CAPCOA (the California Air Pollution Control Officers’ Association) explains Air Quality Index in “Appendix A – Understanding the Air Quality Index,” in its California’s Progress Toward Clean Air – 2014 report.
Firstly, as CAPCOA notes, “The Air Quality Index (AQI) is a tool for reporting daily air quality levels.” A variety of colors (typically green, yellow, orange, red, purple and maroon – going from good to moderate to unhealthful for sensitive individuals or groups to unhealthful for everyone to hazardous), are employed to denote air quality condition. The AQI is an index that also makes use of a numerical scale that incorporates numbers ranging from 0 to 500. “The AQI focuses on health effects that may be experienced within a few hours or days after breathing polluted air.”
Further, “[f]or particulate matter, an AQI value of 101 or higher corresponds to the 24-hour PM2.5 NAAQS [National Ambient Air Quality Standards] of 35 micrograms per cubic meter [of air] (or higher). For ground-level ozone, an AQI value of 101 or higher corresponds to the 8-hour ozone NAAQS of 75 parts per billion [parts of air],” CAPCOA emphasized.1
The way I view the above indicates to me that at an AQI level of at least 101, whether this be for PM 2.5 (fine particulate matter) or ozone (O3), unhealthy air quality (or air pollution) levels (depending upon one’s point of view), have been reached. Put differently, at that level or threshold, the health standard has been exceeded.
Next, CAPCOA in the same report also brought to light “[t]he winter of 2013 was the driest year on record in California and with it came prolonged periods of air stagnation. …Three northern California Air Districts experienced an uncharacteristically large number of days in which fine particulate matter (PM 2.5) concentrations exceeded the national standards.”2
The San Joaquin Valley among a referenced three Air Districts that also include the (San Francisco) Bay Area and Sacramento, had by far, the most exceedance days – 38, as compared to the Bay Area’s 12 and Sacramento’s 15.3
And, related to this, CAPCOA added, “In December 2012, the U.S. EPA [Environmental Protection Agency] made the annual PM2.5 standard more stringent, reducing the standard from 15 to 12 micrograms per cubic meter. The only air basins in the state that do not meet this new annual standard are the South Coast AQMD [Air Quality Management District], San Joaquin Valley APCD [Air Pollution Control District], and Imperial County APCD.”4
Thirdly, with winter and PM 2.5 from wood-burning activity in mind, one air district (San Joaquin Valley) is contemplating adopting a more strict daily PM 2.5 standard.
As it relates, not even a month ago, in “Tighter restrictions on wood-burning in Valley could make for cleaner winter air,” I remarked: “In the Valley during wintertime, and being that as much as 30 percent of fine particulate pollution can be tied to residential wood-burning activity, still, as of this writing the decision to tighten wood-burning restrictions to the more healthful 20-micrograms-per-cubic-meter standard is still very much up in the air. The 30-micrograms-per-cubic-meter-of-air standard (a Valley air district standard), is applied on a 24-hour basis.”
Well, tomorrow, the San Joaquin Valley Air Pollution Control District is scheduled to take up the issue at its Sept. 18th Governing Board Meeting. This is reflected in Item No. 7 on the Governing Board Meeting Agenda. Discussion gets underway at 9 a.m.
Will a more healthful daily PM 2.5 standard be adopted?
I plan to report back with an update soon.
- California’s Progress Toward Clean Air – 2014, “Appendix A – Understanding the Air Quality Index,” California Air Pollution Control Officers’ Association (CAPCOA), p. 34
- Ibid, “The Climate Change Challenge,” p. 3
- Ibid, “Tougher Air Quality Standards,” p. 6