Exposure to outdoor fine particulate matter (PM2.5) is a leading risk factor for mortality. We develop global estimates of annual PM2.5 concentrations and trends for 1998–2018 using advances in ...satellite observations, chemical transport modeling, and ground-based monitoring. Aerosol optical depths (AODs) from advanced satellite products including finer resolution, increased global coverage, and improved long-term stability are combined and related to surface PM2.5 concentrations using geophysical relationships between surface PM2.5 and AOD simulated by the GEOS-Chem chemical transport model with updated algorithms. The resultant annual mean geophysical PM2.5 estimates are highly consistent with globally distributed ground monitors (R 2 = 0.81; slope = 0.90). Geographically weighted regression is applied to the geophysical PM2.5 estimates to predict and account for the residual bias with PM2.5 monitors, yielding even higher cross validated agreement (R 2 = 0.90–0.92; slope = 0.90–0.97) with ground monitors and improved agreement compared to all earlier global estimates. The consistent long-term satellite AOD and simulation enable trend assessment over a 21 year period, identifying significant trends for eastern North America (−0.28 ± 0.03 μg/m3/yr), Europe (−0.15 ± 0.03 μg/m3/yr), India (1.13 ± 0.15 μg/m3/yr), and globally (0.04 ± 0.02 μg/m3/yr). The positive trend (2.44 ± 0.44 μg/m3/yr) for India over 2005–2013 and the negative trend (−3.37 ± 0.38 μg/m3/yr) for China over 2011–2018 are remarkable, with implications for the health of billions of people.
Reduction of preterm births (<37 completed weeks of gestation) would substantially reduce neonatal and infant mortality, and deleterious health effects in survivors. Maternal fine particulate matter ...(PM2.5) exposure has been identified as a possible risk factor contributing to preterm birth. The aim of this study was to produce the first estimates of ambient PM2.5-associated preterm births for 183 individual countries and globally. To do this, national, population-weighted, annual average ambient PM2.5 concentration, preterm birth rate and number of livebirths were combined to calculate the number of PM2.5-associated preterm births in 2010 for 183 countries. Uncertainty was quantified using Monte-Carlo simulations, and analyses were undertaken to investigate the sensitivity of PM2.5-associated preterm birth estimates to assumptions about the shape of the concentration-response function at low and high PM2.5 exposures, inclusion of provider-initiated preterm births, and exposure to indoor air pollution.
Globally, in 2010, the number of PM2.5-associated preterm births was estimated as 2.7 million (1.8–3.5 million, 18% (12–24%) of total preterm births globally) with a low concentration cut-off (LCC) set at 10μgm−3, and 3.4 million (2.4–4.2 million, 23% (16–28%)) with a LCC of 4.3μgm−3. South and East Asia, North Africa/Middle East and West sub-Saharan Africa had the largest contribution to the global total, and the largest percentage of preterm births associated with PM2.5. Sensitivity analyses showed that PM2.5-associated preterm birth estimates were 24% lower when provider-initiated preterm births were excluded, 38–51% lower when risk was confined to the PM2.5 exposure range in the studies used to derive the effect estimate, and 56% lower when mothers who live in households that cook with solid fuels (and whose personal PM2.5 exposure is likely dominated by indoor air pollution) were excluded. The concentration-response function applied here derives from a meta-analysis of studies, most of which were conducted in the US and Europe, and its application to the areas of the world where we estimate the greatest effects on preterm births remains uncertain. Nevertheless, the substantial percentage of preterm births estimated to be associated with anthropogenic PM2.5 (18% (13%–24%) of total preterm births globally) indicates that reduction of maternal PM2.5 exposure through emission reduction strategies should be considered alongside mitigation of other risk factors associated with preterm births.
•Ambient fine particulate matter (PM2.5) exposure is a possible risk factor for preterm birth.•We estimate 2.7–3.4 million preterm births may be associated with PM2.5 exposure in 2010 globally.•South/East Asia, North Africa/Middle East and West sub-Saharan Africa had largest burdens.•Maternal PM2.5 exposure should be considered alongside other preterm birth risk factors.
Substantial quantities of air pollution and related health impacts are ultimately attributable to household consumption. However, how consumption pattern affects air pollution impacts remains ...unclear. Here we show, of the 1.08 (0.74-1.42) million premature deaths due to anthropogenic PM
exposure in China in 2012, 20% are related to household direct emissions through fuel use and 24% are related to household indirect emissions embodied in consumption of goods and services. Income is strongly associated with air pollution-related deaths for urban residents in which health impacts are dominated by indirect emissions. Despite a larger and wealthier urban population, the number of deaths related to rural consumption is higher than that related to urban consumption, largely due to direct emissions from solid fuel combustion in rural China. Our results provide quantitative insight to consumption-based accounting of air pollution and related deaths and may inform more effective and equitable clean air policies in China.
Vehicle emissions contribute to fine particulate matter (PM
) and tropospheric ozone air pollution, affecting human health, crop yields and climate worldwide. On-road diesel vehicles produce ...approximately 20 per cent of global anthropogenic emissions of nitrogen oxides (NO
), which are key PM
and ozone precursors. Regulated NO
emission limits in leading markets have been progressively tightened, but current diesel vehicles emit far more NO
under real-world operating conditions than during laboratory certification testing. Here we show that across 11 markets, representing approximately 80 per cent of global diesel vehicle sales, nearly one-third of on-road heavy-duty diesel vehicle emissions and over half of on-road light-duty diesel vehicle emissions are in excess of certification limits. These excess emissions (totalling 4.6 million tons) are associated with about 38,000 PM
- and ozone-related premature deaths globally in 2015, including about 10 per cent of all ozone-related premature deaths in the 28 European Union member states. Heavy-duty vehicles are the dominant contributor to excess diesel NO
emissions and associated health impacts in almost all regions. Adopting and enforcing next-generation standards (more stringent than Euro 6/VI) could nearly eliminate real-world diesel-related NO
emissions in these markets, avoiding approximately 174,000 global PM
- and ozone-related premature deaths in 2040. Most of these benefits can be achieved by implementing Euro VI standards where they have not yet been adopted for heavy-duty vehicles.
