Urban Air Pollution Responsible for 1.8 million Excess Deaths Globally

Veronica Southerland, PhD

A new modelling study found that approximately 86% of people living in urban areas across the world are exposed to unhealthy particulate matter levels.

This exposure, which affects nearly 2.5 billion people, has led to 1.8 million excess deaths globally in cities in 2019.

Additionally, nearly 2 million asthma cases among children worldwide had been attributed to NO2 pollution in the same year, with 2 out of 3 cases occurring in urban areas.

The new data, which were published in The Lancet Planetary Health, were culled from 2 individual studies that highlighted the need to improve air pollution and reduce emissions exposure, especially among vulnerable groups such as children and the elderly.

PM2.5 Exposure in 2019

In the first study, which was led by Veronica T. Southerland, PhD, George Washington University Milken Institute School of Public Health, investigators estimated trends in fine particulate matter (PM2.5) concentrations and associated mortality for cities worldwide.

Prior to the study, limited research into the disease burdens of PM2.5 were available. The study examined the mortality trends associated with PM2.5 in 13,000 cities globally between 2000 and 2019.

Southerland and investigators found that the average population-weighted PM2.5 concentration across all urban areas globally was 35 micrograms per cubic meter in 2019. No change was observed from 2000.

This level of concentration was equivalent to 7 times the annual average PM2.5 established by the World Health Organization (WHO) guideline, which is 5 micgrograms per cubic meter.

Investigators estimated that 61 in 100,000 deaths in urban areas could be attributed to exposure of PM2.5 in 2019.

Large variations of PM2.5 concentrations were observed in different regions, such as urban areas in South-East Asia, which saw the larget regional increases (27%) during the 19-year study period.

Additionally, the research found that decreasing PM2.5 concentrations in urban areas over the 2 decades did not correspond to the same level of decreases in PM2.5-attributable mortality rates on their own.

“The majority of the world’s urban population still live in areas with unhealthy levels of PM2.5,” said Southerland. “Avoiding the large public health burden caused by air pollution will require strategies that not only reduce emissions but also improve overall public health to reduce vulnerability.”

Pediatric Asthma Linked to Air Pollution

The second study, led by Susan C. Anenberg, PhD, Associate Professor of Environmental and Occupational Health and of Global Health at George Washington University Milken Institute School of Public Health, investigators observed the global implications of nitrogen dioxide gas (NO2) exposure.

To their knowledge, no previous studies had specifically looked at trends in the burden of transport-related NO2 pollution on pediatric asthma incidence in urban areas.

In their study, NO2 concentrations were calculated with a 1km resolution by combining satellite data with datasets on land use. From there, NO2 concentrations were applied to population and baseline asthma rates to estimate pediatric asthma incidence attributable to NO2 exposure in the same 19-year window as the first study.

The findings revealed that 1.85 million new pediatric asthma cases were associated with NO2 exposure in 2019, which made for 8.5% of all new pediatric asthma cases reported that year.

Additionally, approximately 2 in 3 cases of pediatric asthma cases attributable to NO2 occurred in the 13,189 urban areas included in the study.

“In places that have effective air quality management programs, NO2 concentrations have been trending downward for decades, with benefits for children’s respiratory health,” said Anenberg. “Even with these improvements, current NO2 levels contribute substantially to pediatric asthma incidence, highlighting that mitigating air pollution should be a critical element of children’s public health strategies.”

Both studies, “Global urban temporal trends in fine particulate matter (PM2·5) and attributable health burdens: estimates from global datasets,” as well as “Long-term trends in urban NO2 concentrations and associated paediatric asthma incidence: estimates from global datasets” were published online in The Lancet Planetary Health.