Air Pollution Lawsuit: EPA Must Set Soot Designations

Soot pollution is one of the most serious air quality threats in the United States. In 2024, the U.S. Environmental Protection Agency (EPA) sought to address this issue by strengthening the National Ambient Air Quality Standard (NAAQS) for fine particulate matter to improve public health.

When the EPA missed a legal deadline to designate areas that fail to meet the updated 2024 standard, a coalition of health, community, and environmental groups, along with a group of over a dozen states, cities, and counties, filed a lawsuit to force agency action. The litigation sought to force the EPA to issue nonattainment designations as required under the Clean Air Act.

This case highlights that when environmental laws are not enforced as intended, it is possible to seek relief in court. If you have a question about environmental litigation involving lawsuits under state or federal environmental laws and regulations, talk to a local environmental litigation attorney. A lawyer can explain your options relating to state and federal environmental regulations and whether you can take legal action.

What Is Soot and Why Is It Dangerous?

PM2.5 is fine particulate matter. Soot is commonly used as shorthand, though not all PM2.5 is soot in the narrowest technical sense. It consists of particles roughly 2.5 microns or smaller in diameter and is invisible to the naked eye. These particles bypass the body’s defenses, enter the lungs and the bloodstream, and affect other organs.

Soot is one of the most dangerous and widespread air pollutants, impacting millions of people. Exposure to soot has been linked to a host of health-related issues, some requiring emergency room visits, including:

• Asthma attacks and other asthma symptoms
• Heart attacks
• Reduced lung function
• Lung cancer
• Premature death

Common sources of soot include combustion-engine vehicle exhaust, power plants, industrial factories, and wildfire smoke. Soot exposure is widespread and can impact both rural and urban areas, and it disproportionately impacts communities of color.

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Clean Air Act Requirements on Soot Pollution

The Clean Air Act sets requirements for the EPA. Among other requirements, the EPA must designate areas that violate the strengthened 2024 soot standard.

Designations help improve air quality in communities with unhealthy levels of soot pollution. These areas typically include populations of color and those with lower incomes.

Under the Clean Air Act, missing certain nondiscretionary statutory deadlines can be challenged in court through a citizen suit seeking to compel agency action.

The EPA’s 2024 NAAQS Update

Under the Clean Air Act, NAAQS are national air quality standards for six common, harmful pollutants, including particulate matter (PM), which can include soot and ground-level ozone, also known as smog.

The EPA is required to set NAAQS for pollutants at levels that protect public health. In 2024, the EPA strengthened the soot standard based on overwhelming scientific evidence.

When the NAAQS are updated, the Clean Air Act sets a deadline for the EPA to designate areas of the country that violate the updated standard as nonattainment areas. Nonattainment designations trigger specific Clean Air Act planning and control requirements for states and regulated sources.

The rule at the center of the lawsuit was the EPA’s 2024 update to the annual PM2.5 standard. This update strengthened the annual PM2.5 standard to protect public health. Finalizing the stronger standards in the rule was the first step. States and the EPA share responsibility for carrying it out.

Legal Challenge: EPA Missed the Deadline for Area Designations Under NAAQS Standards

When the EPA missed the deadline for area designations, a coalition sued under the Clean Air Act. The coalition members included:

• The Alliance of Nurses for Healthy Environments
• The Environmental Defense Fund
• American Lung Association
• American Public Health Association
• American Thoracic Society
• Center for Biological Diversity
• Northeast Ohio Community Resilience Centre
• Rio Grande International Study Center
• Sierra Club

The Clean Air Task Force, Earthjustice, and the Southern Environmental Law Center serve as legal counsel representing many of these organizations.

Plaintiffs also include more than a dozen cities, states, and counties, with state officials like California Attorney General Rob Bonta bringing the cases. Both sets of plaintiffs filed nearly identical lawsuits against the EPA, challenging its failure to make the required nonattainment designations for the strengthened 2024 PM2.5 standard.

Ruling: EPA Must Make Designations Under Strengthened NAAQS

The U.S. District Court for the Northern District of California held that the EPA must move forward with making the required designations under the strengthened 2024 PM2.5 NAAQS.

The court rejected EPA’s arguments for a gradual implementation of the standard and ordered that EPA officially identify the areas that violate the 2024 standard by February 6, 2027.

This court ruling follows a June 2026 decision by the U.S. Court of Appeals for the D.C. Circuit in another case involving the PM2.5 standard, which upheld the 2024 soot standard after the Trump administration’s EPA sought to have it struck down.

Impact of the Air Pollution Lawsuit

Stricter soot standards can lead to several improvements to public health. Stronger standards can result in fewer hospital visits, reduced asthma cases, and lives saved.

When regulatory processes fail, environmental litigation can be a viable tool for protecting both individual health and community well-being.

Contact an Environmental Litigation Attorney

If you need help understanding your legal options under state and federal environmental laws regarding pollution, contact an environmental litigation attorney.