Press Release Oct 28, 2021

Organizations Welcome EPA’s Plans to Reconsider Ozone Standards

Stronger standards are long overdue to protect nature from dangerous ozone pollution

Washington, DC – The Environmental Protection Agency (EPA) today announced it will reconsider air quality standards for ground-level ozone pollution, revisiting a December 2020 ruling by the Trump administration that retained inadequate standards that failed to protect the environment.

While ozone is good as a protective layer in the stratosphere, ground-level ozone causes asthma attacks and other respiratory problems. It is linked to premature deaths, damages plants and forests, and stunts tree and crop growth. Formed by emissions from cars, trucks, oil and gas development, coal plants and other industrial facilities, ozone is also a greenhouse gas, and curtailing it is a powerful way to help solve the climate crisis.

“The science has long been clear that existing ozone safeguards are not enough to properly protect places like national parks which are home to an incredible biodiversity of plants, wildlife and unique ecosystems,” said Ulla Reeves, Senior Advocacy Manager in the Clean Air Program at the National Parks Conservation Association (NPCA). “Improving these standards will not only help protect parks and other delicate wild ecosystems but will improve air quality for all people, particularly people disproportionately affected, and reduce dangerous emissions that harm our climate.”

There are two types of ozone standards in the National Ambient Air Quality Standards (NAAQS). Primary standards which focus on protecting human health, and secondary standards which focus on protecting nature. Currently both standards are set at 70 ppb (parts per billion) over an eight-hour period. Keeping the secondary standard at the same level as the human health standard imperils biodiversity as science shows that stronger and more distinct standards are necessary to effectively protect nature because of how ozone uniquely harms plants, wildlife and ecosystems.

Georgia Murray, Staff Scientist, Appalachian Mountain Club:

“We welcome an update that follows the science-based evidence and issues stronger national health and ecological ozone standards. Tropospheric ozone continues to pollute outdoor spaces which should instead be healthy and provide safe time together for all. The science clearly shows that a stronger limit is needed to protect public health and also supports separate standards to protect plants and the environment. The negative impacts of ozone to plants and ecosystems are numerous and often insidious including plant leaf damage, altered nutrient and water cycling, disruption of plant-insect interactions, and reduced carbon storage in forests. We urge the Biden Administration to not delay in strengthening the ozone standards to protect our health and the natural environment.”

William C. Janeway, Executive Director, Adirondack Council:

“Ground-level ozone pollution has been harming white pine needles and black cherry leaves and a wide array of other trees and farm crops in New York’s Adirondack Park for decades. Ozone makes it hard for hikers, climbers and park residents to breathe. As it settles to the ground, ozone further acidifies soils and waters already polluted by acid rain. The future of the largest park in the contiguous United States depends on better air-quality. The 9,300-square-mile Adirondack Park is roughly half public forest preserve, protected forever under the state’s constitution; and half is private forest, farms, resorts, businesses, homes and 130 rural communities. The park is home to 11,000 lakes and ponds and 30,000 miles of rivers, brooks and streams. After suffering the worst acid rain damage in the nation, this national treasure is slowly showing signs of recovery, due to improvements in clean air standards since 1990. Deeper reductions in ozone pollution are needed to allow hundreds of damaged lakes, millions of acres of forest and countless brook trout fisheries to regain some portion of their prior vitality. We’re on the right track. We need to keep going.”

Matthew Davis, Senior Director of Government Affairs, League of Conservation Voters:

“Clean air is a basic necessity for healthy and well-functioning ecosystems and food systems. The EPA’s decision to reconsider ozone secondary standards is a key step toward ensuring clean and safe air for the plants and wildlife that depend on it. Existing standards are woefully inadequate and perpetuate harm toward our precious and vulnerable public lands, crops, and buildings. The EPA must work quickly to create stronger, more protective ozone standards in order to fulfill the Biden administration’s commitment to safeguarding all of our communities, protecting public lands, and addressing climate change.”

NPCA and 13 health and environmental groups, half of them represented by Earthjustice, challenged the current ozone standards in a February 2021 lawsuit in response to the EPA and Trump administration’s refusal to strengthen the NAAQS for ozone in 2020.

According to the National Park Service, there have been 250 ozone exceedance days in 24 national parks and national monuments across the country so far this year – almost 70% more than at this point last year. In Sequoia and Kings Canyon National Park in Northern California alone there were 68 high ozone days between April and August, with almost every day in July and August having dangerous ozone levels.

Previously, in August of 2019, the U.S. Court of Appeals for the District of Columbia Circuit said that the current national ambient air quality standards for ozone are too weak to protect nature and the environment. The Environmental Protection Agency should have set standards that actually protect ecosystems in 2020 as the Clean Air Act requires.

The EPA’s announcement today comes in response to a court order for the agency to swiftly decide its intentions for reconsideration. According to a recent report by the American Lung Association, more than 134 million people live in counties that have dangerous levels of ozone – many of which are disproportionately low-income communities and communities of color.

In 2018, NPCA found that more than 95 of America’s national parks are failing to meet federal limits for ozone pollution.


About the 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 nearly 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

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