Air Inequality: Global Divergence in Urban Fine Particulate Matter Trends

Fine particle air pollution (PM2.5) is the largest global environmental risk factor for ill-health and is implicated in >7% of all human deaths. Improved air quality is a key policy goal for cities, yet in-situ PM2.5 measurements are missing for >50% of the world’s urban population. Here, we apply satellite remote sensing to develop a 21-year time series of ground-level PM2.5 concentrations for the 4231 urban areas with populations >100,000 (2.9 billion people) from 1998 -2018. Globally, we find the most polluted cities are generally small (2.5 monitors. Since 1998, we observe a growing divide in urban air quality between cities in lower and higher-income regions, with the PM2.5 disparity increasing by >50% (from 25 to 39 µg m-3) between the highest- and lowest income quartiles of world cities. Within Asia, a sharp divergence is underway, with sustained PM2.5 increases in South Asian cities (+48%) contrasted against dramatic improvements in Chinese cities (-40% since 2011). While 85% of the world’s urban population experiences PM2.5 higher than World Health Organization guidelines, urban PM2.5 concentrations are tightly linked to regional conditions, suggesting that city-level efforts alone may be insufficient to address this major health threat.</p

Global urban temporal trends in fine particulate matter (PM2·5) and attributable health burdens: estimates from global datasets

Background: With much of the world\u27s population residing in urban areas, an understanding of air pollution exposures at the city level can inform mitigation approaches. Previous studies of global urban air pollution have not considered trends in air pollutant concentrations nor corresponding attributable mortality burdens. We aimed to estimate trends in fine particulate matter (PM2·5) concentrations and associated mortality for cities globally. Methods: We use high-resolution annual average PM2·5 concentrations, epidemiologically derived concentration response functions, and country-level baseline disease rates to estimate population-weighted PM2·5 concentrations and attributable cause-specific mortality in 13 160 urban centres between the years 2000 and 2019. Findings: Although regional averages of urban PM2·5 concentrations decreased between the years 2000 and 2019, we found considerable heterogeneity in trends of PM2·5 concentrations between urban areas. Approximately 86% (2·5 billion inhabitants) of urban inhabitants lived in urban areas that exceeded WHO\u27s 2005 guideline annual average PM2·5 (10 μg/m3), resulting in an excess of 1·8 million (95% CI 1·34 million–2·3 million) deaths in 2019. Regional averages of PM2·5-attributable deaths increased in all regions except for Europe and the Americas, driven by changes in population numbers, age structures, and disease rates. In some cities, PM2·5-attributable mortality increased despite decreases in PM2·5 concentrations, resulting from shifting age distributions and rates of non-communicable disease. Interpretation: Our study showed that, between the years 2000 and 2019, most of the world\u27s urban population lived in areas with unhealthy levels of PM2·5, leading to substantial contributions to non-communicable disease burdens. Our results highlight that avoiding the large public health burden from urban PM2·5 will require strategies that reduce exposure through emissions mitigation, as well as strategies that reduce vulnerability to PM2·5 by improving overall public health. Funding: NASA, Wellcome Trust

Reversal of trends in global fine particulate matter air pollution.

Ambient fine particulate matter (PM2.5) is the worlds leading environmental health risk factor. Quantification is needed of regional contributions to changes in global PM2.5 exposure. Here we interpret satellite-derived PM2.5 estimates over 1998-2019 and find a reversal of previous growth in global PM2.5 air pollution, which is quantitatively attributed to contributions from 13 regions. Global population-weighted (PW) PM2.5 exposure, related to both pollution levels and population size, increased from 1998 (28.3 μg/m3) to a peak in 2011 (38.9 μg/m3) and decreased steadily afterwards (34.7 μg/m3 in 2019). Post-2011 change was related to exposure reduction in China and slowed exposure growth in other regions (especially South Asia, the Middle East and Africa). The post-2011 exposure reduction contributes to stagnation of growth in global PM2.5-attributable mortality and increasing health benefits per µg/m3 marginal reduction in exposure, implying increasing urgency and benefits of PM2.5 mitigation with aging population and cleaner air

State-of-the-Science Data and Methods Need to Guide Place-Based Efforts to Reduce Air Pollution Inequity.

BACKGROUND: Recently enacted environmental justice policies in the United States at the state and federal level emphasize addressing place-based inequities, including persistent disparities in air pollution exposure and associated health impacts. Advances in air quality measurement, models, and analytic methods have demonstrated the importance of finer-scale data and analysis in accurately quantifying the extent of inequity in intraurban pollution exposure, although the necessary degree of spatial resolution remains a complex and context-dependent question. OBJECTIVE: The objectives of this commentary were to a) discuss ways to maximize and evaluate the effectiveness of efforts to reduce air pollution disparities, and b) argue that environmental regulators must employ improved methods to project, measure, and track the distributional impacts of new policies at finer geographic and temporal scales. DISCUSSION: The historic federal investments from the Inflation Reduction Act, the Infrastructure Investment and Jobs Act, and the Biden Administrations commitment to Justice40 present an unprecedented opportunity to advance climate and energy policies that deliver real reductions in pollution-related health inequities. In our opinion, scientists, advocates, policymakers, and implementing agencies must work together to harness critical advances in air quality measurements, models, and analytic methods to ensure success. https://doi.org/10.1289/EHP13063

Reversal of trends in global fine particulate matter air pollution

Ambient fine particulate matter (PM) is the world\u27s leading environmental health risk factor. Quantification is needed of regional contributions to changes in global PM exposure. Here we interpret satellite-derived PM estimates over 1998-2019 and find a reversal of previous growth in global PM air pollution, which is quantitatively attributed to contributions from 13 regions. Global population-weighted (PW) PM exposure, related to both pollution levels and population size, increased from 1998 (28.3 μg/m) to a peak in 2011 (38.9 μg/m) and decreased steadily afterwards (34.7 μg/m in 2019). Post-2011 change was related to exposure reduction in China and slowed exposure growth in other regions (especially South Asia, the Middle East and Africa). The post-2011 exposure reduction contributes to stagnation of growth in global PM-attributable mortality and increasing health benefits per µg/m marginal reduction in exposure, implying increasing urgency and benefits of PM mitigation with aging population and cleaner air