Air quality in some East Asian capitals is famously poor, with residents of Beijing taking extreme measures to avoid the health risks associated with heavy pollution.

The problem has grown worse as emerging Asian economies, particularly China, have increased their use of high-sulfur coal and private automobiles.

Now, scientists from the National Oceanic and Atmospheric Administration (NOAA) and the Environmental Protection Agency (EPA) warn that East Asian pollution may be causing smog along the West Coast of the United States, as nitrogen oxides move on air currents across the Pacific Ocean.

National Public Radio reports:

The problem, scientists say, is that Asian countries’ emissions of nitrogen oxides — which sunlight then breaks down in reactions that produce ozone — have tripled since 1990. When those harmful gases circulate to North America, they offset gains in U.S. air quality that have come from cutting nitrogen oxide emissions by 50 percent. … The research was published in the journal Atmospheric Chemistry and Physics. The study looked at levels of ground-level ozone (the key component in smog) from 1980 to 2014. … They concluded that the spike in man-made emissions in Asia “is the major driver” of the rise in ozone levels in the western U.S. for both spring and summer in recent decades.

According to the study, which was funded by NASA, U.S. air pollution whose original source is in Asia has increased by 65%.

In the 2011 Fukushima nuclear reactor disaster, which followed the Japanese tsunami, there were concerns that Pacific air currents could bring radioactive particles across the ocean and into the U.S. Such radiation was first detected in December 2016.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He was named one of the “most influential” people in news media in 2016. His new book, How Trump Won: The Inside Story of a Revolution, is available from Regnery. Follow him on Twitter at @joelpollak.