SJValley air: Good or bad? Depends on who you ask

In its “State of the Air” 2024 report, the American Lung Association reported that 131 million Americans (39 percent) are exposed to harmful-to-health air pollution. At least four million of that total make California’s San Joaquin Valley their home. This demographic is exposed to, among other toxic pollutant emissions, carbon monoxide (CO), oxides of nitrogen (NOx), ozone (O3), particulates (coarse, fine and ultrafine), sulfur dioxide (SO2), VOCs (volatile organic compounds). The report was made public, incidentally, on Apr. 24, 2024.

Meanwhile, the San Joaquin Valley Air Pollution Control District in its more recently released “2023 Annual Report to the Community,” boasts of how, over the past two decades, Valley air quality has much improved. “Despite challenges like wildfires, recent years have seen a notable increase in the days where the Valley’s air meets health standards compared to the days when it exceeds them. In fact, 2023 marked a record-breaking year with the highest number of days meeting health standards, signaling continued positive progress in air quality improvement.” An accompanying graphic indicating “Days Exceeding vs Days Meeting The Health Standards,” shows 47 vs 53 percent in 2002; 25 vs 75 percent in 2012; and 10 vs 90 percent in 2023. (p. 9)

Moreover, the air district wrote: “Notable achievements include meeting key health-based federal air quality standards such as NO2 [nitrogen dioxide], SO2 [sulfur dioxide], CO [carbon monoxide], PM10 [particulate matter less than 10 micrometers in aerodynamic diameter], 1-hour ozone, and the 24-hour PM2.5 standard of 65 μg/m3 [less than 2.5 micrometers in aerodynamic diameter].” (p. 9)

Okay, but it should also be noted that since the latter part of the 20th century, national ambient air quality standards (NAAQS) for ozone and fine particulate matter have been set, revised and revised and then revised again.

In its undated “The National Ambient Air Quality Standards for Particle Pollution: Revised Air Quality Standards for Particle Pollution and Updates to the Air Quality Index (AQI)” document, the Environmental Protection Agency wrote: “On Dec. 14, 2012 the U.S. Environmental Protection Agency (EPA) strengthened the nation’s air quality standards for fine particle pollution to improve public health protection by revising the primary annual PM2.5 standard to 12 micrograms per cubic meter (μg/m3) and retaining the 24-hour fine particle standard of 35 μg/m3.” (p. 1)

Now, while the federal standards have received revisions over the years making them more and more stringent, the Valley air district has also tightened health-based standards up and down the Valley itself on more than one occasion.

As just one example, on Dec. 20, 2012, the air district set its own standard for 24-hour average PM2.5 at 20 μg/m3. Meanwhile, the air district, elsewhere in its “2023 Annual Report to the Community” revealed, “Recently, EPA announced a new 2024 Annual PM2.5 Standard, lowering it from 12.0 μg/m3 to 9.0 μg/m3.”

So what were some of the key average O3 and PM2.5 readings[1] recorded in the Valley in 2023? I start with PM2.5.

For SJV Air Basin Daily Avg. PM2.5 at Highest Site in 2023*, there were 31 exceedances total. As for Multiyear Ozone for SJ Valley Air Basin Ending [in] 2024*, for year 2023, there were 73 exceedance days of the national 8-hour (0.070 parts per million) standard.

Now compare this to comparable data for 2015* when there were 63 exceedances of the SJ Valley Air Basin Daily Avg. PM2.5 at Highest Site, and 97 recorded national 8-hour ozone exceedance days**, respectively.[1]

So, based on this information, what would appear to be the case is a significant improvement in Valley air quality.

Ahead: I’ll take a similar look at the South Coast Air Basin air quality data for the same two years.


1. CalEPA Air Resources Board data

* All data, according to what I understand, is still preliminary.

** An exceedence corresponds to air quality in the Unhealthful for Sensitive Individuals range or worse.

In an earlier version the numbers reported for “Days Exceeding vs Days Meeting The Health Standards” for year 2002 (see above), were reversed. The information is now correct.

Updated: Jun. 7, 2024 at 4:55 a.m. PDT.

Corresponding, connected home-page-featured image: United States Geological Survey

— Alan Kandel

Copyrighted material.

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