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Jeffrey D. Allred, Deseret News
An inversion settles over in Utah County on Tuesday, Feb. 9, 2016.

SALT LAKE CITY — A concentrated effort to reduce emissions across the spectrum of air pollution sources brought levels down dramatically in Southern California over the past 20 years, and with that drop came a signficant improvement in children's respiratory health.

Those findings released Tuesday are in a landmark study researched by the University of Southern California and published in the Journal of the American Medical Association.

Reformulated gasoline fuel, the advent of catalytic converters or emission control devices on cars, a cleaner burning vehicle fleet overall, and industry controls are among a suite of tactics that four Southern California counties implemented to achieve pollution reductions.

"This has not been easy. It has required a lot of work and a lot of effort," said Ed Avol, study co-author and professor of clinical preventative medicine at the university, which hosted a teleconference on the study. "At the same time, the economy has improved, we've seen that business has grown. I think you can have both of these things if you do it in an intelligent way."

Despite doubling its population, Los Angles, Orange, San Bernardino and Riverside counties saw decreases in the following pollutants over 20 years:

• 47 percent in PM2.5

• 49 percent in nitrogen oxides

• 35 percent in PM10

• 12 percent in ozone

Researchers tracked 4,602 children in eight distinct communities in three groups as they aged from 5 to 18 and looked at children with asthma and those without. They also factored in race, exposure to secondhand smoke, and socio-economic demographics.

What they found is the decrease in fine particulate matter, or PM2.5, was correspondingly accompanied by a 32 percent decrease in bronchitic symptoms experienced by children with asthma. For those without asthma, there was a 21 percent reduction in respiratory problems.

Researchers linked the drop in nitrogen oxides (NOX) to a 21 percent decrease in asthmatic symptoms for sufferers and a 16 percent decrease in bronchitic symptoms for children without asthma.

"It has been quite a dramatic 20 years in Southern California," Avol said. "I grew up here, and as a child I can remember pretty clearly the eye irritation, coughing while exercising and occasionally not being allowed to go out on the playgrounds during pollution alerts. And those things, for the most part, are gone. And I don't think people realize what a difference there has been."

Researchers cautioned that the "dramatic" findings shouldn't mean the region can breathe easy.

Southern California still has the worst ozone pollution problem in the country and remains among the worst for particulate pollution generally, researchers said.

"We still have a lot of work to do," said Philip Fine with the regional air pollution control agency in Southern California. "If we can continue to do these same things over the next 10, 20, 30 years, it will have direct benefits to children's health and our residents in general."

Avol stressed the area remains out of compliance with federal clean air standards, but the double-digit decreases in certain pollutants demonstrate a success story derived from the hundreds of changes carried out through programs and policies aimed at cleaning up the air.

"If we look back and think about it, it seems like the most effective programs have been those targeting on-road emissions," Avol said, adding that fuel reformulations, retiring old fleets of vehicles and zeroing in heavy-duty diesel all helped. The region also instituted a slate of requirements at its ports, airports, railway systems and implemented pollution-reducing steps at small businesses such as dry cleaners and those that use fume-emitting paints.

"We were not happy going under the pace we could have under the Clean Air Act. We were going to push forward as fast and hard as we can...That is reflected now because we see dramatic decreases in emissions."

Kiros Berhane, lead author and a university professor of preventative medicine, said the study results are significant because improvements in respiratory health were observed "across the board" for all children.

"We can simply say it is probably one of the clearest pieces of scientific evidence that reductions in pollution can lead to significant improvements in the respiratory health of children," he said. "… There are far-reaching implications that could motivate policy makers to act."

Elisa Nicholas, a Southern California pediatrician and chief executive officer of The Children's Clinic — which provides services to more than 6,000 children with asthma — said the study results demonstrates rules and regulations do work.

"We can't afford to be complacent and satisfied with the status quo because we know we can clean up the air," she said. "Our children cannot choose the air they breathe, so therefore we must clean it up for them."

The pollution reductions have not come without political fallout.

In March, the seven Republican members of Southern California's air quality board voted to ax executive officer Barry Wallerstein. One member, quoted in a Los Angeles Times story, said having jobs is just as important as having clean air. The GOP-dominated board, the member said, wants to ease the burden of pollution regulations.

Berhane cautioned that the study results should not be interpreted as an excuse to press pause on pollution reduction strategies. He said, in fact, the opposite should happen.

"This should be seen, as in my mind, as a call to action as opposed to saying we are done with everything," Berhane said. "We can easily lose the benefits we have gained over the last 20 years."

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