Colorado’s Persistent Ozone Problem

By: Ken Fowler

Colorado has a looming problem. A problem visible most days in the form of a giant smog cloud that hugs the skyline of the Front Range. This smog cloud, caused mostly by emissions from the burning of fossil fuels, is an ozone cloud.

Ozone is an important component of the Earth’s atmosphere that helps protect the Earth’s surface from the Sun’s radiation. Ozone on the ground, however, created when pollutants from the burning of fossil fuels are exposed to sunlight, is a serious health threat. Ozone exposure is connected to a wide range of human health impacts including respiratory and cardiovascular problems, premature mortality, and central nervous system and developmental impacts. The Front Range of Colorado has consistently ranked as one of the most polluted areas in the country for ozone.

The State of Colorado has a legal obligation under the Clean Air Act to reduce ozone pollution and ensure that ozone pollution remains within safe levels for public health. Colorado has failed to meet these obligations for over fifteen years. This has resulted in the Front Range area being recently designated as in Severe nonattainment of the federally set ozone standards.

Under the Clean Air Act, the Environmental Protection Agency (EPA) must set standards for air pollutants within the US. EPA must also designate areas within the country, and each area must attain the specific air pollution requirements. States that hold areas that have not attained a federal air quality standard are required to submit plans to EPA about what steps they will take to bring their area into attainment. EPA is obligated to approve, conditionally approve, disprove, or conditionally disprove state plans based on their likelihood of being able to achieve the federal pollution standards within the statutorily mandated deadline. EPA will then take stock of areas progress every few years to determine if an area has moved towards attainment or farther away. Ozone pollution areas are designated as in Marginal, Moderate, Serious, Severe, or Extreme nonattainment.

For the 2008 ozone federal standards (that were promulgated in 2008) the Front Range was in Serious nonattainment. Colorado submitted a plan of how they were going to bring the Front Range area into attainment far after the deadline. While this late plan was at EPA awaiting approval, the Front Range area was reclassified as in Severe nonattainment of ozone federal pollution standards. This showed that the Serious ozone plan had failed because the plan had already been implemented at a state level while awaiting approval by the EPA and had led to a worse nonattainment classification. Despite this, EPA proposed to approve parts of Colorado’s failed plan. Several nonprofit groups commented on the proposed approval pointing to EPA’s obligation to ensure all areas of the country reach attainment of pollution standards to oppose the proposed approval. Commenters also pointed out that if a state fails to meet its obligations to bring an area into attainment, EPA has an obligation to step in and create a federal plan to bring the area into attainment.

Despite these comments EPA published a final rule approving parts of Colorado’s failed ozone plan on May 9th, 2023. EPA’s approval of Colorado’s failed ozone plan was immediately challenged by nonprofits, the Center for Biological Diversity and 350 Colorado. EPA’s approval of Colorado’s failed plan is now at the 10th Circuit Court of Appeals. If EPA’s approval is vacated that could mean Colorado would have to construct a new plan to bring the Front Range area into attainment. It could also mean that EPA must step in to create a federal plan for the Front Range to bring it into attainment with federal ozone standards. If EPA’s approval is affirmed, Colorado remains obligated to bring the Front Range into attainment with ozone federal standards, a goal that they have consistently drifted farther away from reaching, given that the Front Range is now in Severe nonattainment under the 2008 ozone federal standards.

Whatever the 10th Circuit Court of Appeals outcome, Colorado has a persistent ozone pollution problem that needs to be addressed on a scale larger than one state ozone plan. Coloradans deserve to breathe clean, safe air – a basic public health protection Colorado has struggled to provide for its residents. EPA and Colorado must fulfill their obligations to ensure clean air under the Clean Air Act. The health of millions of Front Range residents relies on it.