California's cancer warning on coffee is ridiculously unscientific, experts say. Here's why the state puts warnings on more than 1,000 foods, places, and chemicals.

Matt Snodderly / Shutterstock.comCalifornia’s Bixby Bridge, south of Monterey.

In California, it seems you’re never far from a reminder about cancer.

You can’t park a car indoors in the Golden State without seeing a warning about the ways your cancer risk might spike.

Earlier this year, a California judge ordered that all coffee sellers in the state must post warnings about the potentially cancer-causing effects of a chemical in coffee called acrylamide. But the ruling is being challenged by the state’s Office of Environmental Health Hazard Assessment because there’s no solid scientific evidence that coffee can cause cancer.

Acrylamide occurs naturally in small quantities when coffee beans – and many other plant-derived foods – are roasted. And research suggests the health benefits of drinking coffee vastly outweigh the risks.

California’s cancer-warning policy comes from a 1986 state law called Proposition 65, enacted to protect California’s drinking-water supply from toxic and potentially cancer-causing chemicals. It also mandates the state keep a master list of all chemicals known to be toxins and requires manufacturers and businesses to warn people about these chemicals if they’re present in products or buildings, even in extremely small doses.

There are more than 1,000 chemicals on California’s warnings list, which grows every year. Some chemicals on it have been proven to cause cancer, but not all. A chemical needs to have only a one-in-100,000 chance of upping your risk for cancer to merit a written warning to consumers.

“We now have so many warnings unrelated to the actual health risk posed to consumers that most people just ignore them,” Democratic Rep. Kurt Schrader of Oregon said in a release this month blasting the new coffee warnings, adding: “When we have mandatory cancer warnings on a cup of coffee, something has gone seriously wrong with the process.”

The way cancer develops in the body is extremely complex, so a person’s cancer risk isn’t just about what they put in their mouth, car, and lungs – it has a lot to do with our genes and family history too.

For that and other reasons, many Californians and cancer experts lament that the warnings aren’t all that helpful as written.

The American Cancer Society says on its website: “The Prop 65 labels only tell you that a product has something in it that might cause cancer or affect reproduction. They don’t say what the substance is, where it is in the product, how you might be exposed to it, what the level of risk is, or how to reduce your exposure.”

Here are a few of the strangest things that carry cancer warnings in California.

Parking your car in an indoor, enclosed parking deck


A concrete parking lot is not the best place for a casual, cancer-risk-free hang.

“Breathing the air in this parking garage can expose you to chemicals including carbon monoxide and gasoline or diesel engine exhaust,” California says on its parking-lot warning. “Do not stay in this area longer than necessary.”

The state insists that phrase is printed on signs in indoor parking decks or just about anywhere that people park inside.

The International Agency for Research on Cancer agrees with California on this one. Diesel oil has more than 30 known components that can cause cancer – though in a well-ventilated parking deck, there shouldn’t be too many fumes.

Drinking coffee

California warns all residents that a cup of joe might cause cancer. A judge ruled earlier this year that the warnings were necessary as coffee contains a tiny dose of a chemical called acrylamide and therefore might be associated with an increased cancer risk. The compound can form when food is cooked at high temperatures through processes like frying, baking, and roasting.

Acrylamide has been linked to cancer in mice and rats when it’s put in their drinking water, but only in very high doses.

“In animal studies, if you give animals a very high dose of acrylamide, it may cause cancer,” Frank Hu, the chair of the nutrition department at the Harvard T.H. Chan School of Public Health, recently told The Seattle Times. “However, there is no evidence that acrylamide intake is related to cancer in humans.”

Researchers who’ve for years studied coffee drinkers think those people probably aren’t at any higher risk of getting cancer.

Instead, the International Agency for Research on Cancer and the American Cancer Society both point to scientific evidence suggesting that drinking coffee may lower a person’s risk of developing some kinds of cancers, including oral, prostate, and liver cancers.

Acrylamide is in all kinds of cooked food we regularly eat, like french fries, potato chips, cookies, and cereal. There’s no evidence yet that the amount of acrylamide in a cup of coffee has any detrimental health effects – in fact, you’d have to drink thousands of times the amount of acrylamide in that cup to get to those levels. It’s much more likely that acrylamide in cigarettes could be worrisome for people.

