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Bay Area Air District Regulation 11, Rule 18: 2025 Draft Amendments to Reduce Health Risks from Air Toxics

February 24, 2026

The Air District’s Regulation 11, Rule 18, adopted in 2017, regulates toxics emissions from existing facilities to prevent unacceptable health risks to nearby communities. The Air District is proposing rule amendments to improve implementation and accelerate risk reduction, with draft updates already released in 2025 and potential adoption in early 2026.

Purpose and Scope of Rule 11-18

Rule 11-18 targets TACs, specific pollutants known to increase the likelihood of cancer, cause serious illness, or present chronic health hazards, as listed in Regulation 2, Rule 5. Approximately 200 chemicals fall into this category. Although thousands of facilities report toxics emissions to the Air District, only a subset is subject to Rule 11‑18 review.

Each year, the Air District calculates a screening health risk and assigns facilities a “prioritization score.” Facilities with scores above a defined screening threshold (10) must undergo a full Health Risk Assessment (HRA). Currently, about 350 facilities across a variety of sectors are expected to undergo Rule 11-18 review. The current list of facilities can be found on the Air District’s website at:

https://www.baaqmd.gov/community-health/facility-risk-reduction-program/facility-risk-reduction-list

Key Requirements Under
Rule 11-18

Health Risk Assessments (HRAs)

Facilities identified through the prioritization process must undergo an HRA. Under the current rule version, the Air District conducts these assessments
internally. Results are compared to established Risk Action Levels to determine which sources contribute most to facility-wide health risks and whether additional action is needed.

Risk Reduction Plans (RRPs)

If an HRA indicates that risks exceed the Risk Action Levels, the site must develop a Risk Reduction Plan (RRP). The plan must outline how the facility will either reduce health risks below the established thresholds or demonstrate that significant risk sources are implementing Best Available Retrofit Control Technology for Toxics (TBARCT).

Why Amendments Are Being Proposed

Since adoption of Rule 11-18, implementation of the rule has taken longer than anticipated, slowing progress in reducing community health risks. To address this, the Air District initiated a two-phase amendment process:

• Phase 1: Procedural improvements and implementation efficiency; and
• Phase 2 (future): Evaluation of increase in rule stringency.

The next stages include preparing the Proposed Rule Package and a Board hearing, anticipated in early 2026.

Highlights of the 2025 Draft Amendments

The 2025 draft amendments are designed to improve consistency and reduce delays, while maintaining Air District oversight.

Key changes include:

• Facility-Prepared Preliminary HRAs: Facilities will prepare their own HRAs using Air District-approved modeling protocols. Work can be done internally or by engaging consultants. The Air District will review the modeling. Shifting HRA preparation to the facility is expected to streamline reviews and increase efficiency.
• Standardized Review Process and Timelines: The process will follow four main stages: modeling protocol, preliminary HRA, public comment, and final HRA. There will be specific timelines for each stage.
• Incorporating New Emissions Data: The amendments clarify how updated emissions information, such as source test results, should be incorporated into HRAs.
• Prioritization Score Updates: Facilities may recalculate and request reconsideration of their prioritization scores.

What This Means for Facilities and Next Steps

The Air District is reviewing public comments on the draft amendments, with proposed updates expected to go to a public hearing before the Board of Directors in early 2026.

Understanding these potential amendments allows facilities to plan for HRA preparation and risk reduction actions efficiently, ensuring compliance under the updated Rule 11-18 framework.

For full details on changes above, please visit: Regulation 11 Rule 18 Reduction of risk from air toxic emissions at existing facilities

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Yorke Engineering has assisted over 2,000 industrial and government facilities across California with EH&S consulting and air quality consulting, as well as permitting and compliance for storm water, wastewater, hazardous waste, industrial hygiene, and safety programs. Learn more here: Services – Yorke Engineering, LLC

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