What's an Ozone Action Day in Austin?

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

Ozone is a reactive gas occurring in the Earth's upper atmosphere that's both natural and man-made, according to the United States Environmental Protection Agency.

It absorbs ultraviolet, or UV, light, which is harmful to people's skin and can cause skin cancer. When you inhale the ozone gas, it can react with the molecules in your respiratory system, causing other 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 lead to 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.