Interstate Transport Rule

Interstate Transport Rule
Name	Interstate Transport Rule
Othernames	Clean Air Interstate Rule (replacement), Cross-State Air Pollution Rule (related)
Enacted	2005–2011
Agency	Environmental Protection Agency
Scope	United States
Subject	Air pollution regulation; sulfur dioxide; nitrogen oxides; ozone; fine particulate matter

Interstate Transport Rule The Interstate Transport Rule addressed cross-border air pollution in the United States by allocating responsibility for emissions that contribute to downwind nonattainment of Clean Air Act National Ambient Air Quality Standards. It connected upwind stationary sources in states such as Texas, Ohio, and Pennsylvania with downwind air quality problems in states like New York, North Carolina, and Illinois. The rule drew on precedents from notable cases and statutes including Massachusetts v. EPA, the Clean Air Interstate Rule (CAIR), and decisions by the United States Court of Appeals for the D.C. Circuit and the United States Supreme Court.

Background and Legal Authority

The Interstate Transport Rule emerged from the interstate pollution provisions of the Clean Air Act—specifically the "good neighbor" provision set by Congress and interpreted by courts in cases involving Sierra Club and state petitioners. The Environmental Protection Agency used modeling approaches similar to those in Clean Air Interstate Rule and technical frameworks influenced by work at the National Oceanic and Atmospheric Administration and the Environmental Protection Agency's Office of Air Quality Planning and Standards. Litigation surrounding interstate transport involved the D.C. Circuit Court of Appeals and litigants such as Alabama Power Company and nonprofit groups like Natural Resources Defense Council. The legal authority relied on statutory sections administered by the EPA Administrator and prior remands from the United States Court of Appeals for the District of Columbia Circuit.

Rule Provisions and Implementation

Provisions allocated emission reduction obligations for sulfur dioxide (SO2) and nitrogen oxides (NOx) to upwind states whose emissions were projected to significantly contribute to downwind nonattainment of National Ambient Air Quality Standards for ozone and fine particulate matter (PM2.5). The EPA employed regional photochemical grid modeling developed by teams at EPA Office of Research and Development and state agencies such as Texas Commission on Environmental Quality and California Air Resources Board analysts. Implementation included state implementation plan (SIP) revisions, emissions trading provisions similar to those in the Acid Rain Program, and coordination with regional planning organizations like the Midwest Ozone Group and the Northeast States for Coordinated Air Use Management. Compliance timelines mirrored NAAQS attainment deadlines overseen by the EPA Administrator and state air agencies.

Affected States and Sources

The rule identified upwind contributors across multiple states in the Midwest, Southeast, and Intermountain West, including large point sources such as coal-fired power plants owned by utilities like Duke Energy, American Electric Power, and FirstEnergy. Downwind states affected included northeastern jurisdictions such as Connecticut, Massachusetts, and New Jersey and mid-Atlantic states like Virginia and Maryland. Mobile and area sources addressed under related programs involved coordination with agencies such as California Air Resources Board for best practices, while interstate coordination leveraged regional bodies including the Regional Greenhouse Gas Initiative and the Power Sector Modeling Consortium.

Litigation and Regulatory Challenges

The Interstate Transport Rule faced multiple challenges in federal courts, with appeals to the United States Court of Appeals for the D.C. Circuit and petitions for review by states, utilities, and environmental groups including American Lung Association and Sierra Club. Key legal issues included the EPA's reliance on modeling, the allocation of state-level obligations, and the scope of jurisdiction under the Clean Air Act as interpreted in precedents such as Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc. and Massachusetts v. EPA. The rule prompted stays and remands; consequential litigation produced successor actions and regulatory adjustments overseen by successive EPA Administrators and litigated by state attorneys general from jurisdictions such as Texas Attorney General and New York Attorney General offices.

Environmental and Health Impacts

By targeting SO2 and NOx reductions, the rule aimed to reduce formation of secondary pollutants including sulfate and nitrate aerosols that contribute to PM2.5 and ozone formation, with expected benefits for respiratory and cardiovascular health documented in studies from institutions like Centers for Disease Control and Prevention, National Institutes of Health, and research published by scholars associated with Harvard School of Public Health. Public health outcomes projected included decreases in hospital admissions, premature mortality, and exacerbation of asthma in urban areas such as Chicago, Philadelphia, and Los Angeles (as a reference region for ozone science). Environmental benefits included improved visibility in protected areas managed by National Park Service units like Great Smoky Mountains National Park and reduced acid deposition impacting watersheds studied by the United States Geological Survey.

Amendments, Replacements, and Current Status

Following litigation, the Interstate Transport Rule was modified, supplemented, or replaced by subsequent regulatory frameworks including the Cross-State Air Pollution Rule and adjustments under different EPA Administrations. Regulatory evolution incorporated enhanced modeling, revised contribution thresholds, and integrations with market approaches such as emissions trading programs modeled after the Acid Rain Program cap-and-trade system. Ongoing policy debates continue in forums including Congress, state legislatures, and federal courts, with enforcement and implementation monitored by agencies such as the Environmental Protection Agency and litigated by parties including state attorneys general, utilities like Exelon Corporation, and environmental organizations such as Natural Resources Defense Council.

Category:Air pollution control in the United States