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A rapid decrease in PM 2.5 concentrations in China has been observed in response to the enactment of strong emission control policies. From 2012 to 2017, total emissions of SO 2 and NO x from China decreased by approximately 63% and 24%, respectively. Simultaneously, decreases in the PM 2.5 concentration in Japan have been observed since 2014, and the proportion of stations that satisfy the PM 2.5 environmental standard (daily, 35 µg/m 3 ; annual average, 15 µg/m 3 ) increased from 37.8% in fiscal year (FY) 2014 (April 2014 to March 2015) to 89.9% in FY 2017. However, the quantitative relationship between the PM 2.5 improvement in China and the PM 2.5 concentration in downwind regions is not well understood. Here, we (1) quantitatively evaluate the impacts of Chinese environmental improvements on downwind areas using source/receptor analysis with a chemical transport model, and (2) show that these rapid emissions reductions improved PM 2.5 concentrations both in China and its downwind regions, but the difference between SO 2 and NO x reduction rates led to greater production of nitrates (e.g., NH 4 NO 3 ) due to a chemical imbalance in the ammonia–nitric acid–sulfuric acid–water system. Observations from a clean remote island in western Japan and numerical modeling confirmed this paradigm shift.

Background: From around 2012, the use of automated equipment for fine particulate matter (PM2.5) measurement with equivalence to a reference method has become popular nationwide in Japan. This enabled us to perform a national health effect assessment employing PM2.5 concentrations based on the standardized measurement method. We evaluated the association between non-accidental mortality and short-term exposure to PM2.5 and coarse particulate matter (PM), with the latter estimated as the difference between suspended particulate matter and PM2.5, for the fiscal years 2012–2014. Methods: This was a time-stratified case-crossover study in 100 highly-populated Japanese cities. Mortality data was obtained from the Ministry of Health, Labour and Welfare. City-specific estimates of PM-mortality association were calculated by applying a conditional logistic regression analysis, and combined with a random-effects meta-analysis. Results: The respective averages of daily mean concentration were 14.6 µg/m3 for PM2.5 and 6.4 µg/m3 for coarse PM. A 10 µg/m3 increase in PM2.5 concentrations for the average of the day of death and the previous day was associated with an increase of 1.3% (95% confidence interval (CI), 0.9–1.6%) in total non-accidental mortality. For cause-specific mortality, PM2.5 was positively associated with cardiovascular and respiratory mortality. After adjustment for PM2.5, we observed a 1.4% (95% CI, 0.2–2.6%) increase in total mortality with a 10 µg/m3 increase in coarse PM. Conclusion: The study revealed that short-term exposure to PM2.5 had adverse effects on total non-accidental, cardiovascular, and respiratory mortality in Japan. Coarse PM exposure also increased the risk of total mortality.

BackgroundMaternal exposure to fine particulate matter (PM2.5) was associated with pregnancy complications. However, we still lack comprehensive evidence regarding which specific chemical components of PM2.5 are more harmful for maternal and foetal health.ObjectiveWe focused on exposure over the first trimester (0–13 weeks of gestation), which includes the early placentation period, and investigated whether PM2.5 and its components were associated with placenta-mediated pregnancy complications (combined outcome of small for gestational age, preeclampsia, placental abruption, and stillbirth).MethodsFrom 2013 to 2015, we obtained information, from the Japan Perinatal Registry Network database, on 83,454 women who delivered singleton infants within 23 Tokyo wards (≈627 km2). Using daily filter sampling of PM2.5 at one monitoring location, we analysed carbon and ion components, and assigned the first trimester average of the respective pollutant concentrations to each woman.ResultsThe ORs of placenta-mediated pregnancy complications were 1.14 (95% CI = 1.08–1.22) per 0.51 μg/m3 (interquartile range) increase of organic carbon and 1.11 (1.03–1.18) per 0.06 μg/m3 increase of sodium. Organic carbon was also associated with four individual complications. There was no association between ozone and outcome.SignificanceThere were specific components of PM2.5 that have adverse effects on maternal and foetal health.

