Air Toxics



Met Data Sets

Fee Schedule


Air Toxics 'Hot Spots" Act

Facility Search Tool

Sample Emission Inventory Plan

Combustion Emission Factors

CAPCOA Facility Prioritization Guidelines

VCAPCD Prioritization Procedure

OEHHA Health Risk Assessment Preparation Manual

Public Hearing on "Significant" Risk Level

CAPCOA Public Notifications Guidelines

APCD "Hot Spots" Public Notification Guidelines


2022 Annual Report

2021 Annual Report

2020 Annual Report

2019 Annual Report

2016 Annual Report

2015 Annual Report

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2007 Annual Report

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2005 Annual Report

2004 Annual Report

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2000 Annual Report

1999 Annual Report



The Air Toxics “Hot Spots” Information and Assessment Act (AB2588, 1987. Connelly) was enacted in September 1987. The goals of the Air Toxics “Hot Spots” Act are to collect emissions data, to identify facilities having localized impacts, to ascertain health risks, to notify nearby residents of significant risks, and to reduce significant risks. The program addresses routine and predictable emissions, but not unforeseen, accidental releases.


The Act requires that:

  • Toxic air emissions from facilities be quantified and compiled into an inventory according to criteria and guidelines developed by the ARB.
  • Each facility be prioritized to determine whether a risk assessment must be conducted.
  • The risk assessments be conducted according to methods developed by the Office of Environmental Health Hazard Assessment (OEHHA).
  • The public be notified of significant risks posed by nearby facilities, and that emissions which result in a significant risk be reduced.


The Toxics “Hot Spots” Act is a public right to know program. A variety of air toxics information developed under the Act is publicly available. The California Air Resources Board (ARB) maintains the toxics emissions data in the Facility Search Tool. The District makes health risk assessments available for public review upon request. The District also publishes annual reports that summarize the health risk assessment program, rank facilities according to the cancer risk posed, identify the facilities posing non-cancer health risks, and describe the status of the development of control measures.


The “Hot Spots” Program has complemented the state’s existing air toxics identification and control programs. It has located sources of substances not previously under evaluation, and it has provided exposure information necessary to prioritize substances for control measures and develop regulatory action.


The Air Toxics “Hot Spots” Process

The Air Toxics “Hot Spots” Act requires the ARB to compile and maintain a list of substances posing chronic or acute health threats when present in the air. Over 600 substances have been listed under the act.


Ventura County facilities are subject to the Act if they manufacture, formulate, use, or release a listed substance and either emit 10 tons or more per year of criteria pollutants (total organic gases, particulate matter, nitrogen oxides, or sulfur oxides) or emit less than 10 tons per year of criteria pollutants and are listed by ARB as a type of facility subject to emission inventory requirements.


The Air Toxics “Hot Spots” Act requires subject facilities to prepare air toxics emission inventory plans and, subsequently emission inventory reports. The Emission Inventory Criteria and Guidelines Report, which was first approved by the ARB I April 1989, provides specifications for acceptable emission inventory plans and reports, and inventory updates. Portions of the guidelines were amended by the ARB several times since then. The current version of the guidelines became effective September 26, 2007.


Facility operators must submit a proposed emission inventory plan indication how emissions will be measured or calculated to the District. The District must approve, modify, or return the inventory plan to the operator for revisions within 120 days. Once the District approves a plan, the facility operator must implement the plan and submit the emission inventory report within 180 days. For certain classes of facilities, the District must prepare industrywide inventories. In this case, individual facility reports are not required. The District determines which facilities will be covered by industrywide inventories based on conditions such as economic hardship and small business status.


Facilities subject to the program must update their emission inventories every four years. The update requirements were streamlined in June 1993, and are now based on each facility’s prioritization category. The new update requirements substantially reduce reporting requirements for all but the significant risk facilities.


After reviewing emission inventory data, the District ranks facilities for purposes of risk assessment into high, intermediate, and low priority categories. Facilities are re-prioritized if their inventory update shows any significant changes.


