Part I: Why Are Houston’s 2015 Ozone Levels Cause for Concern?

This is Part I of our four-part series on Houston ozone and how it affects your health.

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Ozone pollution affects everyone, no matter where they live.

Though the region has made progress on air quality in recent years, Houston suffered a setback in 2015 with a significant spike in its ozone levels. Ozone, also known as smog, is harmful to health and can result in respiratory symptoms such as cough and chest tightness. And with considerable industrial and population growth expected in the next few years, experts are understandably worried about public health risks.

To protect public health, the U.S. Environmental Protection Agency (EPA) sets national standards for ozone concentrations, or limits on the amount of harmful ozone pollution in the air. In 2008, EPA strengthened the standard to 75 parts per billion (ppb), and this year the agency set a more protective standard of 70ppb. A lower number means there is less smog – and less smog means cleaner, healthier air. (In order to evaluate the public’s exposure to ozone, scientists and health officials look at regional monitoring data to determine when ozone levels exceed those federal health-based standards.

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Reviewing the past five years of data from the state environmental agency (Texas Commission on Environmental Quality or TCEQ), we see that 2015 resulted in a set-back of improvements in the ozone concentrations to 2013 levels. The number of air monitors in the Houston area that exceeded the 2008 standard on their fourth highest day (the standard evaluation parameter) jumped from zero in 2014 to 26 in 2015*. That means over half of regional TCEQ monitors recorded ozone levels above the 2008 ozone health standard for at least four days in 2015.

Strikingly, there were even four locations with fourth-highest readings above 90ppb. That’s more than 20ppb above the new standard and will make it difficult for the region to meet air quality standards.

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The quantity and distribution of monitors with high readings demonstrate that the ozone problem isn’t limited to a particular zip code or neighborhood. Analyses from Houston Advanced Research Center, Air Alliance Houston, and Environmental Integrity Project show that Downtown Houston experienced its highest smog level since 2004. And the Fairbanks neighborhood off of U.S. 290 recorded an ozone reading that hasn’t been matched since 2000. The map below shows how some of the highest ozone readings, those above 91ppb, are distributed around the area.

While the eastern areas of the region have more monitors, this map demonstrates that ozone impacts everyone in the region, no matter where they live.

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In school, one year of poor grades doesn’t mean that you’re not graduating. However, it does mean that you need to put in some extra effort the next year to make sure you’re improving and to raise your overall GPA. Houston finds itself in a similar situation. Regulators use three-year averages to determine compliance with federal standards, but if Houston is going to reach them, the region needs big improvements to make up for last year’s poor air quality readings.

This year was undoubtedly troubling for air quality – particularly for those most at risk for health effects – and it’s up to our political and business leaders to ensure that it isn’t the new normal. Instead of letting Houston rise in the ranks of smoggiest cities, let’s make sure the state’s largest city is on the right path toward healthy air.


In Part II of our series, we’ll take a look at health studies from Houston researchers that demonstrate why ozone is bad for your health. Part III will outline flawed arguments put forward by the state of Texas and the Texas Commission on Environmental Quality (TCEQ) in challenging the recently strengthened health-based ozone standard. And in Part IV, we’ll identify health interventions that help reduce risk from ozone pollution as well as emission reduction strategies that can decrease ground-level ozone.

*Regional ozone is measured against a national health-based standard by averaging the fourth-highest annual daily level over a period of three years. This conservative approach allows areas to account for the highest readings that might not be representative of the region due to abnormal weather conditions.

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