L.A.’s summer smog siege concerns USC health scientists
August 20, 2019
As a smog siege grips the Los Angeles region this summer — notching 57 straight days of unhealthy air — air quality officials urge some residents to avoid strenuous activity or stay indoors. Late summer is a bad time of year for air pollution due to hot temperatures, slack winds and high emissions. L.A.’s infamous brown haze has receded over 20 years, but worsened slightly in the past few years. It’s a brew of soot, dust, combustion gases and photochemical ozone. USC experts parse L.A.’s top environmental health threat.
Ed Avol is a professor of clinical preventive medicine and chief of the Division of Environmental Health at the Keck School of Medicine of USC. He’s an expert on respiratory health, smog and health effects due to vehicle traffic. He grew up in Los Angeles and has more than 45 years of experience in air pollution research.
“Late summer is a challenging time for air quality, and it’s likely to get worse with a warming climate. We have ideal conditions here in L.A. for ozone due to long, hot, sunny stagnant days. We tend to see these multi-day weather events, where smog builds up during the day and doesn’t completely blow away overnight. Some pollution carries over into the next day, sloshing back and forth across the basin — inland by day and back toward the coast at night — so it cooks more and more and builds up over the course of a few days,” Avol explained.
He added:
L.A. is smoggy because sunlight and emissions form ozone, onshore breezes push pollution to inland valleys, surrounding mountains prevent it from escaping and inversions seal it from above.
Southern California air quality has improved dramatically over the past 20 years, but dirty air days have increased in recent years as gains against smog stall.
While L.A. air is generally better than a generation ago, the latest science shows health effects occur at lower levels and affect more organs than once thought.
Does everyone suffer the same burden of air pollution?
Jill Johnston is an assistant professor of preventive medicine and director of community outreach and engagement in the Division of Environmental Health at the Keck School of Medicine of USC. She is an expert in environmental justice, air toxics and community health.
“While we’ve seen overall improvement in air quality in California, not all communities receive the same benefits of clean air. The gains are uneven and we still see low-income communities and communities of color face the highest burden of pollution,” Johnston said.
She added:
Urban emissions sources such as freeways, industrial sites and ports concentrate air toxins in poor communities.
Much of coastal L.A. has seen improved air quality, but inland valleys suffer unhealthy air about one day in three.
Science is more sophisticated and shows health damage at lower pollution levels, including damage to organ systems such as prenatal impacts on a fetus and impaired cognition in older adults.
Professor Frank Gilliland, Tuesday, March 31, 2015. USC Photos/Gus Ruelas
Frank Gilliland is a professor of preventive medicine in the Division of Occupational and Environmental Health at the Keck School of Medicine of USC. He is an expert in children’s respiratory health, asthma and epidemiology. He is also a principal investigator of the ongoing USC Children’s Health Study.
“Kids are very vulnerable to air pollution because damage done when they’re developing can’t be undone. The effects are lifelong and they include loss of lung function, asthma, obesity, diabetes and neurological disorders,” Gilliland said.
He added:
A generation ago, smog effects were mostly acute and respiratory: shortness of breath, chest pain, cough or watery eyes.
New evidence shows long-term health damage and disease systemic in the body, even at lower levels of pollution.
Children in smoggy places like L.A. suffer about 10% less lung function; about 25% of childhood asthma could be prevented by reducing nitrogen oxides and ozone.
