As hot, sunny weather continues across Michigan, state air quality officials are warning that the same conditions driving the summer heat are also creating higher levels of ground-level ozone, a pollutant that can pose health risks for some residents.
Alex Kownacki, an air quality meteorologist with the Michigan Department of Environment, Great Lakes, and Energy's Air Quality Division, said ozone forms through a chemical reaction involving pollutants from vehicle exhaust and industrial emissions.
"Ozone is a warm weather pollutant," Kownacki said. "You need heat and sunlight because those pollutants react in the atmosphere to create ozone."
This development comes as the state is grappling with high heat indexes, reaching as high as 100 degrees or more. Lansing has activated its Code Red extreme heat plan, including cooling centers and guidance to avoid prolonged outdoor activity during the hottest part of the day.
“Ozone does not interact well with humidity,” Kownacki said. “There's a lot of theories out there as to why, but it just could be because the air is just so soothy and so heavy that those pollutants are floating around as freely as they normally would or there's more moisture in the atmosphere. So that solar radiation that's coming down to interact with the pollutants to create ozone is being kind of scattered and refracted.”
The pollutant is most common during the summer when temperatures climb above 80 degrees and skies remain mostly sunny.
While hot weather is necessary for ozone to develop, Kownacki noted it does not automatically mean ozone levels will become unhealthy because humidity, wind and other weather conditions also influence its formation.
“Just because we have these hot days and sunny weather does not mean we'll have ozone. But just when things line up, we can see ozone,” Kownacki said. “But in order to have ozone, you need to have these hot temperatures and sunny days.”
The state issues Air Quality Alerts when ozone reaches the orange category on the Air Quality Index, which is considered unhealthy for sensitive groups. Those most at risk include people with asthma, heart disease, and other underlying respiratory or cardiovascular conditions.
Kownacki said so far this year, there’s only been two alert days: today and on June 29.
Officials recommend reducing activities that contribute to ozone formation on alert days, including limiting driving, avoiding refueling vehicles during the hottest part of the day and reducing the use of gasoline-powered lawn equipment.
"Just doing little steps like that can definitely help the overall environment, "Kownacki said.
According to Kownacki, Detroit and communities along Michigan's Lake Michigan shoreline are as most likely to experience elevated ozone levels.
Detroit's ozone is largely driven by local traffic and industrial emissions, while western Michigan often receives pollution transported across Lake Michigan from the Chicago and Gary, Indiana, metropolitan areas.
Kownacki said residents should pay attention to how they feel during ozone events.
"If you notice you feel more strained, it's difficult for you to breathe, that is your body being impacted by ozone, especially with wildfire smoke or PM25,” Kownacki said. “If you notice your nose is getting itchy, your eyes are watering, that's your body directly impacted by that wildfire smoke or that particulate matter in the atmosphere.”
Officials encourage residents, especially those in sensitive groups, to monitor daily air quality forecasts and limit prolonged outdoor activity when Air Quality Alerts are in effect.
With dangerous heat building across Mid-Michigan this week, WKAR News has put together resources to help you stay safe. At the top of our homepage, you can find cooling centers, heat safety tips and information on who is most at risk.
This story is brought to you as part of a partnership between WKAR and Michigan State University's Knight Center for Environmental Journalism.