Fine particulate matter constituents and cardiopulmonary mortality in a heavily polluted Chinese city

Prenatal Exposure to Specific PM2.5 Chemical Constituents and Preterm Birth in China: A Nationwide Cohort Study

Exposure to fine particulate matter (PM_2.5) during pregnancy has been associated with preterm birth (PTB). However, the existing evidence is inconsistent, and the roles of specific PM_2.5 chemical constituents remain unclear. Based on the China Labor and Delivery Survey, we included birth data from 89 hospitals in 25 provinces in mainland China, and conducted a national multicenter cohort study to examine the associations of PM_2.5 and its chemical constituents with PTB risk in China. We applied satellite-based models to predict prenatal PM_2.5 mass and six main component exposure. Multilevel logistic regression analysis was used to examine the associations, controlling for sociodemographic characteristics, seasonality, and spatial variation. We observe an increased PTB risk with an increase in PM_2.5 mass and the most significant association is found during the third trimester when the adjusted odds ratio (OR) per interquartile range increases in PM_2.5 total mass is 1.12 (95% confidence Interval, CI: 1.05-1.20). Infants conceived by assisted reproductive technology (ART) show greater PTB risk associated with PM_2.5 exposure (OR = 1.33, 95% CI: 1.05-1.69) than those conceived naturally (OR = 1.11, 95% CI: 1.03-1.19). We also find black carbon, sulfate, ammonium and nitrate, often linked to fossil combustion, have comparable or larger estimates of the effect (OR = 1.07-1.14) than PM_2.5. Our findings provide evidence that components mainly from fossil fuel combustion may have a perceptible influence on increased PTB risk associated with PM_2.5 exposure in China. Additionally, compared to natural conception, conception through ART may be more susceptible to PM_2.5 exposure.

Distribution characteristics and policy-related improvements of PM2.5 and its components in six Chinese cities

This study presents the distribution characteristics and possible sources of fine particulate matter (PM_2.5) and its components, as well as policy-related pollution reduction in the Chinese cities of Jinan, Shijiazhuang (SJZ), Chengdu, Wuxi, Wuhan, and Harbin (HRB). PM_2.5 samples were collected using mid-volume samplers during the autumn of 2017 in all six cities. The samples were analyzed to determine the ambient PM_2.5 compositions, including the concentrations of water-soluble inorganic ions (WSIIs), carbonaceous aerosols, and elements concentrations. The chemical ratios of organic carbon to elemental carbon and nitrate to sulfate as well as the enrichment factors of elements were calculated to establish the possible sources of PM_2.5 in all six cities. The highest PM_2.5 concentration was 152 μg/m³ in SJZ, while the lowest concentration was 47 μg/m³ in HRB. During the sampling period in these six cities, the PM_2.5 concentrations exceeded the World Health Organization recommended daily average air quality guidelines by 2.4-6.1 times, and WSIIs, carbonaceous aerosols, and elements accounted for 31.8%-61.6%, 9.8%-35.1%, and 0.9%-2.5% of the PM_2.5, respectively. In 2013, the Chinese government formulated the Air Pollution Prevention and Control Action Plan (APPCAP) for controlling air pollution, and effective measures have been implemented since then. Compared with previous studies conducted during 2009-2013 before the implementation of the APPCAP, the concentrations of PM_2.5 and most of its components decreased to varying degrees, and large changes in the chemical ratios of PM_2.5 components were observed. These results indicate that PM_2.5 sources vary among these six cities and that China has improved the ambient air quality in these cities through the implementation of air pollution control policies. The APPCAP have achieved considerable results in continuously reducing pollution concentrations, although the air pollution concentrations observed in this study remain high compared with those of other countries.

Spatiotemporal patterns of PM2.5 elemental composition over China and associated health risks

Trace metals in atmospheric particulate matter (PM) are a serious threat to public health. Although pollution from toxic metals has been investigated in many Chinese cities, the spatial and temporal patterns in PM_2.5 remain largely unknown. Long-term PM_2.5 field sampling in 11 cities, combined with a systemic literature survey covering 51 cities, provides the first comprehensive database of 21 PM_2.5-bound trace metals in China. Our results revealed that PM_2.5 elemental compositions varied greatly, with generally higher levels in North China, especially for crustal elements. Pollution with Cr, As, and Cd was most serious, with 61, 38, and 16 sites, respectively, surpassing national standards, including some in rural areas. Local emissions, particularly from metallurgical industries, were the dominant factors driving the distribution in polluted cities such as Hengyang, Yuncheng, and Baiyin, which are mainly in North and Central China. Elevated As, Cd, and Cr levels in Yunnan, Guizhou Province within Southwest China were attributed to the high metal content of local coal. Diverse temporal trends of various elements that differed among regions indicated the complexity of emission patterns across the country. The results demonstrated high non-carcinogenic risks for those exposed to trace metals, especially for children and residents of heavily cities highly polluted with As, Pb, or Mn. The estimated carcinogenic risks ranged from 6.61 × 10^-6 to 1.92 × 10^-4 throughout China, with As being the highest priority element for control, followed by Cr and Cd. Regional diversity in major toxic metals was also revealed, highlighting the need for regional mitigation policies to protect vulnerable populations.

Complexation of Fe(III)/Catechols in atmospheric aqueous phase and the consequent cytotoxicity assessment in human bronchial epithelial cells (BEAS-2B)

Recent research has shown that the complexation of metals-organics plays an important role in atmospheric particulate matter, whose health effects should be taken into account. This work investigates the interactions between catechols (CAs), i.e., 4-nitrocatechol (4NC) and 4-methylcatechol (4MC), and transition metals (i.e., Fe) in the aqueous phase dark reaction. The formation of Fe/CAs complexes and secondary organics products are analyzed by UV-Vis spectroscopy, stopped-flow spectroscopy, high-resolution mass spectrometry and Raman spectroscopy, while the insoluble particulate matter formed from the CAs/Fe mixtures are characterized by the FTIR, X-ray photoelectron spectroscopy (XPS) and thermogravimetric-quadrupole-mass spectrometry (TG-Q-MS). On the basis of the density functional theory (DFT) calculation and experimental results, the possible formation pathways for the complexes of Fe(III) with 4NC (a proxy for organics) are proposed. The Fe/CAs complexes and organics products perhaps have significant sources of light absorption which play an important role in influencing the intensity of atmospheric radiation and particulate phase photochemistry. Besides, the cytotoxicity is tested as a function of concentrations for CAs/Fe mixtures in BEAS-2B cells. Our results show that CAs/Fe mixtures have strong association with cytotoxicity, indicating the mixtures have potential influence to human health.

Source apportionment and health risk assessment of airborne particulates over central Indo-Gangetic Plain

Sources of airborne particulates (PM₁₀) were investigated in two contrasting sites over central Indo-Gangetic Plain (IGP), one representing a rural background (Mirzapur) and another as an urban pollution hotspot (Varanasi). Very high PM₁₀ concentration was noted both in Varanasi (178 ± 105 μgm^-3; N:435) and Mirzapur (131 ± 56 μgm^-3; N:169) with 72% and 62% of monitoring days exceeded the national air quality standard, respectively. Particulate-bound elements contribute significant proportion of PM₁₀ mass (15%-18%), with highest contribution from Ca (7%-10%) and Fe (2%-3%). Besides, presence of Zn (1%-3%), K (1%-2%) and Na (1%-2%) was also noted. Water-soluble ionic species contributed 15%-19% of particulate mass, primarily by the secondary inorganic aerosols (SIA). Among the SIA, sulphate (5%-7%) and nitrate (4%) were prominent, contributing 59%-62% of the total ionic load, especially in winter. Particulate-bound metallic species and ions were selectively used as signatory molecules and source apportionment of PM₁₀ was done by multivariate factor analysis. UNMIX was able to extract particulate sources in both the locations and crustal resuspensions (dust/-soil) were identified as the dominant source contributing 57%-63% of PM₁₀ mass. Secondary aerosols were the second important source (17%-23%), followed by emissions from biomass/-refuse burning (10-19%). Transport of airborne particulates from upper IGP by prevailing westerly were identified as the important contributor of particulates, especially during high particulate loading days. Health risks associated to particulate-bound toxic metal exposure were also assessed. Non-carcinogenic health risk was within the permissible limit while there is possibility of elevated risk for PM₁₀-bound Cr and Cd, if adequate control measures are not in place.

Particle-induced oxidative damage by indoor size-segregated particulate matter from coal-burning homes in the Xuanwei lung cancer epidemic area, Yunnan Province, China

Size-segregated samples of airborne particulate matter were collected at the coal-burning homes of the Hutou high lung cancer epidemic village and a comparison site Xize village of the Xuanwei County, Yuanan Province, by an Anderson Cascade Impact Sampler in winter and spring to study the toxicological characteristics of different-sized particles. The DNA damage caused by the water-soluble fractions of these size-segregated particles was analyzed by the plasmid scission assay, and the trace element compositions were determined by Inductively Coupled Plasma Mass Spectrometry. The DNA damage rate from the airborne particles in the high lung cancer incidence area was higher than that in Xize village. The different-sized particles have highly varying DNA damage rates, with the values being greater in the small size range than in the large size range. The particle-induced DNA damage rates had a significantly positive correlation with total water-soluble trace elements. Further analysis of the individual elements indicated that the water-soluble heavy metals Zn, Cu, Cd, Rb, Cs, and Sb had a positive correlation with the particle-induced DNA damage, implying that these water-soluble heavy metals played an important role in the DNA damage. The Sr had a negative correlation with the particle-induced DNA damage, suggesting that the water-soluble Sr might counter DNA damage. The mass concentrations of the total and individual water-soluble trace elements were mostly enriched in the small particle size ranges, thus implying the indoor airborne particles in the small size ranges would have a higher health risk.

