Air quality by the numbers – it’s an alphabet soup

At the California Environmental Protection Agency Air Resources Board’s (ARB) “Key Events in the History of Air Quality in California” page, noteworthy air-quality-related events are chronicled.

Referencing the year 1980, the corresponding passage reads: “CA’s population reached 24 million people. Total registered vehicles surpassed 17 million and vehicle miles traveled [VMT] is 155 billion. Cumulative CA vehicle emissions for NOx [nitrogen oxides] and HC [hydrocarbons] remain at 1970 levels of 1.6 million tons/year despite a rise of 45 billion in VMT over these 10 years.” Or, in other words, “cumulative CA vehicle emissions for NOx and HC” held steady, yet VMT jumped by roughly 41 percent. Interestingly, in 1970 state population was 20 million people and the total number of registered California vehicles was 12 million, according to ARB data.

In search of more detailed data, I turned to the California Almanac of Emissions and Air Quality — 2009 Edition —. From Table 3-2 “Statewide Population and VMT Trends,” Golden State population in 1980 is shown to be 23,782,000 people while average daily VMT is 403,567,000.

Meanwhile, from Figure 3.1: “Percent Change in Air Quality and Growth” (from the same Almanac), there are several interesting items.

Between 1988 and 2007, particulate matter of a diameter of 10 microns (PM 10) saw an approximate 23 percent decrease, carbon monoxide (CO) levels fell roughly 73 percent and ozone (O3) declined about 47 percent, this despite a growth in state population of approximately 33 percent with an average daily VMT percentage increase of around 46 percent.

I am especially interested in the drop in ozone. The reason being, living in the San Joaquin Valley and regarding the air basin itself, 2010 was a target year: it was either meet the federal one-hour ozone health standard or pay an annual $29 million penalty for not meeting that standard. The federal one-hour ambient air quality standard for ozone of 120 parts per billion and established in 19791 was, according to several sources, abolished in 2005. Regardless, if the standard in 2010 wasn’t met, what that meant was the $29 million fine was to become effective the following year.2 Long story short, the federal standard in the San Joaquin Valley went unmet that year. So, sure enough, in 2011 Valley motorists – their portion: about $25 million – and business owners – responsible for the remainder – were socked with the fee. So you know, for the penalty to be waived, it is my understanding that three consecutive years with three or less exceedances of the ozone standard need to be realized.

At any rate, provided there are no more than three exceedances this year (the Valley so far this year is on track to not have a single exceedance), and with just three exceedances in 2011 and two in 2012, 2014 may be the year the charge is dropped.3

Just when I thought things were looking up, I’m reminded of the 8-hour ozone standards: the National standard of 75 parts per billion of ozone and the State standard of 70 parts per billion of ozone – there were 83 exceedances of the National 8-hour standard and 103 exceedances of the State 8-hour standard, so far this year.


  1. “Table of Historical Ozone National Ambient Air Quality Standards (NAAQS),” U.S. Environmental Protection Agency,
  2. Accessed via written correspondence with San Joaquin Valley Air Pollution Control District representative.
  3. “Item #7: Update on Ozone Air Quality Progress and Air Alert Initiative,” Healthy Air Living document, San Joaquin Valley Air Pollution Control District, Aug. 15, 2013, p. 11,

– Alan Kandel