On Sunday, nature demonstrated why heat isn’t the only factor. It was 102 degrees but just cloudy enough to slow down the chemical reaction that makes ozone.
There was no breach of either federal ozone standard on Sunday — in the middle of August with very light winds and 100-plus degrees.
Ozone needs oxides of nitrogen from combustion sources, such as your car’s engine, and reactive organic gases, such as fumes from gasoline or dairies. But without both warmth and sunlight, the gas doesn’t form as well.
Take a look at the numbers for Sunday. Fresno’s three monitors never got above 70 parts per billion for ozone. The federal eight-hour standard is 75 parts per billion, and it’s officially an exceedance when the average hits 76.
Monday looks like a similar cloudy start to the day. I saw lightning over the Sierra. If the weather stays dark and unsettled, there may be another August day in the Valley without an exceedance of the ozone standard.
Between 2003 and 2006, the San Joaquin Valley was nearly wall-to-wall with bad-air days each August. Only six August days in those years didn’t breach the ozone standard.
This August, there already have been six good days, and the month isn’t even two weeks old. For me, it’s even a little eerie to see days like Thursday when the highest ozone reading was about what I’d expect on a warm, sunny April day.
The temperature has dropped into the 90s and that helps, because ozone forms better on hot, sunny days. But there were plenty of August days in the 90s back in 2003 or 2004 when ozone exceeded the standard.
Meteorologists have told me the air overhead is moving and mixing a lot this month. Ozone forms best on hot, sunny days that are stagnant, so maybe the air movement is helping.
Last August, there were only five days without exceedances. In 2011, there were only two. To me, the break this year just seems odd.
But don’t be lulled. August and early September can turn brutally hot and stagnant. And with school back in session and more vehicles on the road producing ozone-making gases, the air can turn corrosive quickly.
Not all pollution particles are created equally bad for you. The ones from cars, trucks, fireplaces and cooking are probably getting the worst reactions from your body.
Two University of California scientists came to the conclusion after collecting air samples from Fresno in summer 2008 and winter 2009, identifying the particles in the samples and allowing laboratory mice to inhale them.
Murky air in downtown Fresno
The approach is the first of its kind, according to the UC Davis scientists, Anthony Wexler and Kent Pinkerton. Wexler is the director of the Air quality Research Center at Davis. Pinkerton is professor of pediatrics at the School of Medicine.
Their work on this study will help regulators in the future as they tighten standards to protect human health.
“Right now, air-quality standards are based on the mass of the particulate matter and don’t distinguish between natural sources, like sea spray, and known toxic sources, like diesel exhaust,” said Wexler, who led the study.
The bottom line: New standards some day might be aimed at certain types of particles, instead of all particles. It would save money for industries in the cleanup.
The local air board is planning to soften new restrictions that could stop wood-burning in fireplaces most of the winter in Fresno and Bakersfield.
Wood-burning will be allowed on some no-burn days, leaders said Thursday. But an EPA-certified wood-burning device, such as a stove or heater, would have to be used.
The district will hold public hearings to determine the threshold.
Starting in 2014, the new burn bans will be triggered when soot and other debris reaches 20 micrograms per cubic meter of air. Right now, the threshold is 30.
The exemption level for people using EPA-certified devices will probably be 30 to 35, I’m told.
On an even more technical note, the new restrictions are part of the district’s plan that will be sent to state and federal authorities. But the pollution reductions won’t be claimed until the winter of 2016-2017 in the plan — a matter of bookkeeping on the way to the 2019 attainment date.
The district board moved the restrictions up two years to get the health benefits early.