The Silver Lining of COVID-19: Estimation of Short-Term Health Impacts Due to Lockdown in the Yangtze River Delta Region, China

The outbreak of COVID-19 in China has led to massive lockdowns in order to reduce the spread of the epidemic and control human-to-human transmission. Subsequent reductions in various anthropogenic activities have led to improved air quality during the lockdown. In this study, we apply a widely used exposure-response function to estimate the short-term health impacts associated with PM_2.5 changes over the Yangtze River Delta (YRD) region due to COVID-19 lockdown. Concentrations of PM_2.5 during lockdown period reduced by 22.9% to 54.0% compared to pre-lockdown level. Estimated PM_2.5-related daily premature mortality during lockdown period is 895 (95% confidential interval: 637-1,081), which is 43.3% lower than pre-lockdown period and 46.5% lower compared with averages of 2017-2019. According to our calculation, total number of avoided premature death aassociated with PM_2.5 reduction during the lockdown is estimated to be 42.4 thousand over the YRD region, with Shanghai, Wenzhou, Suzhou (Jiangsu province), Nanjing, and Nantong being the top five cities with largest health benefits. Avoided premature mortality is mostly contributed by reduced death associated with stroke (16.9 thousand, accounting for 40.0%), ischemic heart disease (14.0 thousand, 33.2%), and chronic obstructive pulmonary disease (7.6 thousand, 18.0%). Our calculations do not support or advocate any idea that pandemics produce a positive note to community health. We simply present health benefits from air pollution improvement due to large emission reductions from lowered human and industrial activities. Our results show that continuous efforts to improve air quality are essential to protect public health, especially over city-clusters with dense population.

Study on the characteristics of black carbon during atmospheric pollution conditions in Beijing

Black carbon (BC), not only has a negative impact on human health, but also contributes to visibility degradation and the attenuation of solar radiation due to light absorption. In this paper, we investigated the variations of BC concentration, BC optical characteristics and its effects on the physical and optical properties of atmospheric aerosols based on AERONET data during atmospheric pollution conditions in Beijing from 2012 to 2017. The results indicated that the average annual ground-level BC concentration and BC/PM_2.5 were 8.9 μg m^-3 and 6.7%, respectively, from 2012 to 2017 during atmospheric pollution conditions in Beijing. The annual mean ground-level BC concentration showed weak variation, but the monthly variation was pronounced during atmospheric pollution conditions. Moreover, the BC column concentration had a higher correlation with absorptive aerosol optical thickness (AAOT) at 870 nm (R² = 0.93) than 440 nm (R² = 0.73). The difference in AAOT between 440 nm and 870 nm was more significant under high BC column concentration. The seasonal variation of the BC column concentration that contributed to the AAOT at 870 nm displayed a consistent monthly average variation tendency. The BC column concentrations were divided into three segments of low, moderate, and high according to the results of the approximately normal distribution of the BC column concentration. Compared with high BC concentration, the single scattering albedo (SSA) and asymmetry parameter were enhanced by 0.05 and 0.04 in low BC concentrations, respectively. On the contrary, the fine mode fraction (FMF) was dropped by 12.5% in low BC concentrations. A higher BC concentration contributed to the enhancement in the AAOT and the extinction ratio of the fine mode aerosol. Meanwhile, the atmospheric particles' forward scattering ability was also attenuated under a high BC concentration.

Air pollution characteristics and human health risks in key cities of northwest China

Air pollution events occur frequently in northwest China, which results in serious detrimental effects on human health. Therefore, it is essential to understand the air pollution characteristics and assess the risks to humans. In this study, we analyzed the pollution characteristics of criteria pollutants in six key cities in northwest China from 2015 to 2018. We used the air quality index (AQI), aggregate AQI (AAQI), and health-risk based AQI (HAQI) to assess the health risks and determine the proportion of people exposed to air pollution. Additionally, on this basis, the AirQ_2.2.3 model was used to quantify the health effects of the pollutants. The results showed that PM₁₀ pollution occurred mainly in spring and winter and was caused by frequent dust storms. PM_2.5 pollution was caused mainly by anthropogenic activities (especially coal-fired heating in winter). Because of a series of government policies and pollutant reduction measures, PM_2.5, SO₂, NO₂, and CO concentrations showed a downward trend during the study period (except for a small increase in the case of NO₂ in some years.). However, O₃ showed high concentrations due to the high intensity of solar radiation in summer and inadequate emission reduction measures. The air quality levels based on their classification were generally higher than the Chinese ambient air quality standard classified by the AQI index. We also found that the higher the AQI index was, the more serious the air pollution classified based on the AAQI and HAQI indices was. The HAQI index could better reflect the impact of pollutants on human health. Based on the HAQI index, 20% of the population in the study area was exposed to polluted air. The total mortality values attributable to PM₁₀, PM_2.5, SO₂, O₃, NO₂, and CO, quantified by the AirQ_2.2.3 model, were 3.00%, 1.02%, 1.00%, 4.22%, 1.57%, and 0.95% (Confidence Interval:95%), respectively; the attributable proportions of mortality for respiratory system and cardiovascular diseases were consistent with the change rule of total mortality, because the number of deaths attributable to the latter was greater than that for the former. According to the exposure reaction curves of pollutants, PM₁₀ and PM_2.5 still showed a large change at high concentrations. However, the tendencies of SO₂, NO₂, CO, and O₃ were more obvious under low concentration exposure, which indicated that the expected mortality rate due to lower air pollution concentrations was much higher than the mortality due to high air pollution concentrations.

Impact of emission reduction on aerosol-radiation interaction during heavy pollution periods over Beijing-Tianjin-Hebei region in China

In December 2015, the Beijing-Tianjin-Hebei (BTH) region experienced several episodes of heavy air pollution. The government immediately issued emergency control measures to reduce the pollution, which provided a good opportunity to explore the impact of emission reduction on aerosol-radiation interaction. In this study, four tests were conducted, including the base1 simulation with emission reduction and aerosol-radiation interaction on, the base2 simulation with emission reduction and aerosol-radiation interaction off, the scenario1 simulation without emission reduction and aerosol-radiation interaction on and the scenario2 simulation without emission reduction and aerosol-radiation interaction off. We find that the aerosol-radiation interaction decreased the downward shortwave radiation and the temperature at 2 m, reduced the planetary boundary layer height (PBLH) in the region, and increased the relative humidity at 2 m, which is favorable for pollution accumulation. Our results revealed that the interaction effect due to emission reductions increased downward shortwave radiation by an average of 0-5 W/m², leading to increase in surface temperature of 0-0.05°C, increase in the daytime mean PBL high of 0-8 m, and decrease in daytime mean relative humidity at 2 m of 0.5%. We found that if there were aerosol-radiation interaction, it would enhance the effectiveness of emission control measures on air pollution control. The enhance of PM_2.5 (particulate matter less than 2.5 µm), PM₁₀ (particulate matter less than 10 µm), and NO₂ (nitrogen dioxide) emission reduction effects reached 7.62%, 6.90%, 11.62%, respectively, over this region.

Secondary aerosol formation and its linkage with synoptic conditions during winter haze pollution over eastern China

Eastern China has been facing severe winter haze pollution due mainly to secondary aerosol. Existing studies have suggested that stagnant weather or fast chemical production led to frequent haze in this region. However, few works focus on the linkage between secondary production of sulfate, nitrate, and ammonium (SNA) and synoptic conditions, and their joint contribution to PM_2.5. In this study, by combining in-situ measurements on meteorology and aerosol chemical composition at three main cities together with a regional model with improved diagnose scheme, we investigated the chemical formation and accumulation of main secondary composition, i.e. SNA under typical synoptic conditions. It is indicated that SNA did play a vital role in haze pollution across eastern China, contributing more than 40% to PM_2.5 mass concentration. As most fast developing region, the Yangtze River Delta (YRD) was slightly polluted during stable weather with local chemical production accounting for 61% SNA pollution. While under the influence of cold front, the pollution was aggravated and advection transport became the predominant contributive process (85%). Nevertheless, the chemical production of SNA was notably enhanced due to the uplift of air pollutant and elevated humidity ahead of the cold front, which then facilitated the heterogeneous and aqueous-phase oxidation of precursors. We also found the substantial difference in the phase equilibrium of nitrate over the land surface and ocean due to changes in temperature, ammonia availability and dry deposition. This study highlights the close link between synoptic weather and chemical production, and the resultant vertical and spatial heterogeneity of pollution.

Field Determination of Nitrate Formation Pathway in Winter Beijing

Particulate nitrate (pNO₃^-) has often been found to be the major component of fine particles in urban air-sheds in China, the United States, and Europe during winter haze episodes in recent years. However, there is a lack of knowledge regarding the experimentally determined contribution of different chemical pathways to the formation of pNO₃^-. Here, for the first time, we combine ground and tall-tower observations to quantify the chemical formation of pNO₃^- using observationally constrained model approach based on direct observations of OH and N₂O₅ for the urban air-shed. We find that the gas-phase oxidation pathway (OH+NO₂) during the daytime is the dominant channel over the nocturnal uptake of N₂O₅ during pollution episodes, with percentages of 74% in urban areas and 76% in suburban areas. This is quite different from previous studies in some regions of the US, in which the uptake of N₂O₅ was concluded to account for a larger contribution in winter. These results indicate that the driving factor of nitrate pollution in Beijing and different regions of the US is different, as are the mitigation strategies for particulate nitrate.

Summer storms and their effects on the spectrum and quantity of airborne bioparticles in Bratislava, Central Europe

A thunderstorm is a risk factor for severe respiratory allergy or asthma attacks in patients suffering from pollen/spore allergy. This study aimed to investigate the changes in the spectrum and quantity of pollen and fungal spores in the air of Bratislava during summer storms as well as the impact of selected environmental parameters on these changes. Pollen/spore samples were collected using a Burkard volumetric aerospore trap during summer 2016. To identify those types of pollen/spores that may harm human health during the storm episodes, we analysed how the concentration of individual bioparticles in the air changed during pre-storm/storm/post-storm periods. The effect of environmental variables on the concentration of selected pollen/spore types was evaluated through Spearman's correlation analysis. The results of our study suggest that thunderstorm-related respiratory allergy symptoms in the study area may be caused by (1) spores of Myxomycetes, the airborne concentration of which increases due to an increase in wind speed during the pre-storm period; (2) ruptured pollen and Diatripaceae spores, the concentration of which increases due to increase in precipitation and relative air humidity, respectively, during the storm period; and (3) spores of Fusarium and Leptosphaeria, the concentration of which increases due to increase in precipitation and air temperature, respectively, during the post-storm period.

