Globally, 4 million children get asthma every year due to vehicle-related pollution, according to a study published April 10.
And nearly every one of those cases—92%, to be precise—occur in areas that technically meet World Health Organization guidelines for nitrogen dioxide (NO2) in the air, which is 21 parts per billion or less.
The research, published in The Lancet, used NO2 as a proxy for traffic-pollution exposure. NO2 makes up a significant part of the mix of gases released through vehicle tailpipes and is itself harmful to human health. So are other contaminants that often come with it, like fine particulate matter known as PM2.5 that can lodge deep into people’s lungs, causing respiratory illness, and even slip into the blood stream, which can significantly disrupt children’s physical and cognitive health.
Plenty of studies have found that children who live or attend school in places with high traffic-related air pollution perform worse on cognitive tests, for example. A recent study of 783 children between the ages of six and 10 in the Netherlands found that exposure to high levels of PM2.5 in the womb was “found to cause structural alterations to the cerebral cortex,” the region of the brain responsible with impulse control.
The team behind the Lancet paper, from George Washington University, used 2015 country-level data on asthma incidence in children from 194 countries, as well as metropolitan-area-level data from 125 cities, collected by the Institute for Health Metrics and Evaluation, a research institute at the University of Washington. They then overlaid them with a global data set of NO2 levels, developed by a number of researchers in 2017.
According to Susan Anenberg, an author on the study and an associate professor at George Washington, the findings suggest that millions of these asthma cases were preventable. ”Improving access to transit that doesn’t rely on a combustion engine, like electrified public transit, electric cars, and bicycles, would significantly cut the risk to children from NO2 exposure,” she in a press release.
In 2015, rate of new cases of asthma due to traffic varied from city to city, and it was highest in Shanghai, China, where the researchers estimated 48% of all new childhood asthma cases came from inhaling traffic fumes. Bogota, Columbia and Lima, Peru were the second- and third-worst cities for traffic-related new childhood asthma cases.