According to a new study published in The Lancet Planetary Health, about 4 million children all around the world develop asthma each year because of inhaling nitrogen dioxide (NO2) air pollution.

Written by researchers at the George Washington University Milken Institute School of Public Health, the study is based on data from 2010 to 2015 and estimates that 64 percent of these new cases of asthma develop in urban areas.

The George Washington University study is “the first to quantify the worldwide burden of new pediatric asthma cases linked to traffic-related nitrogen dioxide,” the school says. Although it might seem obvious that kids in cities would be exposed to more pollution than kids from rural areas, the study used a method that takes into account that high exposures of nitrogen dioxide occur near busy roads.

“Our findngs suggest that millions of new cases of pediatric asthma could be prevented in cities around the world by reducing air pollution,” said senior author Susan C. Anenberg, Ph.D. “Improving access to cleaner forms of transportation, like electrified public transport and active commuting by cycling and walking, would not only bring down NO2 levels, but would also reduce asthma, enhance physical fitness, and cut greenhouse gas emissions.

Key findings from the study include:

  • An estimated 4 million kids developed asthma each year from 2010 to 2015 due to exposure to NO2 pollution, which comes primarily from motor vehicle exhaust.
  • An estimated 13 percent of annual pediatric asthma incidence worldwide was linked to NO2 pollution.
  • Among the 125 cities the team studied, NO2’s contribution was greater than 20 percent in 92 cities in both developed and emerging economies.
  • The top 10 highest NO2 contributions were estimated for eight cities in China (37 to 48 percent of pediatric asthma incidence), and for Moscow and Seoul (40 percent).
  • S. cities are affected as well. Los Angeles, New York, Chicago, Las Vegas, and Milwaukee were the cities in the U.S. with the highest percentage of child asthma cases linked to air pollution.

The World Health Organization calls air pollution “a major environmental risk to health” and has established air quality guidelines for NO2 and other air pollutants. The George Washington University researchers estimate that most children lived in areas below the current WHO guidelines of 21 parts per billion for annual average NO2. However, they also found that about 92 percent of the new child asthma cases were in areas that already meet the WHO guideline.

“That finding suggests that the WHO guideline for NO2 may need to be re-evaluated to make sure it is sufficiently protective of children’s health,” said study lead author Pattanun Achakulwisut, Ph.D.

In general, the researchers found, cities with high nitrogen dioxide concentrations also had high levels of emissions of other greenhouse gases, so solutions aimed at reducing greenhouse gas emissions would also prevent new cases of asthma and other serious air pollution-related health problems.

See a video of the researchers discussing the study and its findings.

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