Audit, Compliance and Risk Blog

California regulates Air Toxics “Hot Spots”

Posted by Jon Elliott on Tue, Sep 15, 2020


In 1987, California adopted the Air Toxics “Hot Spots” Information and Assessment Act, responding to increasing concern over toxics in the air (AB 2588 (Connelly, Sterling)).  This law complements California’s enforcement of national requirements governing stationary source emissions of air toxics. The federal Clean Air Act (CAA) required the U.S. Environmental Protection Agency (EPA) to establish and maintain a list of air toxics, named as Hazardous Air Pollutants (HAPs), and to set emissions standards (National Emissions Standards for Hazardous Air Pollutants (NESHAPs) for many HAP emission sources; California incorporates HAP/NESHAP requirements into the state’s Toxic Air Contaminant (TAC) / Airborne Toxic Control Measure (ATCM) program. (I discussed these requirements HERE).

What legislative purposes does the Hot Spots Act serve?

The legislature concluded the following when passing this legislation: 

  • Releases of toxic chemicals “may create localized concentrations of air toxics ‘hot spots’ where emissions from specific sources may expose individuals and population groups to elevated risks of adverse health effects, including ... cancer ....”

  • “Little data is [sic] currently available to accurately assess the amounts, types, and health impacts of routine toxic chemical releases into the air....” 

  • Additional legislation is required to direct the collection and evaluation of information concerning the amounts, exposures, and health effects of hazardous substances regularly released into the air.

  • Additional information on HAP sources is necessary to implement control strategies.

  • It is in the public interest to ascertain and measure the amounts and types of hazardous releases from specific sources, and assess the health risks associated with exposure.

Which agencies administer the Hot Spots Act?

Most of the implementation of AB 2588 is assigned to air districts, operating with guidance from the California Air Resources Board (ARB). These implementation tasks include identification of regulated facilities, evaluation of facilities’ emissions inventory plans and subsequent emissions inventory reports, health risk prioritization and assessment, and determination of which facilities pose “significant health risks” and so are required to develop and implement airborne toxic risk reduction plans. Air districts fund these activities through fees, which include elements established annually by ARB to cover ARB and district costs. 

Which substances are regulated?

The Act assigns ARB to compile and maintain lists of substances subject to this program. ARB assembles over 700 substances, based on a wide variety of criteria, and has compiled three separate lists with distinct reporting requirements, as follows:

  • substances for which emissions must be quantified accurately (i.e., those with quantification methodologies and requirements under other programs, such as the HAP/TAC program),

  • substances for which the production, use, or other presence in an operation must be reported, but need not be quantified, and

  • substances that need only be reported by facilities where they are manufactured.

What are Air Toxics Emissions Inventory requirements?

Facilities subject to the Hot Spots program must submit a comprehensive emissions inventory plan to the air district, in compliance with standards contained in Guidelines issued by ARB. These standards require the following: 

  • flow diagrams identifying actual or potential emissions points and general locations where fugitive emissions may occur; and

  • specification of listed substances being emitted, as well as emissions quantification methods and source test protocols.

These plans describe the procedures that will be followed to complete the inventories. Trade secret protections are available. Requirements apply to most facilities that emit more than 25 tons per year (tpy) of non-toxic “criteria” pollutants (such as particulates or oxides of sulfur), or more than 10 tpy of criteria pollutants plus any Hot Spots Act pollutants. Plans are first due by August 1 of the year after a facility becomes subject to AB 2588 (beginning in 1989). Exemptions are available if all the following conditions are met:

  • facility is subject to the air district’s authority-to-construct and permit-to-operate requirements for stationary sources;

  • air district assesses the facility’s emissions and associated risks, and determines that they do not pose a “significant risk” (ARB Guidelines restate this as a “low level” risk; see below); and

  • air district issues a permit authorizing construction or operation.

Once a facility’s emissions plan has been approved by the air district, the facility must implement the plan (i.e., conduct the emissions inventory) and submit an emissions inventory report within 180 days. Each report must present the following:

  • flow diagrams (as required for the emissions inventory plan, above);

  • specification of listed substances being emitted, documented by the results of each required source test and other analysis specified in the inventory plan and/or specified in the ARB Guidelines;

  • required data elements and formats;

  • completed copies of required forms; and

  • other information required by the air district.

Trade secret protections are available. The air district reviews each report within 90 days, and then informs Cal/OSHA, the state Office of Environmental Health Hazard Assessment (OEHHA), and the relevant city or county health department of its findings and determinations. Air districts also supply all monitoring data contained in the inventory reports to ARB. ARB compiles these data and makes them available to other state and local public agencies, and the public.

Each non-exempt facility must update its emissions inventory every four years. 

What Health Risk Assessments are required?

Air districts are to evaluate each facility’s initial emissions inventory report within 90 days and, in consultation with ARB and OEHHA, prioritize and categorize facilities to determine which require health risk assessments. AB 2588 defines a health risk assessment as “a detailed comprehensive analysis prepared ... to evaluate and predict the dispersion of hazardous substances in the environment and the potential for exposure of human populations, and to assess and quantify both the individual and population wide health risks associated with those levels of exposure.” Air district assessments follow OEHHA guidelines.