Ground-based measurements of black carbon (BC) were performed near an industrial source region in the early summer of 2014 and at a remote island in Japan in the spring of 2015. Here, we report the temporal variations in the transport, size distributions, and mixing states of the BC-containing particles. These particles were characterized using a continuous soot monitoring system, a single particle soot photometer, and an aerosol chemical speciation monitor. The effects of aging on the growth of BC-containing particles were examined by comparing the ground-based observations between the near-source and remote island sites. Secondary formation of sulfate and organic aerosols strongly affected the increases in BC coating (i.e., enhancement of cloud condensation nuclei activity) with air mass aging from the source to the outflow regions. The effects of wet removal on BC microphysics were elucidated by classifying the continental outflow air masses depending on the enhancement ratios of BC to CO (ΔBC ∕ ΔCO), which were used as an indicator of the transport efficiency of BC. It was found that ΔBC ∕ ΔCO ratios were controlled mainly by the wet removal during transport in the planetary boundary layer (PBL) on the timescale of 1–2 days. The meteorological conditions and backward trajectory analyses suggested that air masses strongly affected by wet removal originated mainly from a region in southern China (20–35° N) in the spring of 2015. Removal of large and thickly coated BC-containing particles was detected in the air masses that were substantially affected by the wet removal in the PBL, as predicted by Köhler theory. The size and water solubility of BC-containing particles in the PBL can be altered by the wet removal as well as the condensation of non-BC materials.

Background Particulate matter with an aerodynamic diameter of ≤2.5 µm (PM 2.5 ) is a heterogeneous mixture, and specific substances that affect cardiovascular events remain unknown. We aimed to examine the association of short-term exposure to PM 2.5 and its components with hospital admissions for acute myocardial infarction (AMI). Methods The concentrations of total PM 2.5 and its individual components were continuously measured using Aerosol Chemical Speciation Analysers. From a national-scale administrative database collected from 828 facilities in 47 prefectures across Japan from April 2017 to December 2019, we extracted AMI data for seven prefectures where these aerosol analysers were installed. The primary outcome was the relationship of PM 2.5 and its components with AMI hospitalisation. A time-stratified case-crossover analysis was conducted, and the approximate risk of AMI by pollutant concentrations was estimated using a conditional logistic regression model. In total, 44,232 patients with AMI aged 40–104 years (74.9% male) were examined. Results The estimated effect of an increase in the total PM 2.5 concentration is significantly associated with AMI-related hospitalisation. Upon further examination of the components of PM 2.5 , black carbon has a more substantial influence on AMI development than water-soluble organic compounds, nitrate, and sulphate ions. Conclusions Short-term exposure to PM 2.5 is associated with an increased incidence of AMI. Future research prioritises the components of PM 2.5 , with particular focus on whether a decrease in black carbon concentrations can mitigate the risk of future air quality-related AMI. Plain language summary This study examined whether short-term exposure to fine air particles, known as PM 2.5 , increases the risk of heart attacks. PM 2.5 consists of tiny substances that can enter the lungs and bloodstream. Researchers analysed over 44,000 heart attack cases in seven regions of Japan between 2017 and 2019. They found that higher PM 2.5 levels shortly before each case were linked to more hospital visits for heart problems. Among the components of PM 2.5 , black carbon—produced by car exhaust, factories, and smoke—showed the strongest link to heart attacks. The findings suggest that reducing black carbon in the air may help lower the risk of heart attacks. Cleaner air could lead to better heart health and benefit public well-being. Kojima et al. examine the association of particulate matter with an aerodynamic diameter of ≤2.5 µm (PM2.5) and its components with hospital admissions for acute myocardial infarction (AMI). Short-term exposure to PM2.5 is linked to increased incidence of AMI, with black carbon identified as a key harmful component.

Transboundary air pollution (TAP) and local air pollution (LAP) influence the air quality of urban areas. Fukuoka, located on the west side of Japan and affected by TAP from the Asian continent, is a unique example for understanding the contribution of LAP and TAP. Gaseous species and particulate matter (PM) were measured for approximately three weeks in Fukuoka in the winter of 2018. We classified two distinctive periods, LAP and TAP, based on wind speed. The classification was supported by variations in the concentration of gaseous species and by backward trajectories. Most air pollutants, including NOx and PM, were high in the LAP period and low in the TAP period. However, ozone was the exception. Therefore, our findings suggest that reducing local emissions is necessary. Ozone was higher in the TAP period, and the variation in ozone concentration was relatively small, indicating that ozone was produced outside of the city and transported to Fukuoka. Thus, air pollutants must also be reduced at a regional scale, including in China.

