Update Tuesday, June 11:
The highest ozone peak in June so far has been in Sequoia National Park as dirty air has appeared over most of the San Joaquin Valley in hot, stagnant conditions. It happened Saturday afternoon.
The eight-hour federal ozone standard was exceeded for the first nine days of June, but there are two good pieces of news.
One, the ozone siege has backed off as the weather has cooled down.
And, two, the air didn’t exceed the one-hour federal ozone standard, which is connected to a $29 million annual dirty-air fine. The San Joaquin Valley Air Pollution Control District says there has been dramatic improvement over the last several years for that standard.
The Valley can end the $29 million penalty in the next season or so if the one-hour peaks remain below the federal threshold.
This summer, the district will continue education and alerts to encourage air-friendly behavior — such as refraining from idling when dropping off or picking up students.
This Valley tends to overload with ozone in hot, stagnant conditions. Chemicals from such sources as traffic and gasoline fumes cook into ozone. In those conditions, this region was an ozone oven for the first week of June.
How many days has the Valley exceeded the stricter, eight-hour federal standard and how does it compare to 2012? The California Air Resources Board web site shows 23 days this year, 17 at this point last year.
Parlier has highest ozone reading
Parlier, a city of about 12,000 in Fresno County, had the highest ozone peak over the last week or so, but dirty air has appeared over most of the San Joaquin Valley.
In hot, stagnant conditions, chemicals from such sources as traffic and gasoline fumes cook into ozone. The Valley was an ozone oven for the first week of June.
The Parlier peak was interesting because it happened between 10 a.m. and 11 a.m. on a Sunday. When a small town gets the Valley’s highest peak, I think about a huge plume of dirty air floating in from Fresno after rush-hour commute.
Was there a morning plume of pollutants from folks driving to church in Fresno and Clovis on that Sunday? Was there some kind of malfunction in the Parlier monitor?
I don’t know, but you can see the hourly readings climbed very early in the day. At 7 a.m., Parlier was already exceeding the federal eight-hour ozone threshold.
Elsewhere in the Valley, most monitors detected a bad-air buildup, but there were exceptions. Tracy, Modesto and Stockton didn’t exceed the threshold. Neither did Visalia.
How many days has the Valley exceeded the standard and how does it compare to 2012? The California Air Resources Board web site shows 20 days this year, 17 at this point last year.