral cytokine interferon-β (IFN-β) in BEAS-2B cells while H3N2 exposure alone increased the production of IL-6, IL-8, and IFN-β. Importantly, prior exposure to PM_2.5 enhanced subsequent H3N2 infectivity, expression of viral hemagglutinin protein, as well as upregulation of IL-6 and IL-8, but reduced H3N2-induced IFN-β production. Pre-treatment with a pharmacological inhibitor of nuclear factor-κB (NF-κB) suppressed pro-inflammatory cytokine production induced by PM_2.5, H3N2, as well as PM_2.5-primed H3N2 infection. Moreover, antibody-mediated neutralization of Toll-like receptor 4 (TLR4) blocked cytokine production triggered by PM_2.5 or PM_2.5-primed H3N2 infection, but not H3N2 alone. Taken together, exposure to PM_2.5 alters H3N2-induced cytokine production and markers of replication in BEAS-2B cells, which in turn are regulated by NF-κB and TLR4.

Chemical characteristics and spatiotemporal variation of marine fine particles for clustered channels of air masses transporting toward remote background sites in East Asia

This study investigated the chemical characteristics, spatiotemporal distribution, and source apportionment of marine fine particles (PM_2.5) for clustered transport channels/routes of air masses moving toward three remote sites in East Asia. Six transport routes in three channels were clustered based on backward trajectory simulation (BTS) in the order of: West Channel > East Channel > South Channel. Air masses transported toward Dongsha Island (DS) came mainly from the West Channel, while those transported toward Green Island (GR) and Kenting Peninsula (KT) came mostly from the East Channel. High PM_2.5 commonly occurred from late fall to early spring during the periods of Asian Northeastern Monsoons (ANMs). Marine PM_2.5 was dominated by water-soluble ions (WSIs) which were predominated by secondary inorganic aerosols (SIAs). Although the metallic content of PM_2.5 was predominated by crustal elements (Ca, K, Mg, Fe, and Al), enrichment factor clearly showed that trace metals (Ti, Cr, Mn, Ni, Cu, and Zn) came mainly from anthropogenic sources. Organic carbon (OC) was superior to elemental carbon (EC), while OC/EC and SOC/OC ratios in winter and spring were higher than those in other two seasons. Similar trends were observed for levoglucosan and organic acids. The mass ratio of malonic acid and succinic acid (M/S) was commonly higher than unity, showing the influences of biomass burning (BB) and secondary organic aerosols (SOAs) on marine PM_2.5. We resolved that the main sources of PM_2.5 were sea salts, fugitive dust, boiler combustion, and SIAs. Boiler combustion and fishing boat emissions at DS had higher contribution than those at GR and KT. The highest/lowest contribution ratios of cross-boundary transport (CBT) were 84.9/29.6% in winter and summer, respectively.

Air pollution and child health impacts of decarbonization in 16 global cities: Modelling study

Most research on the air pollution-related health effects of decarbonization has focused on adults. We assess the potential health benefits that could be achieved in children and young people in a global sample of 16 cities through global decarbonization actions. We modelled annual average concentrations of fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) at 1x1 km resolution in the cities using a general circulation/atmospheric chemistry model assuming removal of all global combustion-related emissions from land transport, industries, domestic energy use and power generation. We modelled the impact on childhood asthma incidence and adverse birth outcomes (low birthweight, pre-term births) using published exposure-response relationships. Removal of combustion emissions was estimated to decrease annual average PM_2.5 by between 2.9 μg/m³ (8.4%) in Freetown and 45.4 μg/m³ (63.7%) in Dhaka. For NO₂, the range was from 0.3 ppb (7.9%) in Freetown to 18.8 ppb (92.3%) in Mexico City. Estimated reductions in asthma incidence ranged from close to zero in Freetown, Tamale and Harare to 149 cases per 100,000 population in Los Angeles. For pre-term birth, modelled impacts ranged from a reduction of 135 per 100,000 births in Dar es Salaam to 2,818 per 100,000 births in Bhubaneswar and, for low birthweight, from 75 per 100,000 births in Dar es Salaam to 2,951 per 100,000 births in Dhaka. The large variations chiefly reflect differences in the magnitudes of air pollution reductions and estimated underlying disease rates. Across the 16 cities, the reduction in childhood asthma incidence represents more than one-fifth of the current burden, and an almost 10% reduction in pre-term and low birthweight births. Decarbonization actions that remove combustion-related emissions contributing to ambient PM_2.5 and NO₂ would likely lead to substantial but geographically-varied reductions in childhood asthma and adverse birth outcomes, though there are uncertainties in causality and the precision of estimates.

