Fresno Bee Newsroom Blog

Just when you thought it was safe to inhale

The October whiplash is in full swing. The San Joaquin Valley’s dirty air suddenly made a comeback in the last 10 days, then just as quickly vanished in a storm Monday.

Just a few weeks ago, I had written that the Valley has a good shot at the lowest-ever recorded number of federal eight-hour ozone exceedances. With a rash of exceedances — eight since Oct. 19 — it’s going to be close.

The total now is 91. The record is 93.

South Coast Air Basin in Southern California has 94 exceedances right now. The region has had only one ozone November exceedance in the last five years.

It’s possible the Valley could wind up with more than South Coast this year. That would mean the Valley would have the most in the nation.

There’s another issue in the Valley. A reader points out high hourly readings for tiny particle pollution, wondering why the residential wood-burning ban doesn’t start in October. Right now, the rule kicks in Nov. 1 each year.

As I understand it, the tiny particle threshold — known as the standard for PM-2.5 — is an average over 24 hours. So hourly readings, by themselves, are not considered exceedances.

But the reader pointed out some pretty high hourly readings, saying October is known for these problems. It might be worth taking a longer look at this point.

Remember, wood-burning restrictions begin Friday. Check with the San Joaquin Valley Air Pollution Control District’s web site to see if wood-burning is allowed in your county before you light up.


Étieme says:

In addition to high hourly soot readings, Fresno and Visalia did have daily averages in excess of 30 µg/m³ on October 23rd according to preliminary data. It is true neither site exceeded the federal daily standard of 35 µg/m³.

But unless I am mistaken, the trigger of a predicted average daily reading at or in excess of 20 micrograms of soot per cubic meter of air—the threshold adopted for rule 4901 effective fall 2014, the rule that governs when residential wood-burning is disallowed—was established by the Air District not to meet the federal daily standard of 35µg/m³, rather the yearly standard of 12.5µg/m³, so whether the daily standard will or will not have been violated on some particular day in this October of 2013, as it has on individual days every previous October for the past eleven years, seems rather beside the point. Low temperatures in the high 40s to low 50s, typical for this time of year, are sufficient to induce some people to light fires to heat their homes. It does adversely effect air quality and it does hinder attainment of that yearly average—15 µg/m³ under the old standard, 12.5 µg/m³ under the more health protective standard recently adopted—that is our putative goal.

And I can’t resist noting, once again, something that defies common sense: if we are trying to get to a yearly average of no more than 12.5 micrograms of soot per cubic meter of air, why allow wood-burning on days quite competently predicted to exceed that? If 12.5µg/m³ is our goal, shouldn’t a prediction of 12.5µg/m³ be the trigger? A 30µg/m³ trigger didn’t get us to a yearly average of 15µg/m³; will 20µg/m³ gets us to 12.5µg/m³?

And why are we waiting till 2014 to pursue the 12.5µg/m³ standard using rule 4901?

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