US Clean Air Act (CAA) Air Emission Permitting System (NSR/Title V) and the Dual Federal-State Regulatory Risk

Overview

A key permitting system under the U.S. Clean Air Act (CAA) for major facilities and large emission sources. It consists of two layers: New Source Review (NSR — including Prevention of Significant Deterioration (PSD) and Nonattainment Area NSR), which applies to new construction and major modifications, and the operating permit program (Title V), which applies to all major sources. While built on the federal EPA's National Ambient Air Quality Standards (NAAQS) and Hazardous Air Pollutant (HAP) standards (MACT), state governments (e.g., California's CARB, Texas's TCEQ) often impose their own stricter add-on requirements and permitting procedures, forcing operators to navigate an extremely complex, overlapping compliance burden at both the federal and state levels.

Enforcement Timeline

- 1970: Clean Air Act (CAA) enacted (establishing NAAQS)

- 1977: CAA amendments create the NSR permitting system

- 1990: Major CAA amendments introduce the Title V federal operating permit program and MACT standards

- Ongoing: EPA periodically revises NAAQS thresholds (e.g., the 2024 tightening of PM2.5 standards) and states revise their State Implementation Plans (SIPs)

Related Regulations / Topics

U.S. Clean Air Act (CAA) New Source Review (NSR) Reform: The 2026 "Construction" Definition Amendment NPRM and Modification Practices

The Clean Air Act's New Source Review (NSR) program requires the advance installation of state-of-the-art pollution control equipment (BACT/LAER) for new construction or major modifications at factories and power plants. In July 2026, EPA under the Trump administration published a Notice of Proposed Rulemaking (NPRM) to revise the definitions of "construction" and "major modification" under the NSR regulations. The proposal raises the threshold at which equipment upgrades or efficiency improvement work at existing plants are determined to constitute a "modification" requiring advance NSR permitting, introducing industry-favorable determination criteria (including revised emissions increase calculation methods) that allow companies to begin equipment maintenance and modernization work without going through lengthy prior permitting procedures.

Business Impact

Companies building new or expanded facilities in the United States (semiconductor, automotive, chemical, electronics, etc.) must obtain NSR/PSD permits before construction begins, with lead times ranging from several months to several years. Because standards, review timelines, and technology requirements (BACT/LAER) vary significantly by state, compliant design and data collection that reflect both state environmental agency and federal EPA requirements are essential from the site-selection stage onward.