Air Pollution Declining in L.A., Despite More Cars and People. Study Says

California's strict vehicle emissions standards are being credited for decreasing the levels of air pollution in Los Angeles despite a three-fold increase in Southern California's population since the 1960s and a similar increase in the number of vehicles on the roads, according to new research.

As a result, the "eye-stinging" organic nitrate component in the air has plummeted, and a new chemical analysis of the air has revealed the precise nature of the changes to the California air quality.  

The NOAA's Cooperative Institute for Research in Environmental Sciences (CIRES) at University of Colorado, Boulder led the research, which was recently published in the Journal of Geophysical Research-Atmospheres.

The results are "good news," said lead author Ilana Pollack, a CIRES scientist who works at NOAA's Earth System Research Laboratory in Boulder

"LA's air has lost a lot of its 'sting,'" she said in a statement. "Our study shows exactly how that happened, and confirms that California's policies to control emissions have worked as intended."

The results come shortly after California's May 30 announcement that it will begin to sell carbon allowances as part of a cap-and-trade program to further reduce emissions, Bloomberg Businessweek reported.

While pollution has decreased since the 1960s, "motor vehicles remain the dominant source of emissions in Los Angeles." the University of Colorado report stated.

Pollack said that the takeaway for most people will be that "things have got a lot better" since the days when Los Angeles was covered in dystopian smog that caused countless irritated eyes and throats, reportedly causing the closure of schools and factories until the air cleared.

Though she said the scientific community's interest in how things got better is also of note.

"The emission reductions have 'flipped' some of the chemistry that takes place in the atmosphere," Pollack said. "The relevant precursors in the atmosphere now favor chemical pathways that are more likely to produce nitric acid, and less likely to make ozone and peroxyacetyl nitrate," which is what's associated with the eye irritation in L.A. smog.  

Pollack said the research will help inform future climate decisions by providing a better understanding of present and past observations.