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What's an Ozone Action Day in Austin?

 Cars drive down a highway during the daytime.
Gabriel C. Pérez
Ozone is a reactive gas that can have effects on respiratory and skin health. Primarily, it comes from the combustion of fossil fuels, like gas or diesel.

Thursday is an Ozone Action Day in Austin. This happens when the Texas Commission on Environmental Quality determines the smog levels in the city are high enough to pose health risks.

Ozone, a type of gas, can be good or bad depending on where it is. Ozone in the upper atmosphere protects us from the sun's ultraviolet rays, but when found at the ground level, it's known as smog, which can affect people's health and the environment, according to the Environmental Protection Agency.

When you inhale the ozone gas, it can react with the molecules in your respiratory system, causing health effects, particularly for people with asthma or heart health issues.

Luke Metzger, executive director of Environment Texas, said there are multiple factors that cause high ozone levels.

“It's a combination of everything,” Metzger said. “From cars to tailpipe exhaust to gas stations, all kinds of fumes that are coming from when we gas up our cars, as well as factories, refineries, and then also consumer products like paint.”

Primarily, though, it comes from the combustion of fossil fuels, like gas or diesel.

Ozone Action Days tend to be issued by the state's environmental quality commission when temperatures are warmer, according to a video by TCEQ meteorologist Weslee Copeland.

Copeland says these action days are warnings or forecasts.

“It doesn't guarantee that ozone will actually reach the forecasted levels,” Copeland says. “The purpose of an Ozone Action Day is to alert the public so that they can help take action the next day to prevent ozone formation. They're not necessarily meant to be a public health alert.”

But he says people who may be sensitive to ozone, like people with asthma, can do things to protect their health, such as spending less time outside.

There are things people can do to help reduce ozone levels, including taking public transportation, carpooling, bringing your own lunch to work to avoid idling in drive-thru lanes, and choosing to mow your lawn on a different day.

The Austin area is already teetering on federal compliance standards for the Federal Clean Air Act, Metzger said. If a city averages 70 parts of ozone per billion particles in the span of three years, it could be out of compliance with the act. Violating the act could leadto civil penalties or legal disputes from the EPA.

Metzger said in recent years, Austin has averaged in the high 60s and has passed 70 parts per billion particles a few times as well.

Correction: This story has been updated to correctly explain the difference between ozone in Earth's upper atmosphere and ozone found at ground level.

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Haya Panjwani is a general assignment reporter, with a focus on Travis County. Got a tip? Email her at Follow her on Twitter @hayapanjw.
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