The California Office of Environmental Health Hazard Assessment is challenging the coffee-warning ruling, arguing there’s not enough evidence that coffee causes cancer.

Still, places like Starbucks in California have started pinning up signs to comply with the regulation.

Being on your phone

Phones aren’t chemicals, so they’re not on the official Prop 65 list, but the California Department of Health still warns that the radio frequency energy they emit might cause cancer.

Scientific studies haven’t demonstrated that mobile phone radiation levels are anything to worry about in humans, though researchers have noticed some worrisome tumour growth and heart-tissue damage in rats who were exposed to mobile phone radio frequency radiation, Science Friday recently reported, though the scientists weren’t able to replicate the effects in mice.

California residents are told to not keep their phones in their pockets and to store them away from their bed at night. The health department also suggests people use wired headphones, wireless headsets, and speakerphone capabilities instead of holding their phone up to their ear, and send more texts to avoid keeping phones close to their heads.

Staying at a hotel

Even spending a little time as a tourist in California can increase your cancer risk, the state says.

“When you check in at a hotel, look for a Proposition 65 warning sign at the hotel’s check-in desk, or a warning printed on the registration form,” the state says, adding, “If you have any questions about the warning, ask hotel representatives.”

Not all hotels have the cancer warnings – much of the danger California is worried about in hotels comes from toxins in substances like secondhand smoke or alcohol.

Drinking and smoking are both activities known to increase your risk of developing cancer, so California suggests choosing smoke-free hotels or avoiding smoking areas.

Going to your dentist’s office

Peter Macdiarmid/Getty Images

Getting your teeth worked on can be risky, according to California’s warning system. Some chemicals on the state’s list are used in common dental procedures.

“These include sedation with nitrous oxide; some root canals, crown placements or removals, dental bridge placements; tooth restorations with fillings that contain mercury; and the use of some dental appliances,” California’s warning says.

Having a bite to eat in a restaurant

Going out to eat is not a cancer-risk-free activity either, according to California.

Any place that serves fries, alcohol, or some balsamic vinegars that may contain lead must also serve up this warning to customers: “Certain foods and beverages sold or served here can expose you to chemicals including acrylamide in many fried or baked foods, and mercury in fish, which are known to the State of California to cause cancer and birth defects or other reproductive harm.”

Acrylamide, the chemical that California’s worried about in coffee, is found in some foods cooked at high temperatures. But again, the Food and Drug Administration says the levels of the chemical in foods like fries or crackers are much lower than the levels linked to cancer in animal studies.

The state suggests residents also limit their consumption of grilled foods, since those cooking processes can also contribute to an increased cancer risk.

Enjoying a day at an amusement park

David Paul Ohmer via Compfight cc

Amusement parks aren’t all fun and games, according to Prop 65.

California cautions that exhaust from rides, lead in railings, secondhand smoke from fellow parkgoers, and greasy food could all raise cancer risk.

It’s true that the chemicals in those things have been found to be linked with higher rates of cancer, but you’ll find all of them outside amusement parks too.

Drinking alcohol

Though some of California’s cancer warnings seem silly, others are very sound.

Scientists have known for years that the more alcohol you drink, the higher your risk may be of developing cancer in the throat, liver, breast, or colon.

Cancer doctors in the US say even as little as one glass a day of an alcoholic drink can contribute to your risk of developing cancer.

California cancer warnings can give people the sense that just about anything they do might cause cancer.

Evans Vestal Ward / Bravo / NBCU Photo Bank via Getty Images.

The Los Angeles Times editorial board in September outlined how useless the state’s warnings can be.

“The signs they post don’t provide the context to help people make educated decisions about the risk they face,” the board wrote in the editorial. “Many don’t even identify which chemical or chemicals are at issue.”

That leaves consumers who are inundated with cancer warnings at a loss for how to reduce their risk. But California is expected to tweak its policies later this year.

New rules set to be in place by August 30 will require companies to name at least one risky chemical in any product that comes with a cancer warning. Warnings will also have to include a note telling people they can find more information on the state’s website about how to reduce their exposure to toxic chemicals.

With those changes, California’s ubiquitous cancer warnings may at least get a bit more helpful and specific.

Business Insider Emails & Alerts

Site highlights each day to your inbox.

Follow Business Insider Australia on Facebook, Twitter, LinkedIn, and Instagram.