California Air Resources Board

With amendments to the Federal Clean Air Act in 1977, Congress declared a national goal to remedy visibility impairment at selected national parks and wilderness areas of the United States, known as Class 1 Areas. California has 29 Class 1 Areas managed by either the National Parks Service or the U.S. Forest Service.

In 1999, U.S. Environmental Protection Agency (U.S. EPA) promulgated the Regional Haze Rule. The Regional Haze Rule established requirements for states to develop State Implementation Plans (SIP) for regional haze. These SIPs are required to include long-term strategies and interim goals to demonstrate progress towards reducing visibility impairment in Class 1 areas affected by human-caused emissions of air pollution. 

Five Regional Planning Organizations (RPO) assist in the coordination of regional haze-related activities. The RPO that California belongs to is called the Western Regional Air Partnership (WRAP). WRAP oversees analyses of monitoring data and preparation of technical tools for regional haze planning efforts in the western states. 

2025 Regional Haze Progress Report for the Second Implementation Period

On December 26, 2024, CARB published a draft of the Regional Haze Progress Report for the Second Implementation Period for 30-day public review. CARB received no public comments on the draft. CARB subsequently submitted the final report to U.S. EPA on January 29, 2025. This document serves as a progress report for the second regional haze planning period, which covers the period from 2018 to 2028, and is intended to fulfill Regional Haze Rule requirements.

• CARB submittal letter to U.S. EPA (January 29, 2025)
• Regional Haze Progress Report for the Second Implementation Period (December 26, 2024)

Second Regional Haze Plan

California's second Regional Haze Plan describes progress made in California's Class 1 areas towards the national goal and details the long-term strategy to meet interim visibility goals set for 2028. The Board adopted California's second Regional Haze Plan at a public meeting held on June 23-24, 2022; it was submitted to U.S. EPA on August 9, 2022.

• CARB transmittal letter to U.S. EPA
• Resolution 22-11 adopting the Plan
• Public Hearing Transcript for June 24,2022
• CARB Public Meeting Notice
• California's Second Regional Haze Plan
• Appendices to California's Second Regional Haze Plan
• Responses to public comments received on draft Plan

California's second regional haze progress report was embedded in the Regional Haze Plan submitted to U.S. EPA on August 9, 2022. A technical supplement to the progress report was submitted to U.S. EPA on August 23, 2023. 

• Progress Report Supplement transmittal letter to U.S. EPA
• Progress Report Supplement

Prior to releasing the draft Regional Haze Plan for public review, CARB provided federal land managers with the opportunity to review the plan. Comments provided by the federal land managers are included in Appendix I. Along with a comment letter, staff from the National Park Service (NPS) provided two data calculation files. These data files are available below for download.

• NPS data file 1
• NPS data file 2

NPS staff suggested that CARB make available device level emissions data for certain stationary sources considered. For reference, a data file with device level emissions data for stationary sources brought forward to the third screening step (discussed in Appendix G) is available below for download.  

• Stationary source emissions data file

As part of the Regional Haze Plan development process, CARB has hosted two public workshops. 

First Workshop

The first workshop was held on September 17, 2020. The agenda and presentation materials from this workshop are available below for download. 

• Public Workshop Notice
• Agenda
• Presentation

Second Workshop

A second workshop was held on March 4, 2022. The workshop notice, workshop materials, and staff presentation are available below for download. A recording of the workshop is available through the link below. 

• Public Workshop Notice
• Workshop Materials 
• Staff Presentation
• Workshop Recording

2014 Progress Report

The 2014 Progress Report assessed visibility improvements since 2004 and demonstrated California is on course to meet visibility goals for 2018.

U.S. EPA approved the 2014 Progress Report, effective May 1, 2015.  

• Final Rule (80 FR 17327, April 1, 2015)

After Board approval of the 2014 Progress Report at a public hearing on May 22, 2014, it was submitted to U.S. EPA on June 16, 2014.

• California Regional Haze Plan 2014 Progress Report

First Regional Haze Plan

California's first Regional Haze Plan demonstrated reasonable progress in reducing haze by 2018, the first benchmark year on the path to improved visibility.

U.S. EPA approved California's Regional Haze Plan in the Federal Register on June 14, 2011.

• Final Rule (76 FR 34608, June 14, 2011)

The Board approved California's Regional Haze Plan at a public hearing on January 22, 2009; it was submitted to U.S. EPA on March 16, 2009.

• CARB transmittal letter to U.S. EPA 
• Resolution 09-4 adopting the Plan
• CARB Public Hearing Notice
• Final California Regional Haze Plan

Workshop

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

• Public Workshop Notice 
• Agenda 
• Handout - California Class 1 Areas 
• Staff Presentation

Parameters Used for AB2588 Diesel Engine Screening Risk Tables

Use these steps when calculating a screening health risk assessment score for a facility with stationary diesel engines.
 

Example Calculation:

Step 1:
Engine size = 180 hp (maximum rated horsepower)
Emission factor = 0.40 g/bhp-hr (certified emission rate at maximum load - assume 1.0g/bhp-hr if unknown)
Annual hours of operation = 29 h (includes all operating hours, including maintenance and testing, except actual emergency hours)
Distance to nearest receptor = 53 m (measured from the engine to the nearest residential or commercial receptor)

Step 2: The 180 hp engine is closest in size to the 200 hp engine, so we will use the 200 hp table for this example.

Step 3: Click on the 200 hp table and find the matrix that is closest to 0.40 g/bhp-hr.

