Title 42 › CHAPTER 85 — AIR POLLUTION PREVENTION AND CONTROL › SUBCHAPTER I — PROGRAMS AND ACTIVITIES › Part C — Prevention of Significant Deterioration of Air Quality › subpart ii — visibility protection › § 7491
Protect and restore clear views in certain national parks and other special federal lands by cutting human-made air pollution. Within six months after August 7, 1977, the Secretary of the Interior had to check all mandatory class I federal areas and mark those where clear visibility is an important value. Within one year after that date, the Administrator had to publish a list of those areas. Within 18 months the Administrator had to study and report to Congress how to measure, model, prevent, and fix visibility problems and identify the kinds of pollution sources that cause them. Within 24 months the Administrator had to write rules so States make reasonable progress toward the national visibility goal. State plans must set emission limits, timetables, and a 10–15 year strategy. Major stationary sources that existed on August 7, 1977, and that were less than 15 years old then must, unless exempted, install and run the best available retrofit pollution-control technology as soon as practicable (but no later than five years after plan approval). The Administrator can exempt a major source if it won’t significantly harm visibility, but not large power plants (750 megawatts or more) unless the owner proves they are far enough away. Any exemption also needs the agreement of the federal land manager. Key terms (one line each): manmade air pollution — pollution caused by human activities; mandatory class I Federal areas — special federal lands protected for visibility; visibility impairment — reduced view distance or color changes in the air; reasonable progress — progress judged with costs, time, energy and other impacts, and the source’s remaining life in mind; best available retrofit technology — the most effective pollution controls for an existing source, judged with costs and other impacts in mind; as expeditiously as practicable — as quickly as possible but no later than five years after plan approval; major stationary source — a list of large industrial sources that can emit 250 tons or more of a pollutant (examples include big power plants, refineries, cement plants, and many others).
Full Legal Text
The Public Health and Welfare, Source: USLM XML via OLRC
Legislative History
Reference
Citation
42 U.S.C. § 7491
Title 42, The Public Health and Welfare
Last Updated
Sep 22, 2026
Release point: 119-110