Inhalation Unit Risk Factor (IUR) for Ethylene Oxide

OEHHA is releasing a draft document for public review that summarizes the carcinogenicity data and derives an updated cancer inhalation unit risk factor (IUR) for ethylene oxide. 

Cancer IURs are used to estimate lifetime cancer risks associated with inhalation exposure to a carcinogen. Information on ethylene oxide levels in the air can be found at California Air Resources Board’s Ethylene Oxide FAQ Page.

Public Comment Period

The public review period for the draft updated ethylene oxide IUR begins on May 14, 2026, and is scheduled to end on June 29, 2026. To submit a public comment electronically, please click below:

Public Workshops

OEHHA will hold three workshops to provide the public with an opportunity to ask questions and provide public comment about the cancer IUR for ethylene oxide. 

Northern California – in person and virtual 
June 2, 2026, 4:00 PM – 7:00 PM 
Sierra Hearing Room, CalEPA Headquarters Building  
1001 I Street, Sacramento, CA 95814 
Zoom Webinar Link 

Southern California – in person 
June 4, 2026, 11:00 AM – 1:00 PM 
Auditorium, Ronald Reagan State Building 
300 South Spring Street 
Los Angeles, CA 90013 

Central California
Details will be announced at a later date

2023 Draft Inhalation Unit Risk Factor for Ethylene Oxide

On April 7, 2023, OEHHA released a draft document for public review that summarized the carcinogenicity data and derived an updated cancer inhalation unit risk factor (IUR) for ethylene oxide. 

A 60-day public comment period was held from April 7, 2023 to June 14, 2023.  

Two public workshops were held during the comment period.

Background on the Air Toxics Hot Spots Program

The Air Toxics "Hot Spots" Information and Assessment Act (AB 2588, Connelly) was enacted in 1987 and requires stationary sources of pollutants to report the types and quantities of certain substances routinely released into the air. The goals of the Air Toxics "Hot Spots" Act are to collect emission data, to identify facilities having localized impacts, to ascertain health risks, to notify nearby residents of significant risks, and to reduce those significant risks to acceptable levels. OEHHA is legislatively mandated to develop guidelines for conducting health risk assessments under the Air Toxics Hot Spots Program (Health and Safety Code section 44360(b)(2)). In response to this statutory requirement, OEHHA developed a Technical Support Document that describes the methodology for deriving inhalation unit risk factors and cancer slope factors for carcinogenic Hot Spots air pollutants. The methodology in the Technical Support Document explicitly considers possible differential effects on the health of infants, children, and other sensitive subpopulations under the mandate of the Children’s Environmental Health Protection Act (Senate Bill 25, Escutia, Chapter 731, Statutes of 1999, Health and Safety Code Sections 39669.5 et seq.), including procedures for evaluating increased susceptibility to carcinogens. 

Link to Public Comments

Downloads

Chemical Reference