Ozone Watch Days Are Down, Despite Intense Sun and Heat

With near record heat, clear skies, and stagnant winds, conditions have been ideal for the production of ozone. But we're not seeing as many ozone watch days this year, as we have in the recent past.

Ozone is the key ingredient of smog. It's produced when certain tailpipe and industrial emissions react with sunlight.  The more sun, the quicker the reaction.  And with little to no wind, there's nothing to blow it away.  But despite the hot, sunny, and dry summer we've had so far, there have been fewer ozone watch days.  Only 14 in the past five months.  That down from 19 days over the same period last year, and 25 days in 2009.

David Brymer is the Air Quality Division Director with TCEQ.  He says over the last decade or so, there's been about a 50 percent drop in the amount of nitrogen oxides and volatile organic compounds pumped into the air. 

"Those key ozone precursors have greatly diminished in concentration, based on cleaner engines that are on the roadway, as well as significant reductions from industry."

Brymer says each year, Houston typically sees two peaks for ozone watch days.  The first is late May to early June.  The other, late August to early September.

"Bottom line is, if we have a lot more low-wind-speed, hot days over the next month, month-and-a-half, we are likely to have some additional high ozone days."

Brymer says it's been about a year-and-a-half since the TCEQ looked at whether the recession might be a factor in the trend toward fewer ozone watch days.  At that time, the commission found no significant drop in port activity, or in the number of miles people were driving.  

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David Pitman

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