EPA’s new air pollution rules: U-M expert provides insight

February 9, 2024
Concept illustration of air pollution. Image credit: Nicole Smith, made with Midjourney


The Environmental Protection Agency’s new rules for restricting the amount of fine particulate matter released into the air moves the current annually allowed amount from 12 micrograms per cubic meter of air to 9 micrograms per cubic meter of air.

The EPA says the change—viewed by many as the agency’s most significant move to improve air quality in a decade—means preventing 4,500 premature deaths annually, saving 290,000 lost work days and saving as much as $46 billion in net health benefits.

Stuart Batterman
Stuart Batterman

University of Michigan researcher Stuart Batterman, professor of environmental health science and global public health at the School of Public Health, and professor of water resources and environmental engineering at the College of Engineering, studies the impacts of the environment on health, including air pollution control engineering, air quality monitoring, indoor air quality, exposure assessment and environmental epidemiology.

What are your thoughts on the EPA’s decision?

This is good news. Achieving the new standard will save thousands of lives each year. The EPA has been regulating levels of airborne particulate matter since 1971 and we’ve seen some striking changes over this time. First, the scientific evidence shows that health impacts occur at lower and lower levels, and thus the EPA has changed the level and form of the standards some half-dozen times. This trend will continue, but it’s still a catch-up game and standards lag the science. For example, the World Health Organization has a guideline level for fine particulate matter of only 5 micrograms per cubic meter, almost twice as stringent as the EPA’s new standard.

A second and related trend is the very significant advances in understanding the diverse impacts caused by exposure. Particulate matter not only causes cardiovascular and respiratory illness, but it also increases the risk of adverse birth outcomes, psychiatric disorders and Alzheimer’s disease, to name a few. A third trend is even newer. As old so-called legacy pollution sources like coal-fired power plants are phased out and as forest fire smoke increases, the chemical composition of contributing sources and even the toxicity of this pollutant is shifting. The new standard is helpful, but it’s not going to be the final word.

Any details on how long before this change might improve overall air quality?

The EPA lays out a schedule giving about eight years to reach the standard—assuming that legal challenges don’t upset the plan. While each area is different, the gradual phase-out of dirty fuels like coal, the introduction of electric vehicles and continuing replacement of older technologies with cleaner ones bode well for improved air quality. Also, emissions and new air permits in these areas will get more scrutiny and may be strengthened. However, a big wild card is how frequently and intensively wildfire smoke affects air quality. Last year had two dramatic episodes in July that can offset progress.

Could you describe how and why fine particulate matter is harmful to humans?

Particulate matter is anything solid or liquid that is airborne.The term fine is a bit of a misnomer. It means small, specifically less than 2.5 micrometers in diameter, referring to what’s called equivalent aerodynamic diameter. These are tiny particles, irregularly shaped and diverse in chemical composition. If the particle was a sphere, it would be about 25 times smaller than the diameter of human hair, and most airborne particles are much, much smaller. This size allows these particles to reach the deepest portion of the lung, get absorbed into blood and even cross the blood-brain barrier. These particles can cause many harmful effects that cause or worsen disease.

Do the detrimental health effects extend to plants, animals, water?

In ways, yes, but really there’s no simple answer. Mammals including pets could be similarly affected as humans. Plants and water bodies certainly do experience effects from air pollution, including acidification and accumulation of toxics like PCBs and mercury, and most people are surprised to learn that levels of these chemicals in Great Lakes fish don’t arise from industrial outfalls and rivers feeding into the lakes, but actually from air pollutants. However, the new standard was revised specifically to protect human health.

How do industries limit the amount of fine particulate matter they release into the air?

It’s not just industry. We have shown major emissions from diesel engines that are used in heavy-duty vehicles, including trucks and construction equipment. Both industrial and these mobile sources can reduce their emissions by going electric, if we have a clean grid, and by using cleaner fuels, improved emission controls, increased efficiency and sometimes by changing manufacturing processes.

Does a change such as this potentially mean the air won’t be as quickly affected by wildfires or other natural or man-made disasters that create air pollution, such as in 2023 when wildfires led to dangerously unhealthy air quality in the U.S. and Canada?

That’s a key question and a key loophole in the regulatory system. All of the air quality planning, rules and permits in Michigan and elsewhere won’t stop a wildfire. Forest management practices can help, but the EPA and the state haven’t had much impact yet and there are obstacles. In Michigan, for example, about half the forest land is privately owned and most landowners do not participate in programs designed to lower fire risk, despite some incentives from the state.

Another issue affecting the clean air program is that the EPA allows states to discount forest fire plumes and smoke events, thus, they may not feed into the long-term average concentration that determines attainment with the air quality standard. This is a little technical, but what happens, for example, is that people in Detroit will be breathing air that’s polluted by both industry and forest fires, but legally the area could still meet the clean air standard because the smoky days are considered “exceptional events” that do not feed into the regulatory determination. This has not happened yet for particulate matter but it has happened for other pollutants, specifically ozone last year. I believe that we need a more comprehensive approach to protect public health.

Anything individuals can do to improve air quality?

There’s lots people can do to minimize their own exposure to particulate matter. Advocating for designated trucking routes, promoting stricter emission controls and even monitoring your own quality using low-cost sensors are positive actions. Lastly, I’ll note that while the EPA standards apply outdoors, you can remove particulate matter quite effectively in your home, business or school using filters rated MERV 13 and up. Often, the default furnace filters are just sieves that don’t remove the small particles. This is important since most of us are indoors most of the time.