July 25, 2019
When it comes to particulate emissions, it appears Michigan is headed in the right direction. Over the past 10 years, Michigan's annual ambient particulate matter concentrations have been trending downward. Air monitors show concentrations are below federal standards throughout Michigan, in some areas by a large margin.
Particulate matter emissions are primarily composed of smoke, dust, dirt, soot, fly ash, and condensing vapors. Industrial processes that cause these emissions include combustion, incineration, construction, mining, metal smelting, metal processing, and grinding. Non‑industrial sources include motor vehicle exhaust, road dust, wind-blown soil, forest fires, volcanic activity, and farm operations.
Particulate matter is divided into multiple subcategories for, among other things, regulatory purposes. Particulate matter with a diameter of less than 10 micrometers in diameter is referred to as PM10. Very fine particulate matter equal to or less than 2.5 micrometers in diameter is referred to as PM2.5. Respiratory and cardiac problems can be directly linked to PM2.5 exposure.
Air monitors throughout the state measure concentrations of PM2.5 and PM10. The Michigan Department of Environment, Great Lakes, and Energy’s (EGLE) Air Quality Division (AQD) staff calculate the three-year average and compare these values to the National Ambient Air Quality Standards (NAAQS), set by the United States Environmental Protection Agency (USEPA). The USEPA has set the NAAQS to be protective of even the most sensitive groups of people, such as children, the elderly, and those with existing lung conditions. This information is also used to determine an area’s attainment status. Being in attainment means an area is below the NAAQS for that pollutant.
It is believed several factors may be contributing to improving outdoor particulate concentrations over the past several years. Continued pollution prevention and reduction efforts by manufacturers and cleaner motor vehicles may explain some improvements. Additionally, a shift in many industries away from "dirtier" fuels like coal and diesel to natural gas, such as in electric generation, could be a big reason for the positive trends.
Based on the recent history and trends in electrical generation and motor vehicles, we expect particulate matter concentrations in the outdoor air to continue to decrease. EGLE's AQD will maintain our program to monitor these concentrations with respect to the NAAQS to continue to be protective of human health and the environment.