Association between early prenatal exposure to ambient air pollution and birth defects: evidence from newborns in Xi'an, China

BACKGROUND

The aim of this study was to investigate an association between birth defects and exposure to sulfur dioxide (SO2), nitrogen dioxide (NO2) and particles ≤10 μm in an aerodynamic diameter (PM10) during early pregnancy in Xi'an, China.

METHODS

Birth defect data were from the Birth Defects Monitoring System of Xi'an, and data on ambient air pollutants during 2010-15 were from the Xi'an Environmental Protection Bureau. A generalized additive model (GAM) was used to investigate the relationship between birth defects and ambient air pollutants.

RESULTS

Among the 8865 cases with birth defects analyzed, the overall incidence of birth defects was 117.33 per 10 000 infants. Ambient air pollutant exposure during the first trimester increased the risk of birth defects by 10.3% per 10 μg/m3 increment of NO2 and 3.4% per 10 μg/m3 increment of PM10. No significant association was found between birth defects and SO2. Moreover, NO2 increased risk of neural tube defects, congenital heart disease, congenital polydactyly, cleft palate, digestive system abnormalities and gastroschisis, and PM10 was associated with congenital heart disease and cleft lip with or without cleft palate.

CONCLUSIONS

Chinese women should avoid exposure to high levels of NO2 and PM10 during the first 3 months of pregnancy.

Association between short-term exposure to ambient air pollution and hospital visits for depression in China

Depression is one of the leading causes of disability, but the etiology remains unclear. Recently, it has been suggested that air pollution is a potential risk factor for depression. However, the results remained inconsistent. So we conducted this study to assess the association between short-term exposure to ambient air pollution and hospital visits for depression in China. Daily hospital visits for depression from January 18, 2013 to June 10, 2018 were extracted from a regional health information system (HIS) covered 1.34 million population in Ningbo, China. We collected daily air pollutant concentrations and meteorological data from environmental air quality monitoring sites and meteorological stations in the study area. Quasi-Poisson regression models with generalized additive models (GAM) were applied to explore the associations between air pollution and hospital visits for depression. Stratified analyses were also conducted by gender, age, and season to examine the effects modification. The results disclosed that air pollutants including PM_2.5, PM₁₀, SO₂, CO, and NO₂ were positively correlated with hospital visits for depression. The strongest effects all occurred on lag0 (the same) day, and the corresponding excess risks (ERs) were 2.59 (95%CI: 0.72, 4.49) for PM_2.5, 3.08 (95%CI: 1.05, 5.16) for PM₁₀, 3.22 (95%CI: 1.16, 5.32) for SO₂, 4.38 (95%CI: 1.83, 6.99) for CO, and 4.94 (95%CI: 2.03, 7.92) for NO₂ per IQR increase, respectively. The associations were found to be stronger in the elderly (≥65 years) and cold season. Furthermore, the effects of CO and NO₂ remained significant in most two-pollutant models, suggesting that traffic-related air pollutants might be more important triggers of depression.

Spatiotemporal and probability variations of surface PM2.5 over China between 2013 and 2019 and the associated changes in health risks: An integrative observation and model analysis

We used statistical methods and the GEOS-Chem model to interpret the observed spatiotemporal and probability variations of surface PM_2.5 concentrations in China from December 2013 to November 2019, as well as to assess the drivers for the variations and the implications for health risks associated with long-term and short-term exposure to PM_2.5. Annual and seasonal PM_2.5 concentrations have decreased over most areas in China during the 6-year period. We decomposed the observed day-to-day variation of PM_2.5 concentrations in eastern Chinese cities and found that it showed two distinct major spatial modes, which fluctuated in strength seasonally. The first mode, characterized by most of Eastern China being in the same phase, was mainly associated with the regional ventilation of pollutants. The second mode showed a dipolar pattern between the Beijing-Tianjin-Hebei area and the Yangtze River Delta area and was more prominent in summer. Using model simulations, we showed that this dipole mode was chemically driven by the secondary formation of sulfate in summer. We further used a gamma distribution to succinctly interpret the changes in the probability distributions of PM_2.5. We found that the nationwide decline in seasonal mean PM_2.5 concentrations mainly reflected decreased occurrences of extremely high PM_2.5 concentrations, which was strongly driven by the interannual variation of meteorology. These changes in the annual means and probability distributions of PM_2.5 since December 2013 has led to significant decline of the estimated mortality risks associated with long-term and short-term PM_2.5-exposures. Regions that were less polluted saw the largest relative benefit per unit decrease in PM_2.5 concentration, due to the steepness of the exposure-response curve at the low-concentration end. Our integrated methodology effectively diagnosed the drivers of PM_2.5 variability and the associated health risks and can be used as part of the decision tool for PM_2.5 pollution management over China.

Black carbon over an urban atmosphere in northern peninsular Southeast Asia: Characteristics, source apportionment, and associated health risks

Black carbon (BC) has been demonstrated to pose significant negative impacts on climate and human health. Equivalent BC (EBC) measurements were conducted using a 7-wavelength aethalometer, from March to May 2016, over an urban atmosphere, viz., Chiang Mai (98.957°E, 18.795°N, 373 m above sea level), Thailand in northern peninsular Southeast Asia. Daily variations in aerosol light absorption were mainly governed by open fire activities in the region. The mean mass-specific absorption cross-section (MAC) value of EBC at 880 nm was estimated to be 9.3 m² g^-1. The median EBC mass concentration was the highest in March (3.3 μg m^-3) due to biomass-burning (comprised of forest fire and agricultural burning) emissions accompanied by urban air pollution within the planetary boundary layer under favorable meteorological conditions. Daily mean absorption Ångström exponent (AAE_470/950) varied between 1.3 and 1.7 and could be due to variations in EBC emission sources and atmospheric mixing processes. EBC source apportionment results revealed that biomass-burning contributed significantly more to total EBC concentrations (34-92%) as compared to fossil-fuel (traffic emissions). Health risk estimates of EBC in relation to different health outcomes were assessed in terms of passive cigarette equivalence, highlighting the considerable health effects associated with exposure to EBC levels. As a necessary action, the reduction of EBC emissions would promote considerable climate and health co-benefits.

Cytotoxicity and toxicoproteomic analyses of human lung epithelial cells exposed to extracts of atmospheric particulate matters on PTFE filters using acetone and water

Differences of cytotoxicity associated with exposure to different extracts of atmospheric particulate matters (PMs) are still not well characterized by in vitro toxicoproteomics. In this study, in vitro cytotoxicity assays and toxicoproteomic analyses were carried out to investigate toxic effects of PM collected using polytetrafluoroethylene (PTFE) filters extracted with acetone for PM_2.1 and water for PM_2.1 and PM₁₀ on A549 human lung epithelial cells. The cytotoxicity assays based on cell viability, cell apoptosis and reactive oxygen species generation indicated that PM_2.1 extracted with acetone had the highest toxicity. iTRAQ labeling and LC-MS/MS analyses indicated that the number of differentially expressed proteins in A549 cells affected by PM_2.1 extracted with acetone was noticeably higher than that of the other two groups. Hierarchical cluster analyses showed that the influences of the extracts of PM_2.1 and PM₁₀ using water on the proteome of A549 cells were similar, whereas significantly different from the effect of PM_2.1 extracted with acetone. Pathways analyses indicated that PM_2.1 extracted with acetone influenced the expression of proteins involved in 14 pathways including glycolysis/gluconeogenesis, pentose phosphate pathway, proteasome, etc. PM_2.1 extracted with water affected the expression of proteins involved in 3 pathways including non-homologous end-joining, ribosome and endocytosis. However, PM₁₀ extracted with water affected the expression of proteins involved in only spliceosome pathway. The extracts of PM using different extractants to detach PM from PTFE filters influenced the cytotoxic effects of PM and the proteome of A549 cells. Therefore, extractants should be assessed carefully before the investigations on cytotoxicity to improve the compatibility of experimental results among research teams.

Associations between fine particulate matter constituents and daily cardiovascular mortality in Shanghai, China

Limited evidence is available for the associations between fine particulate matter (PM_2.5) constituents and daily cardiovascular disease (CVD) mortality in China. In present study, a time-series analysis was conducted to evaluate the associations of PM_2.5 constituents (two carbonaceous fractions, eight water-soluble inorganic ions and fifteen elements) with daily CVD mortality in Pudong New Area of Shanghai, China, from 2014 to 2016. Results showed that the effect estimates for the associations of PM_2.5 and its constituents with CVD mortality were generally strongest when using the exposures of the previous two day concentrations. The associations of organic carbon, sulfate, ammonia, potassium, copper, arsenic, and lead with daily CVD mortality were robust to the adjustment of PM_2.5 total mass, their collinearity with PM_2.5 total mass, and criteria gaseous air pollutants. An interquartile range increase in the previous two day concentrations of PM_2.5, organic carbon, sulfate, ammonia, potassium, copper, arsenic, and lead were associated with significant increments of 2.21% (95% confidence interval [95%CI]: 0.54%, 3.88%), 2.83% (95% CIs: 1.16%, 4.50%), 1.90% (95% CIs: 0.35%, 3.45%), 2.29% (95% CIs: 0.80%, 3.77%), 0.94% (95% CIs: 0.13%, 1.75%), 1.53% (95% CIs: 0.37%, 2.69%), 2.08% (95% CIs: 0.49%, 3.68%) and 1.98% (95% CIs: 0.49%, 3.47%) in daily CVD mortality, respectively, in single-pollutant models. In conclusion, this study suggested that organic carbon, sulfate, ammonia, potassium, copper, arsenic, and lead might be mainly responsible for the associations between short-term PM_2.5 exposures and increased CVD mortality in Shanghai, China.

