Legendary late-night TV host Johnny Carson made the thick, automobile-generated smog that covered Los Angeles the butt of jokes for decades, but times have changed. In the past 50 years, California’s Los Angeles Basin has shown a 98 percent decrease in levels of some vehicle-related air pollutants even as area denizens now burn three times as much gasoline and diesel fuel.
Between 2002 and 2010 alone, the concentration of volatile organic compounds (VOC) dropped by half, according to a new study led by the National Oceanic and Atmospheric Administration (NOAA) and published in the Journal of Geophysical Research-Atmospheres. “The reason is simple. Cars are getting cleaner,” says Carsten Warneke, a NOAA-funded scientist with the Cooperative Institute for Research in Environmental Sciences, at the University of Colorado at Boulder.
Primarily emitted from the vehicle tailpipes, VOCs are a key ingredient in 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, although it doesn’t mean that ozone levels have dropped as steeply, because the air chemistry is complex. Levels of ozone pollution in the basin are down, but don’t yet meet U.S. Environmental Protection Agency standards.
Warneke expects the decrease in VOC emissions by cars to continue, given that engine efficiency continues to improve and older, higher polluting vehicles will be taken off the roads.
Source: American Geophysical Union