Wildfires, lack of rain pose threat to Minnesota's air quality

A few dozen yards from the interstate in downtown St. Paul, environmental specialist Jerrod Eppen checked on a series of air quality sensors bolted onto a rooftop.

The sensors, which give continuous and hourly readings to the Minnesota Pollution Control Agency's laboratory, have been collecting data in the same neighborhood for years.

Unlike in decades past, the most pressing concern this summer for the chemists, meteorologists and analysts who monitor Minnesota's air isn't with the emissions coming from the highway below, or with the smoke from power plants along the Mississippi River. It's with the ferocious wildfires and lack of rain nearly 2,000 miles away in northern Alberta, Canada.

While nearly every measure of air quality in Minnesota has been steadily improving for decades, wildfires have been getting worse. The smoke, primarily from fires in Alberta, British Columbia and Washington state, is carried by jet streams across the continent to Minnesota along with harmful and tiny particulate matter and smog-producing pollutants.

The data show it's been getting worse every year since 2015. Historically, the MPCA would issue one or two air alerts from wildfire smoke a year. Last year, seven of 10 air alerts were because of wildfires. Already this spring the MPCA has issued a smoke alert for the Twin Cities and also for southwest Minnesota.

It's not unheard of for Canadian wildfires to have affected air quality here by early June, said Daniel Dix, MPCA air quality meteorologist. But the early start to the fire season is a bad sign after three straight years of record-breaking fires.

"It's still just a matter of time before the Pacific Northwest starts to light up," he said. "It could be a rough year."

The general improvement in air quality is one of the nation's great success stories. It started with the passage of the federal Clean Air Act in 1970, experts say. Long-gone are the days when state enforcers like Grant Merritt, one of the first directors of the MPCA in the early 1970s, would drive around the state spotting the wrong colors of smoke billowing out of paper mills, refineries or even tar companies run by the Minnesota Department of Transportation (MnDOT).

Improvements made in the 1970s were incremental, driven primarily through lawsuits, Merritt said. Those lawsuits typically began when he or others on his small staff happened to catch companies in the act of belching pollutants, such as the time one staffer was driving down Hwy. 61 from a family trip in the North Shore and spotted smoke that was too black coming out of a MnDOT tar company, Merritt said.

"So I called the commissioner of MnDOT and started a lawsuit and we solved that problem," he said.

The biggest gains recently have come from cleaner burning power plants as more utilities switch from coal to natural gas.

"People don't realize that back in the '40s and '50s the air quality here in the Twin Cities was terrible because it was all coal powered," Dix said. "You can still look at pictures and see the skies were pretty nasty."

Total emissions of four of the most prevalent air pollutants produced in the state, including nitrogen dioxide, sulfur dioxide, volatile organic compounds and particulate matter, were cut nearly in half from 2002 to 2016. MPCA officials attribute that drop to better technology and tougher government regulations.

Also helping was that in 2015, Xcel Energy switched one coal power plant to natural gas and installed much more efficient equipment at its massive Sherburne County plant, according to a 2018 MPCA report.

But cuts to emissions produced in the state don't necessarily lead to equal improvements in air quality. With more pollutants coming in from sources like western wildfires, the improvements to air have been slower, but still significant.

The Environmental Protection Agency keeps daily records of air quality logs collected at roughly a dozen Minnesota sites since 1980. It assigns a value of that day's air quality, called an index, with any number above 100 indicating that pollutants or smog have reached an unhealthy level, especially for the elderly, people with heart conditions and children with asthma.

The average annual index dropped statewide by about 20 percent from 1980 to 2018. That drop occurred even as technology has gotten much better and scientists are able to detect more pollutants than they could 30 years ago.

While they were once the main cause of pollution, power plants, factories and vehicle traffic now produce less than 40 percent of the pollutants in Minnesota's air. The main sources today — wildfires, construction and agricultural equipment, backyard fires and home heating and cooling systems, have proved much more difficult to regulate.

Wildfires, in particular, show no signs of slowing down, Dix said.

"We've just had more and more years of heat and drought and there's a lot more fuel to burn out west and into the northwest," Dix said.

Pollution is no longer concentrated in cities, but is widespread throughout the state, said Luke Charpentier, MPCA supervisor of air monitoring.

Chemists have spotted ozone spikes in southwestern Minnesota, where it's pretty clear those pollutants aren't being created, he said.

While the air is generally cleaner than it was a decade ago, it is still dangerous. There is no safe level of certain toxic particles, according to a study released this month by the MPCA and the Minnesota Department of Health. The study estimated that air pollution contributes to up to 4,000 deaths a year, especially among the elderly and people with pre-existing conditions.

To get a better handle on where pollution is tracking, the MPCA will be increasing the number of detection sites throughout the state.

It will add more than 20 monitors to fill in coverage caps in north and central Minnesota, which will provide neighborhood-level data about air quality in real-time and help meteorologists track how fast and in what direction wildfire smoke is moving across the state, Charpentier said.

"Air doesn't stop at a border," Charpentier said. "It blows in and ozone will go a long ways."

Greg Stanley • 612-673-4882