A chemical dynamic model for the infiltration of outdoor size-resolved ammonium nitrate aerosols to indoor environments

In the present study, we developed a chemical dynamic model to describe the infiltration of size-resolved ammonium nitrate aerosols from outdoor to indoor environments. This model considered the penetration factor, deposition rate, and the reversible reaction process, which was quantified by the diffusive molar flux on the surface of ammonium nitrate aerosols depending on indoor temperature, humidity, and concentrations of nitric acid (HNO₃ ) and ammonia (NH₃ ). To verify the model, we employed a single-particle aerosol mass spectrometer with an automated switching system to simultaneously measure size-resolved outdoor and indoor ammonium nitrate aerosols. Comparisons between the predicted and measured concentrations of these aerosols showed a mean relative error of 4.8 ± 18.3%. To analyze the sensitivity of model parameters, several parameters were perturbed. This analysis indicated that parameters related to HNO₃ were more sensitive than those related to NH₃ because the indoor gas phase concentration of NH₃ was much higher than that of HNO₃ .

Utilizing daily excessive concentration hours to estimate cardiovascular mortality and years of life lost attributable to fine particulate matter in Tehran, Iran

BACKGROUND

Evidence for associations between fine particulate matter (PM_2.5) and cardiovascular diseases (CVDs) in Iran is scarce. Given large within-day variations of PM_2.5 concentration, using the daily mean of PM_2.5 (PM_2.5mean) as exposure metric might bias the health-related assessment. This study applied a novel indicator, daily excessive concentration hours (DECH), to evaluate the effect of ambient PM_2.5 on CVD mortality and years of life lost (YLL) in Tehran, the capital city of Iran.

METHODS

Hourly concentration data for PM_2.5, daily information for meteorology and records of registered cardiovascular deaths from 2012 to 2016 were obtained from Tehran, Iran. Daily excessive concentration hours of PM_2.5 (PM_2.5DECH) was defined as daily total concentration-hours exceeding 35 μg/m³. Using a time-series design, we applied generalized linear models to assess the attributable effects of PM_2.5DECH and PM_2.5mean on CVD mortality and YLL.

RESULTS

For an interquartile range (IQR) rise in PM_2.5DECH, total CVD mortality at lag 0-10 days and YLL at lag 0-8 days increased 2.26% (95% confidence interval (CI): 0.85-3.69%) and 23.24 (6.07-40.42) person years, respectively. Corresponding increases were 3.45% (1.44-5.49%) and 35.21 (10.85-59.58) person years for an IQR rise in PM_2.5mean. Significant associations between PM_2.5 pollution (i.e., PM_2.5mean and PM_2.5DECH) and cause-specific cardiovascular health (i.e., mortality and YLL) were only identified in stroke. Subgroup analyses showed that male and people aged 0-64 years suffered more from PM_2.5 pollution. Furthermore, we attributed a greater CVD burden to PM_2.5DECH (1.67% for mortality and 2.67% for YLL) than PM_2.5mean (0.63% for mortality and 0.70% for YLL) during the study period.

CONCLUSIONS

This study strengthened the evidence for the aggravated CVD mortality burden associated with short-term exposure to PM_2.5. Our findings also suggested that PM_2.5DECH might be a potential alternative indicator of exposure assessment in PM_2.5-related health investigations.

Assessment of the spatio-temporal pattern of PM2.5 and its driving factors using a land use regression model in Beijing, China

With the acceleration of urbanization and industrialization, atmospheric pollution has become a major issue, restricting the sustainable development of the urban environment. Since 2013, Beijing has been among China's most seriously affected regions in terms of haze pollution. Atmospheric pollution is closely linked to land use, particularly the spatial patterns of green and urban land. Therefore, the quantification of the relationship between fine particulate matter (PM_2.5) concentration and its driving factors in Beijing is of considerable significance for environmental management and spatial epidemiological studies. A land use regression (LUR) model was constructed to simulate the spatio-temporal distribution of PM_2.5 concentration. In this study, the independent variables (driving factors) included land use, meteorological factors, population, roads, the digital elevation model, and the normalized difference vegetation index. The five models had adjusted R² of 0.887, 0.770, 0.742, 0.877, and 0.798, respectively. Land use and meteorological factors were the main factors affecting PM_2.5 concentration. The driving factors of land use on a large scale and roads on a small scale had a significant impact on PM_2.5 emissions. Beijing's PM_2.5 concentrations in 2015 showed clear spatio-temporal characteristics. The highest (lowest) average PM_2.5 concentration was recorded in winter (summer). In terms of spatial distribution, PM_2.5 concentrations showed a "low in the northwest and high in the southeast" trend. The most polluted areas were mainly distributed in the central city and the southeastern and southwestern regions. The PM_2.5 concentration boundary was essentially consistent with the boundary of land use type. Different land use types promoted or inhibited PM_2.5 concentrations, with a difference of more than 20 μg/m³ PM_2.5 between the two land use categories. Thus, PM_2.5 concentrations should be controlled by optimizing the spatial and temporal patterns of land use.

Particulate air pollution and ischemic stroke hospitalization: How the associations vary by constituents in Shanghai, China

BACKGROUND

The identification of constituents of fine particulate matter (PM_2.5) air pollution that had key impacts of ischemic stroke (the predominant subtype of stroke) is important to understand the underlying biological mechanisms and develop air pollution control policies.

OBJECTIVES

To explore the associations between PM_2.5 constituents and hospitalization for ischemic stroke in Shanghai, China.

METHODS

We conducted a time-series study to explore the associations between 27 constituents of PM_2.5 and hospitalization for ischemic stroke in Shanghai, China from 2014 to 2016. The over-dispersed generalized additive models with adjustment for time, day of week, holidays, and weather conditions were used to estimate the associations. We also evaluated the robustness of the effect estimates for each constituent after adjusting for the confounding effects of PM_2.5 total mass and gaseous pollutants and the collinearity (the residual) between this constituent and PM_2.5 total mass. We also compared the associations between seasons.

RESULTS

In total, we identified 4186 ischemic stroke hospitalizations during the study period. The associations of ischemic stroke were consistently significant with elemental carbon and several elemental constituents (Chromium, Iron, Copper, Zinc, Arsenic, Selenium, and Lead) at lag 1 day in single-constituent models, models adjusting for PM_2.5 total mass or gaseous pollutants and models adjusting for collinearity. The associations were much stronger in cool season than in warm season.

CONCLUSIONS

The current study provides suggestive evidence that elemental carbon and some metallic elements may be mainly responsible for the risks of ischemic stroke hospitalization induced by short-term PM_2.5 exposure.

Asymmetrically Spatial Effects of Urban Scale and Agglomeration on Haze Pollution in China

Rapid urbanization in China not only promotes the rapid expansion of urban population and economic agglomeration, but also causes the aggravation of haze pollution. In order to better clarify the asymmetric and nonlinear effects of urban scale and agglomeration on haze pollution, this paper quantitatively evaluates the spatial spillover effects of population size and economic agglomeration on haze pollution in 342 Chinese cities from 2001 to 2016 by using exploratory spatial data analysis (ESDA) and spatial econometric model. The results show the following: (1) During the research period, the distribution of urban scale, agglomeration, and haze pollution in China presented complex asymmetrical features, with the former two presenting a “core–periphery” distribution mode, while the latter having a tendency to spread around. In addition, under the influence of urban population size and economic agglomeration, haze pollution in Chinese cities presents significant spatial autocorrelation, with the agglomeration degrees showing a fluctuating upward trend during the study period. (2) Both urban scale and urban agglomeration have positive global spatiotemporal correlation with haze pollution. Local spatial correlation features are more obvious in China’s emerging urban agglomerations like Beijing–Tianjin–Hebei and Yangtze River Delta. (3) The spatial effects of haze pollution are better evaluated by spatial Durbin model (SDM) with spatial fixed effects, obtaining a coefficient of 0.416, indicating haze in neighboring cities affected each other and had significant spillover. By decomposing the effect of urban scale and agglomeration on haze as direct and indirect effects, the direct effect of urban population size and the indirect effect of urban economic agglomeration are found to be more prominent, reflecting that significant asymmetrical characteristics exist in the spatial effects of urban size and agglomeration on urban haze. (4) Among the control variables that affect China’s rapid urbanization, the level of urban economic development has a positive effect on haze pollution, while the high-level industrial structure and improved technical level can effectively reduce haze pollution. Continuous decline of haze concentration of Chinese cities in recent years has been indicating the spatial relationships between haze and urban size and agglomeration have a decoupling trend. The findings contribute to theory by emphasizing the spillover effect and spatial heterogeneities of geographical factors, and have implications for policy makers to deal with haze pollution reasonably and effectively.

Long-term (2006-2015) variations and relations of multiple atmospheric pollutants based on multi-remote sensing data over the North China Plain

In this analysis, the Aqua/MODIS aerosol optical thickness (AOD), Aura/OMI tropospheric NO₂ and SO₂ column concentration from 2006 to 2015 were used to statistically analyze the spatial distribution characteristics and variation trends of three polluted parameters from three temporal scales of monthly, seasonal and annual average. The results showed that the minimum values of NO₂ and SO₂ column concentrations both appeared in July and August, and the maximum values appeared in December and January, which was contrary to the variations in AOD. The highly polluted levels were mainly distributed in Shijiazhuang, Xingtai, and Yancheng cities of Hebei Province, and gradually transported to Zhengzhou, Henan Province, north and southwest of Shandong Province, and Tianjin, along the main line of Taiyuan-Linyi, Shanxi Province. AOD and NO₂ had significant differences on the seasonal average scale, whereas SO₂ had little changes. These pollutants had declined year by year since 2011, in the 10-year period, AOD and SO₂ respectively decreased by 17.14% and 10.57%, and only NO₂ rose from 8.69 × 10¹⁵ molecules/cm² in 2006 to 9.10 × 10¹⁵ molecules/cm² in 2015 with the increase rate of 4.79%. Integrated with MODIS-released fire products and the Multi-resolution Emission Inventory for China (MEIC), high AOD values in summer were usually accompanied by frequent biomass burning, and heavy heating demand of coal burning led to largest NO₂ and SO₂ levels in winter. Both inter-annual variations of MEIC NOx and OMI-observed NO₂ responded to emission reductions of vehicle exhaustions positively, but vehicle population in Henan and Shandong provinces need to be further controlled. The significant decline of SO₂ is mainly attributed to the enforcement of de-sulfurization devices in power plants. Our study found that in the treatment of complex atmospheric pollution, in addition to strict control of common sources of emissions from AOD, NO₂ and SO₂, it is also necessary to consider their individual characteristics.

