October 6, 2026
Richmond City Council:
Chevron Refinery
Preliminary Health Risk
Assessment (HRA)
Presented by
Ariana Husain, Engineering Manager
Dr. Rohan Radhakrishna, MD, MPH, MS, Health Officer
•
Agenda
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• Regulation 11, Rule 18 (Rule 11-18)
• What is a Health Risk Assessment?
• Chevron Refinery – Preliminary Health Risk Assessment Results • Next Steps
•
Regulation 11, Rule 18
(Rule 11-18)
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October 6, 2026 • Chevron Refinery – Preliminary HRA 4
Purpose of Rule 11-18
Adopted in 2017, Rule 11-18 : Reduction of Risk from Air Toxic Emissions at Existing Facilities serves to:
• Identify facilities that pose elevated health risks due to toxic air contaminant emissions
• Assess health risk with a Health Risk Assessment (HRA) • Require facilities with estimated health risk equal to or above the risk action levels to reduce health risks
•
What is a Health Risk
Assessment?
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October 6, 2026 • Chevron Refinery – Preliminary HRA 6
Health Risk Assessment (HRA)
An estimate of the increased chance of negative
health impacts for individuals that may be exposed to
toxic air contaminants, based on the best scientific
information available
Air District HRAs follow state procedures as developed
by the Office of Environmental Health and Hazard
Assessment (OEHHA)
Purpose:
- Serve as a screening tool
- Protect public health
- Identify potential concerns
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Terms: Emissions, Exposure, and Risk
Emissions Exposure Health Risks
Amount and
type of
pollutants
emitted
Quantity of
emissions
breathed in*
Potential risk
from breathing
in*
* Exposure and health risk assessment also consider non-inhalation pathways, such as soil ingestion and dermal exposure to contaminated soil.
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HRA Components
Emissions Exposure
Weather
Terrain
Time Toxicity/
Potency
Health
Risks
* Exposure and health risk assessment also consider non-inhalation pathways, such as soil ingestion and dermal exposure to contaminated soil.
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Cancer & Non-Cancer Risk
• Cancer risk is an estimate of the chance that an individual may develop cancer from long-term exposure to toxic air contaminants, known as carcinogens
• Non-cancer risk is an estimate of the potential non-cancer health effects from exposure to toxic air contaminants (TACs)
• Acute: Short-term exposure (1-hr)
• Chronic: Long-term exposure
October 6, 2026 • Chevron Refinery – Preliminary HRA 10 Maximum Risk
Maximally Exposed Individual (MEI): The MEI
represents a worst-case scenario used to
evaluate the highest potential health risk from
exposure to routine facility emissions.
• Health risks evaluated include cancer risk
and chronic risk
Point of Maximum Impact (PMI): The PMI is
conventionally used instead of MEI for acute
risk assessments, while retaining the same
meaning.
October 6, 2026 • Chevron Refinery – Preliminary HRA 11 Key Assumptions of an HRA
• Representative Year: Based on a single year of facility emissions that has been determined to be representative of typical operations
• Steady-State Emissions: Assumes emissions remain constant over the applicable exposure duration (e.g., 30 years for residential exposure) • Maximum Exposed Individual (MEI) or Point of Maximum Impact (PMI): Results are reported for the location where the highest modeled risk occurs, which may or may not represent the risk experienced by most people • Exposure Scenarios: Risk is evaluated for multiple receptor types, including:
- Residents
- Off-site workers
- Students (schools)
• Single-Facility Assessment: Estimates health risk attributable only to emissions from stationary sources at the facility being evaluated. Does not include emissions from nearby sources or regional background air pollution October 6, 2026 • Chevron Refinery – Preliminary HRA 12 What an HRA Does Not Do
An HRA Does Not:
• Determine in what way a specific individual will be affected by facility emissions
• Include the effects of operational upsets that happen over a short period of time (hours, days)
• Provide an exact measurement of concentrations at any specific location • Estimate cumulative health impacts from emissions from mobile sources or nearby facilities
•
Chevron Refinery
Preliminary HRA
Results
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October 6, 2026 • Chevron Refinery - Preliminary HRA 14 Preliminary Results
Maximum Health Risk Estimates
Health Risk Preliminary
Results
Risk Action Level
(RAL)
Cancer Risk 37 in a million 10 in a million
Chronic Risk 0.26 1.0
Acute Risk 1.2 1.0
RALs are the health risk thresholds that, if met or exceeded, the facility is required to develop and implement a Risk Reduction Plan.
October 6, 2026 • Chevron Refinery – Preliminary HRA 15 Significant Sources: Cancer Risk
A significant source of cancer risk is a source that contributes a cancer risk greater than or equal to 1.0 in a million at the MEI location • Significant sources are fugitives (leaks), storage tanks, and generators • The significant sources identified account for more than 70% of the total estimated cancer risk.
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• Chevron Refinery
- Preliminary HRA 16
October 6, 2026 • Chevron Refinery - Preliminary HRA 17 Significant Source: Acute Risk
A significant source of acute risk is a source that contributes an acute risk greater than or equal to 0.20 at the PMI location
• The bio-reactor, part the refinery's wastewater treatment system, contributes more than 80% of the total acute risk at the PMI location.
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• Chevron Refinery
- Preliminary HRA 18
October 6, 2026 • Chevron Refinery - Preliminary HRA 19 What Does This Mean to Me?
•
Next Steps
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October 6, 2026 • Chevron Refinery - Preliminary HRA 21 Next Steps:
• The public and Chevron Refinery have 90-days to comment on the preliminary HRA. The comment period is from August 25 to November 23, 2026 at 5 p.m.
• The Air District reviews all comments and may make changes to the preliminary HRA based on new information received. These changes may result in a decrease or increase in the preliminary risk results. • If the risk remains at or above the risk action levels in Rule 11-18, Chevron Refinery will be required to create and implement a risk reduction plan October 6, 2026 • Chevron Refinery - Preliminary HRA 22 How to Submit Comments
Public comment on the preliminary report closes on November 23, 2026, at 5 p.m.
Submit comments by:
Email: [email protected] include the subject line: FID10_hra_[last name/group identifier]
Regulation 11-18 Chevron Preliminary HRA
Public Notice Response
Bay Area Air District – Engineering Division
375 Beale Street, Suite 600
San Francisco, CA 94105
Attn: Ariana Husain
Snail Mail:
Public Comment Tool: http://bit.ly/46WGTyC 1
2 3
October 6, 2026 • Chevron Refinery - Preliminary HRA 23 Resources
Visit our Rule 11-18 Facility Risk Reduction page to view:
• The full Preliminary HRA report for Chevron Refinery
• Summary of the Preliminary HRA for Chevron Refinery
• Fact Sheet of the Preliminary HRA for Chevron Refinery • Rule 11-18 Frequently Asked Questions
• Rule 11-18: Understanding Health Risk Assessments fact sheet
• List of facilities subject to Rule 11-18 requirements Chevron Refinery Preliminary HRA
Resources
General 11-18 Resources
•
Questions?
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