Conditions determine Ozone Action Days

By: Kevin Bunch | C&G Newspapers | Published July 25, 2014

METRO DETROIT — It is easy to think of smokestacks belching dark plumes into the sky and consider those the major, localized consequence of air pollution, but with the right weather conditions, problems can be as invisible as the air we breathe every day.

A combination of heat, wind, and pollutants can lead to the creation of ozone gas near ground level, which can be dangerous to breathe for people with respiratory problems, according to Grant Brooks, communications specialist with the Southeast Michigan Council of Governments.

On those days, SEMCOG calls for Ozone Action Days, which are calls not only for the vulnerable to stay safe, but for the general public to try to reduce emissions. The program has been in effect for about 20 years, with warnings being highlighted by the media or even roadside signs.

“We may have particles that are heavy for people to breathe, so we have to call those days for the elderly, and those who have possibly asthma, as well,” Brooks said. “What that day is, is making people aware — for those who have respiratory issues or are seniors — that they should possibly stay inside on those days.”

Additionally, Brooks said they will ask motorists not to idle their vehicles, as the car exhaust can contribute to the ozone problems. He added that they also ask people not to get gas for their car during the day, as even opening the gas cap can give off fumes that worsen the situation.

“We ask for people not to use aerosols. If you are running a barbecue, we ask you to use gas instead of charcoal,” he said. “If you’re going boating, don’t idle the boat. If you’re waiting for someone, turn your engine off. It’s just small things you can do to help out.”

Laura DeGuire, environmental quality specialist with the Michigan Department of Environmental Quality, said the state monitors the air from April 1 through the end of September for the pollutants and weather conditions that can cause ozone to form at ground level.

While most people may be familiar with ozone in the upper atmosphere, where it protects life on Earth from harmful radiation, DeGuire said at low altitudes it is unhealthy to breathe.

Though the emissions are a part of the ingredients, the heat from the sun’s rays coupled with the longer summer days effectively cooks it all together into the gas, she said.

“It’s basically just cooking a stew,” DeGuire said. “You have your pollutants, your heat source, and it goes through various chemical changes and creates elevated levels of ozone. We’ve done a really good job reducing the amount of ozone, but because it’s seasonally driven, there’s some times of the year we’re going to have challenges with ozone formation.”

Pollutants do not necessarily have to be local, either — Brooks said they see materials blown in from Ohio and Canada, as well as particulates from local industry and cars.

DeGuire said the MDEQ employs meteorologists who are familiar with the atmospheric and weather conditions that can lead to ozone’s formation. Using the monitoring stations spread throughout the state, they are able to make the call on whether or not local municipalities or organizations should declare an Ozone Action Day.

If they do recommend it, Brooks said SEMCOG handles that announcement for metro Detroit. Typically speaking, there are only a couple days at a time before atmospheric conditions change.

“We usually only have one or two days (in a row) at the most; one year, we may have seen three in a row,” Brooks said. “Last year didn’t have many ozone action days at all.”

He said that while they are typically declared on the same days that temperatures reach into the upper 80s and 90s, conditions do not necessarily have to be that hot if the pollutants are being blown in from another area.

DeGuire said people interested in getting real-time air quality information could visit and click on the MiAir icon.