Valley Air Quality: Is It Really Getting Better?

The local Building Industry Association (BIA) has issued a news release (www.biasjv.org) and launched a marketing campaign claiming that the San Joaquin Valley "has seen considerable improvements in air quality over the past decade" and that public perception that air quality has not improved is due to exaggerations by environmental activists.

Certainly we've been hearing from the media that our air quality is poor. Spending any amount of time outdoors in the summer or winter would seem to confirm it. But, has air quality actually improved significantly over the past decade as the BIA asserts? The California Air Resources Board (ARB) maintains a vast amount of air quality monitoring data at its Web site (www.arb.ca.gov). To answer the question, let's look at the monitoring data over the past decade.

Air pollution consists of a complex mix of chemicals and particles. In the San Joaquin Valley we are most concerned with ozone in the summer and particulate matter in the winter. Ozone (O₃) is formed by the chemical reaction of nitrogen oxides (NO_x) and reactive organic gases (ROG, principally hydrocarbons) in the presence of sunlight. Sources of NO_x and ROG include anything that burns fuel (e.g., gasoline, natural gas, wood, and oil), solvents, petroleum processing and storage, and pesticides. Ozone causes breathing difficulties, lung tissue damage, and damage to rubber and some plastics.

Particulate matter is the mixture of small airborne particles that we breathe. Particles smaller than 10 microns (PM₁₀) are harmful to humans. For comparison, a human hair is 50 to 100 microns in diameter. In recent years, particulate matter less than 2.5 microns (PM_2.5) has been recognized as especially harmful. Sources of particulate matter include windblown dust, agriculture and construction, combustion, and residential and agricultural burning. Particulate matter increases respiratory disease and can cause lung damage, cancer, and premature death.

The ARB compiles detailed emissions inventories for most California counties. The following table lists the top ten emissions sources of each type in Tulare County in 2002.

Top 10 Emissions Sources in Tulare County 2002
Ozone Precursors - Summer				Particulates – Winter
Reactive Organic Gases		Nitrogen Oxides		Particulate Matter
Source	Percent	Source	Percent	Source	Percent
Waste burning and disposal	29.3%	Farm equipment	25.0%	Farming operations	26.1%
Farming operations	23.1%	Heavy duty diesel trucks	18.5%	Unpaved road dust	19.7%
Light duty passenger	6.8%	Light duty trucks	9.5%	Paved road dust	18.8%
Light duty trucks	6.7%	Off-road equipment	7.6%	Waste burning and disposal	9.3%
Pesticides/fertilizers	4.4%	Light duty passenger	7.3%	Fugitive windblown dust	5.2%
Consumer products	4.3%	Food and agricultural processing	6.6%	Wildfires	4.5%
Farm equipment	2.7%	Trains	4.3%	Food and agriculture	3.7%
Architectural coatings	2.4%	Medium heavy duty diesel trucks	4.0%	Residential fuel combustion	3.4%
Recreational boats	1.9%	Other (fuel combustion)	2.5%	Construction and demolition	2.8%
Off-road equipment	1.8%	Medium duty trucks	1.9%	Chemical	2.3%

The following two graphs are constructed based on 10 years of ARB monitoring data (1993 to 2002). Two sets of data are shown: the average for the entire San Joaquin Valley and measurements from the Visalia monitoring station. The graphs show the number of days per year the regulatory standard was exceeded. For ozone, the eight-hour average standard was used rather than the older one-hour standard. Experts agree that the eight-hour standard is more representative of ozone health impacts.

Based on the state monitoring data, it appears that the average Valley ozone and PM₁₀ concentrations have actually increased slightly over the last ten years. It would be difficult to agree with the BIA that there have been “considerable improvements in air quality over the past decade.” As The Fresno Bee succinctly put it, “the BIA asks us to cheer because we’re no longer drowning in 13 feet of water. We’re concerned because the water’s only down to 10 feet and we’re still drowning” (November 13, 2003).

Kimball R. Loeb

Air Quality Chair

Mineral King Group