Asia air pollution increasing smog in West
By Doyle Rice, USA Today
Air pollution from China, India and several other Asian countries has wafted across the Pacific Ocean over the past 25 years, increasing levels of smog in the western U.S., a study finds.
Smog, also known as ground-level ozone, is harmful to human health, because it can exacerbate asthma attacks and cause difficulty breathing. It also harms sensitive trees and crops. It’s different than the “good” ozone up in the stratosphere, which protects life on Earth from the sun’s harmful ultraviolet rays.
Scientists measured ozone levels recorded at springtime for the past 25 years in 16 national parks in the western U.S., including Yellowstone, Yosemite and Grand Canyon. The parks’ locations farther away from cities, where smog is typically expected, made them ideal spots for the study.