If your impression of Minnesota’s summer skies this year seems hazy, it’s appropriate.
Data from the Minnesota Pollution Control Agency shows that days with so-called “orange alert” warnings for ozone and particulate matter in the air are setting a record pace this year.
The warnings caution people in sensitive groups, particularly older people, children and those with lung conditions, from spending time outdoors. Sometimes the warnings extend to everyone.
“Up to this point of the year, sitting in early June, we’ve seen a lot more alerts compared to past years,” said Nick Witcraft, an air quality meteorologist with the MPCA. “This has been the most active ozone season up to this point in the year. We’ve had more days this year with smoke compared to 2021 at this same time of year, and that’s mainly because the fire season has gotten off to a quicker start in Canada.”
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For many Minnesotans, 2021 stands out: It was the smokiest in memory, with nearly double the number of days with particulate warnings compared to any other year this century. Air quality measurements are a relatively recent phenomenon, so there’s no easy way to compare the pollution levels from decades ago.
Data compiled by Witcraft show that days with a 24-hour average measurement for particulate matter over a rating of 100 now number eight for 2023, including Tuesday. It’s only a fraction of the 23 days recorded in 2021, but the average the decade before the smoky year 2021 was 2.5 days of orange alerts per year.
Ozone warnings have been even more numerous, although they are related to warnings connected to wildfires. On non-smoke alert days, sunlight can interact with lingering combustion products from wildfires to elevate ozone levels, just as vehicle or other emissions often do.
So far in 2023, there have been 12 days with ozone alerts and measurements over 71 parts per billion — the most since 2005 when Minnesota had 19 such days for the whole year, covering the period of recent, modern monitoring systems.
The air quality coincides with huge fires springing up in Canada in recent weeks, in western provinces and most recently in Quebec, with smoke plumes clearly visible from space in NASA imaging.
Canadian authorities are calling for an international response to the fires.
Witcraft says the air quality is highly variable from year to year, as fire patterns change, but that climate change may play a role. “Given climate change, there's a tendency for drier patterns and warmer patterns. So, it may make it a little more likely heading forward to see more instances of this smoke and poor air quality.”
A study published in Nature in 2020 estimated that outdoor air pollution of all types was responsible for 5 to 10 percent of premature deaths in the U.S. annually — not to mention an untold toll of discomfort, illness and disability.
Also, the data originate from a network of air quality monitors established in Minnesota in 2000. The state had fewer monitors and older technology before that, as well as different federal standards for air quality.
“I have no doubt we had worse pollution prior to 2000, when vehicles and power plants were much dirtier,” Witcraft said.