Changes in tropospheric air quality related to the protection of stratospheric ozone in a changing climate

Ultraviolet (UV) radiation drives the net production of tropospheric ozone (O3) and a large fraction of particulate matter (PM) including sulfate, nitrate, and secondary organic aerosols. Ground-level O3 and PM are detrimental to human health, leading to several million premature deaths per year globally, and have adverse effects on plants and the yields of crops. The Montreal Protocol has prevented large increases in UV radiation that would have had major impacts on air quality. Future scenarios in which stratospheric O3 returns to 1980 values or even exceeds them (the so-called super-recovery) will tend to ameliorate urban ground-level O3 slightly but worsen it in rural areas. Furthermore, recovery of stratospheric O3 is expected to increase the amount of O3 transported into the troposphere by meteorological processes that are sensitive to climate change. UV radiation also generates hydroxyl radicals (OH) that control the amounts of many environmentally important chemicals in the atmosphere including some greenhouse gases, e.g., methane (CH4), and some short-lived ozone-depleting substances (ODSs). Recent modeling studies have shown that the increases in UV radiation associated with the depletion of stratospheric ozone over 1980-2020 have contributed a small increase (~ 3%) to the globally averaged concentrations of OH. Replacements for ODSs include chemicals that react with OH radicals, hence preventing the transport of these chemicals to the stratosphere. Some of these chemicals, e.g., hydrofluorocarbons that are currently being phased out, and hydrofluoroolefins now used increasingly, decompose into products whose fate in the environment warrants further investigation. One such product, trifluoroacetic acid (TFA), has no obvious pathway of degradation and might accumulate in some water bodies, but is unlikely to cause adverse effects out to 2100.

Ambient air pollution and gestational diabetes mellitus: An updated systematic review and meta-analysis

OBJECTIVE

We aimed to evaluate the relationship between the composition of particulate matter (PM) and gestational diabetes mellitus (GDM) by a comprehensively review of epidemiological studies.

METHODS

We systematically identified cohort studies related to air pollution and GDM risk before February 8, 2023 from six databases (PubMed, Embase, Web of Science Core Collection, China National Knowledge Infrastructure, Wanfang Data Knowledge Service Platform and Chongqing VIP Chinese Science and Technology Periodical databases). We calculated the relative risk (RR) and its 95% confidence intervals (CIs) to assess the overall effect by using a random effects model.

RESULTS

This meta-analysis of 31 eligible cohort studies showed that exposure to PM_2.5, PM₁₀, SO₂, and NO₂ was associated with a significantly increased risk of GDM, especially in preconception and first trimester. Analysis of the components of PM_2.5 found that the risk of GDM was strongly linked to black carbon (BC) and nitrates (NO₃^-). Specifically, BC exposure in the second trimester and NO₃^- exposure in the first trimester elevated the risk of GDM, with the RR of 1.128 (1.032-1.231) and 1.128 (1.032-1.231), respectively. The stratified analysis showed stronger correlations of GDM risk with higher levels of pollutants in Asia, except for PM_2.5 and BC, which suggested that the specific composition of particulate pollutants had a greater effect on the exposure-outcome association than the concentration.

