As much of Southern California struggles through a summer of unrelenting smog, a study released Wednesday offers a stark reminder of why air quality matters.

Researchers believe that thousands of people die each year because of exposure to the region’s poor-quality air. Pollution levels routinely exceed the levels deemed safe by health professionals.

In the Los Angeles-Long Beach-Glendale area, about 1,341 people are estimated to die each year because of bad air.

That makes the L.A. area’s air quality the deadliest in the nation.

The Riverside-San Bernardino-Ontario metropolitan area was second-worst, with about 808 people estimated to die annually because of air pollution.

ORANGE COUNTY SMOG

The situation isn’t as dire in Orange County, but the county is hardly immune: The study found that the Santa Ana-Irvine area incurred 64 estimated deaths a year because of air pollution.

Also troubling for Orange County is that pollution is expected to get worse here because of population growth and drought-fueled wildfires, according to Michael Kleinman, a UC Irvine occupational and environmental medicine professor who studies inhalation of toxins.

“We have more traffic; we have more cars. It’s inevitable to have more emissions and more output,” Kleinman said. “When you have more fires and they’re more intense, there’s more exposure to people throughout the South Coast Air Basin, and Orange County is not immune.”

The study released Wednesday was conducted by the American Thoracic Society, a group of health care professionals that focuses on understanding pulmonary diseases, critical illnesses and sleep-related breathing disorders, and New York University’s Marron Institute of Urban Management.

Nationally, the deaths were estimated at 9,330 a year, which is comparable to the number of lives lost annually to drunken driving.

The study’s lead author, Kevin Cromer, a professor at the NYU institute, said by telephone that he hopes the results will raise public awareness and better inform policymakers.

“We are just providing previously unavailable information that can help air quality managers and cities make more meaningful decisions,” said Cromer, who has expertise in population health and environmental medicine.

The study was based on air pollution data for both fine-particle and ozone levels in U.S. metropolitan areas recorded in 2011, 2012 and 2013.

RESULTS ARE CONSERVATIVE

The numbers of deaths and illnesses were estimated through computer analysis that took into account epidemiological studies linking various health effects to air pollution exposure.

The researchers noted that they believe their results are conservative. They did not count deaths from cancers that take decades to develop or deaths from the exacerbation of other chronic illnesses such as diabetes.

Cromer and his colleagues also created a website, HealthoftheAir.org, that allows users to input ZIP codes to learn the estimated numbers of deaths and illness in regions throughout the nation.

Dr. Ahmet Baydur, a pulmonary expert and professor of clinical medicine at USC’s Keck School of Medicine, said the people most at risk are those whose lungs already are damaged by smoking and people with emphysema, chronic bronchitis and severe asthma.

Of particular concern are people who need to treat themselves with oxygen from portable oxygen tanks, he said.

Air pollution causes inflammation that creates mucus and swelling that block internal air passageways, he said. Inflammation from air pollution also can trigger heart attacks, Baydur said.

In addition to deaths, the study estimated the number of acute illnesses attributable to air pollution. That was done by tallying the expected number of heart attacks, cardiac and respiratory hospitalizations and emergency room visits.

Kleinman said even healthy people should avoid exercising outdoors when air quality is poor. He also said proper maintenance of older cars is important for reducing the pollution that can diminish health over a lifetime.

“It depends on who would you rather pay: Your mechanic one time or more health bills?” he said.

LUNG-IRRITATING OZONE

In the Riverside-San Bernardino-Ontario area, these illnesses were estimated at 1,416 a year; the L.A.-Long Beach-Glendale area had about 3,255 illnesses.

The study further estimated the number of times people called in sick, missed school or otherwise had to curtail their activities because of air pollution.

In the Los Angeles-Long Beach-Glendale area, that number exceeded 2 million. The Inland area had 1.3 million such days.

The study was released as Southern California’s ocean-to-mountains air basin is weathering a tough smog season.

As of Monday, the region had exceeded the federal health standard for lung-irritating ozone on at least 90 days.

That’s 24 more unhealthful days than last year, with the worst pollution in the Crestline, Redlands and San Bernardino areas.

Baydur said research has shown the cost of reducing air pollution is much less than the cost for health care and lost productivity associated with bad air.

He is a member of the American Thoracic Society, which recommends a more protective ozone standard of 60 parts per billion.

“Anything we can do to reduce particle and gaseous air pollutants will be extremely helpful in the long run,” Baydur said.

Officials with the South Coast Air Quality Management District welcomed the study.

“Studies such as this one help illustrate the important public health impacts of air pollution,” said Jo Kay Ghosh, the air district’s health-effects officer.

“The good news is that air pollution levels are going down here in Southern California, but we clearly need to continue our efforts to adopt policies and programs that will help us to achieve clean air here in the region.”

Dr. Dean Baker, a professor of occupational and environmental medicine at UCI, said the findings demonstrate the need for a more aggressive approach to air quality. He criticized a December vote by the South Coast Air Quality Management District board to adopt an industry-backed plan to reduce emissions from power plants and other smokestack polluters.

“It is too bad that the elected officials on the board of the AQMD have been moving to ease regulation of air pollution, apparently considering the health of businesses to be more important than the health of people living in Los Angeles and Orange counties,” Baker said in an email.

Contact the writer: 714-796-3686 or cperkes@scng.com