In California’s Los Angeles Basin, levels of some vehicle-related air pollutants have decreased by about 98 percent since the 1960s, even as area residents now burn three times as much gasoline and diesel fuel.
Between 2002 and 2010 alone, the concentration of air pollutants called volatile organic compounds (VOCs) dropped by half, according to a new study by NOAA scientists and colleagues.
“The reason is simple: Cars are getting cleaner,” said Carsten Warneke, a NOAA-funded scientist with the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder.
VOCs, primarily emitted from the tailpipes of vehicles, are a key ingredient in the formation of ground-level ozone which, at high levels, can harm people’s lungs and damage crops and other plants.
The magnitude of the drop in VOC levels was surprising, even to researchers who expected some kind of decrease resulting from California’s longtime efforts to control vehicle pollution.
“Even on the most polluted day during a research mission in 2010, we measured half the VOCs we had seen just eight years earlier,” Warneke said. “The difference was amazing.”
The study was published online today in the Journal of Geophysical Research-Atmospheres, a journal of the American Geophysical Union.
The 98 percent drop in VOCs in the last 50 years does not mean that ozone levels have dropped that steeply; the air chemistry that leads from VOCs to ozone is more complex than that. Ozone pollution in the Los Angeles Basin has decreased since the 1960s, but levels still don’t meet ozone standards set by the Environmental Protection Agency.