Air Pollution Emitted Near the Equator More Detrimental Than Previously Thought

A new study reveals that air pollution emitted from countries near the equator has a bigger impact on the formation of global ozone.

The study, published in the journal Nature Geosciences, showed that the location where the air pollution is emitted is much more important than how much the air pollution is when it comes to total ozone levels worldwide.

"Emissions are growing in places where there is a much greater effect on the formation of ozone," explained Jason West, an associate professor of Environmental Sciences at University of North Carolina-North Chapel and lead author of the study, in a press release. "A ton of emissions in a region close to the equator, where there is a lot of sunlight and intense heat, produces more ozone than a ton of emissions in a region farther from it."

For the study, the researchers used computer models to simulate the total amount of ozone in the atmosphere between 1980 and 2010. The researchers also used a unique European data set of ozone observations from commercial aircraft to confirm the strong increases in the ozone above Asia. To determine what contributed more to the increased production of global ozone, the researchers superimposed a map of how much pollution the world was emitting in 1980 onto where the world was emitting it in 2010, and vice versa.

The researchers found locations of the emissions are more important than its magnitude when it comes to ozone. According to West, the reason behind this is the composition of ozone itself. Ozone is a greenhouse gas and toxic air pollutants that is not emitted but formed when ultraviolet light hits nitrogen oxides.

Higher temperatures in regions near the equator speeds up the chemical reactions that form ozone. Furthermore, the warmer temperatures near the equator increase the vertical motion of air, transporting ozone-forming chemicals higher in the troposphere.

Their findings are apparent when the emissions from China between 1980 and 2010 are compared to the emissions of India and Southeast Asia. China's emission has increased more than India's and Southeast Asia's. However, India and Southeast Asia appear to have contributed more to the total global ozone increase due to their proximity to the equator.