In establishing priorities, the District considers the potency, toxicity, and quantity of hazardous materials released from the facility, the proximity of the facility to potential receptors, and any other factors that the District determines indicates that a facility may pose a significant risk.


The California Air Pollution Control Officers Association (CAPCOA) has developed Air Toxics “Hot Spots” Program facility Prioritization Guidelines to provide districts with suggested procedures for use in prioritizing facilities. These Guidelines were updated in August of 2016. The Ventura county Air Pollution control board adopted prioritization procedures based on the CAPCOA Guidelines. The Prioritization Procedures were amended to incorporate the updated CAPCOA Guidelines on December 12, 2023


Within 150 days of the designation of priorities, high priority facilities must prepare and submit a health risk assessment to the District. A risk assessment, as defined under the Air Toxics “Hot Spots” Act, includes a comprehensive analysis of the dispersion of hazardous substances into the environment, the potential for human exposure, and a quantitative assessment of both individual and population wide health risk associated with those levels of exposure. The District may grant a 30-day extension for submittal of the risk assessment. The risk assessments are reviewed by the District and OEHHA.


OEHHA has developed the Air Toxics Hot Spots Program Risk Assessment Guidelines, February 2015, to provide procedures for use in preparing the health risk assessments required under the Air Toxics “Hot Spots” Act. These guidelines replaced an earlier version released in 2003. The update to the Risk Assessment Guidelines was triggered by SB 25, Children’s Environmental Health Protection, which required that the increased sensitivity to toxics of infants and children be specifically addressed. CAPCOA and ARB adopted the Risk Management Guidance for Stationary Sources of Air Toxics which should be used in preparing “Hot Spots” risk assessments. Use of the OEHHA guidelines is required by law. The ARB has developed the Hotspots Analysis and Reporting Program (HARP) software, which can be used to prepare “Hot Spots” risk assessments. Meteorological data for risk assessment dispersion modeling is available from ARB for Point Mugu, Camarillo Airport, and Oxnard Airport. Additional meteorological data sets are also available from District operated air monitoring stations located in El Rio, Ojai, Piru, Simi Valley, and Thousand Oaks.


The CAPCOA Toxics Committee has also developed Public Notification Guidelines. The purpose of these guidelines is to assist districts in developing their public notification procedures. The Ventura County Air Pollution Control Board has adopted public notification procedures for use in Ventura County based on the CAPCOA Guidelines.


Facilities found to have a significant risk must conduct an airborne toxics risk reduction audit and develop a plan to implement airborne toxics risk reduction measures. The audit and plan must be submitted to the District within six months of the determination. It must describe the risk reduction methods the facility will use to reduce its risk below the level of significance within five years; however, the District may shorten or lengthen the time period (up to five additional years) under certain conditions.


Fee Schedule

The Air Toxics “Hot Spots” Act requires that the ARB develop and adopt a fee regulation that recovers the state’s costs to implement the program. The regulation also requires each district to adopt a fee schedule which recovers the costs to the district, or a district may request that the ARB adopt a fee schedule for them. The regulation establishes each district’s share of the state’s costs. The fee regulation is reviewed annually and updated to accommodate changes in the facilities subject to the program. In response to this requirement, the Ventura County Air Pollution Control Board adopted Rule 46. Under Rule 46, fees are based on prioritization scores and health risk assessment results.


Generally, fee rates increase with increasing risks. Each district is responsible for billing and collecting fees from all facilities subject to the Act and for remitting the district’s share of the state costs to the ARB.



In summary, the Air Toxics “Hot Spots” Act establishes a formal air toxics emission inventory and risk quantification program. The goal of the Air toxics “Hot spots” Act is to collect emission data indicative of routine predictable releases of toxic substances to the air; to identify facilities having localized impacts; to evaluate health risks from exposure to the emissions; to notify nearby residents of significant risks; and to reduce risks below the level of significance. Information gathered from this program has complemented the state’s existing toxic air contaminant program. Additionally, the program has been a motivating factor for facility owners to voluntarily reduce their facility’s toxic emissions.