In California, 5 decades of decreasing emissions



Volatile organic compounds (VOCs), which are emitted by vehicles and are a leading source of air pollution, have been on the decline in Los Angeles, Calif., one of the densest and most poorly ventilated cities in the United States, a new study finds. Comparing detailed measurements from two aircraft campaigns in the Los Angeles basin in 2002 and 2010, Warneke et al. found that the VOC concentrations in the region's atmosphere declined significantly during those 8 years. Using data from literature statistics and a monitoring network, the authors further show that in the Los Angeles basin, concentrations of VOCs and carbon monoxide (CO) have declined by 2 orders of magnitude compared to the 1960s—a reduction of 7.5% every year since the 1960s in spite of the fact that the sale of fuels has increased threefold during the same interval of time.