CONCLUSIONS

Our study found that ambient air pollutant is a critical factor for GDM and further studies on specific particulate matter components should be considered in the future.

A global review of the state of the evidence of household air pollution's contribution to ambient fine particulate matter and their related health impacts

Direct exposure to household fine particulate air pollution (HAP) associated with inefficient combustion of fuels (wood, charcoal, coal, crop residues, kerosene, etc.) for cooking, space-heating, and lighting is estimated to result in 2.3 (1.6-3.1) million premature yearly deaths globally. HAP emitted indoors escapes outdoors and is a leading source of outdoor ambient fine particulate air pollution (AAP) in low- and middle-income countries, often being a larger contributor than well-recognized sources including road transport, industry, coal-fired power plants, brick kilns, and construction dust. We review published scientific studies that model the contribution of HAP to AAP at global and major sub-regional scales. We describe strengths and limitations of the current state of knowledge on HAP's contribution to AAP and the related impact on public health and provide recommendations to improve these estimates. We find that HAP is a dominant source of ambient fine particulate matter (PM2.5) globally - regardless of variations in model types, configurations, and emission inventories used - that contributes approximately 20 % of total global PM2.5 exposure. There are large regional variations: in South Asia, HAP contributes ∼ 30 % of ambient PM2.5, while in high-income North America the fraction is ∼ 7 %. The median estimate indicates that the household contribution to ambient air pollution results in a substantial premature mortality burden globally of about 0.77(0.54-1) million excess deaths, in addition to the 2.3 (1.6-3.1) million deaths from direct HAP exposure. Coordinated global action is required to avert this burden.

Air pollution as a substantial threat to the improvement of agricultural total factor productivity: Global evidence

OBJECTIVE

This study aims to provide empirical evidence about whether and to what extent air pollution affects the global agricultural total factor productivity (TFP).

METHODS

The research sample covers 146 countries all over the world during 2010-2019. Two-way fixed effects panel regression models are used to estimate air pollution's impacts. A random forest analysis is conducted to assess the relative importance of independent variables.

RESULTS

The results show that, on average, a 1% increase in fine particulate matter (PM_2.5) and tropospheric ozone (O₃) concentration would cause the agricultural TFP to decline by 0.104% and 0.207%, respectively. Air pollution's adverse impact widely exists in various countries with different development levels, pollution degrees, and industrial structures. This study also finds that temperature has a moderating effect on the relationship between PM_2.5 and agricultural TFP. PM_2.5 pollution's detrimental impact is weaker (stronger) in a warmer (cooler) climate. In addition, the random forest analysis confirms that air pollution is among the most crucial predictors of agricultural productivity.

CONCLUSIONS

Air pollution is a substantial threat to the improvement of global agricultural TFP. Worldwide actions should be taken to ameliorate air quality, for the sake of agricultural sustainability and global food security.

Air pollution impacts on in-hospital case-fatality rate of ischemic stroke patients

BACKGROUND

A growing body of evidence suggests that air pollution exposure is associated with an increased risk for cardiovascular diseases. Data regarding the impact of long-term air pollution exposure on ischemic stroke mortality are sparse.

METHODS

The German nationwide inpatient sample was used to analyse all cases of hospitalized patients with ischemic stroke in Germany 2015-2019, which were stratified according to their residency. Data of the German Federal Environmental Agency regarding average values of air pollutants were assessed from 2015 to 2019 at district-level. Data were combined and the impact of different air pollution parameters on in-hospital case-fatality was analyzed.

