Levels of some automobile-related pollutants in Los Angeles have plummeted by 98 percent since the 1960s, even as gasoline consumption nearly tripled during the same period, a new study says. Levels of volatile organic
compounds (VOCs), which are emitted from the tailpipes of cars and are a key ingredient in ground-level smog, have dropped steadily and fell by about half between 2002 and 2010, researchers found. “The reason is simple: Cars are getting cleaner,” said Carsten Warneke, a researcher at the University of Colorado and lead author of the study, published in the Journal of Geophysical Research. Using data from the National Oceanic and Atmospheric Administration and California air quality measurements, the scientists calculated that VOC levels declined by an average of 7.5 percent per year. Researchers attributed the steep decline to the required use of catalytic converters, introduction of fuels less prone to evaporate, and improved engine efficiency.