Air quality in Southwest Minneapolis remains good, but officials with the Minnesota Pollution Control Agency (MPCA) are exploring why levels of one pollutant have increased at one Minneapolis site this year.
Levels of particles less than 2.5 millionths of a meter in size (PM2.5) were 25% higher in the Phillips neighborhood between March and June than during the same period in 2019, according to the agency.
That stands in contrast to another monitoring site at the convergence of interstates 94 and 35W, where PM2.5 levels were down 20% compared with last year.
Levels of nitrogen dioxide, a pollutant that comes primarily from automobiles, also decreased by about 20% in the same period. Kari Palmer, air assessment manager with the MPCA, said PM2.5 levels across the Twin Cities and the state are still safe.
The U.S. Environmental Protection Agency considers PM2.5 levels safe if the average concentration is below 12 micrograms per cubic meter of air over a year or 35 micrograms per cubic meter of air over one day. Between March and July, levels in the Phillips neighborhood were still below 12 micrograms per cubic meter, Palmer said.
The agency isn’t sure why levels at the site increased between 2019 and 2020, she said. Other than the Fourth of July, there weren’t any individual days with higher-than-usual concentrations of the pollutant, and traffic — a source of PM2.5 — decreased during that period.
PM2.5 comes from diesel, gasoline and wood-burning emissions, along with other chemicals, such as ammonia and nitrogen oxide. It can be inhaled deep into the lungs, and elevated levels are associated with an increased rate of heart attacks, bronchitis, asthma attacks and respiratory symptoms, according to the MCPA.
A study this spring from Harvard’s T.H. Chan School of Public Health found that long-term increases in PM2.5 concentrations elevate the risk of COVID-19 mortality. “From a biological standpoint, this is not unexpected,” Jim Kelly, manager of environmental surveillance and assessment with the Minnesota Department of Health, told members of a City Council committee in September.
He said more study is needed to further specify the link between COVID-19 and air pollution.
Across Minnesota, PM2.5 levels have decreased since about 2014, Palmer said, attributing it in part to fewer coal-fired power plants and cleaner cars and diesel fuel.
The agency continues to take steps to reduce air pollution of all types, including PM2.5. Efforts include providing grants to help the owners of diesel vehicles to switching to cleaner equipment, replacing old school buses and expanding electric vehicle charging infrastructure.