Federal Court Blocks Proposition 65 Acrylamide Warnings Based on Scientific Uncertainty

On May 2, 2025, a federal court in California issued a permanent injunction blocking the state from requiring Proposition 65 warnings for acrylamide in food. The court granted summary judgment in favor of the California Chamber of Commerce, which first filed suit in 2019 to block the addition of acrylamide to the list of chemicals known to cause cancer or reproductive toxicity and for which consumer warnings must be provided under Proposition 65.

Acrylamide is used to make plastics and to treat drinking water, but studies have also shown that it can be present at low levels in certain foods, including grains and potatoes, when cooked at high temperatures. The listing of acrylamide under Proposition 65 has been controversial since its inclusion in 2019. A judge previously issued a preliminary injunction blocking the acrylamide warning requirement in 2021, which Friday’s decision makes permanent.

The court concluded that the state’s acrylamide listing violated the First Amendment’s prohibition against compelled speech. Its determination hinged on the lack of a scientific consensus as to whether acrylamide poses a cancer risk to humans. While studies have shown that large doses of acrylamide can cause cancer in mice and rats, the court noted that “the parties’ experts strongly disagree that the results of these animal studies can be extrapolated to humans,” and that “authorities such as the [U.S. Food and Drug Administration], National Cancer Institute, and American Cancer Society have questioned whether there is sufficient scientific proof dietary acrylamide is a cancer risk to humans.”

The court based its First Amendment decision on two factors: (1) whether the acrylamide warnings are factual and contained uncontroversial information, and (2) whether the warnings are justified by a substantial government interest and are not unduly burdensome. The court first concluded that the warnings are controversial, and not factual, based on the scientific disagreement around acrylamide’s risks to humans. It then concluded that there is not a significant government interest in requiring the warnings, which are misleading, do not advance the state’s interest in informing consumers about known cancer risks, and unduly burden the businesses that are required to provide them to consumers.

This decision is a notable departure from the normal course of Proposition 65 enforcement, in which substances are frequently added but rarely removed from the Proposition 65 list. The court’s reasoning could open the door for future First Amendment challenges to other Proposition 65 listings that lack strong scientific support.

The case is California Chamber of Commerce v. Becerra et al., case number 2:19-cv-02019, in the U.S. District Court for the Eastern District of California.

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