RESULTS

Overall, 1,505,496 hospitalizations of patients with ischemic stroke (47.7% females; 67.4 % ≥70 years old) were counted in Germany 2015-2019, of whom 8.2 % died during hospitalization. When comparing patients with residency in federal districts with high vs. low long-term air pollution, enhanced levels of benzene (OR 1.082 [95%CI 1.034-1.132],P = 0.001), ozone (O_3, OR 1.123 [95%CI 1.070-1.178],P < 0.001), nitric oxide (NO, OR 1.076 [95%CI 1.027-1.127],P = 0.002) and PM_2.5 fine particulate matter concentrations (OR 1.126 [95%CI 1.074-1.180],P < 0.001) were significantly associated with increased case-fatality independent from age, sex, cardiovascular risk-factors, comorbidities, and revascularization treatments. Conversely, enhanced carbon monoxide, nitrogen dioxide, PM_10, and sulphur dioxide (SO₂) concentrations were not significantly associated with stroke mortality. However, SO_2-concentrations were significantly associated with stroke-case-fatality rate of >8 % independent of residence area-type and area use (OR 1.518 [95%CI 1.012-2.278],P = 0.044).

CONCLUSION

Elevated long-term air pollution levels in residential areas in Germany, notably of benzene, O₃, NO, SO_2, and PM_2.5, were associated with increased stroke mortality of patients.

RESEARCH IN CONTEXT

Evidence before this study: Besides typical, established risk factors, increasing evidence suggests that air pollution is an important and growing risk factor for stroke events, estimated to be responsible for approximately 14 % of all stroke-associated deaths. However, real-world data regarding the impact of long-term exposure to air pollution on stroke mortality are sparse. Added value of this study: The present study demonstrates that the long-term exposure to the air pollutants benzene, O₃, NO, SO₂ and PM_2.5 are independently associated with increased case-fatality of hospitalized patients with ischemic stroke in Germany. Implications of all the available evidence: The results of our study support the urgent need to reduce the exposure to air pollution by tightening emission controls to reduce the stroke burden and stroke mortality.

Prediction of effect of wind speed on air pollution level using machine learning technique

Air pollution is one of the most challenging issues poses serious threat to human health and environment. The increasing influx of population in metropolitan cities has further worsened the situation. Quantifying the air pollution experimentally is quite a challenging task as it depends on many parameters viz., wind speed, wind temperature, relative humidity, temperature etc. It requires the investment of huge money and manpower for controlling air pollution. Machine learning technique-based computer modelling reduces both of the parameters. In the present work, the dependence of air pollution level on wind speed and temperature has been taken up using machine learning in the form of ANN and LSTM model. The recorded data of air pollution level (PM2.5) is collected from a measurement station of Lucknow city situated at Central School, CPCB. The data is used in an Artificial Neural based network and in an LSTM model to predict suitably the level of air pollution for a known value of average wind speed and temperature without experimental measurements. LSTM model is found to predict the pollution level better than ANN for the developed ANN networks.

Characteristics, health risks, and premature mortality attributable to ambient air pollutants in four functional areas in Jining, China

Air pollution is one of the leading causes for global deaths and understanding pollutant emission sources is key to successful mitigation policies. Air quality data in the urban, suburban, industrial, and rural areas (UA, SA, IA, and RA) of Jining, Shandong Province in China, were collected to compare the characteristics and associated health risks. The average concentrations of PM_2.5, PM₁₀, SO₂, NO₂, and CO show differences of -3.87, -16.67, -19.24, -15.74, and -8.37% between 2017 and 2018. On the contrary, O₃ concentrations increased by 4.50%. The four functional areas exhibited the same seasonal variations and diurnal patterns in air pollutants, with the highest exposure excess risks (ERs) resulting from O₃. More frequent ER days occurred within the 25-30°C, but much larger ERs are found within the 0-5°C temperature range, attributed to higher O₃ pollution in summer and more severe PM pollution in winter. The premature deaths attributable to six air pollutants can be calculated in 2017 and 2018, respectively. Investigations on the potential source show that the ER of O₃ (r of 0.86) had the tightest association with the total ER. The bivariate polar plots indicated that the highest health-based air quality index (HAQI) in IA influences the HAQI in UA and SA by pollution transport, and thus can be regarded as the major pollutant emission source in Jining. The above results indicate that urgent measures should be taken to reduce O₃ pollution taking into account the characteristics of the prevalent ozone formation regime, especially in IA in Jining.

