The majority of people across the world live in urban areas, where they are exposed to unhealthy air pollution levels. A pair of studies by the same team of researchers has estimated the scale of the threat facing these people in terms of disorders and deaths.
The studies, which appeared recently in the journal The Lancet Planetary Health, showed that about 86% of people living in global urban areas are exposed to harmful levels of airborne particulate matter (PM2.5). This exposure accounts for an estimated 1.8 million excess deaths in cities globally every year.
Data also revealed that nitrogen dioxide (NO2) pollution resulting from motor vehicle emissions caused nearly two million asthma cases among children across the globe. Two in three of these cases were seen in urban areas.
Investigating air pollution threats in cities
According to estimates, around 55 percent of the world’s population lives in cities. Researchers said 86 percent, or 2.5 billion, of these people, are exposed to unhealthy PM2.5 levels.
PM2.5 encompasses very tiny pollutants that are present in smoke and airborne dust. These particles have a diameter of no more than 2.5 micrometers. Their levels are usually higher in areas with high numbers of factories and industrial sites.
In a different research, it was estimated that more than two in every five persons in the US live in cities with a serious pollution problem.
PM2.5 exposure has been linked to several health issues, including lung disorders and heart disease.
In current studies, researchers examined PM2.5 levels and death trends between 2000 and 2019 for over 13,000 cities worldwide. The latest year for which data was available was 2019.
The team found in the first study that average PM2.5 levels in the air were up to 300 percent more than the 2021 unhealthy exposure threshold set by the World Health Organization (WHO). Some 1.8 million excess deaths occurred as a result in 2019 alone.
By “excess deaths,” reference is to the difference between actual and expected deaths going by historical trends.
Data showed that the highest number of deaths linked to air pollution occurred in South-East Asia. The figure was 84 deaths per 100,000.
Researchers observed in the second inquiry that NO2 pollution caused 1.85 million new asthma cases among children worldwide in 2019. These cases represented about nine percent of all the disorder cases reported during the year.
A critical need to improve air quality
These studies add to growing evidence on the need to improve urban air quality. They suggest an urgent necessity for a transition away from or less reliance on fossil fuels.
Children and the elder are at most risk from greater air pollution in cities around the world, according to the researchers.
The investigations reveal how moves to decarbonize cities globally can benefit the health of everyone. Measures in that direction can also help to cut climate-related risks.
Benefits that could accrue from decarbonizing are in tandem with findings in the Children, Cities, and Climate preliminary report from the London School of Hygiene & Tropical Medicine (LSHTM).
LSHTM researchers reported recently that PM2.5 components influence the degree of health risks to humans from air pollution.
The examination of trends over time and across regions makes these studies especially valuable. This gives a better picture of the situation worldwide. Data showed that improvements in air quality in some cities are being countered by declines in many others. As a result, the global burden of diseases caused by air pollution increases.
There is a need for more research to more accurately estimate the extent of the health threat that air pollution poses. Dr. Robert Hughes, LSHTM Clinical Research Fellow, believes that the studies could have underestimated rather than overestimated health risks.