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.