Mortality Attributable to Ambient Air Pollution: A Review of Global Estimates

Since the publication of the first epidemiological study to establish the connection between long-term exposure to atmospheric pollution and effects on human health, major efforts have been dedicated to estimate the attributable mortality burden, especially in the context of the Global Burden of Disease (GBD). In this work, we review the estimates of excess mortality attributable to outdoor air pollution at the global scale, by comparing studies available in the literature. We find large differences between the estimates, which are related to the exposure response functions as well as the number of health outcomes included in the calculations, aspects where further improvements are necessary. Furthermore, we show that despite the considerable advancements in our understanding of health impacts of air pollution and the consequent improvement in the accuracy of the global estimates, their precision has not increased in the last decades. We offer recommendations for future measurements and research directions, which will help to improve our understanding and quantification of air pollution-health relationships.

Two-year-long high-time-resolution apportionment of primary and secondary carbonaceous aerosols in the Los Angeles Basin using an advanced total carbon-black carbon (TC-BC(λ)) method

In recent years, carbonaceous aerosols (CA) have been recognized as a significant contributor to the concentration of particles smaller than 2.5 μm (i.e., PM_2.5), with a negative impact on public health and Earth's radiative balance. In this study, we present a method for CA apportionment based on high-time-resolution measurements of total carbon (TC), black carbon (BC), and spectral dependence of absorption coefficient using a recently developed Carbonaceous Aerosol Speciation System (CASS). Two-year-long CA measurements at two different locations within California's Los Angeles Basin are presented. CA was apportioned based on its optical absorption properties, organic or elemental carbon composition, and primary or secondary origin. We found that the secondary organic aerosols (SOA), on average, represent >50 % of CA in the study area, presumably resulting from the oxidation of anthropogenic and biogenic volatile organic components. Remarkable peaks of SOA in summer afternoons were observed, with a fractional contribution of up to 90 %. On the other hand, the peak of primary emitted CA, consisting of BC and primary organic aerosol (POA), contributed >80 % to the CA during morning rush hours on winter working days. The light absorption of BC dominated over the brown carbon (BrC), which contributed to 20 % and 10 % of optical absorption at the lower wavelength of 370 nm during winter nights and summer afternoons, respectively. The highest contribution of BrC, up to 50 %, was observed during the wildfire periods. Although the uncertainty levels can be high for some CA components (such as split between primary emitted and secondary formed BrC during winter nights), further research focused on the optical properties of CA at different locations may help to better constrain the parameters used in CA apportionment studies. We believe that the CASS system combined with the apportionment method presented in this study can offer simplified and cost-effective insights into the composition of carbonaceous aerosols.

Black carbon and elemental characterization of PM2.5 in dense traffic areas in two cities in Fiji, a Small Island Developing State

PM_2.5 characterizations are essential in understanding its impact on the health of the exposed population. Sampled PM_2.5 by Mani et al. (2020) was characterized to determine atmospheric metal concentration and inhalation health risk in Suva and Lautoka Cities, the only two cities in Fiji and one of the largest in the South Pacific Islands. Twenty-two elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Si, Sr, V, Zn) were analyzed using ICP-OES. Black Carbon (BC) sampling was also done at three different sites in Suva City, namely, Fiji National University Samabula Intersection site, Suva City Bus Station site and the Reservoir Road Community Settlement Site as well as at Lautoka City Bus Station. Mean BC concentrations over the sampling period were found to be 3.9 ± 2.9 (median = 3.3 μg/m³), 2.6 ± 2.7 μg/m³ (median = 1.7 μg/m³), 2.4 ± 2.3 μg/m³ (median = 1.7 μg/m³) and 4.0 ± 4.7 μg/m³ (median = 2.4 μg/m³) respectively. Health risk assessments (Carcinogenic Risk (CR) and Non-Carcinogenic Risk (HQ)) were also done to assess the risk of inhalation exposure in adults and children. The Hazard Index for children in Lautoka (HI = 1.03) was found to slightly exceed the safe level of 1. This study provides the first inventory of atmospheric particulate bound metal concentrations and diurnal BC profiles in Fiji and informs policy makers and scientists for further studies.

