The California Office of Environmental Health Hazard Assessment (OEHHA) is set to overturn a controversial recent court decision that proposed all coffee shops and makers in the state brand their product with a cancer warning label. The new government regulation is another chapter in the long-running battle over whether a cup of coffee is a legitimate cancer risk.

In 2010, a lawsuit was filed on behalf of the Council for Education and Research on Toxics, against Starbucks and a number of other "ready-to-drink" coffee shops. The suit suggested that the amount of a chemical called acrylamide in coffee was of such dangerous levels that it should require cancer hazard signs at every point-of-sale for the product.

The lawsuit referred back to a particular Californian law, passed in 1986, called Proposition 65. This regulation required businesses to clearly notify citizens when they were being exposed to chemicals known to cause cancer or have reproductive toxicity. The OEHHA maintains an up to date list of chemicals deemed toxic enough to apply to Proposition 65.

The acrylamide story

Acrylamide, as a potential cancer-causing agent, has been on the Proposition 65 list since 1990, and a 2002 study from Swedish researchers highlighted how high levels of acrylamide can form in food when it is cooked at elevated temperatures. Since this study there has been a flurry of research into the formation of acrylamide in a number of foods, ultimately leading to this long-running Californian court case regarding coffee.

The science is still mixed on the ultimate connection between acrylamide and cancer in human beings. In animal studies, when the chemical was administered in drinking water, it was certainly found to increase rates of several types of cancers. The dosages delivered in these studies, however, were extraordinarily high, leading some to question how transferable the results were to humans.

In humans it is still unclear whether any clear correlation can be made between consumption of food containing low levels of acrylamide and cancer. In theory, acrylamide is converted into a secondary compound in the human body that is known to cause DNA damage and mutations. But in reality it is still unclear whether general dietary exposure in humans actually leads to cancer.

A systematic review of a number of studies found no statistically significant association between dietary acrylamide intake and several cancers. While a small volume of the data studied did find some minor increased cancer risks, the majority of data found no association. In general, the big challenge in these kinds of large scale, self-reported observational studies is that it is incredibly difficult to clearly quantify an individual's exposure to the chemical.

The World Health Organization's International Agency for Research on Cancer classified acrylamide as a "probable human carcinogen" in 1994. This is the IARC's second highest carcinogen classification and is based on research suggesting there may be limited evidence of carcinogenicity in humans but sufficient evidence in experimental animals.

A toxic cup of coffee

Looking at acrylamide and coffee, the data gets even more unclear. Acrylamide undeniably is formed in coffee during the bean roasting process. How much acrylamide ends up in a cup of coffee though is still unclear. And even more unclear is what constitutes a safe level of acrylamide that can be consumed.

The long Californian court case reached a conclusion in late March, 2018. The defendants, led by the National Coffee Association (NCA), stridently claimed that coffee contains only minute trace amounts of acrylamide that have not been proven to have any negative effect on humans. The NCA also pointed toward a growing body of scientific evidence that suggests coffee can actually confer a number of beneficial health effects.

The judge was not entirely swayed by the defendant's case and in a surprising decision wrote, "Since defendants failed to prove that coffee confers any human health benefits, defendants have failed to satisfy their burden of proving that sound considerations of public health support an alternate risk level for acrylamide in coffee."

So, despite the expected torrent of appeals and objections, that was pretty much that. Californian coffee shops would have to serve some kind of cancer warning alongside each cup served. But the California Office of Environmental Health Hazard Assessment recently stepped in to undercut the court's decision.

In a relatively unprecedented move, the OEHHA is proposing a new regulation to specifically exempt coffee from the Proposition 65 law. In the proposed statement, the OEHHA writes, "The proposed regulation states that drinking coffee does not pose a significant cancer risk, despite the presence of chemicals created during the roasting and brewing process that are listed under Proposition 65 as known carcinogens."

The new proposal adds that Proposition 65 does not apply when the toxic chemicals are found in low enough levels to not pose a significant cancer risk. Here, the OEHHA points toward a recent review of coffee and cancer from the World Health Organization that included the examination of over 1.000 studies. The conclusion of the meta-review was to downgrade coffee's official cancer risk classification due to the fact that there is not enough evidence to link coffee to a variety of cancers.

Raphael Metzger, the attorney representing The Council for Education and Research on Toxics in the case was unsurprisingly stunned by the OEHHA's move, which essentially overturned the judge's decision in a case he had won.

"The takeaway is that the state is proposing a rule contrary to its own scientific conclusion. That's unprecedented and bad," says Metzger. "The whole thing stinks to high hell."

The coffee war is by no means over, in either the world of law or science. The OEHHA regulation faces a public hearing in August before any potential implementation over the subsequent six months.