EPA Tightens Limits on Ambient Soot in New Final Rule

The Environmental Protection Agency (EPA) recently issued updated air pollution standards that will reduce the limits for fine particulate matter, also called soot, for the first time in more than a decade.

Fine particulate matter (PM2.5) in the atmosphere is created through many manmade and natural processes. Human-generated sources include emissions from burning fossil fuels, including combustion processes, industrial activity, and transportation-related emissions like diesel engines. PM2.5 can also be created through natural functions like volcanic eruptions and atmospheric chemical reactions between airborne pollutants.

Short- and long-term exposure to PM2.5 can cause a myriad of health problems, primarily in the neurological and respiratory systems, due to the ability of the particulates to reach deep within the lungs, where they can enter the bloodstream. According to the EPA, exposure to PM2.5 can lead to asthma, decreased lung and respiratory function, arrhythmia, and heart attacks, as well as other chronic illnesses.

Under the new rule's provisions, the acceptable atmospheric concentration of PM2.5 will be reduced from 12 micrograms per cubic meter (µg/m3) to 9 µg/m3. In a statement, EPA Administrator Michael Regan said that the updated rule “will save lives and make all people healthier”.

The move is being regarded as “historic” as atmospheric soot standards have not been lowered since 2012 and reverses decisions by both the Obama and Trump administrations not to reduce the standard due to economic considerations.

The economic effects of the more stringent rules are the basis for opposition to the rule change. Critics argue that the 9 µg/m3 limit is “not realistic”, and would be a burden on industry, especially the energy and manufacturing industries, which will have to invest heavily in technology to reduce emissions. Additionally, concerns regarding the enforcement of these rules, and the costs of doing so, have been raised.

Proponents note that the positive effects of the rule would not only be environmental and health related, but also economic. A White House press release on the rule notes that the tougher rules will prevent “up to 4,500 premature deaths and 290,000 lost workdays,” which would equate to a $46 billion net benefit in human health in 2032 when the rule will be fully enforced.