Ozone Season begins in Houston

March 1 marks the beginning of ozone season in Houston. From now until November 30, we’ll watch out for Ozone Action Days, report on air quality in real time with houstoncleanairnetwork.com, and keep Houstonians informed about ozone air pollution and its potential to impact their health.

What can we expect in 2016? Well, 2015 was a bad year for ozone air pollution, as we showed in an analysis late last year. There were 30 high ozone days that year, up from just 14 in 2014. The general trend in ozone has been downward for some time, but 2015 put a bump in that road. This graph from Alex Cuclis at the Houston Advanced Research Center shows the trend in ozone days over time.

Ozone Days HGB thru 2015

For the full version of Mr. Cuclis’ report, click here.

How 2016 shapes up will have to do with (among other things) the weather and the amount of ozone precursor pollutants emitted in Houston. Let’s look at each factor in turn.

Weather. As you probably know, climate change is driving temperatures up globally, and in Houston. You’ve probably seen many graphs of rising temperatures similar to this NASA chart shared by Climate Progress.


2015 continued the trend, setting another record for warmest year on record. To really appreciate just how hot 2015 was, you have to compare it to the other hottest years on record, as is done in this chart by the National Centers for Environmental Information (reproduced in this article by Discover Magazine).

As you can see, 2015 was by far the hottest year ever. Sources including the UK Met Office are already predicting that 2016 will set another record. This is bad news for Houston’s ozone forecast.

Ozone precursor pollutants. The second factor is the amount of ozone precursor pollutants emitted in our region. Ozone isn’t emitted directly into our air. It forms via a photochemical reaction with other air pollutants, nitrogen oxides and volatile organic compounds, that are emitted into the air. (For a refresher on ozone science, check out this video from the EPA.)

We reduce precursor emissions to reduce ozone formation. But precursor emissions haven’t been significantly reduced in several years. The charts below show NOx and VOC emissions in the eight county ozone nonattainment region for the period 2011-2014. (The TCEQ prepares these “emissions inventories,” and unfortunately the data lags behind by about a year. 2015 data won’t be available for some time.)

NOx Emissions HGB

As you can see, emissions of nitrogen oxides have not decreased in several years. Volatile Organic Compound emissions have decreased only slightly.

VOC Emissions HGB

So, we can expect another hot year, and pollution trends suggest we won’t see any less ozone precursor pollution in the region. This means we could easily have a bad ozone season in 2016, with twenty to thirty high ozone days throughout the year.

That’s too many. At Air Alliance Houston, our goal is a Houston in which no one’s health is ever threatened by air pollution. Even one high ozone day would be one too many. Twenty to thirty days would mean more asthma attacks, more heart attacks, and more premature deaths linked to ozone pollution.

What can we do about it? First, we can encourage Texas and the EPA to work together to implement the new ozone standard. If Texas continues wasting resources on a misguided lawsuit against the federal government, rather than spending them to reduce pollution, Texans will continue to suffer. If Texas would work with the EPA to begin reducing ozone pollution now, we would see more health benefits sooner.

Second, Houstonians can use the resources Air Alliance Houston provides to be aware of ozone pollution in Houston and limit our exposure. You can sign up for email alerts from the TCEQ so that you will know when ozone is likely to be a problem. You can also follow Air Alliance Houston on Facebook and Twitter, where we reliably share real-time information about ozone pollution.

Finally, and most importantly, you can check houstoncleanairnetwork.com, our real-time map of ozone pollution for the Houston region. Houstoncleanairnetwork.com was created by Air Alliance Houston and the University of Houston and is provided to you for free. You can also download our free app for iPhone and Android.

With these tools at your disposal, you should be able to monitor ozone pollution and limit your exposure. Unless the state and the TCEQ get serious about reducing ozone pollution, we are likely to need these tools for a long time.