Cleaning up the San Joaquin Valley’s ‘low down and dirty’ air

California's agriculturally rich but often air-pollution shrouded San Joaquin Valley
California’s agriculturally rich but often air-pollution shrouded San Joaquin Valley

It is obvious I have done quite a lot of writing on air quality matters in the San Joaquin Valley. The Valley is where I live and, sadly, it is among this nation’s most notorious or worst offender areas for polluted air. Both childhood and adult asthma numbers here seem disproportionately high compared to other regions. These distinctions, if they can even be called distinctions, leads me to believe area air quality health standards are each year violated more often than not.

As such and as a resident, it would seem only natural I’d be interested in knowing how the Valley has been faring air-quality improvement-wise. Others may likewise want to know. So, where better to turn to than “The California Almanac of Emissions and Air Quality – 2009 Edition” (Almanac) and, in particular, “Chapter 4: Air Basin Trends and Forecasts – Criteria Pollutants, Section 4: San Joaquin Valley Air Basin.” It should also be noted here that other state metro regions are profiled as well.

Valley air basin background

According to the Almanac, the San Joaquin Valley Air Basin of the Central Valley consists of San Joaquin, Stanislaus, Merced, Madera, Fresno, Kings, Tulare and the Valley or western portion of Kern counties covering nearly 23,500 square miles. Most of the region falls below the 1,000-foot elevation level with most of the area’s population residing below that at 500 feet in elevation and lower.

“In contrast to other California areas, air quality in the San Joaquin Valley is not dominated by emissions from one large urban area. Instead, there are a number of moderately sized urban areas spread along the main axis of the Valley. This wide distribution of emissions complicates the challenge faced by air quality control agencies. Overall, about 10 percent of California’s population lives in the San Joaquin Valley, and pollution sources in the region account for about 13 percent of the total statewide criteria pollutant emissions,” the California Environmental Protection Agency Air Resources Board (ARB) in the Almanac notes. Approximately 4 million people currently make the Valley their home.

Due to geography and meteorology, the Valley traps air pollution – ozone or smog in summer and particulates in winter. What makes the Valley the air pollution incubator it is, are its geography and meteorology combined with all the residential, industrial, business and transportation activity part and parcel of the region’s makeup.

Pollution profile

So, where in the Valley is the pollution coming from?

Here’s the breakdown: motor vehicles (57%); off-road vehicles, lawn and garden equipment and consumer products (20%); industrial sources (11%); outdoor burning (9%); and fireplaces and wood stoves (3%), according to the San Joaquin Valley Air Pollution Control District (Air District).

The main pollutants of concern, meanwhile, are: nitrogen oxides (NOx); nitrogen dioxides (NO2); reactive organic gases (ROG); course particulates (PM 10); fine particulates (PM 2.5); sulfur oxides (SOx); and carbon monoxides (CO).

The Almanac reveals, since 1990, with the exception of PM 10 which, for all intents and purposes is unchanged, Valley emissions levels have fallen. This is despite a consistent rise in population and a considerable increase in vehicle miles traveled (VMT).

Valleywide, population in 1990 was 2.645 million. Compare that to the region’s current 4 million. Average daily VMT, meanwhile, has grown from 58.326 million in 1990 to right around 103 million today. Whereas Valley population during that time grew by roughly 51 percent, there was a 77 percent jump in VMT, indicating VMT has been outpacing growth in population.

The Air District in no uncertain terms states: “The Valley is particularly vulnerable to air pollution formation because of its topography, climate, and growing population. Surrounding mountains trap airborne pollutants near the Valley floor where people live and breathe. In addition, the Valley’s hot, summer temperatures promote the formation of harmful ground-level ozone (also known as smog). Finally, as population levels increase, so does air pollution. More people equals more cars and more activities that contribute to poor air quality.”

As if this weren’t enough, oftentimes air pollution from elsewhere makes its way here.

“Contrary to popular belief, the majority of our air pollution is created right here at home. Data indicates that approximately 27 percent of the total air pollution in the northern portion of the District comes from the Bay Area. In the central portion of the District, the percentage drops to eleven and in the southern area, transport air pollution constitutes nine percent of the total air pollution inventory,” the Air District emphasizes.

Regardless of the percentages, the pollution arriving from elsewhere isn’t helping matters.


Bet your bottom dollar population growth will continue and what this means is that more pressure will be put on air, land, water and other resources in addition to infrastructure. That’s a given.

What I cannot say decisively, although it is my suspicion, if land use and mobility patterns are not adjusted and thus do not become much more efficient, and residents and others don’t start embracing in far greater numbers the technology that is available that will make life and living much more sustainable, then my thinking is this: expecting continued Valley air quality improvement is unrealistic, what with the expected increase in population. Not only this, but I’ll go so far as to say that not only will air quality improvement come to a screeching halt, but more than likely there will be a backsliding taking place meaning conditions will get worse before getting better.

In bringing San Joaquin Valley air to a state of healthy repair, it is imperative then that the Sustainable Communities and Climate Protection Act of 2008 (California Senate Bill 375), the Global Warming Solutions Act of 2006 (California Assembly Bill 32) and the 2008 passage of the Safe, Reliable High-Speed Passenger Train Bond Act for the 21st Century (California Proposition 1A) be carried out in an efficient, intelligent, productive and prudent manner to not only guarantee success but indeed get results. The Valley – and the state too for that matter – must get this right!

– Alan Kandel