California requires Proposition 65 cancer warnings on hundreds of products, ranging from tobacco and gasoline to beer and french fries. But there are no warnings on processed meats, like hot dogs, corned beef and bacon, despite an international agency’s findings in 2015 that those foods cause cancer in humans.

A doctors’ group is going to court Wednesday to try to cure that omission.

“California has been violating the law for nearly five years by failing to add processed meat to the Proposition 65 list,” Mark Kennedy, a lawyer with the Physicians Committee for Responsible Medicine, said in a statement accompanying the lawsuit in Sacramento County Superior Court.

Prop. 65, approved by California voters in 1986, requires warning labels on products the state has found to be likely causes of cancer or birth defects. There have been disputes over some listings, such as coffee, briefly added by court order in 2018 and then removed by state health officials, but California has generally followed the findings of medical researchers at home and abroad.

In June 2015, the International Agency for Research on Cancer, an arm of the World Health Organization, classified processed meats such as hot dogs, ham, sausages, corned beef and beef jerky, as “carcinogenic to humans,” its highest level of risk. The findings were based on more than 400 studies.

The World Health Organization said researchers had concluded about 34,000 cancer deaths a year worldwide could be attributed to diets high in processed meat. Eating 50 grams of processed meat per day, about the amount in a hot dog, increases the risk of colorectal cancer by 18%, the organization said.

The Physicians Committee is a Washington, D.C., nonprofit that advocates preventive medicine and promotes a plant-based diet. In its lawsuit, the committee said the California agency that administers Prop. 65, the Office of Environmental Health Hazard Assessment, has ignored a clear legal duty to add substances to the warning list if the international agency has found them to be carcinogenic.

State court rulings since 1989 leave the office with “no discretion; those chemicals identified by the IARC as cancer-causing must be listed,” the suit said.

It said the state office argued in 2017 that it had to wait for the international agency’s full study to be published, despite a state court ruling rejecting such a delay in an earlier case. The study was published in March 2018, but the office said it was still reviewing the issue, periodically promising imminent action and assuring the Physicians Committee in September that it would make a decision by this January, the suit said.

“This is the exact agency ‘foot-dragging’ that was the basis for the enactment of Proposition 65,” the suit declared. Filed against Gov. Gavin Newsom and state agencies, it seeks a court order requiring California to add processed meat to the cancer-warning list.

There was no immediate comment from the state Office of Environmental Health Hazard Assessment.

Bob Egelko is a San Francisco Chronicle staff writer. Email: begelko@sfchronicle.com Twitter: @BobEgelko