The impact of air pollutants on ambulance dispatches: A systematic review and meta-analysis of acute effects

A number of systematic reviews have investigated the association between air pollutants and health impacts, these mostly focus on morbidity and mortality from hospital data. Previously, no reviews focused solely on ambulance dispatch data. These data sets have excellent potential for environmental health research. For this review, publications up to April 2019 were identified using three main search categories covering: ambulance services including dispatches; air pollutants; and health outcomes. From 308 studies initially identified, 275 were excluded as they did not relate to ambulance service dispatches, did not report the air pollutant association, and/or did not study ambient air pollution. The main health outcomes in the remaining 33 studies were cardiac arrest (n = 14), cardiovascular (n = 11) and respiratory (n = 10) dispatches. Meta-analyses were performed to summarise pooled relative risk (RR) of pollutants: particulate matter less than 2.5 and 10 μm (PM_2.5, PM₁₀), the fraction between PM₁₀ and PM_2.5 (coarse) and suspended particulate matter (SPM) per 10 μg/m³ increase, carbon monoxide (CO) per 1 ppm increase and of sulphur dioxide (SO₂), nitrogen dioxide (NO₂), and ozone (O₃) per 10 ppb increment and ambulance dispatches. Statistically significant associations were found for ambulance dispatch data for all-respiratory and PM_2.5 at 1.03 (95% CI:1.02-1.04) and at 1.10 (95% CI:1.00-1.21) for asthma and NO₂ associations. For dispatches with subsequent paramedic assessment for cardiac arrest with PM_2.5, CO and coarse dispatches at 1.05 (95% CI:1.03-1.08), 1.10 (95% CI:1.02-1.18) and 1.04 (95% CI:1.01-1.06) respectively. For dispatches with subsequent physician diagnosis for all-respiratory and PM_2.5 at 1.02 (95% CI:1.01-1.03). In conclusion, air pollution was significantly associated with an increase in ambulance dispatch data, including those for cardiac arrest, all-respiratory, and asthma dispatches. Ambulance services should plan accordingly during pollution events. Furthermore, efforts to improve air quality should lead to decreases in ambulance dispatches.

Assessing the association between fine particulate matter (PM2.5) constituents and cardiovascular diseases in a mega-city of Pakistan

Concerning PM_2.5 concentrations, rapid industrialization, along with increase in cardiovascular disease (CVD) were recorded in Pakistan, especially in urban areas. The degree to which air pollution contributes to the increase in the burden of CVD in Pakistan has not been assessed due to lack of data. This study aims to describe the characteristics of PM_2.5 constituents and investigate the impact of individual PM_2.5 constituent on cardiovascular morbidity in Karachi, a mega city in Pakistan. Daily levels of twenty-one constituents of PM_2.5 were analyzed using samples collected at two sites from fall 2008 to summer 2009 in Karachi. Hospital admission and emergency room visits due to CVD were collected from two large hospitals. Negative Binominal Regression was used to estimate associations between pollutants and the risk of CVD. All PM_2.5 constituents were assessed in single-pollutant models and selected constituents were assessed in multi-pollutant models adjusting for PM_2.5 mass and gaseous pollutants. The most common CVD subtypes among our participants were ischemic heart disease, hypertension, heart failure, and cardiomyopathy. Extremely high levels of PM_2.5 constituents from fossil-fuels combustion and industrial emissions were observed, with notable peaks in winter. The most consistent associations were found between exposure to nickel (5-14% increase per interquartile range) and cardiovascular hospital admissions. Suggestive evidence was also observed for associations between cardiovascular hospital admissions and Al, Fe, Ti, and nitrate. Our findings suggested that PM_2.5 generated from fossil-fuels combustion and road dust resuspension were associated with the increased risk of CVD in Pakistan.

Respirable Particulate Constituents and Risk of Cause-Specific Mortality in the Hong Kong Population

Emerging studies examined the associations of particulate matter constituents with nonaccidental and cardiorespiratory diseases, but few have investigated more specific causes of cardiorespiratory diseases or other system diseases, especially in Asia. We estimated the association between respirable particulate matter (PM₁₀) constituents and a spectrum of deaths using a quasi-Poisson time-series model in Hong Kong. Positive associations were identified between cause-specific deaths and elemental carbon, organic carbon (OC), nitrate, and potassium ion (K⁺), but only the associations for OC and K⁺ were robust in the two-constituent models adjusting for other constituents. The estimated effects of OC were strongest on mortality from the respiratory system with cumulative percent excess risk (ER%) of 3.82% (95% CI: 0.96%, 6.92%) per interquartile range (6.7 μg/m³) increase over 7 days prior to death (lag_0-7), especially for pneumonia (ER%: 4.32%; 95% CI: 0.70%, 8.26%). The digestive system was most sensitive to K⁺ with cumulative ER% of 6.74% (95% CI: 0.37%, 14.01%) per interquartile range (0.6 μg/m³) increase. This study indicates that PM₁₀ constituents from biomass burning (OC and K⁺) were more toxic than other constituents for deaths in Hong Kong, especially for mortalities from respiratory and digestive systems. These findings should have potential biological and pollution control implications.

Comparison of Short-Term Associations between PM2.5 Components and Mortality across Six Major Cities in South Korea

Association between short-term exposure to fine particulate matter (PM_2.5) and mortality or morbidity varies geographically, and this variation could be due to different chemical composition affected by local sources. However, there have been only a few Asian studies possibly due to limited monitoring data. Using nationwide regulatory monitoring data of PM_2.5 chemical components in South Korea, we aimed to compare the associations between daily exposure to PM_2.5 components and mortality across six major cities. We obtained daily 24-h concentrations of PM_2.5 and 11 PM_2.5 components measured from 2013 to 2015 at single sites located in residential areas. We used death certificate data to compute the daily counts of nonaccidental, cardiovascular, and respiratory deaths. Using the generalized additive model, we estimated relative risks of daily mortality for an interquartile range increase in each pollutant concentration, while controlling for a longer-term time trend and meteorology. While elemental carbon was consistently associated with nonaccidental mortality across all cities, nickel and vanadium were strongly associated with respiratory or cardiovascular mortality in Busan and Ulsan, two large port cities. Our study shows that PM_2.5 components responsible for PM_2.5-associated mortality differed across cities depending on the dominant pollution sources, such as traffic and oil combustion.

Health burdens of ambient PM2.5 pollution across Chinese cities during 2006-2015

With frequent severe haze and smog episodes in Chinese cities, an increasing number of studies have focused on estimating the impact of fine particulate matter (PM_2.5) on public health. However, the current use of national and provincial demographic data might mask regional differences and lead to inaccurate estimations of pollution-related health impacts across cities. We applied the Global Burden of Disease methodology to develop a dataset of premature deaths attributed to ambient PM_2.5 in 129 Chinese cities in 2006, 2010 and 2015, based on the information of baseline mortality rates and population densities at the city level. Our results suggested that ambient PM_2.5 pollution led to 631,230 (95% confidence interval: 281,460-873,800) premature deaths in those cities in 2015, which was similar to that in 2010, but 42.8% higher than that in 2006. The reduction of premature deaths was not as obvious as the improvement in air quality in recent years, primarily owing to the aging Chinese population. For large and medium/small cities, the effects of PM_2.5 abatement on alleviating public health burdens were lower than those for megalopolises and metropolises; however, such large and medium/small cities are at risk of increasing future PM_2.5 pollution levels due to rapid development. Significant differences in PM_2.5-induced premature deaths indicated the need for specific policies to mitigate the health burden of air pollution in different types of Chinese cities.

Association between chemical components of PM2.5 and children's primary care night-time visits due to asthma attacks: A case-crossover study

BACKGROUND

Few papers have examined the association between the chemical components of PM_2.5 and health effects. The existence of an association is now under discussion.

METHODS

This case-crossover study aimed to examine the association between the chemical components of PM_2.5 and night-time primary care visits (PCVs) due to asthma attacks. The subjects were 1251 children aged 0-14 years who received medical care for asthma at a municipal emergency clinic. We measured daily average concentrations of hydrogen ion, sulfate ion, nitrate ion and water-soluble organic compounds (WSOCs), which are components of PM_2.5. We estimated the odds ratios (ORs) of PCVs per unit increment (inter quartile ranges) in each chemical component of PM_2.5 for the subgroups of warmer months and colder months separately.

RESULTS

No association was seen between PCVs and PM_2.5 mass concentrations the day before the PCVs in either warmer or colder months. In the warmer months, an association was seen with the concentrations of WSOCs and hydrogen ion the day before the PCVs (OR = 1.33; 95% CI: 1.00-1.76, OR = 1.18; 95% CI: 1.02-1.36, respectively). Furthermore, a negative association was seen between sulfate ion and PCVs (OR = 0.85; 95%CI: 0.74-0.98). No associations were observed in the colder months.

CONCLUSIONS

We observed a positive association between PCVs and certain concentrations of WSOCs and hydrogen ions in warmer months. In contrast, sulfate ion showed a negative association.

