A new study from NASA scientists regarding global air quality has found the U.S. and Europe to be among the largest emitters of nitrogen dioxide, a common emission from cars, power plants, and industrial activity.
However, the study—published in the Journal of Geophysical Research—also showed the two regions dramatically decreased the expulsion from 2005 to 2014, the U.S. between 20% and 50% and Europe by as much as 50%.
According to Bryan Duncan, an atmospheric scientist with NASA’s Goddard Space Flight Center, the new study proves that when governments take action regulating a pollutant the results are observable.
“Since 2004, an instrument aboard NASA’s Aura satellite has measured levels of nitrogen dioxide in Earth’s atmosphere,” said Duncan. The device is called the Dutch-Finnish Ozone Monitoring Instrument.
The global study focused on 195 cities. Nitrogen dioxide hotspots over cities can act as an indicator for overall air quality, according to NASA.
NASA scientists compared the nitrogen dioxide detected by the instrument with information about the regions, such as emission controls regulations, national gross domestic product, and urban growth. The high-resolution data allowed scientists to observe changes from individual sources within cities, such as power plants.
In regards to the changes experienced in the U.S. and Europe, the researchers credit environmental regulations that spur technological development as responsible for the decrease in pollutants.
In the same timespan China saw a 20% to 50% increase in nitrogen dioxide, mainly in the North China Plain. However, Beijing, Shanghai, and the Pearl River Delta decreased nitrogen dioxide outputs by as much as 40%.
The Johannesburg and Pretoria regions of South Africa were more complex.
According to NASA scientists, previous observations yielded contradictory data from the metropolitan areas. In 2008, the two areas required new cars to have better emissions controls. But industrial areas surrounding them showed signs of both decreasing and increasing output of nitrogen dioxide.
“The decreases may be associated with fewer emissions from eight large power plants east of the cities since the decrease occurs over their locations,” according to NASA. “However, emissions increases occur form various other mining and industrial activities to the south and further east.”
In the Middle East, Iraq, Kuwait, and Iran increased nitrogen dioxide levels, which NASA believes corresponds to the countries’ economic growth. Syria’s nitrogen dioxide levels started decreasing in 2011, which is likely from the Syrian Civil War.
An interactive air quality map can be found here.