Exploring the gospel principles of earth stewardship

Air Pollution Case Study: Los Angeles

Hazy skies in Los Angeles

Hazy skies in Los Angeles

If I asked you to make a list of notable features of Los Angeles, chances are “smog” would show up somewhere beneath Hollywood and Disneyland.  A less glamorous aspect of life in the Southland, to be sure, but one the region is known for, and with good reason.  While air quality has improved in the region since regulatory efforts really got underway in the 1970’s, no matter which way you look at it, it’s still not a pretty picture.


“Smog” is a pretty imprecise term.  A contraction of “smoke” and “fog”, it was first coined to describe air pollution episodes in colder places, where smoke and other pollutants got trapped under foggy inversion layers.  In contrast, LA’s worst air quality tended to occur during hot days with clear skies.  A professor at CalTech was the first to identify ozone, an odorless, colorless gas, as the primary pollutant in LA “smog.”  Ozone, unlike some other pollutants, is not emitted directly.  Rather, it’s formed as hydrocarbons (also known as reactive organic gases, or ROG) and oxides of nitrogen (NOx) react in the presence of sunlight.  Ozone levels tend to rise on hot days with little air movement.  Southern California’s famous sunshine and valley geography unfortunately make it the perfect place to make ozone.

And make ozone is does!  Regulators use an 8-hour average measurement to give an idea of ozone levels throughout the day.  In 1973, the first year for which reliable, air-basin-wide data exist, the maximum 8-hour average was a whopping 315 parts per billion (ppb).  In 2012, it dropped to 112ppb.  A substantial improvement, certainly, but still quite a bit higher than the level of the federal health standard, currently set at 75ppb.  Unfortunately, high ozone isn’t just a once-or-twice-a-year phenomenon.  In 1973, the greater Los Angeles metro area saw 174 days with ozone over the level of the current federal health standard.  In 2012, there were 112 days over the standard.  Little wonder, then, that the region is one of only two areas in the country designated “Extreme” for ozone air pollution by U.S. EPA (the other is the San Joaquin Valley, just north of Los Angeles, in central California).

Although ozone is Southern California’s biggest air quality challenge, it’s worth noting that the region also does not attain the federal fine particle (PM2.5) standard, and has a serious problem with directly-emitted air toxics.


As you can imagine, there’s been considerable effort put into figuring out just where all of the NOx and ROG that drive ozone production are coming from.  It’s tempting to think that “industry” is the source of all our problems, and to point fingers at the belching smokestacks of factories and refineries.  Certainly those sources are significant, but they’re not the primary problem in Los Angeles—not by a long shot.  Every few years the state and local air pollution control agencies make a thorough assessment, called an emissions inventory.  The most recent inventory was completed in 2008, and points to cars, trucks, trains, construction equipment—the “mobile sources”—as the major sources of NOx and ROG.  Fully half of ROG emissions and nearly 90% of NOx emissions come from this sector.  What that means is that the problem is us—every person who drives a car or takes a bus is adding to the problem.  To paraphrase (badly, my apologies) the cartoonist Walt Kelly, “We have met the source of our pollution, and the source is us.”

Why You Should Care

But perhaps you’re thinking that, since you don’t routinely haunt LA’s congested freeways, you’re off the hook.  Not so fast.  By far the biggest subcategory of pollution from the mobile sector is heavy-duty trucks, the kind that haul goods arriving from overseas at the Ports of LA and Long Beach to rail yards around the Los Angeles area, or to distribution centers in the desert areas east of Los Angeles, and then off to the rest of the U.S.  If you live anywhere in the western or midwestern U.S., chances are that most of the items for sale at your local big box retailer arrived in a container ship at one of the Southern California ports, were trucked to a distribution center or to a rail yard in the area, and then traveled via truck or train (or both) to your neighborhood.  Certainly the impacts of our consumer habits are felt more acutely in the Asian cities where factories produce the goods we consume, but getting those products onto the shelves and into the hands of consumers comes at the cost of significant pollution in the Los Angeles area.

The communities near the distribution centers and rail yards—places like Mira Loma, the City of Industry, Colton, and Commerce, among others—are especially hard hit.  Not surprisingly, these are some of the Southland’s less affluent communities.  I’ve argued before that doing our part to make sure everyone has access to clean air is an important part of discharging our duty to care for the less fortunate.  Cutting down on consumption is one way we can help effect this change.  Supporting the work of community activists working on issues related to rail yard pollution and encouraging government action to mitigate health risks for these communities are others.

Suggestions for Further Reading

If you’d like to read more about the history of the air pollution problem in Los Angeles, I highly recommend Smogtown.  It’s an engaging and informative read by a journalist and a former government spokesperson who clearly did their homework.  I learned a lot.

Next Up

Next month I’ll be presenting another air pollution case study–particle pollution along Utah’s Wasatch Front.  Stay tuned!