Assessment of satellite-estimated near-surface sulfate and nitrate concentrations and their precursor emissions over China from 2006 to 2014

China is the largest anthropogenic aerosol-generating country worldwide; however, few studies have analyzed the PM_2.5 chemical components and their underlying precursor emissions over long periods and across the national domain. First, global 3-D tropospheric chemistry and transport model (GEOS-Chem)-integrated satellite-retrieved aerosol optical depth (AOD) and vertical profiles were used to estimate near-surface sulfate and nitrate levels at 10-km resolution over China from 2006 to 2014. Ground measurement validation of our satellite model yielded correlation coefficients (r) of 0.7 and 0.73 and normalized mean bias (NMB) values of -37.96% and - 32.73% for sulfate and nitrate, respectively. Second, analyses of the spatiotemporal distributions of sulfate and nitrate as well as the vertical density Ozone Monitoring Instrument (OMI)-measured SO₂ (PBL_SO₂) and NO₂ (TVCD_NO₂) indicated that the highest nitrate and sulfate levels occurred in the North China Plain (~25 μg/m³) and Sichuan Basin (SCB) (~30 μg/m³), respectively. The long-term variations in the estimated components and precursor gases indicated that the large sulfate decline was positively correlated with the SO₂ emission reduction due to the mandatory desulfurization implemented in 2007. The annual growth rate of sulfate relative to the national mean was -6.19%/yr, and the concentration decreased by 17.10% from 2011 to 2014. Energy consumption increases and a lack of control measures for NO₂ resulted in persistent increases in NO₂ emissions and nitrate concentrations from 2006 to 2010, particularly in the SCB. With energy consumption structure advancements, reductions in NO₂ emissions and corresponding nitrate levels over three typical regions were prominent after 2012. Third, the estimated national-scale uncertainties of satellite datasets at 0.1° × 0.1° were 26.88% for sulfate and 25.55% for nitrate. Differences in the spatial distributions and temporal trends between our estimated components and precursor gases were mainly attributed to the dataset accuracy, the data pre-processing strategy, inconsistent column density and near-surface mass concentration, meteorological variables and complex chemical reactions.

Characterization of carbonaceous fractions in PM2.5 and PM10 over a typical industrial city in central China

Aerosol samples of PM_2.5 and PM₁₀ were collected every 6 days from March 2012 to February 2013 in Huangshi, a typical industrial city in central China, to investigate the characteristics, relationships, and sources of carbonaceous species. The PM_2.5 and PM₁₀ samples were analyzed for organic carbon (OC), elemental carbon (EC), char, and soot using the thermal/optical reflectance (TOR) method following the IMPROVE_A protocol. PM_2.5 and PM₁₀ concentrations ranged from 29.37 to 501.43 μg m^-3 and from 50.42 to 330.07 μg m^-3, with average levels of 104.90 and 151.23 μg m^-3, respectively. The 24-h average level of PM_2.5 was about three times the US EPA standard of 35 μg m^-3, and significantly exceeds the Class II National Air Quality Standard of China of 75 μg m^-3. The seasonal cycles of PM mass and OC concentrations were higher during winter than in summer. EC and char concentrations were generally highest during winter but lowest in spring, while higher soot concentrations occurred in summer. This seasonal variation could be attributed to different seasonal meteorological conditions and changes in source contributions. Strong correlations between OC and EC were found for both PM_2.5 and PM₁₀ in winter and fall, while char and soot showed a moderate correlation in summer and winter. The average OC/EC ratios were 5.11 and 4.46 for PM_2.5 and PM₁₀, respectively, with individual OC/EC ratios nearly always exceeding 2.0. Higher char/soot ratios during the four seasons indicated that coal combustion and biomass burning were the major sources for carbonaceous aerosol in Huangshi. Contrary to expectations, secondary organic carbon (SOC) which is estimated using the EC tracer method exhibited spring maximum and summer minimum, suggesting that photochemical activity is not a leading factor in the formation of secondary organic aerosols in the study area. The contribution of SOC to OC concentration for PM_2.5 and PM₁₀ were 47.33 and 45.38%, respectively, implying that SOC was an important component of OC mass. The serious air pollution in haze-fog episode was strongly correlated with the emissions of pollutants from biomass burning and the meteorological conditions.

Exploring the characteristics and sources of carbonaceous aerosols in the agro-pastoral transitional zone of Northern China

Carbonaceous aerosols are linked to severe haze and health effects, while its origins remain still unclear over China. PM_2.5 samples covering four seasons from Jan. 2016 to Jan. 2017 were collected at six sites in Chifeng, a representative agro-pastoral transitional zone of North China focusing on the characteristics and sources of organic carbon (OC) and elemental carbon (EC). The annual averages of OC, EC were 9.00 ± 7.24 μg m^-3, 1.06 ± 0.79 μg m^-3 with site Songshan in coal mining region exhibited significantly enhanced levels. The residential heating emissions, air stagnation, and secondary organic formation all contributed the higher OC, EC levels in winter. Meanwhile, the impacts from open biomass burning were most intensive in spring. The retroplumes via Lagrangian model highlighted a strong seasonality of regional sources which had more impacts on EC increases. The Positive Matrix Factorization (PMF) model resolved six primary sources, namely, coal combustion, biomass burning, industrial processes, oil combustion, fugitive dust, and fireworks. Coal combustion and biomass burning comprised large fractions of OC (30.57%, 30.40%) and EC (23.26%, 38.47%) across the sites, while contributions of industrial processes and oil combustion clearly increased in the sites near industrial sources as smelters. PMF and EC tracer method gave well correlated (r=0.65) estimates of Secondary OC (SOC). The proportion of coal combustion and SOC were more enhanced along with PM_2.5 elevation compared to other sources, suggesting their importances during the pollution events.

The Shape of the Concentration-Response Association between Fine Particulate Matter Pollution and Human Mortality in Beijing, China, and Its Implications for Health Impact Assessment

BACKGROUND

Studies found approximately linear short-term associations between particulate matter (PM) and mortality in Western communities. However, in China, where the urban PM levels are typically considerably higher than in Western communities, some studies suggest nonlinearity in this association. Health impact assessments (HIA) of PM in China have generally not incorporated nonlinearity in the concentration-response (C-R) association, which could result in large discrepancies in estimates of excess deaths if the true association is nonlinear.

OBJECTIVES

We investigated nonlinearity in the C-R associations between with PM with aerodynamic diameter [Formula: see text] ([Formula: see text]) and mortality in Beijing, China, and the sensitivity of HIA to linearity assumptions.

METHODS

We modeled the C-R association between [Formula: see text] and cause-specific mortality in Beijing, China (2009-2012), using generalized linear models (GLM). [Formula: see text] was included through either linear, piecewise-linear, or spline functions to investigate evidence of nonlinearity. To determine the sensitivity of HIA to linearity assumptions, we estimated [Formula: see text]-attributable deaths using both linear- and nonlinear-based C-R associations between [Formula: see text] and mortality.

RESULTS

We found some evidence that, for nonaccidental and circulatory mortality, the shape of the C-R association was relatively flat at lower concentrations of [Formula: see text], but then had a positive slope at higher concentrations, indicating nonlinearity. Conversely, the shape for respiratory mortality was positive and linear at lower concentrations of [Formula: see text], but then leveled off at the higher concentrations. Estimates of excess deaths attributable to short-term [Formula: see text] exposure were, in some cases, very sensitive to the linearity assumption in the association, but in other cases robust to this assumption.

CONCLUSIONS

Our results demonstrate some evidence of nonlinearity in [Formula: see text]-mortality associations and that an assumption of linearity in this association can influence HIAs, highlighting the importance of understanding potential nonlinearity in the [Formula: see text]-mortality association at the high concentrations of [Formula: see text] in developing megacities like Beijing. https://doi.org/10.1289/EHP4464.

Characterisation of the Carpinus betulus L. Phyllomicrobiome in Urban and Forest Areas

Urban green areas are highly valued by citizens for their contribution to the quality of life in cities. Plants play an important role in mitigating airborne pollutants and are assisted in this role by the metabolic capacities of the millions of microbial cells that colonize leaf surfaces (phyllosphere). Many factors influence phyllosphere microbial community composition and function, but to what extent does airborne pollution in cities impact the composition of microbial communities and their functional degradation genes? Here we describe the characterization of the phyllospheric bacterial communities of Carpinus betulus L. trees (hornbeam) across three locations: the city center of Warsaw (Poland), a forest in a UNESCO World Heritage Site (Białowieża), and a forest in one of the world’s oldest operational oil fields (Bóbrka). C. betulus contained higher particulate matter (PM) concentrations, with higher concentrations of palladium and radon in the PM, on leaves in Warsaw than in the forests. Volatile organic compound (VOC) analyses of sampled air revealed higher concentrations of butanone methyl propanal, butylbenzene, and cyclohexane in Bóbrka than Warsaw and Białowieża, while in Warsaw, xylene and toluene were higher. Shotgun microbiome sequencing uncovered a dominance of Gammaproteobacteria (71%), mainly Pseudomonas spp., Actinobacteria, Alpha- and Betaproteobacteria, and Firmicutes. Community composition and function differed significantly between the forests and Warsaw city center. Statistically more hydrocarbon degradation genes were found in Białowieża compared to Warsaw and Bóbrka, and in vitro tests of diesel degradation and plant growth promotion traits of culturable representatives revealed that Białowieża held the highest number of bacteria with plant beneficial properties and degradation genes. This study provides the first detailed insights into the microbiome of C. betulus and sets the stage for developing to a more integrated understanding of phyllosphere microbiota in cities, and their relationships with human health.

