Warm and sunny with a big slice of ozone on the menu Friday in the Baton Rouge area _lowres

Advocate staff file photo by PATRICK DENNIS -- Jesus Espajo, with Green Seasons, works around crape myrtles while mowing the median along Bluebonnet Boulevard near Jefferson Highway. Because of an ozone day alert in the Baton Rouge area on Friday, officials are asking residents to restrict activities like mowing the lawn during the daytime.

Sunny skies and warm temperatures expected Friday prompted the state Department of Environmental Quality to announce the first ozone action day for the year for the Baton Rouge area.

Parishes affected are East Baton Rouge, West Baton Rouge, Iberville, Livingston, Ascension and Pointe Coupee.

Forecasts call for the air quality to be in the “orange” realm, which means it could reach unhealthy levels for some people, including the elderly and people with respiratory diseases such as asthma. Also, children and adults should limit how much time they spend on outdoor activities.

Ozone levels could remain elevated on Saturday, although not as high as Friday. Saturday has a forecast of “yellow,” meaning ozone could be a problem for a small group of people who are unusually sensitive to pollution.

Unlike many other forms of air pollution, ozone isn’t something that comes out of a smokestack or the tailpipe of a car. Instead, it forms when nitrogen oxides and volatile organic compounds from combustible engines, like those on cars, and from industrial activities combine in the air during sunny, hot days. When there is little wind expected, like on Friday, this ozone can accumulate in an area and cause health problems.

“Ozone grows in the presence of sunlight,” said Vivian Aucoin, senior environmental scientist with the air permits division at DEQ. “That’s why we love those afternoon thunderstorms.”

The action day serves as an alert to sensitive people to limit their outdoor activities and asks people to limit some daytime activities like mowing the lawn or refueling a car. Other things people can do include carpooling, bringing a lunch to work to avoid driving at noon and postponing painting jobs that use oil-based paints or solvents.

Industry also participates by postponing certain activities like painting or even some operations if possible.

It may seem strange in an area with so much industrial activity that postponing mowing the lawn until the evening could have an impact on ozone, but it does.

Aucoin said many residential causes, such as car exhausts, fueling a vehicle or using lighter fluid instead of an electric starter to barbecue, contribute because the pollution stays close to the ground where people breathe.

“The emissions the industry puts off goes into the air and there is some mixing (with winds),” Aucoin said. That mixing can help keep any ozone that forms from becoming too concentrated.

Air consists of layers, she explained, and the layers close to the ground don’t move as quickly as air higher up.

Although the six-parish area currently meets the federal standard for ozone, set at 75 parts per billion, the U.S. Environmental Protection Agency is expected to announce a proposal later this year to make the standard harder to meet. The agency has said it’s considering lowering the ozone standard to between 65 ppb and 70 ppb or even down to 60 ppb.

Follow Amy Wold on Twitter, @awold10.