Air Toxic "Hot Spots" Act

August 16, 2016
August 25, 2016
August 25, 2016
September 22, 2016


California enacted The Air Toxics "Hot Spots" Information and Assessment Act in 1987. The Act establishes a formal air toxics emission inventory risk quantification program, which is managed by California air districts.

The program goals include:

  • collection of data on the emission of toxic air contaminants
  • identification of facilities having localized impacts
  • health risk assessment
  • public notification on health risks
  • reduction of the risks of "significant-risk facilities" below the level of significance. 

The program has been a motivating factor for facility owners to voluntarily reduce their facility's toxic emissions


A copy of the 2015 Annual Report can be found here (PDF).


The Act requires:

  • facilities to report of types and quantities of certain toxic substances routinely or predictably emitted;
  • air districts to determine whether or not a health risk assessment (HRA) must be conducted for the facility;
  • that HRAs be conducted according to methods developed by the Office of Environmental Health Hazard Assessment (OEHHA);
  • that the public be notified of significant risks posed by nearby facilities, and;
  • facilities posing significant risks to prepare and implement risk reduction audits and plans within 6 months of the determination.

The Air Toxics "Hot Spots" Process

A.  Applicability

The California Air Resources Board (CARB) compiles and maintains a list of substances posing chronic or acute health threats when present in the air. The Act identifies by reference over 600 substances, which are subject to the program.

A facility is subject to the Act if it:

  1. manufactures, formulates, uses, or releases a substance subject to the Act (or another substance, which reacts to form such a substance) and emits 10 tons or more per year of total organic gases, particulate matter, nitrogen oxides or sulfur oxides, or;
  2. is listed in any district's existing toxics use or toxics air emission survey, inventory or report released or compiled by a district, or;
  3. manufactures, formulates, uses, or releases a substance subject to the Act (or substance, which reacts to form such a substance) and emits less than 10 tons per year of criteria pollutants and is subject to emission inventory requirements.

B. Emission Inventory Plans and Reports

Facilities meeting the applicability criteria must prepare air toxics emission inventory plans and emission inventory reports. CARB's Emission Inventory Criteria and Guidelines provide assistance in preparing these documents.

Facilities must submit a proposed emission inventory plan to the AQMD detailing how emissions will be measured or calculated, which the AQMD must approve, modify, or return the inventory plan to the operator for revisions within 120 days.

Once the AQMD approves a plan, the facility operator must implement the plan and submit the emission inventory within 180 days.

Facilities subject to the program must update their emission inventories every four years.

C. Risk Assessment

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

The AQMD's priority categories consider potency, toxicity, quantity, and volume of hazardous materials released, and a facility's proximity to potential receptors. Additional information on prioritization along with guideline documentation can be found at

Within 150 days of designation, high priority facilities and other facilities identified by the AQMD must prepare and submit a health risk assessment (HRA) to the AQMD. The HRA includes a comprehensive analysis of the dispersion of hazardous substances, the potential for human exposure, and a quantitative assessment of both individual and population wide health risks. OEHHA's Air Toxics Hot Spots Program Guidance Manual for Preparation of Health Risk Assessments supercedes previously published risk assessment methods.

D.  Public Notification

Once the HRA is reviewed by OEHHA and approved by the AQMD, the facility must notify all exposed persons of the risk assessment results if the AQMD determines that there is a potentially significant health risk.

ARB provides general and specific data on toxics at ARB also provides facility inventory data at More up to date data may be available from the AQMD depending upon the facility's reporting cycle.

E.  Risk Reduction

Facilities determined to have a significant risk must conduct an airborne toxic risk reduction audit and develop a plan to implement risk reduction measures. These facilities must submit the audit and plan to the AQMD within 6 months of the determination. The documents must describe the risk reduction methods the facility will use to reduce its risk below the level of significance within 5 years. The AQMD may shorten or lengthen the time period under certain conditions.

The Act prescribes penalties for failure to comply or for knowingly submitting false information. Civil penalties range from $500 to $25,000 for each day in violation. The Act also penalizes for facilities for failure to submit a complete audit and plan or failure to implement the measures set forth in the plan.

Fee Schedule

CARB adopted a fee regulation, which recovers the state's implementation costs. Further information on the regulation and its annual status reports can be found at

The regulation establishes each district's share of state costs and provided the AQMD the authority to adopt Rule 306, Air Toxics Fees (PDF) to recover the AQMD's program costs. The AQMD must collect fees from all facilities subject to the Act and remit the district's share of the state costs to the CARB.

Fee categories are based on prioritization scores and health risk assessment results. Fees are based on toxic emissions and facility risk priority to the extent possible and generally increase with increasing risks. Sources not remitting fees to the AQMD within 60 days of receipt of the fee notice are subject to additional late fees. Further detail is found in Rule 306.

Contact Information

For additional information about the AQMD's Toxics Hot Spots Program, please contact Jorge DeGuzman at 916 874-4860 or