A Review of Aerosol Chemical Composition and Sources in Representative Regions of China during Wintertime

Comparisons of aerosol composition and sources in different cities or regions are rather limited, yet important for an in-depth understanding of the spatial diversity of aerosol pollution in China. In this study, the data originating from 25 different winter aerosol mass spectrometer (AMS)/aerosol chemical speciation monitor (ACSM) studies were used to provide spatial coverage of the Beijing-Tianjin-Hebei (BTH), Guanzhong (GZ), Yangtze River Delta (YRD), and Pearl River Delta (PRD) regions. The spatial distribution and diurnal variations in aerosol composition and organic sources were analyzed to investigate the aerosol characteristics in the four regions. It was found that there were differences in the compositions of non-refractory particulate matter across the regions, e.g., more sulfate in the PRD versus more nitrate in the YRD, as well as in the organic sources, e.g., more coal combustion in BTH versus more biomass burning in GZ. The characteristics of the composition of NR-PM are similar when the campaigns were classified according to the winter of different years or the cities of different regions. The diurnal variation of the PRD-sulfate indicated its regional nature, whereas the organics from burning sources in two regions of northern China exhibited local characteristics. Based on these findings, we suggest that strict control policies for coal combustion and biomass burning emissions should be enforced in the BTH and GZ regions, respectively.

Chemical Characteristics of PM2.5 and Water-Soluble Organic Nitrogen in Yangzhou, China

Chemical characterization of fine atmospheric particles (PM2.5) is important for effective reduction of air pollution. This work analyzed PM2.5 samples collected in Yangzhou, China, during 2016. Ionic species, organic matter (OM), elemental carbon (EC), and trace metals were determined, and an Aerodyne soot-particle aerosol mass spectrometer (SP-AMS) was introduced to determine the OM mass, rather than only organic carbon mass. We found that inorganic ionic species was dominant (~52%), organics occupied about 1/4, while trace metals (~1%) and EC (~2.1%) contributed insignificantly to the total PM2.5 mass. Water-soluble OM appeared to link closely with secondary OM, while water-insoluble OM correlated well with primary OM. The PM2.5 concentrations were relatively low during summertime, while its compositions varied little among different months. Seasonal variations of water-soluble organic nitrogen (WSON) concentrations were not significant, while the mass contributions of WSON to total nitrogen were remarkably high during summer and autumn. WSON was found to associate better with secondary sources based on both correlation analyses and principle component analyses. Analyses of potential source contributions to WSON showed that regional emissions were dominant during autumn and winter, while the ocean became relatively important during spring and summer.

Short-term and long-term exposures to fine particulate matter constituents and health: A systematic review and meta-analysis

BACKGROUND

Fine particulate matter (Particulate matter with diameter ≤ 2.5 μm) is associated with multiple health outcomes, with varying effects across seasons and locations. It remains largely unknown that which components of PM_2.5 are most harmful to human health.

METHODS

We systematically searched all the relevent studies published before August 1, 2018, on the associations of fine particulate matter constituents with mortality and morbidity, using Web of Science, MEDLINE, PubMed and EMBASE. Studies were included if they explored the associations between short term or long term exposure of fine particulate matter constituents and natural, cardiovascular or respiratory health endpoints. The criteria for the risk of bias was adapted from OHAT and New Castle Ottawa. We applied a random-effects model to derive the risk estimates for each constituent. We performed main analyses restricted to studies which adjusted the PM_2.5 mass in their models.

RESULTS

Significant associations were observed between several PM_2.5 constituents and different health endpoints. Among them, black carbon and organic carbon were most robustly and consistently associated with all natural, cardiovascular mortality and morbidity. Other potential toxic constituents including nitrate, sulfate, Zinc, silicon, iron, nickel, vanadium, and potassium were associated with adverse cardiovascular health, while nitrate, sulfate and vanadium were relevant for adverse respiratory health outcomes.

CONCLUSIONS

Our analysis suggests that black carbon and organic carbon are important detrimental components of PM_2.5, while other constituents are probably hazardous to human health. However, more studies are needed to further confirm our results.

Estimating Ground-Level Concentrations of Multiple Air Pollutants and Their Health Impacts in the Huaihe River Basin in China

Air pollutants existing in the environment may have negative impacts on human health depending on their toxicity and concentrations. Remote sensing data enable researchers to map concentrations of various air pollutants over vast areas. By combining ground-level concentrations with population data, the spatial distribution of health impacts attributed to air pollutants can be acquired. This study took five highly populated and severely polluted provinces along the Huaihe River, China, as the research area. The ground-level concentrations of four major air pollutants including nitrogen dioxide (NO₂), sulfate dioxide (SO₂), particulate matters with diameter equal or less than 10 (PM₁₀) or 2.5 micron (PM_2.5) were estimated based on relevant remote sensing data using the geographically weighted regression (GWR) model. The health impacts of these pollutants were then assessed with the aid of co-located gridded population data. The results show that the annual average concentrations of ground-level NO₂, SO₂, PM₁₀, and PM_2.5 in 2016 were 31 µg/m³, 26 µg/m³, 100 µg/m³, and 59 µg/m³, respectively. In terms of the health impacts attributable to NO₂, SO₂, PM₁₀, and PM_2.5, there were 546, 1788, 10,595, and 8364 respiratory deaths, and 1221, 9666, 46,954, and 39,524 cardiovascular deaths, respectively. Northern Henan, west-central Shandong, southern Jiangsu, and Wuhan City in Hubei are prone to large health risks. Meanwhile, air pollutants have an overall greater impact on cardiovascular disease than respiratory disease, which is primarily attributable to the inhalable particle matters. Our findings provide a good reference to local decision makers for the implementation of further emission control strategies and possible health impacts assessment.

Pollution characteristics in a dusty season based on highly time-resolved online measurements in northwest China

To investigate the pollution characteristics and potential sources in a dusty season, an online analyzer was used to measure trace gases and major water-soluble ions in PM₁₀ from April 1st to May 29th, 2011 in Lanzhou. The average concentrations of HONO, HNO₃, HCl, SO₂ and NH₃ were 0.93, 1.16, 0.48, 9.29 and 5.54 μg/m³, respectively, and 2.8, 2.76, 8.28 and 2.48 μg/m³ for Cl^-, NO₃^-, SO₄^2- and NH₄⁺. In the non-dust period, diurnal variations of SO₄^2-, NO₃^- and their gaseous precursors showed similar change trend. NH₄⁺ showed unimodal pattern whereas NH₃ illustrated a bimodal pattern. HCl and Cl^- showed an opposite diurnal pattern. In the dust event, temporal profiles of HCl and Cl^-, SO₂ and SO₄^2- all presented similar change trend, and SO₄^2- and Cl^- preceded dust ions (Ca²⁺ and Mg²⁺) 13 h. The ratios of NO₃^- to SO₄^2- were 0.65 in the non-dust period and 0.31 in the dust event. In the dust event, the sulfur oxidation ratio (SOR) was a factor of 1.33 greater than that in the non-dust period, and [SO₄^2-]/[SO₂] was 2.31 times of that in the non-dust period. The source apportionment using Probabilistic Matrix Factorization (PMF) suggested that fugitive dust (58.09%), secondary aerosols (33.98%), and biomass burning (7.93%) were the major sources in the non-dust period whereas dust (67.01%), salt lake (29.68%), biomass burning (0.8%), and motor vehicle (2.51%) were the primary sources in the dust event. Concentration weighted trajectory (CWT) model indicated that NO₃^-, Cl^- and K⁺ could be regarded as local source species, the potential sources of Na⁺, Mg²⁺ and Ca²⁺ concentrated in the two large areas with the one covered in the junction areas of Xinjiang, Qinghai and Gansu and another one covered the places around in Lanzhou, the potential sources of SO₄^2- were mainly localized in the areas adjacent to Lanzhou.

Complexation of Iron and Copper in Ambient Particulate Matter and Its Effect on the Oxidative Potential Measured in a Surrogate Lung Fluid

We investigated the complexation state of atmospheric iron and copper and its impact on the oxidative potential (OP) of ambient PM_2.5 (PM, particulate matter). A novel fractionation scheme was developed to segregate three different fractions of Fe and Cu present in ambient PM_2.5: (i) complexed with hydrophobic organic compounds, (ii) complexed with hydrophilic organic compounds, and (iii) free or inorganic metal fraction. A solid phase extraction (C-18) column was used to separate these fractions. The fractionation scheme applied to the ambient PM_2.5 samples collected from an urban site showed that up to 70-90% of water-soluble Fe and Cu were complexed with the organic compounds. The capability of the complexes of Fe(II) and Cu(II) with Suwanee river fulvic acid (SRFA), a proxy for the atmospheric organic compounds, to generate reactive oxygen species (ROS) (·OH and H₂O₂) in a surrogate lung fluid (SLF) was measured. The complex of Fe-SRFA showed a strong synergistic effect in the generation of ·OH in SLF, while that of Cu-SRFA showed an additive effect. Overall, our results indicate that organic complexation of the metals in ambient PM could significantly alter their OP and needs to be considered while assessing their health impacts.

Temporal variation of oxidative potential of water soluble components of ambient PM2.5 measured by dithiothreitol (DTT) assay

The exposure to ambient fine particulate matter (PM_2.5) can induce oxidative stress, contributing to global burden of diseases. The evaluation of the oxidative potential (OP) of PM_2.5 is thus critical for the health risk assessment. We collected ambient PM_2.5 samples in Hangzhou city, China for four consecutive quarters in the year 2017 and investigated the oxidation property of PM_2.5 components by the dithiothreitol (DTT) assay. The annual mean of ambient PM_2.5 mass concentrations in 2017 was 63.05 μg m^-3 (median: 57.34, range: 6.67-214.33 μg m^-3) with the significant seasonal variations ranking as winter > spring > summer > autumn. Secondary inorganic aerosol (SIA) species including SO₄^2-, NO₃^- and NH₄⁺ totally account for >50% of PM_2.5 mass. The annual mean volume-normalized DTT activity (DTTv) showed a relatively high value of 0.62 nmol/min/m³ (median: 0.62, range: 0.11-1.66 nmol/min/m³) and DTTv of four seasons was roughly at the same level, indicating a high annual exposure level of ambient PM_2.5. SIA species were correlated well with the corresponding DTTv and showed significant diurnal variations with strong or moderate correlations at day and weak correlations at night, suggesting strong secondary formation in daytime with contribution to the particulate OP. The annual mean mass-normalized DTT activity (DTTm) had a relatively low value of 6.39 pmol/min/μg (median: 5.63, range: 1.99-22.70 pmol/min/μg), indicating low intrinsic oxidative toxicity. The DTTm of four seasons ranked as autumn > winter > spring > summer, indicating seasonal variations of the DTT-active components. The PM_2.5 mass concentration is more related to exposure levels than intrinsic properties of components, while OP is determined by the components rather than PM_2.5 mass concentration. Our results provide an insight into reactive oxygen species-induced health risk of PM_2.5 exposure and decision for subsequent emission control.

