The staggering impact of air pollution

New research in The Lancet has provided more grim estimates for the impact of air pollution. It may be causing an additional 1.85 million cases of asthma in children per year, as well as 1.8 million excess deaths.

One paper, focusing on the pollutant nitrogen dioxide, estimates that the gas is responsible for 1.85 million paediatric asthma cases per year.

“Our study found that nitrogen dioxide puts children at risk of developing asthma and the problem is especially acute in urban areas,” says study author Professor Susan Anenberg, a researcher in environmental and occupational health at the George Washington University, US.

“The findings suggest that clean air must be a critical part of strategies aimed at keeping children healthy.”

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The researchers examined an existing dataset that looked at nitrogen dioxide concentrations in 58 countries during 2010–12.

They then compared these concentrations to data on asthma diagnoses, determining baseline levels of asthma and excess cases.

They used this comparison to estimate that there were over a million excess asthma cases per year globally, rising from 1.22 million cases in 2000 (out of a total of over 6.14 million cases) to 1.85 million cases in 2019 (out of a total of 7.73 million cases).

A second paper, by the same group of researchers, also estimates that in the year 2019 alone, 1.8 million excess deaths could be linked to air pollution.

This paper examined global levels of PM2.5 matter – air particulates that are less than 2.5 micrometres in diameter (or less than a 10th of the width of thin human hair). This data was compared with mortality data from 13,160 urban centres around the world between 2000 and 2019.

While PM2.5 concentrations had dropped globally over the past decade, the effects of this weren’t even. In Europe and the Americas, PM2.5-attributable deaths dropped in this period, but rose everywhere else. In some places, because of demographic changes, PM2.5-attributable deaths rose even as overall PM2.5 pollution dropped.

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In total, the researchers found that 2.5 billion people were living in urban areas where the air pollution was higher than World Health Organisation guidelines, leading to 1.8 million excess deaths in 2019 alone.

This estimate is lower than a paper published in Nature last year, which predicted four million annual premature deaths from air pollution, with consumption in G20 nations being responsible for roughly half of the deaths. Both studies have used different methods, datasets, and definitions of air-pollution related deaths. The true annual death toll from air pollution may not be easy to find precisely, but it’s likely in the millions.

“Reducing fossil-fuel-powered transportation can help children and adults breathe easier and may pay big health dividends, such as fewer cases of paediatric asthma and excess deaths,” says Anenberg.

“At the same time, it would also reduce greenhouse gas emissions, leading to a healthier climate.”

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