Regional Haze

This page last reviewed March 22, 2018

California Regional Haze Plan 2014 Progress Report approved by U.S. EPA

California Class 1 Areas Particulate pollution, including sulfates, nitrates, organics, soot, fine soil dust, and coarse particles, contributes to the regional haze that impairs visibility, in addition to affecting public health. California's efforts to achieve State and federal air quality standards for health benefits will also improve visibility.

The Federal Clean Air Act of 1977 declared a national goal to remedy existing visibility impairment and  prevent future haze caused by man-made air pollution at selected national parks and wilderness areas of the United States, known as Class 1 Areas. California has 29 mandatory Class 1 Areas managed by either the National Parks Service or the U.S. Forest Service.

In 1999, the U.S. Environmental Protection Agency (U.S. EPA) promulgated a regional haze regulation that calls for states to establish goals and emission reduction strategies to make initial improvements in visibility at their respective Class 1 Areas. In 2009, ARB prepared a Regional Haze Plan (RH Plan) for California demonstrating reasonable progress in reducing haze by 2018, the first benchmark year on the path to improved visibility.

U.S. EPA funded five Regional Planning Organizations throughout the country to coordinate regional haze rule-related activities between states in each region. California belongs to the Western Regional Air Partnership (WRAP), the consensus organization of western states, tribes, and federal agencies, which oversees analyses of monitoring data and preparation of technical reports regarding regional haze in the western United States.
Detailed information about California’s Class 1 Areas, analysis of data collected, specific RH Plan tasks, technical reports, and public meetings can be found at the links below.
Listserve sign-up: Go to the Regional Haze Listserve page to learn more about receiving information when changes are made to this website.


2014 Progress Report

Cover of 2014 Progress Report
The U.S. EPA approved the California Regional Haze Plan 2014 Progress Report, effective May 1, 2015.  A copy of the final rule is available below:

The 2014 Progress Report assessed visibility improvements since 2004 and demonstrated California is on course to meet visibility goals for 2018.  The 2014 Progress Report and associated documents, including  the transmittal letter to U.S. EPA, can be found at the links below:

Regional Haze Plan

Cover of Regional Haze Plan


The U.S. EPA approved the California Regional Haze Plan in the Federal Register on June 14, 2011. A copy of the final notice is available below: On January 22, 2009, ARB approved the California Regional Haze Plan.  The RH Plan documents, the letter submitting the plan to U.S. EPA, and the resolution adopting the Plan, are found at the links below:

BART Requirement
(Best Available Retrofit Technology)
Industrial facilities in certain Standard Industrial Classification (SIC) code categories, which have major sources of haze pollutants from emissions units that were approved, constructed, or brought on line between August 9, 1962 and August 9, 1977, may be required to retrofit those emissions units to reduce haze pollutants. The report Identification of BART-Eligible Sources in the WRAP Region describes this requirement and Appendix H lists the facilities in California that were initially evaluated. However, many older sources preliminarily listed for California have already been retrofit to BART level. The final results of the BART determination are listed in the Final RH Plan.

IMPROVE Monitoring Network
(Interagency Monitoring of Protected Visual Environments)
There are 17 specialized monitors in or near California’s Class 1 areas that measure levels of haze pollutants. The Visibility Information Exchange Web System (VIEWS) webpage stores all of the data nationwide, as well as that from California sites. To view data formatted for analysis for the West, go to the WRAP's Technical Support System (TSS).


Public Workshop

On December 15, 2008, ARB held a webcast workshop in Sacramento. The agenda and presentation materials are available below for downloading.

Status Report on Regional Haze Regulations 

The Air Resources Board conducted a public meeting on June 22, 2000, at its Sacramento offices to present information on federal regional haze requirements and how they will affect California.

Western States Public Workshops on Regional Haze Framework 

In order to get the widest possible input from the affected public, the WRAP held a series of workshops throughout the West. The purpose of the workshops was to seek public comment on proposed alternatives for reducing sulfur oxides (SOx) emissions over the next 18 years, including the use of emissions trading as a backstop option. California is not participating in this program, the SO2 Annex, which applies primarily to coal-burning power plants and industries in some of the other western states. The Annex is a regional sulfur dioxide trading market for stationary sources in lieu of Best Available Retrofit Technology (BART).