California’s Draft Cancer Risk Values Signal a More Demanding Era for Air Risk Management

On May 14, 2026, the California Office of Environmental Health Hazard Assessment (OEHHA) released draft cancer risk values for acrolein and ethylene oxide. The draft risk assessments state that both chemicals can pose an unacceptable cancer risk, with estimated risks up to 10 times higher than benzene. For industry, the significance is not only scientific. It is regulatory, legal and operational.

The timing matters. OEHHA is making these assessments as the United States Environmental Protection Agency (EPA) proposes to reverse rules on ethylene oxide emissions and moves to dismantle the Integrated Risk Information System (IRIS) and the risk values developed through that program. If the federal position changes, much of the reasoning behind current ethylene oxide litigation could also shift, making California’s action potentially significant for industry, and not just in California because other states could follow their lead as is often the case.

OEHHA states that recent air monitoring data and new scientific insights led the state to issue draft risk values for cancer risk from inhalation exposure. The agency has also been clear that this does not mean air quality has suddenly changed. The concern is based on a new estimation of current risk using updated science.

That distinction matters for industry. A change in risk value can alter how existing emissions are understood, even when facility operations have not changed. The same air concentrations can become more consequential when the risk benchmark changes.

For both of these draft assessments, OEHHA’s current relies on ambient air measurements from two CARB monitoring events in the Study of Neighborhood Air near Petroleum Sources (SNAP). These studies were done in Lost Hills (Kern County) and Inglewood Oil Field (Los Angeles County). This creates an important question for facilities: how representative are those measurements of local conditions, local sources and local background levels?

California is already preparing to expand that understanding. Governor Gavin Newsom has requested $2.5 million for the California Air Resources Board (CARB) and OEHHA to conduct expanded air monitoring studies to identify sources of ethylene oxide and acrolein. Once sources are identified, CARB and OEHHA are expected to evaluate ways to reduce public exposure and risk.

For acrolein, this draft is a huge change. Previously acrolein was only assessed for its non-cancer risk. This will be the first time that a cancer risk assessment is added and it has been identified as one of California’s emerging air toxics of concern. The draft IUR is 7.9 x 10-4 ug/m3, which is actually higher than the IUR of benzene, 2.9 x 10-5 ug/m3. This could greatly increase the risk factor from certain industries.

The change for ethylene oxide is no less dramatic. OEHHA is proposing to update the IUR for ethylene oxide from 8x8x10-5 ug/m3, which is similar to benzene, and increase it to 3.0 x 10-3 ug/m3. This is an increase of 34x over the original and 10x higher than benzene.

Both acrolein and ethylene oxide come from a wide range of industrial, residential and endogenous sources, which makes risk attribution challenging.

Acrolein is produced by burning organic matter, including wildfires, an ongoing issue in California that is potentially getting worse. It is also associated with burning fossil fuels in cars and power plants, smoking, vaping and cooking. Industrially, acrolein is used as an intermediate chemical in the manufacturing of certain plastics and resins.

Acrolein may also become more relevant for facilities with significant combustion sources, particularly where large fuel combustion equipment operates close to homes, schools, businesses or other sensitive receptors.

Ethylene oxide is commonly used as a sterilizing agent in the medical and food industries. It is also an intermediate in the manufacturing of detergents, plastics, textiles, solvents and antifreeze.

Ethylene oxide presents a particularly difficult policy challenge because it is both a toxic air contaminant and a critical sterilant. The United States Food and Drug Administration (FDA) states that about half of sterile medical devices in the United States are sterilized with ethylene oxide. The practical question is not simply how to reduce emissions. It is how to reduce community risk without disrupting access to sterile medical devices and other essential products.

This mix of sources means facilities need more than a general understanding of emissions. They need defensible data that shows what is happening at and around their sites, especially when background levels, off-site sources and local conditions may influence monitoring results.

Risk will also depend on local context. A facility located near homes, schools or other sensitive receptors may face a different risk profile than a similar facility farther from occupied structures. Air districts will also consider cumulative toxic air contaminant burden, meaning acrolein or ethylene oxide may be only one part of a broader facility risk calculation.

California’s review process could take up to a year. OEHHA originally opened the public comment period from May 14 through June 29, 2026, but has since extended the deadline to July 29, 2026, for both acrolein and ethylene oxide. The state will then hold public workshops around California, followed by a second public comment period.

After that, the draft findings will move through peer review before a final vote by the Scientific Review Panel on Toxic Air Contaminants.

That timeline gives industry a narrow but meaningful window to prepare. Facilities do not need to wait for final risk values before evaluating their exposure profile. Waiting could leave operators reacting to state findings rather than contributing accurate site-specific information to the discussion.

In the meantime, California industry should consider conducting air studies in and around their facilities. State administrative leaders have made their intent clear: they want to reduce public risk from these chemicals. For many operations, eliminating the use or generation of acrolein and ethylene oxide will be nearly impossible, leaving exposure reduction and risk demonstration as the practical path forward.

Industry must be able to demonstrate that its operations are not increasing risk for the surrounding community. Professional support matters because the data must be accurate, defensible and useful. Fenceline monitoring, source tracing and local background studies can help facilities understand whether they are contributing to elevated concentrations.

For acrolein, the challenge is not only the risk value. It is also measurement. Emissions quantification remains uncertain for some source categories, and the absence of a CARB-approved stationary source test method means facilities may need to approach testing and interpretation carefully.

Testing strategy matters. For highly potent air toxics, detection limits can shape the risk conversation. Poorly designed testing can create results that are difficult to explain later, even when the data do not reflect a meaningful facility contribution.

That information can also provide a counterpoint to broader state data where local conditions differ. The strongest position is proactive. Facilities that identify potential problem areas early can make self-corrections before regulators impose additional requirements that may disrupt operations.

OEHHA’s draft risk values signal a more demanding approach to air toxics risk in California. The science, regulatory process and legal context are moving together. Facilities that rely on uncertainty may find themselves exposed as the state builds its own record.

The better path is to understand site-specific conditions now. Defensible air data gives industry a clearer view of risk, supports practical decisions and helps demonstrate accountability to regulators and communities.