Step 4: Identify the row that corresponds to 30 hours (closest to 29 hours) and read across until you find the risk value that is directly under 50 meters (closest to 53 meters). 

Step 5: Repeat as necessary and sum the results to get the total facility risk.

Step 6: Submit results of screening risk calculation to the local air district upon request.

Because some receptors may be located closer to the engine than the point of maximum impact (the PMI or area of highest risk), we have created tables that retain the higher risk numbers for distances closer than the PMI in order to ensure that these screening tables are still health conservative.

Back to Screening Risk Spreadsheets

Assembly Bill (AB) 2588 (Connelly), the Air Toxics "Hot Spots" Information and Assessment Act, requires air pollution control and air quality management districts (districts) to prioritize facilities to determine which facilities must perform a health risk assessment. These facilities, for purposes of risk assessment, are ranked into high, intermediate, and low priority categories. Each district is responsible for establishing the prioritization score threshold at which facilities are required to prepare a health risk assessment. In establishing priorities, the districts are to consider the potency, toxicity, quantity, and volume of hazardous materials released from the facility, the proximity of the facility to potential receptors, and any other factors that the district determines may indicate that the facility may pose a significant risk.

In order to assist the districts with this requirement, the California Air Pollution Control Officers Association (CAPCOA) Toxics Committee, in cooperation with the Office of Environmental Health Hazard Assessment (OEHHA) and the California Air Resources Board (CARB), developed the Air Toxics "Hot Spots" Program, Facility Prioritization Guidelines (July 1990). The purpose of the guideline is to provide districts with suggested procedures for prioritizing facilities. However, districts may develop and use prioritization methods which differ from the CAPCOA guidelines. In 2016, CAPCOA updated these guidelines to incorporate the changes made to the OEHHA risk assessment methodology. The most up-to-date guidelines can be viewed on CAPCOA's Facility Prioritization Guidelines page. In addition, a copy of the document can also be found below:

August 2016 "Hot Spots" Program Facility Prioritization Guidelines

Overview

The purpose of the Fee Regulation is to recover State costs of implementing and administering the Air Toxics "Hot Spots" Program. The fees assessed through this regulation fund various CARB, OEHHA and district activities. The fees are used to support State and local activities to develop air toxics emission inventory guidelines, provide emission inventory technical assistance, develop and maintain a statewide air toxics emission inventory database, review and approve air toxics emission inventories, prioritize facilities for health risk assessment purposes, develop health risk assessment guidelines, review and approve health risk assessments, implement public notification requirements for facilities whose emissions present a significant health risk, and implement risk reduction requirements and risk reduction guidance to facilities.

Annual Status Reports

The Annual Status Report on State Fees and a list of fees for each facility are shown below.

Future Fee Regulations

The "Hot Spots" Fee Regulation has been streamlined for future fiscal years. The fee amounts for each risk level will remain the same, but the annual process to approve those fees has been altered. Instead of a new Fee Regulation every year, CARB will use the formula that has been used in previous years to calculate fees for facilities in the "Hot Spots" Program. If the State Facility Fee Rates that allow CARB to calculate fees must be changed, a formal Fee Regulation must then be adopted by CARB and approved by the Office of Administrative Law. That means any changes to fee rates would have to go through the regular public comment period with a notice sent to all interested parties and stakeholders.

Fee Regulation for Fiscal Year 2001-2002 Approved by OAL June 10, 2002

The fee rates in the FY 01-02 Fee Regulation are currently being applied to facilities subject to AB 2588 State fees. For the years between 2001 and 2013, the average State fee for a fee-paying facility was between $35 and $200 per year.

At the October 25, 2001, Board hearing, the Board approved CARB staff's proposal for amending the Air Toxics "Hot Spots" Fee Regulation for fiscal year 2001-2002. Revisions were made to include updated facility data submitted by the local air districts. These modifications were made available on November 30, 2001, in a published document and were available on this site for a 15-day public comment period. CARB received no written comments during the 15-day comment period. The final package was filed with the Office of Administrative Law (OAL) on April 26, 2002.

The Staff Report for the amendments to the Fee Regulation, available since September 7, 2001, contained the proposed amendments to the Fee Regulation and the justification for those amendments, the revised regulatory language, and the results of an economic impact analysis of the proposed amendments.

For more information on Fee Regulation for fiscal year 2001-2002, visit Rulemaking.

Criteria

Health &Safety Code (H&SC) 39607(e) requires CARB to establish and periodically review criteria for designating areas as attainment or nonattainment for the State standards.  The current criteria are in the California Code of Regulations (CCR), title 17, sections 70300 through 70306, and appendices 1 through 3.

Designations

H&SC 39608 requires CARB to use the designation criteria to designate areas of California as attainment, nonattainment, or unclassified for the State standards and to conduct an annual review of the designations, updating them as warranted.  H&SC 40925.5 provides for the redesignation of a nonattainment area as nonattainment-transitional by operation of law.  The current designations are in the CCR, title 17, sections 60200 through 60210.

H&SC 40718 requires CARB to publish maps showing the areas with one or more violations of any State or national standard. These maps are found in the annual State area designation staff reports as well as on the CARB website.

Recent and historical State Implementation Plan (SIP) activity related to Western Nevada County, a nonattainment area for ozone National Ambient Air Quality Standard under the jurisdiction of the Northern Sierra Air Quality Management District.

• 2023 Ozone Attainment Plan for Western Nevada County
• 2018 Western Nevada County Planning Area Ozone Attainment Plan
• 2018 Reasonably Available Control Technology SIP for Western Nevada County