Air Quality Litigation Trends: Beyond Legacy Factories

Key Takeaways:

• Airborne pollution litigation is expanding well beyond legacy factory cases. New frontiers include AI data centers, biomass facilities, and aircraft emissions.
• Ethylene oxide (EtO) remains the most developed toxic-tort area, with recent verdicts and settlements shaping how these cases are litigated across states.
• Reduced federal enforcement does not translate to less litigation. Clean Air Act citizen suits and state-law claims are filling the gap.
• Cases are becoming more data-intensive, and the infrastructure driving the next economy is generating new permitting flashpoints.

Airborne pollution litigation is expanding beyond traditional regulatory enforcement. The Clean Air Act remains the primary federal framework, but residents, advocacy organizations, and state authorities increasingly combine citizen-suit provisions with state-law claims such as nuisance, negligence, and trespass. Improved monitoring, changing risk assessments, and the growth of energy-intensive infrastructure are also raising new questions about permitting, source attribution, and available remedies.

Several trends are converging. Toxic-tort cases involving established chemicals continue alongside transportation class actions, permit challenges involving emerging industries, and citizen enforcement actions. Plaintiffs still face demanding questions of exposure, causation, standing, and class-wide proof. Defendants must account for risk that may persist even when a facility holds a permit or federal policy is changing.

Ethylene Oxide: A Mature but Unsettled Docket

Ethylene oxide, or EtO, remains one of the most developed airborne toxic-tort areas. The chemical is widely used to sterilize medical devices, while long-term exposure has been associated with elevated cancer risk by the Environmental Protection Agency. Residents near sterilization facilities in several states have alleged that years of emissions caused cancer, among other injuries.

Outcomes have varied. A 2022 Illinois trial produced a substantial plaintiffs’ verdict, followed by a $408 million settlement in 2023 resolving hundreds of claims tied to a Willowbrook facility. Other juries have found for defendants. These results show how facility history, emissions modeling, medical evidence, and state law can shape each case. Regulatory uncertainty adds another layer. EPA tightened standards for commercial sterilizers in 2024 but proposed reconsideration in 2026. Private claims and permitting challenges are likely to continue regardless of the rule’s final form.

Data Centers and On-Site Power

Artificial intelligence (AI) data centers are creating a newer air-quality frontier. Their electricity demand may require grid expansion, dedicated generation, or temporary gas turbines. This can prompt disputes over whether supporting generation requires a Clean Air Act permit.

One pending citizen suit alleges that gas-fired turbines used to power an AI data center in Mississippi operated without required permits. The defendants dispute the claims. As data center demand grows, developers can expect closer scrutiny of backup generation, combined emissions and impacts on neighboring communities.

Particulates, Biomass and Community Claims

Particulate litigation is also moving beyond familiar smokestack cases. Residents in Gloster, Mississippi, have sued operators of a wood-pellet facility, alleging releases of particulate matter and other pollutants, visible wood dust, health concerns, and property damage. The defendants dispute that facility emissions caused adverse local health effects and point to emissions-control investments.

The dispute highlights a broader issue for biomass and other projects associated with the energy transition: climate or economic benefits do not eliminate local air-quality obligations. Future cases may test the gap between broad sustainability claims and neighborhood-level emissions, monitoring, and permitting records.

Aircraft Emissions and State-Law Theories

Aircraft-related claims may further widen the field. In a proposed class action involving Seattle-Tacoma International Airport (Sea-Tac), nearby residents allege exposure to several pollutants from aircraft operations. In November 2024, a federal judge allowed state-law negligence, trespass and nuisance theories to proceed against airlines and the port. The ruling did not decide liability or certify a class.

If similar claims advance, courts will need to address source attribution, federal preemption, class boundaries, and whether common evidence can establish exposure and injury. Airports, airlines, and public authorities may also face pressure for more detailed emissions monitoring.

A More Fragmented Enforcement Picture

Federal policy will remain important, but reduced or redirected federal enforcement does not necessarily mean less litigation. States retain permitting and enforcement authority, while Section 304 of the Clean Air Act permits qualifying citizen suits after statutory notice. In 2025, the U.S. Supreme Court declined to review appellate rulings that had preserved broad citizen-enforcement authority under federal environmental statutes.

Looking ahead, airborne pollution cases are likely to become more data-intensive and geographically varied. Lower-cost sensors, emissions inventories, dispersion models, and operating data may sharpen claims while creating new disputes over reliability. Regulatory reversals will generate administrative challenges, and growth tied to AI, logistics, energy, and advanced manufacturing will create new permitting flashpoints.

Air litigation is no longer confined to legacy factories. It increasingly follows the infrastructure and technology shaping the next economy.

This article is part of EisnerAmper's Environmental Series, which explores how environmental litigation is evolving across fire and water.

For organizations navigating the operational and financial impact of environmental litigation, EisnerAmper's Settlement Administration provide the fund administration, damages quantification, and expert-witness support these matters demand. Contact our team to learn more.