Association between PM2.5 Exposure and All-Cause, Non-Accidental, Accidental, Different Respiratory Diseases, Sex and Age Mortality in Shenzhen, China

Background: China is at its most important stage of air pollution control. Research on the association between air pollutants and human health is very important and necessary. The purpose of this study was to evaluate the association between PM2.5 concentrations and residents' mortality and to compare the effect of PM2.5 on the different diseases, accidental deaths, sex or age of residents from high polluted areas with less polluted areas. Methods: The semi-parametric generalized additive model (GAM) with Poisson distribution of time series analysis was used. The excess risk (ER) of mortality with the incremental increase of 10 µg/m³ in PM2.5 concentration was calculated. Concentration-response relationship curves and autocorrelation between different lags of PM2.5 were also evaluated. Results: PM2.5 exposure was significantly associated with the mortality of residents. The strongest ERs per 10 µg/m³ increase in PM2.5 were 0.74% (95% CI: 0.11⁻1.38%) for all-cause, 0.67% (95% CI: 0.01⁻1.33%) for non-accidental, 1.81% (95% CI: 0.22⁻3.42%) for accidental, 3.04% (95% CI: 0.60⁻5.55%) for total respiratory disease, 6.38% (95% CI: 2.78⁻10.11%) for chronic lower respiratory disease (CLRD), 8.24% (95% CI: 3.53⁻13.17%) for chronic obstructive pulmonary disease (COPD), 1.04% (95% CI: 0.25⁻1.84%) for male and 1.32% (95% CI: 0.46⁻2.19%) for elderly. Furthermore, important information on the concentration-response relationship curves was provided. Conclusions: PM2.5 can increase the risk of residents' mortality, even in places with less air pollution and developed economy in China.

Oxidative Potential by PM2.5 in the North China Plain: Generation of Hydroxyl Radical

Adverse health effects of ambient PM_2.5 ( d_p < 2.5 μm) can be associated with the production of reactive oxygen species (ROS), among which hydroxyl radical (•OH) is the most reactive. However, •OH generated by PM_2.5 has not been quantified and studied in the North China Plain (NCP), which has suffered from heavy air pollution in recent years. In this study, PM_2.5 samples were collected at an urban site (Beijing) and a suburban site (Wangdu), extracted in a cell-free surrogate lung fluid (SLF), and •OH generated in the extracts were quantified. The results show that more •OH is produced on heavily polluted days than that on clean days (2.0 and 1.6 times higher in Beijing and Wangdu, respectively). The production of •OH per unit mass (ng/μg·PM_2.5) decreases with the increase of ambient PM_2.5 concentration because SO₄^2-, NO₃^-, and NH₄⁺ dominate the increased PM_2.5, while these secondary inorganic components do not contribute to the generation of •OH. Trace metals (e.g., Fe, Cu, Se) and carbonaceous species (organic carbon and elemental carbon) correlate well with the •OH production, indicating that particles from combustion sources including coal combustion, vehicle exhaust, and industry contribute more to •OH generation.

The association between short-term ambient air pollution and daily outpatient visits for schizophrenia: A hospital-based study

Schizophrenia is a devastating neuropsychiatric disorder with increasing concern. Limited studies have been conducted to assess the relationship between short-term exposure to ambient air pollution and schizophrenia attacks. This study aimed to investigate the associations between short-term air pollution exposure and schizophrenia outpatient visits based on a time-series study performed in China. Daily data of schizophrenia outpatient admissions and air pollution from 1 October 2010 to 31 December 2013 were collected in Xi'an, a heavily-polluted city in China. We utilized a time-series Poisson regression model to examine the associations between short-term air pollution and schizophrenia outpatient visits with different lag days. A total of 34,865 outpatient-visits for schizophrenia were identified. A 10 μg/m³ increase of PM₁₀, SO₂, and NO₂ concentrations corresponded to 0.289% (95% Cl: 0.118%, 0.460%), 1.374% (95% Cl: 0.723%, 2.025%), and 1.881% (95% Cl: 0.957%, 2.805%) elevation in outpatient-visits for schizophrenia at lag 0, and the associations appeared to be stronger, although not statistically significantly, in females and in middle and older age adults (40 and over). The most significant associations were observed on the concurrent day in different lag models. In conclusion, short-term exposure to ambient air pollution (PM₁₀, SO₂, and NO₂) can be associated with increased risk of daily outpatient visits for schizophrenia, which may contribute to the further understanding of the potential adverse effects of air pollution in schizophrenia and other neuropsychiatric disorders.

Wintertime nitrate formation during haze days in the Guanzhong basin, China: A case study

In this study, the formation of nitrate aerosol from 16 to 24 December 2015 in the Guanzhong basin, China is simulated using the WRF-Chem model. The predicted near-surface O₃, NO₂, and fine particulate matters (PM_2.5) in the basin and inorganic aerosols and nitrous acid (HONO) in Xi'an are generally in good agreement with the observations. Sensitivity studies show that the heterogeneous HONO sources play an appreciable role in the nitrate formation in the basin, contributing 9.2% of nitrate mass concentrations during heavy haze days. Nitrate formation is also affected by sulfate due to their competition for ammonia, particularly in urban areas. A 50% decrease in SO₂ emissions enhances the nitrate concentration by 6.2% during heavy haze days on average in the basin, and a 50% increase in SO₂ emission reduces the nitrate concentration by 9.7%. The roles of HONO and sulfate competition in nitrate formation are strongly modulated by ammonia. Agricultural emissions predominate the nitrate level in the basin (93.5%), but the non-agricultural sources cannot substantially influence nitrate formation (3.7%-14.6%). Reducing agricultural emission is an effective control strategy to mitigate nitrate pollution in the basin.

Mortality burden attributable to PM1 in Zhejiang province, China

BACKGROUND

Limited evidence is available on the health effects of particulate matter with an aerodynamic diameter of <1 μm (PM₁), mainly due to the lack of its ground measurement worldwide.

OBJECTIVES

To identify and examine the mortality risks and mortality burdens associated with PM₁, PM_2.5, and PM₁₀ in Zhejiang province, China.

METHODS

We collected daily data regarding all-cause (stratified by age and gender), cardiovascular, stroke, respiratory, and chronic obstructive pulmonary disease (COPD) mortality, and PM₁, PM_2.5, and PM₁₀, from 11 cities in Zhejiang province, China during 2013 and 2017. We used a quasi-Poisson regression model to estimate city-specific associations between mortality and PM concentrations. Then we used a random-effect meta-analysis to pool the provincial estimates. To show the mortality burdens of PM₁, PM_2.5, and PM₁₀, we calculated the mortality fractions and deaths attributable to these PMs.

RESULTS

Daily concentrations of PM₁, PM_2.5, and PM₁₀ ranged between 0-199 μg/m³, 0-218 μg/m³, and 0-254 μg/m³, respectively; Mortality effects were significant in lag 0-2 days. The relative risks for all-cause mortality were 1.0064 (95% CI: 1.0034, 1.0094), 1.0061 (95% CI: 1.0034, 1.0089), and 1.0060 (95% CI: 1.0038, 1.0083) associated with a 10 μg/m³ increase in PM₁, PM_2.5, and PM₁₀, respectively. Age- and gender-stratified analysis shows that elderly people (aged 65+) and females are more sensitive to PMs. The mortality fractions of all-cause mortality were estimated to be 2.39% (95% CI: 1.28, 3.48) attributable to PM₁, 2.53% (95% CI: 1.42, 3.63) attributable to PM_2.5, and 3.08% (95% CI: 1.95, 4.19) attributable to PM₁₀. The ratios of attributable cause-specific deaths for PM₁/PM_2.5, PM₁/PM₁₀, and PM_2.5/PM₁₀ were higher than the ratios of their respective concentrations.

CONCLUSIONS

PM₁, PM_2.5 and PM₁₀ are risk factors of all-cause, cardiovascular, stroke, respiratory, and COPD mortality. PM₁ accounts for the vast majority of short-term PM_2.5- and PM₁₀-induced mortality. Our analyses support the notion that smaller size fractions of PM have a more toxic mortality impacts, which suggests to develop strategies to prevent and control PM₁ in China, such as to foster strict regulations for automobile and industrial emissions.

Differential toxicities of fine particulate matters from various sources

Fine particulate matters less than 2.5 µm (PM2.5) in the ambient atmosphere are strongly associated with adverse health effects. However, it is unlikely that all fine particles are equally toxic in view of their different sizes and chemical components. Toxicity of fine particles produced from various combustion sources (diesel engine, gasoline engine, biomass burning (rice straw and pine stem burning), and coal combustion) and non-combustion sources (road dust including sea spray aerosols, ammonium sulfate, ammonium nitrate, and secondary organic aerosols (SOA)), which are known major sources of PM2.5, was determined. Multiple biological and chemical endpoints were integrated for various source-specific aerosols to derive toxicity scores for particles originating from different sources. The highest toxicity score was obtained for diesel engine exhaust particles, followed by gasoline engine exhaust particles, biomass burning particles, coal combustion particles, and road dust, suggesting that traffic plays the most critical role in enhancing the toxic effects of fine particles. The toxicity ranking of fine particles produced from various sources can be used to better understand the adverse health effects caused by different fine particle types in the ambient atmosphere, and to provide practical management of fine particles beyond what can be achieved only using PM mass which is the current regulation standard.