Southern California has had a severe smog problem for decades. In the ’60s, ’70s and ’80s, the smog was so bad in Pasadena that often one could not even see the mountains because of the ugly haze.   

Then, in about 1990, things started getting better. Southern California’s heavy ozone days as measured by the Air Quality Index, which assigns colors to numbers ranging from 0 (green) to 300 (purple), dropped from just over 200 in 1993 to at times a little more than 100 during 2015. This was due mainly to increased regulation of vehicle emissions.

Unfortunately, this trend has reversed itself in the last two years, with 2017 so far having had 145 “bad” air days for ozone, according to the South Coast Air Quality Management District.

The term “smog,” an amalgamation of the words smoke and fog, is thought to have been invented in the early 20th century. Smog is a type of air pollution that can cause serious health and environmental problems, plus it has unaesthetic qualities that greatly degrade the quality of life.   

One component of smog is ozone, which can be especially dangerous to human health. A colorless gas, ozone, which has been linked to lung disease and childhood asthma, is composed of three oxygen atoms and is formed when emissions from power plants, factories, cars and trucks are exposed to heat, sunlight and various chemicals in the atmosphere.

Ever wonder about the discomfort or pain you may feel in the chest after breathing on a smoggy day? That’s caused by ozone. We need it in the upper atmosphere to block the sun’s ultraviolet radiation, which can cause mutations and skin cancer, but close to the ground it can be a serious health hazard.

In addition to ozone, the chemistry of smog in Southern California is complex. Other chemical components include nitrogen oxides (NOx), sulphur oxides, hydrocarbons, smoke and particulates, among others. NOx and sulphur oxide compounds, products of the burning of gasoline and diesel fuel in car and truck engines, as well as industrial fumes, are mainly responsible for the brown haze component in smog. Not only unsightly, these chemicals are also not good for your eyes and lungs. Less visible components of smog include carbon monoxide, which is deadly at certain levels, and chlorofluorocarbons.  All together the chemicals that comprise smog are a noxious mixture.

The catastrophic fires that have recently wreaked havoc in Southern California are also a huge contributor to our smog problem. If you live near a fire, be very careful about breathing the air, which can cause sickness and shorten life. The inversion layer, an atmospheric phenomenon common in Southern California that traps pollution from fires and other sources close to the ground, can make the problem even worse.

So why is the number of bad air days rising again in the LA area, the nation’s most air-polluted region? If emissions from cars and other sources are down, as we’ve been told, this is not what would be expected. One idea is that an increase in the number of hot days (for example, the heat waves we had this last summer and fall) is causing an increase in the production of ozone and other pollutants in the atmosphere. More hot days can also exacerbate the inversion layer problem. Perhaps this can be attributed to climate change, but so far the jury is out.

However, air quality officials are also starting to wonder if the data and models showing a steady decline in smog-forming pollution from cars, trucks, oil refineries, ports, and other big polluters are possibly flawed. Again, the jury is still out on this, according to recent stories in the Los Angeles Times.

Ultimately, to solve the smog problem, gasoline and diesel engines, as well as other air pollution sources, need to be replaced with near-zero emission power sources, such as electric, hydrogen fuel engines and other emerging technologies. 


John Grula, PhD, is affiliated with the Southern California of Scientists.