Press Release Feb 7, 2024

Parks, outdoor groups celebrate strengthened air pollution standards as a win for people and parks

"These stronger standards will provide additional clean air protection for national parks, from Sequoia and Kings Canyon in California to Gateway Arch and Mammoth Cave National Parks in Missouri and Kentucky." —Ulla Reeves, Interim Director of NPCA's Clean Air Program

On February 7, 2024, the Environmental Protection Agency announced an updated primary national air quality standard under the Clean Air Act which provides protections for sensitive populations against fine particulate matter, an air pollutant known to harm human health and obscure scenic views across national parks. While the updated standard serves as a win for public health, EPA failed to update secondary standards, missing an opportunity to extend protections beyond human health to park visibility, animals and crops. Still, the strengthened primary annual standard serves as a big step in recognizing the harmful effects of PM2.5 and acknowledges years of efforts from the National Parks Conservation Association and the Appalachian Mountain Club.

NPCA and AMC have steadfastly advocated for ecosystems and national park health in EPA’s consideration of stronger standards to protect scenic views, sensitive ecosystems and nature. In addition, the two groups shared concerns with the Office of Management and Budget as they reviewed the final rule. Lastly, they supported allied organizations in calling for the primary standards to be strengthened to align with scientific findings about the levels necessary to fully protect people’s health from particulate matter pollution.

Statement from Ulla Reeves, Interim Director of NPCA’s Clean Air Program:

“We are pleased that EPA finalized a rule that strengthens critical aspects of the standard to protect people’s health from fine particulate pollution. While we hope more can be done in the future, these stronger standards will provide additional clean air protection for national parks, from Sequoia and Kings Canyon in California to Gateway Arch and Mammoth Cave National Parks in Missouri and Kentucky. These places and many others suffer from excessively hazy skies.

“People who travel thousands of miles to behold these national treasures should not bear risks to their health resulting from air pollution. We look forward to working with EPA to ensure this rule benefits parks and people far and wide, so that all can enjoy stunning vistas, clean air and cultural resources for generations to come.”

Statement from Georgia Murray, Staff Scientist, Appalachian Mountain Club:

“This important rule will allow us to enjoy cleaner air in the outdoors. The Clean Air Act continues to be an important and effective tool for protecting our health and environment from air pollutants, and EPA has appropriately advanced a strong fine particulate health standard. For people and for the planet, it is essential that EPA strengthen fine particulate national standards to align with the latest science and protect both public health and natural resources.”

The EPA strengthened the annual standard from 12 to 9 micrograms per cubic meter for PM2.5, fine inhalable particles 2.5 micrometers and smaller, which are primarily emitted from power plants, industrial facilities and automobiles. Long-term exposure to particulate matter is associated with respiratory issues, bronchitis and even premature death. Particulate matter is the main component of haze pollution, which has devastating consequences on visibility and people’s health and that of park ecosystems, including plants and wildlife. Particulate matter is composed of many different compounds that are independently harmful to soil, wildlife, aquatic ecosystems and plants. In addition, PM2.5 can bioaccumulate through the food chain and deposition can alter soil and plant chemistry while affecting plants’ ability to metabolize and photosynthesize correctly. Secondary particulate matter is also a significant component of acid rain.


About National Parks Conservation Association: Since 1919, the nonpartisan National Parks Conservation Association has been the leading voice in safeguarding our national parks. NPCA and its more than 1.6 million members and supporters work together to protect and preserve our nation’s most iconic and inspirational places for future generations. For more information, visit

About Appalachian Mountain Club: The Appalachian Mountain Club (AMC) is a 501 ©(3) non-profit organization dedicated to fostering the protection, enjoyment, and understanding of the outdoors. Since 1876 we have been working to protect the mountains, forests, waters, and trails you love in the Northeast and Mid-Atlantic regions. We envision a world where our natural resources are healthy, loved, and always protected, and where the outdoors occupies a place of central importance in every person’s life. We encourage you to experience, learn more, and appreciate the outdoors knowing that your participation supports the conservation and stewardship of the natural world around you. Learn more at

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