Fresno Bee Newsroom Blog

One-hour, eight-hour standard, it’s confusing

I apologize if there’s been some confusion about an air-quality blog I wrote a few weeks ago — remember the one about the “silver lining” during an ozone siege?

A few readers have asked how there could be a silver lining if there are more eight-hour breaches of the standard than last year. The silver lining — or good news — was that the air didn’t breach the one-hour standard.

Eight-hour is a much tougher standard, the average of eight one-hour readings. The one-hour standard refers to the peak reading during a one-hour period.  They are quite different.

Now, let’s talk about comparing the eight-hour exceedence totals with last year’s totals. It’s a dangerous thing to do early in the season.

At the time of that blog item, there were 23 exceedences this year compared to 17 last year. So isn’t the air actually getting worse? Why didn’t I point that out in the item? Well, check it now, and you’ll see why it’s dangerous to jump to any conclusion right now.

There are 25 exceedences through this week, compared to 26 at this point last year. I was simply giving a running total in my blog item a few weeks ago.

One last thing. Improvement is a gradual thing in air quality, and the San Joaquin Valley is far from clean or healthy.

In summertime, the goal is eliminating ozone exceedences. Last year, the Valley had 105. Alongside South Coast Air Basin in the Southern California area, that’s the worst in the country.

But compare the numbers this year to 2003.

There were 38 exceedences at this point in 2003, and there had been a one-hour exceedence. During that period in 2003, I counted 17 days when the ozone concentration was above 100 parts per billion — an exceedence happens at 76.

This year, there have been 25 exceedences and only three days when ozone exceeded 100 parts per billion. Clearly, the air quality is improving, but not very quickly for many people.

Air-quality activists say the improvement comes partly because of the relocation of the Arvin air monitor in Kern County. That air monitor showed the most exceedences in the nation. The new one — two miles away — doesn’t record as many bad days.

There are many other arguments about the improvement. I’ll leave that for the readers to comment.

I want to leave you with the clear message: A few weeks ago during record-breaking heat, the Valley didn’t exceed the one-hour standard, which is connected with a $29 million annual fine paid mostly by motorists here.

But the air still is a long way from the goal.

Update: Silver lining in that cloud of smog

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.