California updates cancer risk science for acrolein, ethylene oxide

California says draft health assessments find acrolein and ethylene oxide may pose cancer risks over 10 times higher than benzene, starting a review and comment period.

California’s environmental health agency is warning that two toxic air contaminants, acrolein and ethylene oxide, may be far more dangerous than previously estimated, a shift that comes as federal regulators move in the opposite direction.

In a draft finding released Thursday. the state’s Office of Environmental Health Hazard Assessment said the chemicals could pose an estimated cancer risk more than 10 times higher than benzene. a known carcinogen linked to leukemia and other cancers.. The agency said the draft values are part of an early step in a formal review process. before final risk levels are adopted.

“ If the early air monitoring results bear out, and if the draft cancer values developed are close to what eventually becomes final, then each air contaminant poses an unacceptable cancer risk,” OEHHA director Kris Thayer said.

The update reflects California’s changing view of which pollutants are most harmful. Over decades, regulators have shifted attention away from more visible hazards like smog and toward pollutants that are often harder to spot but can contribute to cancer, heart disease and other health effects.

It also arrives just two months after the Trump administration’s Environmental Protection Agency moved to roll back standards for ethylene oxide. or EtO.. The EPA said the change was aimed at saving millions of dollars in compliance costs for facilities that use the chemical to sterilize medical equipment.. Its justification was that the decision would “safeguard the supply of essential medical equipment.” Experts have said the rollback could expose more people to health risks.

For California residents, the stakes appear high even beyond the toxicology update. A recent national report from the American Lung Association found that 82% of Californians live in counties with unhealthy air, nearly double the national average.

“This is an important step to better understanding the harms of pollutants impacting Californians’ health. ” said Will Barrett. assistant vice president for nationwide clean air policy at the American Lung Association. who reviewed OEHHA’s findings for The Times.. “Following the latest available health science to determine risk is crucial to protecting health.”

Ethylene oxide is a colorless gas commonly used to sterilize medical devices. particularly those that cannot be cleaned using steam or radiation.. Acrolein. by contrast. can be generated when materials burn. including cigarettes. e-cigarettes and vapes. wood. plastics and gasoline from vehicles and ships and aircraft.. It can also be released when cooking fats and oils at high temperatures. and it has been found in water associated with oil and gas operations.. Acrolein is also an ingredient in some pesticides used in irrigation canals.

Officials said there are everyday ways to reduce exposure to both contaminants.. They urged people to avoid smoking tobacco and using e-cigarettes and vaping products. and to stay away from smoke from fires and diesel and gasoline exhaust. which can also help reduce EtO exposure.. In the kitchen. they said. people should avoid very high temperatures when cooking with oils or fats and should use a range hood fan when possible.

OEHHA said both chemicals have been present in California’s air for years. but the new assessments are based on updated health science.. The agency said it estimates cancer risk for each contaminant to exceed 800 in 1 million. placing that risk level on par with diesel exhaust estimates when that pollutant first emerged as a major public health concern in the 1990s.

In response to the findings, Gov.. Gavin Newsom’s May budget revision, released Thursday, includes $2.5 million in funding for the California Air Resources Board and OEHHA.. The money is intended to support research aimed at reducing exposure to acrolein and ethylene oxide. including identifying and tracking major sources and converting the findings into public health policy outcomes.

OEHHA’s assessment provides the first cancer risk value for acrolein since it was classified as “probably” cancer-causing to humans by the International Agency for Research on Cancer in 2020.. The state previously identified ethylene oxide as a carcinogen, but the new assessment updates its risk levels using newer research.

Those risk calculations rely on air monitoring data, which officials said vary across the state based on location, nearby sources and other factors.

California officials framed the science update as part of a broader effort to strengthen environmental protections while federal regulators loosen them.. Courtney Smith. principal deputy executive officer with the Air Resources Board. said the state’s work is particularly important at a time when protections are being rolled back elsewhere.

“Especially in light of some of the national rollbacks we’re seeing on protections for public health. it really underscores how important the work that we’re doing here in California is. ” Smith said.. “Not only for protecting the health of Californians. but also to ensure that there is rigorous. solid science available to other entities as well who may want to pursue additional protections.”

Health effects described by the federal Agency for Toxic Substances and Disease Registry include headaches. dizziness. nausea. fatigue and respiratory irritation after short-term inhalation of EtO.. Longer-term exposure raises the risk of cancers of white blood cells. such as non-Hodgkin’s lymphoma. as well as breast cancer.

For acrolein, inhalation can cause nose and throat irritation and a decreased breathing rate. Chronic exposure, including through cigarette smoke, has been linked to asthma, chronic obstructive pulmonary disease and respiratory cancers.

The announcement also comes as California continues to receive poor marks on air quality.. In the American Lung Association’s annual “State of the Air” report, the five U.S.. counties with the worst smog pollution are all in California.. Bakersfield was the metropolitan area with the worst year-round particle pollution for the seventh consecutive year. while Los Angeles had the worst ozone pollution for 26 of the last 27 years.

“Californians face the most significant smog and soot challenges in the nation, but our air agencies have followed the science to build policies and programs to make real headway,” Barrett said.

Barrett argued that the state’s new findings point to the need for ongoing local action. especially as the federal government moves to reduce regulations.. He said California must keep investing in cleaning up truck fleets. expanding public education. and strengthening the underlying science used to guide policy.

The Thursday release also begins a 45-day public comment period. After that, the draft assessments may be revised before undergoing additional public comment and peer review by the state’s Scientific Review Panel on Toxic Air Contaminants, with eventual adoption to follow.

California air quality acrolein ethylene oxide cancer risk OEHHA Environmental Protection Agency air contaminants