Three Ozone Action Days in Houston

Houston recently experienced its first Ozone Action Day of 2015.

Then its second. Then its third.

Yes, Thursday, April 30; Friday, May 1; and Saturday, May 2 were all Ozone Action Days in Houston. If you follow Air Alliance Houston on Facebook or Twitter, you likely saw quite a few posts from us that looked like this:

If you don’t follow us, you might not be familiar with “Ozone Action Days.” Ozone is the most common air pollutant in Houston, forming plumes that can travel throughout the eight-county “Houston-Galveston-Brazoria” ozone nonattainment area (a “nonattainment area” is one that does not meet a federal air pollution standard). Ozone is a pollutant that can cause everything from itchy eyes and shortness of breath to asthma attacks, cardiac arrest, and death. When high ozone is predicted, the Environmental Protection Agency (EPA) and the Texas Commission on Environmental Quality (TCEQ) issue an “Ozone Action Day.” Ozone Action Days are announced online and via email. A few sources of action day announcements are below.

  • The TCEQ issues a daily air quality forecast and announces ozone actions days online. You can also sign up for email or text alerts from the TCEQ.
  • The TCEQ’s Twitter account also posts the daily air quality forecast during the week. TCEQ has never acknowledged this, but Air Alliance Houston takes credit for these daily posts. We gently criticized TCEQ for not using social media for several weeks before they began posting daily forecasts. Thanks again TCEQ!
  • The EPA posts daily forecasts at AirNow. The TCEQ forecast is pulled from EPA’s forecast, so either source works just fine.
  • The National Weather Service also allows you to search for air quality alerts by ZIP code.

If you are signed up for Ozone Action Day alerts from EPA or TCEQ, you will receive an email around 2:00 PM the day before an Action Day. During an Ozone Action Day, you should monitor ozone with the Houston Clean Air Network, our FREE website and mobile phone app for iPhone and Android.

The more we learn about ozone, the worse we realize it is for our health. (Did you know that ozone might even be linked to diabetes?) Research at Rice University has showed that multiple days of exposure to ozone pollution lead to cumulative and worsened health outcomes. The following statement about this impact comes from Dr. Kathy Ensor, one of the authors of several of Rice’s studies:

“For asthmatics, the biggest concern for Houstonians is a three-day exposure to elevated ozone levels, but there is also significant concern for elevated levels on a single day. Overall, the risk of an asthma attack increases by 5% when ambient ozone levels increase 20 ppb over a three-day period. Considering periods when the ozone levels are between 50 to 70 ppb, the increased risk of an asthma attack is 13% when ambient ozone levels increase by 20ppb during a three-day period. The increased risk is 10% for increases of this level in a single day. If we move to higher levels of ozone in the range of 70 to 90 ppb, these risks increase to 45% and 21%, respectively.”¹

This is troubling because multiple high-ozone days in a row is indeed what we often see in Houston. The three day period of April 30 – May 2 had elevated ozone in the 50 to 70 ppb range, with higher spikes at isolated times and places. This means that we would expect increased incidence of asthma attacks during that time period. Drs. Ensor and Raun continue to research this issue, as do other academics and advocates in the Houston region. Over the next months and years, we will continue to introduce tools such as that allows citizens to monitor ozone, limit their exposure, and protect their health.

1. Key references:

Ensor, K. B., Raun, L. H. and Persse, D. (2013). A Case-Crossover Analysis of Out-of-Hospital Cardiac Arrest and Air Pollution. Circulation. V127, pp 1192-1199.

Raun, L. H., Ensor, K. B. and Persse, D. (2014) Using community level strategies to reduce asthma attacks triggered by outdoor air pollution: a case crossover analysis. Environmental Health, 13:58.

Raun, L. and Ensor, KB. 2012. Association of out-of-hospital cardiac arrest with exposure to fine particulate and ozone ambient air pollution from case-crossover analysis results: are the standards protective? James A. Baker III Institute for Public Policy of Rice University. HPF-pub-RaunEnsorParticulateExposure-101212.pdf