Ground and satellite observations show that air pollution regulations in the United States (US) have resulted in substantial reductions in emissions and corresponding improvements in air quality over ...the last several decades. However, large uncertainties remain in evaluating how recent regulations affect different emission sectors and pollutant trends. Here we show a significant slowdown in decreasing US emissions of nitrogen oxides (NOₓ) and carbon monoxide (CO) for 2011–2015 using satellite and surface measurements. This observed slowdown in emission reductions is significantly different from the trend expected using US Environmental Protection Agency (EPA) bottom-up inventories and impedes compliance with local and federal agency air-quality goals. We find that the difference between observations and EPA’s NOₓ emission estimates could be explained by: (i) growing relative contributions of industrial, area, and off-road sources, (ii) decreasing relative contributions of on-road gasoline, and (iii) slower than expected decreases in on-road diesel emissions.
Top‐down estimates using satellite data provide important information on the sources of air pollutants. We develop a sector‐based 4D‐Var framework based on the GEOS‐Chem adjoint model to address the ...impacts of co‐emissions and chemical interactions on top‐down emission estimates. We apply OMI NO2, OMI SO2, and MOPITT CO observations to estimate NOx, SO2, and CO emissions in East Asia during 2005–2012. Posterior evaluations with surface measurements show reduced normalized mean bias (NMB) by 7% (NO2)–15% (SO2) and normalized mean square error (NMSE) by 8% (SO2)–9% (NO2) compared to a species‐based inversion. This new inversion captures the peak years of Chinese SO2 (2007) and NOx (2011) emissions and attributes their drivers to industry and energy activities. The CO peak in 2007 in China is driven by residential and industry emissions. In India, the inversion attributes NOx and SO2 trends mostly to energy and CO trend to residential emissions.
Plain Language Summary
Satellite observations are widely used to estimate air pollutant emissions and evaluate their trends. We design a new method based on Bayesian statistics to estimate emissions of major air pollutants in East Asia according to their sources (e.g., energy, industry, transportation, etc.). Results from this approach show better agreement with independent surface measurements than the previous estimates that use observations to optimize emissions by species and estimates that compile emissions using activity data and emission factors. This method provides a new perspective to analyze the trend of air pollutants by sources and is crucial for countries and regions that lack detailed and timely emission estimates for each source sector.
Key Points
A new sector‐based multispecies inversion framework is developed to estimate NOx, SO2, and CO emissions using satellite observations
The sector‐based inversion leads to smaller biases and errors in surface NO2 and SO2 simulations than a species‐based inversion
The framework provides a new perspective to analyze the trend of emissions by sectors and evaluates bottom‐up estimates
Quantitative estimations of atmospheric aerosol absorption are rather uncertain due to the lack of reliable information about the global distribution. Because the information about aerosol properties ...is commonly provided by single-viewing photometric satellite sensors that are not sensitive to aerosol absorption. Consequently, the uncertainty in aerosol radiative forcing remains one of the largest in the Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC AR5 and AR6). Here, we use multi-angular polarimeters (MAP) to provide constraints on emission of absorbing aerosol species and estimate global aerosol absorption optical depth (AAOD) and its climate effect. Our estimate of modern-era mid-visible AAOD is 0.0070 that is higher than IPCC by a factor of 1.3-1.8. The black carbon instantaneous direct radiative forcing (BC DRF) is +0.33 W/m
+0.17, +0.54. The MAP constraint narrows the 95% confidence interval of BC DRF by a factor of 2 and boosts confidence in its spatial distribution.
Emissions from the transportation sector are a major contributor to ambient air pollution, the leading environmental health risk factor globally. This study aims to quantify the contribution of ...tailpipe emissions from global transportation, disaggregated by four sub-sectors, to the global disease burden associated with ambient fine particulate matter (PM2.5) and ground-level ozone in 2010 and 2015. We use the GEOS-Chem global chemical transport model to simulate transportation-attributable PM2.5 and ozone concentrations, combined with epidemiological health impact assessment methods consistent with the Global Burden of Disease 2017 study to estimate the associated burden of disease. We estimate that emissions from the transportation sector were associated with 361 000 (95% CI, 258 000-462 000) PM2.5 and ozone deaths in 2010 and 385 000 (95% CI, 274 000-493 000) in 2015. These results translate into 11.7% of total global ambient PM2.5 and ozone deaths in 2010 and 11.4% in 2015. Together, PM2.5 and ozone concentrations from transportation tailpipe emissions resulted in an estimated 7.8 million years of life lost and approximately $1 trillion (2015 US$) in health damages globally in 2015. Among transportation sub-sectors, on-road diesels contributed most to the health burden from transportation tailpipe emissions in nearly all trade blocs, for both PM2.5 and ozone, though other sub-sectors also contributed substantially (particularly on-road non-diesel vehicles for ozone mortality, and shipping and non-road mobile sources for PM2.5 mortality). These results indicate that despite recent adoption of more stringent vehicle emission regulations in many countries, the transportation sector remains a major contributor to the air pollution disease burden globally. Future work may explore the degree to which currently adopted policies, as well as expected growth in the transportation sector in India, Africa, and other rapidly developing locations, will influence future transportation-attributable public health burdens.
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