Earth Log

Earth Log: Dirty air started up again, so here's my ozone riff

Dirty air made a comeback on the day that I wrote about the record-setting clean streak in August -- if I only had such influence over rainfall.

But it did spark interest in ozone. Several readers wanted to talk about this notorious warm-season pollutant that can scar your lungs and trigger asthma attacks.

One reader made an intriguing connection on Twitter about vast fallowing of farm acreage. Maybe reduced ag production because of drought created clean days?

Maybe, but I think there are bigger influences, namely weather. The South Coast Air Basin in Southern California had the same kind of clean streak in August -- and that didn't happen because of fallowed farmland.  

I think the air in California was stirred up by the monsoonal flow of air and continued breezes and mixing of the air. I heard the same sentiment in a discussion with several meteorologists this week.

Air quality authorities add that stricter rules and investments in clean-air technologies play a leading role in cleaner summers. 

On a phone call with another reader, I somehow got into an extended riff about ozone.

Ozone does not come out of the tailpipe of your car.

It forms in the air, using two key gases -- oxides of nitrogen from cars, trucks and other sources and volatile organic compounds found in fumes from such sources as gasoline, dairies and paints.

Ozone forms best when there's heat, sunshine and almost no wind. In other words, the Valley is the perfect incubator. That's why it is one of the worst basins in the country for ozone.

What should you do to protect yourself? Go inside.

Scientists have explained to me that ozone breaks apart when it strikes something -- a tree, a building, a window. You can find reasonable protection from ozone if you go indoors during siege.

The Valley's worst ozone readings take place in the afternoon, so do your outside exercising in the morning.

When the sun goes down, the oxides of nitrogen from traffic break down ozone. So in a city such as Fresno or Los Angeles where traffic continues after dark, the ozone levels actually drop even though pollution continues.

But when morning breaks, the whole cycle starts over again. And maybe the ozone gets worse if the weather pattern is stagnant.

Ozone tends to taper off around the country in September, but not here. September can quickly turn into an ozone inferno here. Even October can have its bad moments here.

At the same time, this season could set a record in the Valley for fewest exceedances of the federal eight-hour ozone standard. The Valley has seven fewer at this point in the season than it did in 2013, which finished with a record low of 89 exceedances.

One more thing I always add: The goal is zero exceedances. So we still have a long way to go.