California Air Resources Board

What you need to know: The latest science from the Office of Environmental Health Hazard Assessment (OEHHA) shows two toxics, acrolein and ethylene oxide, can potentially pose unacceptable cancer risks. In response, California Governor Gavin Newsom is proposing a $2.5 million effort to advance scientific understanding and identify actions to reduce exposure and protect public health.  
 

SACRAMENTO — Today the Office of Environmental Health Hazard Assessment (OEHHA) released draft risk values for two air pollutants — acrolein and ethylene oxide. This new research found both chemicals can potentially pose elevated cancer risks to many Californians, with some communities facing greater exposure.  

The assessments are based on new research and a greater understanding of the related health risks. They come as the U.S. Environmental Protection Agency (US EPA) is proposing to roll back its own rules for ethylene oxide emissions and re-evaluating the underlying science, making it more critical than ever for California to conduct its own assessments. 

“We must stay focused on improving air quality,” said California EPA Secretary Yana Garcia. “As the US EPA slashes air quality-related research and protections, California is doubling down on independent, best-in-class science that paves the way to healthier air for all Californians.”   

Heath risks from acrolein and ethylene oxide  

Acrolein and ethylene oxide both pose an estimated cancer risk exceeding 800 in 1 million based on the draft cancer risk values and early research. This is more than 10 times higher than the cancer risk from benzene and puts it on par with the cancer risk diesel exhaust posed when it was first identified as a major concern in the late nineties.  

This estimated cancer risk characterizes current risk and does not represent a significant recent shift in regional air quality. Estimates of cancer risk reflect the best available science and indicate a cause for concern. However, fully understanding the extent of this risk and the sources will require additional study and remain an active area of research. 

OEHHA’s assessment for acrolein provides the first cancer risk value for this chemical since it was classified as “probably cancer-causing to humans” in 2020. In addition to cancer risk, acrolein can irritate your eyes, nose and throat in the short term, causing symptoms like watery eyes, coughing, or a burning feeling. Long-term exposure to higher levels can harm the respiratory system, leading to problems such as congestion, shortness of breath, worsened asthma, and ongoing irritation.  

Ethylene oxide can also irritate your nose and throat and cause headaches, dizziness, nausea, fatigue, and stomach distress.  These effects may disappear after exposure stops but irritation can become persistent after long-term exposure. Ethylene oxide also is considered a reproductive toxicant. 

Sources of acrolein and ethylene oxide 

Acrolein is produced when materials burn such as during wildfires, cigarette and vaping smoke, and from burning fossil-fuel to power cars, trucks, ships and aircraft. It also can form during chemical reactions in the atmosphere and be found in water used in oil and gas exploration.  

Ethylene oxide is used to sterilize medical equipment and as an ingredient to manufacture other chemicals. Ethylene oxide is also produced in small amounts from natural processes and can be formed during combustion. 

How to protect yourself  

There are simple steps you can take to lower your exposure to acrolein in everyday life: 

• Avoid smoking tobacco or using e‑cigarettes and other vaping products.  
• Avoid exposure to tobacco smoke, especially for children.  
• Try to avoid breathing smoke from fires or exhaust from diesel and gasoline vehicles and equipment.  
• When cooking with oils or fats, avoid very high temperatures and use a ventilation fan when possible.  

Learn about how to protect yourself from wildfire smoke by visiting Smoke Ready California. 

Many of these recommendations will help reduce exposure to ethylene oxide to including avoiding breathing smoke from tobacco or fires and exhaust from diesel or gasoline engines. The use of air filtration devices may reduce overall exposure to airborne chemicals, especially for sensitive individuals such as young children, seniors, and those with lung disease such as COPD or asthma. 

State response 

In response to these findings, Governor Gavin Newsom is proposing $2.5 million in funding as part of the May Budget Revision for the California Air Resources Board (CARB) and OEHHA to complete critical, foundational scientific research needed to support additional actions to reduce risks from acrolein and ethylene oxide.  

This includes expanding air monitoring to identify major sources of these chemicals and support additional research to better understand how Californians are being exposed to develop the most effective ways to reduce the health risks, working with local air districts.  

While ongoing initiatives—such as deploying cleaner vehicles—continue to help reduce overall air pollution, further targeted actions are needed to reduce their risk. Taking additional actions requires a clearer, science-based understanding of their sources and contributions. 

“All Californians should be able to breathe freely knowing the air is clean and safe,” said OEHHA Director Kris Thayer. “We will continue to use rigorous scientific methods and public peer review, which make our acrolein and ethylene oxide assessments a credible foundation for evaluating the risks they pose, especially for the most sensitive members of our communities.” 

The funding will strengthen California’s ability to generate emissions data, conduct atmospheric modeling, evaluate health risks and turn scientific findings into policy outcomes that protect public health. 

“Research and a solid scientific understanding of acrolein and ethylene oxide is fundamental to protecting public health. With OEHHA’s new cancer risk values for these toxics, CARB is committed to building a greater understanding of these chemicals in our air, their impacts on public health and the best, most effective ways to remediate the risk,” said CARB Chair Lauren Sanchez.  

OEHHA and CARB’s work on these chemicals is part of the state's Air Toxics “Hot Spots” Program. The program collects emission data, identifies facilities having localized impacts, determines health risks, notifies nearby residents of significant risks and works to reduce those risks, while keeping affected communities informed. The additional progress needed on these toxics will be guided by the proposed research initiative and a statewide planning effort to ensure that mitigation progress remains scientifically grounded, practical, and effective. 

Learn more and get involved 

CARB and OEHHA have launched new webpages to help communities and individuals access information about acrolein and ethylene oxide. Three public workshops also will be held to provide more information, answer questions and gather community feedback.  

Public workshops will be held at: 
 
Northern California 
June 2, 2026, 4:00 PM – 7 PM 
Sierra Hearing Room, Cal EPA Building 
1001 I Street, Sacramento, CA 95814  
Zoom Link 

Southern California 
June 4, 2026, 10:00 AM – 1:00 PM 
Auditorium, Ronald Reagan State Building 
300 South Spring Street, Los Angeles, CA 90013 

Central California 
Details for a workshop in Central California will be announced at a later date. 

A 45‑day public comment period is now open. OEHHA and CARB encourage Californians to share their perspectives through the workshops and the public comment process. After the initial public comment period, the assessments will be revised, undergo another 30-day public comment period, be peer reviewed by the state’s Scientific Review Panel (SRP) on Toxic Air Contaminants, and adopted pending approval by the SRP.