A Los Angeles judge has ruled that California law requires coffee companies to carry a cancer warning label.

Superior Court judge Elihu Berle said in a proposed decision Wednesday that Starbucks and other coffee companies failed to show the threat from a chemical compound produced in the coffee roasting process was insignificant.

The Council for Education and Research on Toxics, a non-profit group, sued Starbucks and about 90 other companies, including grocery stores and retail shops, under a state law that requires warnings on a wide range of chemicals that can cause cancer. One of those chemicals is acrylamide, a carcinogen present in coffee.

"While plaintiff offered evidence that consumption of coffee increases the risk of harm to the fetus, to infants, to children and to adults, defendants' medical and epidemiology experts testified that they had no opinion on causation," Berle wrote. "Defendants failed to satisfy their burden of proving by a preponderance of evidence that consumption of coffee confers a benefit to human health."

Superior Court judge Elihu Berle said in a proposed decision Wednesday that Starbucks and other coffee companies failed to show the threat from a chemical compound produced in the coffee roasting process was insignificant. (Gregory Bull/Associated Press)

The coffee industry had claimed the chemical was present at harmless levels and should be exempt from the law because it results naturally from the cooking process to make the beans flavourful.

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

'Possible carcinogen'

In 2016, the International Agency for Research on Cancer — the cancer agency of the World Health Organization — moved coffee off its "possible carcinogen" list.

Studies indicate coffee is unlikely to cause breast, prostate or pancreatic cancer, and it seems to lower the risks for liver and uterine cancers, the agency said. Evidence is inadequate to determine its effect on dozens of other cancer types.

Coffee has been shown, over and over again, to be a healthy beverage. - William Murray, president and CEO of National Coffee Association

The lawsuit was brought under the Safe Drinking Water and Toxic Enforcement Act, passed by voters as Proposition 65 in 1986. It allows private citizens, advocacy groups and attorneys to sue on behalf of the state and collect a portion of civil penalties.

The law has been credited with reducing chemicals that cause cancer and birth defects, such as lead in hair dyes, mercury in nasal sprays and arsenic in bottled water. But it's also been widely criticized for abuses by lawyers shaking down businesses for quick settlements.

"Coffee has been shown, over and over again, to be a healthy beverage," said William Murray, president and CEO of the National Coffee Association, in reaction to the decision. "This lawsuit has made a mockery of Prop. 65, has confused consumers, and does nothing to improve public health."

'Better for public health'

The lawsuit has been brewing for eight years and is still not over. A third phase of trial will later determine any civil penalties that coffee companies must pay.

With potential penalties up to $2,500 US per person exposed each day over eight years, that figure could be astronomical in a state with close to 40 million residents, though such a massive figure is very unlikely.

Attorney Raphael Metzger, who brought the lawsuit and drinks a few cups of coffee a day, said he wants the industry to remove the chemical from its process. Coffee companies have said that's not feasible and would make their product taste bad.

"Getting it out is better for public health than leaving it in and warning people," Metzger said. "That's especially important for coffee drinkers because coffee drinkers are addicted."

The coffee industry had claimed the chemical was present at harmless levels and should be exempt from the law because it results naturally from the cooking process to make the beans flavourful. (Richard Vogel/Associated Press)

Metzger's client brought a similar case later taken up by the state attorney general that resulted in potato-chip makers agreeing in 2008 to pay $3 million US and remove acrylamide from their products rather than post startling warnings that can be found throughout California and are largely ignored.

Parking garages, for example, post signs saying, "This area contains chemicals known to the state of California to cause cancer, birth defects and other reproductive harm."

Regulations adopted in recent years now require more specific warnings that list the chemical consumers may be exposed to and list a website with more information. Parking garages, for example, will have to post that breathing air there exposes drivers to carbon monoxide and gas and diesel exhaust and that people should not linger longer than necessary.

Many coffee companies have already posted warnings that specifically say acrylamide is found in coffee and is among chemicals that cause cancer. However, many of those warnings are posted in places not easily visible, such as below the counter where cream and sugar are available.

Law places burden on coffee companies

In the first phase of the trial, Berle said the defence failed to present enough credible evidence to show there was no significant risk posed by acrylamide in coffee.

The law put the burden on the defence to show that the level of the chemical won't result in one excess case of cancer for every 100,000 people exposed. Berle said the epidemiology studies presented were inadequate to evaluate that risk.

Having failed to show there was no significant risk to drinking coffee, the industry had to show during the trial's second phase that there should be a less strict level for coffee because of health benefits from drinking it.

The World Health Organization's research arm says very hot drinks probably have the potential to cause cancer in humans 2:07

Berle said the coffee companies failed to show that.

The judge can reverse his tentative ruling, but that rarely happens.

About a dozen of the defendants in the case have settled at some point during the long legal process and agreed to post warnings, Metzger said. With some defendants dismissed or affiliated with larger companies about 50 defendants remain.

Among the latest to settle was 7-Eleven, which agreed to pay $900,000. BP West Coast Products, which operates gas station convenience stores, agreed to pay $675,000.