Air districts prioritize facilities within high, intermediate, and low priority categories. When assigning priorities, air districts are to consider “potency, toxicity, quantity, and volume of hazardous materials released from [these] facilities, the proximity of the facility to potential receptors, including ... hospitals, schools, daycare centers, worksites, and residences, and any other factors that the district finds and determines may indicate that the facility may pose a significant risk to receptors.” Air districts are required to hold public hearings prior to establishment of priorities and ranking. 

Low priority facilities generally are exempt from fees and report submissions. Facilities can gain or lose exemptions as their handling and emissions of regulated substances change. A facility can also lose its exemption if a “sensitive receptor” is established within 500 meters of the facility. 

Within 150 days after designation by its air district, each high priority facility must prepare and submit a health risk assessment to its air district. Upon request, the district is to make each health risk assessment available for public review. After preliminary review of emissions impact and modeling data, the district submits the health risk assessment to OEHHA for review, comments, and findings relating to health effects. Districts consult with ARB as necessary to adequately evaluate the emissions impact and modeling data contained in the health risk assessments.

Air districts must approve or return for revision a health risk assessment within one year after receipt. If the operator does not resubmit the health risk assessment within 60 days after an air district’s request for revision, the district may modify the assessment. After a health risk assessment is approved, a facility must provide notice to all exposed persons regarding the results of an assessment which indicates a significant health risk associated with emissions from the facility. 

What Airborne Toxic Risk Reduction measures can be required?

The Hot Spots Act was amended in 1992 to create requirements that any facility determined by its air district to pose a “significant health risk” take steps to reduce the health risks posed by emissions of listed air toxics. Individual air districts are to define significant health risk; many use the “high priority” designation developed through the health risk assessments discussed above.

The 1992 amendments require each such facility, within six months after being designated as a significant health risk, to conduct an airborne toxic risk reduction audit of operations that emit air toxics. Audits must consider airborne toxic risk reduction measures (ATRRMs) that could be implemented to reduce risks, including in-plant changes in processes or feedstocks to reduce or eliminate toxic air emissions involving chemicals regulated under the Hot Spots program. These measures are not to include measures that would increase risks from exposures in other environmental media, or increase risks to workers or consumers. ARB has developed a strategy for the assessment and identification of communities with “high cumulative exposure burden” from TACs and criteria pollutants. 

The facility must incorporate the audit and ATRRMs into an airborne toxic risk reduction (ATRR) plan to reduce emissions enough to eliminate the “significant” risk within five years, and submit the ATRR plan along with the audit report. Air districts may impose shorter implementation periods on facilities they find to pose “an unreasonable health risk,” which also is left to each district to define. For example, the Bay Area Air Quality Management District (BAAQMD) applies the following standards:

  • Before January 1, 2020, any of the following health risk levels: 

    • a cancer risk of 25 per million (25/M); 

    • a chronic hazard index of 2.5 (relative to the chronic reference exposure level); or 

    • an acute hazard index of 2.5 (relative to the acute reference exposure level).

  • Effective January 1, 2020: 

    • a cancer risk of 10 per million (10/M); 

    • a chronic hazard index of 1.0; or

    • an acute hazard index of 1.0.

Alternatively, a district can extend a facility’s implementation period for up to an additional five years upon a finding that economic conditions require a longer period and the additional health risk is acceptable.  ATRR plans must be certified by the person responsible for the processes and operations, a licensed professional engineer or an environmental assessor.  ARB provides guidance to assist with this process.

Now what?

The Hot Spots program is nearly 30 years old, but continues to evolve. For example, in 2017 the BAAQMD claimed that its Rule 11-18 is “the most health-protective toxic air pollution risk control measure in the nation.”

Self-evaluation checklist

Does the organization conduct any activities that emit pollutants regulated under the Air Toxics Hot Spots program?

Has each such facility in California submitted required emissions inventories to its local air district?

Has each such facility in California received a health hazard ranking from its air district, and if so has it performed any required health risk assessment?

Has any such facility in California been required to conduct an airborne toxic risk reduction audit, and if so has the audit been performed?

Has any such facility in California implemented airborne toxic risk reduction measures?

Has any such facility located outside California performed any of these tasks, and if so: which ones with what outcomes?

Where can I go for more information?


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About the Author

Jon Elliott is President of Touchstone Environmental and has been a major contributor to STP’s product range for over 30 years. 

Mr. Elliott has a diverse educational background. In addition to his Juris Doctor (University of California, Boalt Hall School of Law, 1981), he holds a Master of Public Policy (Goldman School of Public Policy [GSPP], UC Berkeley, 1980), and a Bachelor of Science in Mechanical Engineering (Princeton University, 1977).

Mr. Elliott is active in professional and community organizations. In addition, he is a past chairman of the Board of Directors of the GSPP Alumni Association, and past member of the Executive Committee of the State Bar of California's Environmental Law Section (including past chair of its Legislative Committee).

You may contact Mr. Elliott directly at:

Image by Ralf Vetterle from Pixabay

Tags: OSHA, CAA, Cal/OSHA, California, Air Toxics, NESHAPs, TAC, ATCM, Hot Spots Act, OEHHA, BAAQMD, HAPs, ARB