In the first such move in 12 years, the U.S. Environmental Protection Agency (EPA) has finalised a more stringent standard for fine particulate pollution, or PM2.5.

This announcement marks a significant advancement in health and clean air protections for families, workers, and communities. According to EPA projections, this change is expected to save lives and bolster economic growth throughout the nation by improving health outcomes and reducing work absences.

The EPA sets May 6, 2024 as the landmark date when the finalised rule officially takes effect, heralding a significant shift in how air quality is monitored and communicated to the public.

What are the new standards?

On February 7, 2024, the EPA announced the agency’s proposed rule change reducing the primary annual PM2.5 National Ambient Air Quality Standard (NAAQS) from 12 μg/m3 to 9 μg/m3 (1). While no amount of exposure to air pollution is healthy, lowering the regulatory PM2.5 standard will result in reduced overall exposure leading to meaningful, positive impacts on American health outcomes. The revised standards will help keep authorities legally accountable and committed to protecting Americans from greater PM2.5 exposure.

The revised standard was published to the Federal Register on March 6, thereby codifying the rule in the U.S. Federal Code. According to the Clean Air Act (CAA), the EPA is required to develop ambient air quality standards, or pollutant concentration limits, for six common air pollutants from industrial and mobile sources, including PM2.5 (2). The limits are designed to reduce the risk of adverse health outcomes from air pollution.

PM2.5 is a widespread and dangerous pollutant. Measuring 2.5 micrometers or smaller, fine particulate matter can penetrate deep into the lungs and enter the bloodstream, causing respiratory and cardiovascular diseases.

The revision is grounded in the best available current science. The overwhelming body of scientific research demonstrates that greater exposure to PM2.5 is tied to a range of short-term and long-term illnesses, including childhood asthma, breast cancer, and premature death (3)(4)(5).

“The overwhelming evidence linking adverse health outcomes to PM2.5 exposure continues to build, and as a scientist, the pace at which policy moves in response to scientific evidence can be incredibly frustrating,” said Dr. Christi Chester Schroeder, Air Quality Science Manager at IQAir.

The new standard brings the United States into closer alignment with the recommended World Health Organization (WHO) annual PM2.5 guideline of 5 μg/m3.

Dr. Schroeder continued: “It is very exciting to see the fruition of the U.S. federal government’s review and decision to enact a more stringent annual PM2.5 standard. Many nations around the world look to the U.S. EPA when creating or modifying their own federal standards. The reduction of this limit is sure to have a ripple effect as nations around the world review and hopefully reduce their own ambient air quality standards.”

Refining the Air Quality Index: A Vital Update for Public Health

The U.S. EPA uses a tool called the Air Quality Index (AQI) to communicate public health information based on ambient pollutant concentrations. The AQI converts pollutant concentration data into a numerical index value on a scale ranging from 0 to 500. This full scale is broken down into narrower ranges, with each range designated with specific health-related messaging communicating information regarding exposure health risk to the general public.

The designation of “good” is assigned when the AQI spans within the range of 0 to 50, “moderate” is 51 to100, “unhealthy for sensitive groups” is 101 to 150, “unhealthy” is 151 to 200, “very unhealthy” is 201 to 300, and “hazardous” is 301+.

The points on the scale where the health messaging changes to the next category are referred to as breakpoints. The breakpoints are defined by the EPA and based on the scientific evidence correlating pollutant concentration with risk to human health. The lowest breakpoint on the scale, between AQI values of 50 and 51, are typically defined by the primary NAAQS. In accordance with the new federal standard, the U.S. EPA has revised the lowest breakpoint making an AQI of 50, the highest level still achieving a “good” designation, equivalent to a PM2.5 concentration of 9.0 µg/m3, whereas previously it was equivalent to 12.0 µg/m3.

In addition to the updated threshold for “Good” air quality, breakpoints at the upper end of the unhealthy, very unhealthy, and hazardous categories have also been amended. These new AQI breakpoints aim to raise public awareness by providing clearer air quality information, emphasising the health risks of PM2.5. These adjustments to the AQI reflect the latest scientific evidence regarding the concentration-dependent PM2.5 health impacts.

Projected health benefits

Through the bolstered air quality standard, the U.S. EPA reports that by 2032 Americans can expect to see:

• Up to 4,500 premature deaths avoided
• 290,000 lost workdays prevented
• Up to $46 billion in net health benefits
• For every $1 spent, there could be as much as $77 in human health benefits

While it’s hard to think of health benefits in economic terms, reducing hospital visitations, avoiding long-term, debilitating illnesses, and maintaining a healthy and productive lifestyle can reduce health care costs and keep people employed –important considerations for any household’s budget.

According to the U.S. EPA, concentrations of PM2.5 in the United States have decreased 45 percent since 2000. Over the same time, the U.S. Gross Domestic Product (GDP) rose by 52 percent.

Cleaner air could especially benefit vulnerable communities. Lack of access to clean air reduces school test scores, memory, and school performance and worsens already existing conditions like asthma and allergies (6). The revised standard will help address disparities in air quality access while lowering the associated risks of air pollution. Fortunately, the agency projects that 99 percent of U.S. counties will meet the new air quality standard by 2032 due in part to existing efforts to mitigate air pollution on a federal, state, local, and Tribal Nation level.

Conclusion

The new air quality standard is set to go into effect on May 6, 2024. Responsible public policy and innovative technology will converge to in an effort to mitigate air pollution. The new standard offers hope for reducing heart and lung disease by tackling poor air quality sources and communicating those dangers through the revised air quality index. By tackling the pollution challenge at its source, the EPA could safeguard lives.