China’s air pollution is traveling across the Pacific Ocean and into the United States, according to a new study.
The study, published this week in Nature Geoscience, found that ozone, which can contribute to respiratory problems when inhaled, has been making its way from China to the western United States. In China, according to the study, ozone levels in the troposphere — the lowest level of the earth’s atmosphere — went up by about 7 percent between 2005 and 2010.
“The dominant westerly winds blew this air pollution straight across to the United States,” lead researcher Willem Verstraeten of the Royal Netherlands Meteorological Institute said in a statement. “In a manner of speaking, China is exporting its air pollution to the West Coast of America.”
The movement of this ozone pollution into the United States has offset about 43 percent of the western region’s efforts to reduce ozone emissions, the study found. The federal government implemented policies that decreased the production of nitrogen oxides — which, when in contact with volatile organic compounds and sunlight, form ozone — by 20 percent in the western U.S., Agence France-Presse reports. Still, the region didn’t see a major decrease in air ozone levels, and this study might point to the reason why.
This isn’t the first time China has been identified as the source of U.S. air pollution. Last year, a study in the Proceedings of the National Academy of Sciences found that pollution blown across the ocean from China can account for 12 to 24 percent of sulfate concentrations on the West Coast. In 2006, the study found, pollution blown in from China caused Los Angeles, California to experience an extra day of unhealthy smog levels.
But that study also found that China’s manufacturing for export sector contributed to 36 percent of the country’s emissions of sulfur dioxide, a pollutant that, like ozone, can exacerbate respiratory problems. Manufacturing for export was also responsible for 27 percent of its nitrogen oxide emissions, 17 percent of its black carbon and 22 percent of its carbon monoxide. Since the United States is among China’s top trading partners, that means that the country plays a role in these manufacture for export emissions. The United States has also exported much of its manufacturing to China, which means that the creation of products designed by U.S. companies happens there and not in the U.S.
China — especially major cities like Shanghai and Beijing — is known for its severe air pollution. In 2013, off-the-charts air pollution in Shanghai cancelled flights and forced children and the elderly to stay indoors. For a week, air quality levels in the city remained at “heavily” and “severely” polluted, and visibility was severely limited by smog. And last October, many of Beijing’s marathoners needed masks and sponges to complete the race.
However, Beijing’s air quality might be improving a bit — a study from Greenpeace found that air pollution fell by 13 percent over the first quarter of 2015. That study also found that particulate levels fell by 31 percent in Hebei province, which neighbors Beijing. The study’s results may mean that China’s efforts to reduce pollution in certain regions are working: regions where new pollution controls weren’t implemented where generally more polluted over the course of the quarter, according to the study.
China has been making efforts to cut down on its air pollution and curb some of its greenhouse gas emissions. Last year, the country announced a target of peaking its carbon dioxide emissions by 2030, and promised to increase the share of energy it gets from non-fossil fuel sources to about 20 percent by the same year. The country also pledged to cap its coal use by 2020.
The study points out that the findings mean that pollution control efforts in a single country may not be enough to improve air quality there.
“We conclude that global efforts may be required to address regional air quality and climate change,” the authors write.