The Clean Air Scientific Advisory Committee (CASAC) published its assessment of ground-level ozone standards Friday and virtually unanimously urged the U.S. Environmental Protection Agency (EPA) to strengthen fundamental protections against ground-level ozone pollution, also known as smog. CASAC is the EPA’s key panel of outside expert science advisors on air quality, and its scientific advice is vitally important to the National Ambient Air Quality Standarads (NAAQS) review process.

Eighteen independent experts on CASAC reviewed the existing ozone NAAQS, and all, except one, “concluded that the scientific evidence unequivocally demonstrates that the current primary and secondary standards are not protective of public health and public welfare.” Based on the scientific evidence, those members recommended that the EPA revise the health-protective ozone NAAQS to fall within the range of 55 to 60 parts per billion rather than the current standard of 70 parts per billion. By the same 17 to 1 margin, they recommended that the EPA finally adopt a strong separate secondary ozone standard to protect trees, crops, and entire ecosystems.

“EPA must listen to its board of expert, independent scientists and commit to protecting public health and the environment,” said Earthjustice Attorney Marvin C. Brown. “The scientific evidence is clear: EPA must immediately strengthen smog standards to protect public health and the environment. We urge EPA to move its reconsideration process expeditiously forward with final action consistent with CASAC’s strong recommendation by spring 2024. More delay in this rulemaking will further expose our most vulnerable populations to deadly ground-level ozone.”

The current ozone NAAQS were set in 2015. They were hastily reviewed and retained in a December 2020 decision that sparked significant criticism.

Ground-level ozone is a highly toxic air pollutant created by sunlight mixing with emissions released by cars, power plants, industrial facilities, and oil and gas processes. It is the principal component of smog and is one of the most dangerous and persistent forms of air pollution in the United States. Babies and children, older people, individuals with lung diseases, and people who work outdoors are most at risk of suffering the health consequences of exposure to ozone pollution. These consequences include asthma attacks that can cause adults to miss work and children to miss school and compel people to seek medical treatment. Ozone also likely causes people to die. Children, who are more likely to have asthma than adults, often play outside the most when ozone levels are dangerously high. Smog also impairs the growth of many plants and trees and harms entire ecosystems.