Air Apparent: L.A.'s Bright Skies Are Not As Clear As They Seem

A view of downtown Los Angeles during an extreme smog event in 1995. | Metro Library and Archive/Flickr/Creative Commons License

The act of breathing is pretty straightforward, and, when everything is functioning properly, is an unconscious musculatory response.

Yet the chemical composition of the air we are breathing is not so clear-cut, which means we need to be intensely aware of what we are inhaling (and at what time of day we are drawing this essential oxygen into our lungs).

Angelenos have been sensitive to this dilemma for some time. In the 1920s, when more than 430,000 cars were registered in L.A. (one for every three people; today the ratio is closer to one-to-one), the region's residents began to recognize that their Ford Model Ts, Pierce-Arrow Runabouts, and Cadillac Coupes were befouling the air.

No one could have any doubt about this toxic consequence by the 1940s: a thick dark layer of smog blanketed the basin. Yes, there were deniers, which Detroit auto manufacturers paid well to cloud the issue, but in retrospect we know they were dead wrong. The sky didn't lie.

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Yet its relative clarity today -- we can actually see the surrounding mountains and hills that but thirty years ago were muffled in a brown smear -- is also misleading. That's the troubling news embedded in the American Lung Association's annual "State of the Air" report.

Change of High Ozone Days since 1996. | Source: State of the Air 2013.

First the upbeat evidence: the state in general and the Southland in particular have experienced fewer ozone alerts than occurred in 2000; in L.A. that amounted to nearly 24 more healthful days. The overall levels of pollution moreover are also lower than they were at the beginning of this century.

However feel-good this data may be, air quality in Los Angeles still does not get a passing grade, receiving an F for levels of ozone, 24-hour, and annual rates of particle pollution. "If you live in Los Angeles County," the ALA announces in the guarded language of science, "the air you breathe may put your health at risk."

The organization says the same thing about virtually every urban county in California, each of which, from San Diego and Riverside to Santa Barbara, Santa Clara, and Alameda, earns a solid F. Flunking, too are the Big Ag counties of the San Joaquin and Central valleys and their peers to the south, such as Imperial -- and any place downwind of their exhaust-spewing, dust-spiraling, and fertilizer-laced operations. Only San Francisco gets a gold star on its report card.

Subtracting those in the City by the Bay and other salubrious climes, some coastal, others mountainous, leaves an estimated 90% of Californians breathing a lot of bad air. Its poor quality is compromising our lungs and impairing our collective health.

Some suffer more than others. Those living around oil refineries in El Segundo and Richmond, for example, bear a greater burden than do those residing upwind or at some remove from these plants' airborne toxins. Inhabitants of mountainous Placer and Nevada counties have the bad luck to inhale wind-driven pollution from lowland farms. Residents of the sprawling Inland Empire suffer from local auto emissions but even more from those that the stiff westerlies drive east every afternoon to pile up against the San Gabriel and San Bernardino mountains; what happens on the Westside doesn't stay there.

These environmental injustices are compounded in Los Angeles, especially when set within the regional freeway grid.

Aerial view of smog over Los Angeles, 1949. | Photo: Courtesy USC Libraries Special Collections/Los Angeles Examiner Collection, 1920-1961

Start with the fact that these high-speed roadways, and their multi-stacked interchanges, were blasted through or pounded into some of the city's most underprivileged, economically distressed, and politically disenfranchised neighborhoods and barrios. These communities' public health was sacrificed so that a generally more-well-heeled population could zoom overhead.

This harmful history comes with a cautionary health warning. Until very recently the maxim was that if you lived within one thousand feet of any of the highways that slice through Watts, Compton, or the Eastside (or cross-cross the valleys) your odds of breathing poor air is higher than those who lived farther away from, say, the 5, 10, 60 or the 101.

Now we learn that the pollution plume streaming out of auto tailpipes and 18-wheeler exhaust stacks is more dangerous to more people because it is far more mobile and penetrating than previously thought. Researchers at UCLA and the California Air Resources Board made this discovery when recently they tracked the flow of emissions that billows up from L.A.'s highways.

Using a zero-emission vehicle mounted with an array of sensitive instruments to measure ultrafine particles and calculate the presence of those bad boys of air pollution -- carbon monoxide and nitric oxide -- they drove along surface streets that run perpendicular to a series of heavily trafficked freeways. Rather than do so during peak rush hours, morning and afternoon, they selected 4:30 to 6:30 a.m. as their timeframe.

The results, published in December 2012 issue of Atmospheric Environment, are distressing. The early morning hours prove critical to the spread of a plume that can extend a mile or more from the source, upwards of five times farther than was believed to be the case.

More unsettling, this pollution has the capacity to infiltrate homes at that distance as well. Notes a UCLA press release about this path-breaking research: "Although closed windows help block the particles from seeping inside, previous studies have shown that indoor pollution levels still reach 50 to 70 percent of outdoor levels." Within the newly broadened impact zone, we cannot avoid inhaling these toxins even as we slumber.

"This is happening around every freeway," says project head Suzanne Paulson of UCLA's Department of Atmospheric and Oceanic Sciences and the Institute of the Environment and Sustainability, "and a similar situation likely happens around the world in the early morning hours. The particles tend to end up indoors, so a lot of people are being exposed inside their homes and schools."

Should those pre-dawn hours be your preferred time to exercise in the Great Outdoors, you might want to reconsider. In Southern California the typical overnight cooling leads to what is called a nocturnal surface inversion; it traps freeway-generated pollution close to the ground and then breezes move the concentrated soup downwind. This "nocturnal boundary layer" does not decay until after the sun rises, the atmosphere heats, and the winds kick up, mixing this unhealthy low-lying plume with cleaner air above.

If your aerobic regime and route takes you into the noxious zone, whose durability is more pronounced in the dark mornings of winter than in sun-kissed summer morns, you are increasing your risks of an array of health-related problems. For adults that could include asthma, heart disease, strokes and for children it might mean pre-term births, low-birth weights, and diabetes.

Given that an estimated twenty-five percent of the Southland's population lives within this danger zone, millions are directly affected.

I'm among them. Our home in Claremont lies right within the area of greatest impact, a mile south of the car-clogged 210 Freeway. Worse, the self-described City of Trees was one of the researchers' testing sites and their analysis of its geographical siting suggests it is particularly vulnerable to drifting pollution. The early morning air flow at the overpass of Mountain Avenue and the 210 is "the least variable [in the study] due to the adjacent [San Gabriel] mountains to the north which produce a strong, thermally-induced, mountain-valley wind system."

Ruh-roh.

What I have loved most about my early-morning, quick-paced treks is pushing up that very same sloping avenue into the face of the cool northerly breeze, with the dark foothills and rim-lit mountains guiding me up the now-concretized alluvial fan. My daily routine, which has seemed so heart strengthening, energy boosting, and resilience building may have been undercutting those beneficial outcomes.

It almost makes me want to stop breathing.

About the Author

Char Miller is the Director and W.M. Keck Professor of Environmental Analysis at Pomona College, and author of numerous books, including "Public Lands, Public Debates: A Century of Controversy"
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