Daily PM2.5 (particulate matter with aerodynamic diameter ≤2.5 μm) samples were simultaneously collected at two background sites (Wajima Air Monitoring Station (WAMS) and Fukue-Jima Atmosphere and Aerosol Monitoring Station (FAMS)) in Japan in the East Asian winter and summer monsoon periods of 2017 and 2019, to compare the characteristics of air pollutants among different regions and to determine the possible variation during the long-range transport process. Polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and water-soluble inorganic ions (WSIIs) were analyzed. Despite the PM2.5 concentrations at FAMS (8.90–78.5 µg/m3) being higher than those at WAMS (2.33–21.2 µg/m3) in the winter monsoon period, the average concentrations of ∑PAHs, ∑NPAHs, and ∑WSIIs were similar between the two sites. Diagnostic ratios indicated PAHs mainly originated from traffic emissions and mostly aged, whereas NPAHs were mostly secondarily formed during long-range transport. WSIIs at WAMS were mainly formed via the combustion process and secondary reactions, whereas those at FAMS mainly originated from sea salt and dust. Backward trajectories revealed the air masses could not only come from Asian continental coastal regions but also distant landlocked areas in the winter monsoon period, whereas most came from the ocean in the summer monsoon period. These findings can provide basic data for the establishment of prediction models of transboundary air pollutants in East Asia.

To estimate the sources of polycyclic aromatic hydrocarbons (PAHs) and their contributions to the total PAH emissions, more than 40 PAHs and organic tracers in PM2.5 collected in 3 cities of Japan were measured and a positive matrix factorization (PMF) model analysis was performed. During the warm season, high PAH concentrations were detected in Nagoya, which is located in the port area. Total PAHs were classified into five sources: biomass combustion, semivolatile PAHs, and ship and industrial emissions, which were major, and road traffic and plastic combustion, which were minor. Analysis of the ship and industrial emissions revealed that the concentrations of these sources in the severe PAH pollution event in Nagoya exceeded 15 ng/m3 and the significant contribution exceeded 80%. In addition, PAHs indicating a risk of carcinogenicity, such as 1 to 2B by IARC and 1 to B2 by U.S. EPA, had the highest contribution to this factor among the five factors such as biomass burning and ship and industrial emissions. Our results suggest that sources of high PAH emissions exist in the port areas of Nagoya. The PMF analysis performed in this study, using combustion organics as indicators, is expected to aid other countries and regions in identifying the sources of PAHs for their effective control.

To determine the effects of long-range transport of aerosols from an upwind area in East Asia to a downwind area in Japan, we chemically analyzed aerosols collected simultaneously on Tuoji Island (Shandong Province, China), Fukue Island (Nagasaki Prefecture, Japan), and Cape Hedo (Okinawa Prefecture, Japan). We focused on changes in the metallic composition of PM2.5 aerosols during long-range transport. The average mass concentrations of PM2.5 at the three sites decreased in the order Tuoji Island > Fukue Island ≈ Cape Hedo (48.3 ± 4.5, 13.9 ± 1.5, and 13.2 ± 0.9 μg/m3, respectively). The fraction of coarse particles in total suspended particles estimated by (1–PM2.5/TSP) was highest on Cape Hedo, indicating that the contribution of sea salts was increased by long-range transport of the aerosols over the ocean. Enrichment factor analysis revealed that at all three sites, Al, K, Ca, Mn, Fe, Co, Sr, and Ba originated from soil; whereas Cr, Ni, Cu, Zn, As, Mo, Ag, Cd, Sn, Sb, Tl, and P appeared to be of anthropogenic origin. Na was the most abundant element on Cape Hedo, indicating the addition of sea salts during aerosol transport. The V concentration was highest at Fukue Island, which was ascribed to V emission from ships. Sixty-one percent of the V on Fukue Island and 62% of the V on Cape Hedo were determined to have originated from ships, implicating of data obtained on dates during which backward trajectory analysis indicated that the same air mass passed over Tuoji Island, Fukue Island, and Cape Hedo in that order.

(1) Background: To date, little research has epidemiologically examined whether the concentration of particulate matter (PM) 2.5 and its ionic components is related to the prevalence of skin symptom exacerbations. Therefore, this study aimed to clarify this association in patients with allergic diseases. (2) Methods: From 1 February to 31 May 2020, we evaluated the daily prevalence of skin symptoms in outpatients with allergic diseases being treated at Fukuoka National Hospital, Fukuoka, Japan, and measured the concentration of PM2.5 and its ionic components. (3) Results: Univariate analysis showed a statistically significant association between skin symptoms and the concentration of PM2.5 and the ionic components SO42−, NH4+, K+, and Mg2+; multivariate analysis showed a statistically significant association between the daily prevalence of skin symptom and the concentration of the ionic components SO42− or Mg2+. (4) Conclusions: Our findings indicate that the concentration of some PM2.5 ionic components may affect skin symptom in patients with allergic diseases.