SDAPCD Toxic Air Contaminants
In February 2025, the SDAPCD revised Rule 1200 and Rule 1210 which included a revision of the definition of a 'Toxic Air Contaminant.' The revision to the definition now incorporates the State-approved lists of toxic air contaminants (TACs) and health risk values by statutory reference rather than requiring a rule revision when a new pollutant needs to be considered in risk assessments.
A Toxic Air Contaminant as defined by District Rule 1200(c)(23) means a substance which:
(i) Is required to be included on the
list of toxic substances compiled and maintained by ARB pursuant to Section
44321 of the California Health and Safety Code; and
(ii) Has
cancer and/or non-cancer (chronic and/or acute) health effect values
established by OEHHA pursuant to Section
44360 of the California Health and Safety Code.
The APCD has consolidated the list of substances that qualify as TACs based on these requirements in the link below.
SDAPCD TAC List (PDF) (Excel)
Applicability Guidelines for TACs
The TAC list above includes the date that health values were last updated as well as the date that the TAC was added to this list. The list began on February 13, 2025 when the amendments to Rule 1200 and Rule 1210 were approved. When evaluating different types of projects, the SDAPCD will use the following guidelines to determine which TACs may be applicable depending on the type of project:
For reviewing permit applications, Rule 1200 requires SDAPCD to consider all TACs in effect on the date action is taken on the application (ATC issuance). In the event health risk values are added or revised after the application is deemed complete, the Applicant and/or SDAPCD shall make necessary changes to the HRA.
Risk Reduction and Audit Plans are considered permit applications therefore Rule 1200 requires SDAPCD to consider all TACs in effect on the date action is taken on the application (ATC issuance). In the event health risk values are added or revised after the application is deemed complete, the Applicant and/or SDAPCD shall make necessary changes to the HRA.
Emissions invenotry reporting requirements for pollutants are governed by CARB's EICG Regulation. Follow CARB's guidance for which pollutants must be included in your emissions inventory. Also visit the District's Emissions Inventory webpage for more information.
When calculating prioritization scores, SDPACD follows our prioritization procedure. If a pollutant is required to be reported for that calendar year and OEHHA adopts new or revised health standards that calendar year, the new health standards will be used.
These Health Risk Assessments are required as a result of a facility's prioritization score. The pollutants and health standards evaluated in the HRA are the same as those used in the prioritization score.
Recently Adopted Health Values for TACs
As The California Office of Environmental Health Hazard Assessment (OEHHA) adopts new health values, new compounds become TACs. Below are the most recently adopted TACs or recently revised health values along with some background information. Please visit OEHHA's Air webpage to see the most up to date notices of adoption or information about compounds under consideration for new health values.
1/3/2025
-
Isoprene - Notice
of Adoption of Cancer Inhalation Unit Risk Factor for
Isoprene
- Isoprene is used to make synthetic isoprene rubber, which is used mainly in the manufacture of vehicle tires and footwear, and to produce butyl rubber for manufactured goods such as hoses and liners in tubeless tires. In addition, the manufacture of styrene-isoprene-styrene polymers is used to make thermoplastic rubber and pressure sensitive or thermosetting adhesives. CARB requested that OEHHA derive an IUR for isoprene due to its presence in biogas emissions and in the air of residential areas near oil and gas operations.
10/6/2023
-
Trimethylbenzenes - Notice
of Adoption of Reference Exposure Levels for
Trimethylbenzenes
- Trimethylbenzenes are used in surface coatings, paints, printing inks, cleaning fluids, and hydraulic fracturing fluids and are common components in petroleum refinery distillation fractions, such as gasoline, and are found as constituents of biogas.
8/4/2023
-
Cobalt and Cobalt Compounds - Notice
of Adoption of Revised Cancer Inhalation Unit Risk Factors for
Cobalt Sulfate Heptahydrate and Water-Soluble Cobalt
Compounds
- OEHHA adopted revised cancer inhalation unit risk (IUR) and slope factors for cobalt and water-soluble cobalt compounds.
- Cobalt air emissions sources in California include the petroleum industry, cement kilns, semiconductor and electronic components facilities, aerospace product and parts manufacturing, alloy manufacturing, and battery manufacturers.
Additional Information
CARB Consolidated Table - The Consolidated Table of OEHHA / CARB Approved Risk Assessment Health Values is a quick look-up table of all cancer potency values and noncancer acute, 8-hour, and chronic Reference Exposure Levels (RELs) that are available for use in the AB 2588 Air Toxics "Hot Spots" Program
OEHHA Air - This webpage is maintained by the California Office of Environmental Health Hazard Assessment (OEHHA) and has information related to OEHHA's Hot Spots Guidelines and the current and new health risk values.
OEHHA Listserv - OEHHA undergoes a public process before adopting new health values. Sign up for OEHHA's Listserv to be notified of public comment periods and adoption of new health values.