What to know about California's Prop. 65

A California judge this week ruled in favor of the Council for Education and Research on Toxics, which charged that coffee sellers like Starbucks did not disclose that acrylamide, a possible carcinogen, can be found in coffee.

According to court documents, Superior Court Judge Elihu Berle said that coffee companies failed to show that there was not a significant health risk from a carcinogen in coffee.

Acrylamide is one of nearly a thousand chemicals listed in the state's Safe Drinking Water and Toxic Enforcement Act, which was passed in 1986. The environmental safety regulation is more commonly referred to as Proposition 65.

"Acrylamide was added to the Proposition 65 list in 1990 because studies showed it produced cancer in laboratory rats and mice," Sam Delson of the Office of Environmental Health Hazard Assessment (OEHHA) told ABC News in an email.

According to ABC News chief medical correspondent Dr. Jennifer Ashton, acrylamide is a by-product that forms in the roasting and baking process.

"When talking about a toxin you need either a very potent toxin or a high frequency or a very large dose and when you're talking about coffee. Obviously, the concern is the high frequency," she said.

Ashton also pointed out that medical literature and studies have previously shown "clear and massive associations" between coffee and improved health. Some of the health benefits include "reduced risk of certain types of cancer like skin cancer, liver cancer, a reduced risk of Type 2 Diabetes, Parkinson's, the list goes on and on," she said.

So what is Proposition 65?

Prop. 65 was designed to protect the state’s water sources and require businesses to inform consumers about potential exposure to harmful toxins.

The law requires that California's governor publish an annual list of chemicals that are known to cause cancer or birth defects. Businesses are required to place a Prop. 65 warning on products that contain any of these toxins. The warning, however, does not necessarily imply that a product violates safety standards or requirements. Some businesses are exempt from Prop. 65, such as those with fewer than 10 employees, as well as governmental agencies and public water systems.

The warning signs have become ubiquitous around California, displayed everywhere from gas stations to apartment complexes to water bottles. The nearly a thousand chemicals on the list can be found in common household products, manufacturing and construction or motor vehicle exhaust.

Acrylamide forms when food is cooked or processed at high temperatures. It can be found in "French fries, potato chips, other fried and baked snack foods, roasted asparagus, canned sweet potatoes and pumpkin, canned black olives, roasted nuts, coffee, roasted grain-based coffee substitutes, prune juice, breakfast cereals, crackers, some cookies, bread crusts, and toast," Delson said.

OEHHA developed "safe harbor levels" for exposure to acrylamide that do not require Prop. 65 warnings. "For cancer effects, the significant risk level for acrylamide is 0.2 micrograms per day," Delson said.

Opponents of the regulation feel many small businesses face unfair lawsuits as a result of the law. To counteract that, Prop. 65 was amended in 2013 to outline a specific protocol for how citizens can file complaints against companies.

California Gov. Jerry Brown also announced in 2013 that he planned to offer additional reforms to the regulation. In 2017, he signed AB 1583, which requires the attorney general to provide a letter to both the enforcer and alleged violator when a lawsuit is deemed merit-less or has factual basis.

Businesses who defy Prop. 65 can face fines up to 2,500 per violation per day.

"Cancer warning labels on coffee would be misleading. The U.S. government’s own Dietary Guidelines state that coffee can be part of a healthy lifestyle," the NCA said in a press release. "The World Health Organization(WHO) has said that coffee does not cause cancer."