How the Air Clean Plan and carbon mitigation measures co-benefited China in PM2.5 reduction and health from 2014 to 2020

China implemented a stringent Air Clean Plan (ACP) since 2013 to address environmental and health risks caused by ambient fine particulate matter (PM_2.5). However, the policy effectiveness of ACP and co-benefits of carbon mitigation measures to environment and health are still largely unknown. Using satellite-based PM_2.5 products produced in our previous study, concentration-response functions, and the logarithmic mean Divisia index (LMDI) method, we analyzed the spatiotemporal dynamics of premature deaths attributable to PM_2.5 exposure, and quantitatively estimated the policy benefits of ACP and carbon mitigation measures. We found the annual PM_2.5 concentrations in China decreased by 33.65 % (13.41 μg m^-3) from 2014 to 2020, accompanied by a decrease in PM_2.5-attributable premature deaths of 0.23 million (95 % confidence interval (CI): 0.22-0.27), indicating the huge benefits of China ACP for human health and environment. However, there were still 1.12 million (95 % CI: 0.79-1.56) premature deaths caused by the exposure of PM_2.5 in mainland China in 2020. Among all ACP measures, clean production (contributed 55.98 % and 51.14 % to decrease in PM_2.5 and premature deaths attributable to PM_2.5) and energy consumption control (contributed 32.58 % and 29.54 % to decrease in PM_2.5 and premature deaths attributable to PM_2.5) made the largest contribution during the past seven years. Nevertheless, the environmental and health benefits of ACP are not fully synergistic in different regions, and the effectiveness of ACP measures reduced from 2018 to 2020. The co-effects of CO₂ and PM_2.5 has become one of the major drivers for PM_2.5 and premature deaths reduction since 2018, confirming the clear environment and health co-benefits of carbon mitigation measures. Our study suggests, with the saturation of clean production and source control, more targeted region-specific strategies and synergistic air pollution-carbon mitigation measures are critical to achieving the WHO's Air Quality Guideline target and the UN's Sustainable Development Goal Target in China.

Black carbon toxicity dependence on particle coating: Measurements with a novel cell exposure method

Black carbon (BC) is a component of ambient particulate matter which originates from incomplete combustion emissions. BC is regarded as an important short-lived climate forcer, and a significant public health hazard. These two concerns have made BC a focus in aerosol science. Even though, the toxicity of BC particles is well recognized, the mechanism of toxicity for BC as a part of the total gas and particle emission mixture from combustion is still largely unknown and studies concerning it are scarce. In the present study, using a novel thermophoresis-based air-liquid interface (ALI) in vitro exposure system, we studied the toxicity of combustion-generated aerosols containing high levels of BC, diluted to atmospheric levels (1 to 10 μg/m³). Applying multiple different aerosol treatments, we simulated different sources and atmospheric aging processes, and utilizing several toxicological endpoints, we thoroughly examined emission toxicity. Our results revealed that an organic coating on the BC particles increased the toxicity, which was seen as larger genotoxicity and immunosuppression. Furthermore, aging of the aerosol also increased its toxicity. A deeper statistical analysis of the results supported our initial conclusions and additionally revealed that toxicity increased with decreasing particle size. These findings regarding BC toxicity can be applied to support policies and technologies to reduce the most hazardous compositions of BC emissions. Additionally, our study showed that the thermophoretic ALI system is both a suitable and useful tool for toxicological studies of emission aerosols.