The world’s biggest cities and urban areas face some of the worst air quality on the planet, according to a new report published by HEI (Health Effects Institute). The report, Air Quality and Health in Cities, released by HEI’s State of Global Air Initiative, provides a comprehensive and detailed analysis of air pollution and global health impacts for more than 7,000 cities around the world, focusing on two of the most harmful pollutants; fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂).

In 2019, 1.7 million deaths linked to PM_2.5 occurred in the 7,239 cities included in the analysis. Cities in Asia, Africa, and Eastern and Central Europe saw the greatest health im­pacts from PM_2.5 exposures.

Population-weighted annual average PM_2.5 concentrations in the five most populous cities in each region in 2019. HEI

In 2019, 86% of the cities included in this report exceeded the WHO’s 10 µg/m³ guideline for annual NO₂ exposure, impacting about 2.6 billion people. While PM_2.5 pollution tends to get more attention on known hotspots around the world, less data has been available for NO₂ at this global scale.

Population-weighted annual average NO₂ concentrations in the five most populous cities in each region in 2019. HEI

The report, using data from 2010 to 2019, found that global patterns for exposures to these two key air pollutants are strikingly different. While exposures to PM_2.5 pollution tend to be higher in cities located in low- and middle-income countries, exposure to NO₂ is high across cities in high-income as well as low- and middle-income countries.

Regional urban medians of death rates attributable to PM_2.5 in 2019 (deaths per 100,000). HEI

The report was produced by the State of Global Air Initiative, a collaboration between the Health Effects Institute and the Institute for Health Metrics and Evaluation’s Global Burden of Disease project.

HEI is a nonprofit corporation chartered in 1980 as an independent research organization to provide high-quality, impartial, and relevant science on the health effects of air pollution. HEI typically receives balanced funding from the U.S. Environmental Protection Agency and the worldwide motor vehicle industry. Other public and private organizations periodically support special projects or certain research programs.