Environmental Protection Agency: How Air Pollution Affects the View
Environmental Protection Agency

EPA brochure describing the health and environmental effects of haze.

Environmental Protection Agency: Introduction to Visibility
Environmental Protection Agency

Report by William Malm, National Park Service and Colorodo State Institute for Research on the Atmosphere 

Environmental Protection Agency: Explore the Regional Haze Storymap
Environmental Protection Agency

Visibility is improving, but we can do more to protect America’s magnificent views and scenic vistas from pollution.

Environmental Protection Agency: Regional Haze Program
Environmental Protection Agency

In 1999, the U.S. Environmental Protection Agency announced a major effort to improve air quality in national parks and wilderness areas.

Environmental Protection Agency: Criteria Air Pollutants
Environmental Protection Agency

The Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS) for six common air pollutants (also known as “criteria air pollutants”).

Environmental Protection Agency: Ground-level Ozone Basics
Environmental Protection Agency

Ozone can be “good” or “bad” for health and the environment depending on where it’s found in the atmosphere.

Environmental Protection Agency: Setting and Reviewing Standards to Control Ozone Pollution
Environmental Protection Agency

National Ambient Air Quality Standards (NAAQS) for ground-level ozone, or ozone pollution, specify a maximum allowed measurement for ozone (O3) to be present in outdoor air.

Environmental Protection Agency: Air Quality Designations for Ozone
Environmental Protection Agency

The Clean Air Act requires EPA to designate areas in the United States after the agency sets a new National Ambient Air Quality Standard (NAAQS) or revises an existing standard

Environmental Protection Agency: Particulate Matter (PM) Basics
Environmental Protection Agency

PM stands for particulate matter (also called particle pollution): the term for a mixture of solid particles and liquid droplets found in the air.

Environmental Protection Agency: Setting and Reviewing Standards to Control Particulate Matter (P...
Environmental Protection Agency

National Ambient Air Quality Standards (NAAQS) for PM pollution specify a maximum amount of PM to be present in outdoor air.