Proposition 65 requires warnings for about 900 chemicals, according to the Associated Press.

"From a practical standpoint would we recommend people stop drinking coffee as a result of the judge's decision?"

The chip-makers opted to do that rather than post cancer warnings like those that are found, and largely ignored, throughout California.

"Reducing coffee or French fries to their acrylamide content isn't how we study diet and nutrition".

Earlier this week, a California judge ruled that coffee companies will need to place a cancer warning label on their products, due to the supposed presence of a cancer-causing agent known as acrylamide.

The National Coffee Association is considering an appeal and other legal options in response to the ruling. However, the World Health Organization has made a decision to put the coffee on its possible carcinogenic list about two years ago.

"Defendants do not dispute that they failed to provide warnings to consumers that the ready to drink coffee they sold contained high levels of acrylamide".

The ruling came despite eased concerns in recent years about the possible dangers of coffee, with some studies finding health benefits.

Wait: Coffee is capable of both preventing cancer and causing cancer?

"I see it as part of California's historical, knee-jerk, "this is bad and we have to regulate it" mentality, which is not always a bad thing", said Tommy Medley, owner of the White Rabbit since it opened in late 2013.

The Korean company also said that Starbucks in the USA will take collective action with other coffee chains such as Dunkin' Donuts to prove that the threat from acrylamide, a chemical compound produced in the roasting process, is insignificant. "Defendants failed to satisfy their burden of proving ... that consumption of coffee confers a benefit to human health". He typically drinks two to three cups of coffee a morning - never after noon - out of enjoyment, rather than dependence, he said. Meanwhile the California political system, which listens carefully to the small industry of nonprofits and attorneys that make a living by filing suits, has been unwilling to do more than nibble around the browned edges of Prop 65's famous irrationalities.

"The parties do not dispute that roasting coffee causes the release of the chemical acrylamide, and that brewed coffee contains acrylamide", Berle writes. The tentative decision follows a lawsuit brought against more than 90 companies including Starbucks, Peet's, Whole Foods and Target for failing to adhere to the state's required chemical warnings, and could subject them to millions of dollars in fines. The next phase of the trial will determine the civil penalties to be levied on the defendants.

The health debate surrounding coffee is still muddled, however.

Amy Trenton-Dietz, a public health specialist at the University of Wisconsin-Madison, said the California ruling contrasts with what science shows. Acrylamide is the product of a chemical reaction that happens between certain sugars and the amino acid asparagine when the food is heated.

"If the concentration level is so low, then what's the meaning of labeling those foods?" he said.

According to the NGO, all the coffee products sold by Starbucks and other vendors contain acrylamide, a substance that is cancerogenic.