If you drink decaf coffee, there’s a chemical often used in the process of making it that some advocates want to ban.

The group Clean Label Project says companies like Starbucks and Dunkin’ use methylene chloride to remove the caffeine. While the Environmental Protection Agency banned the chemical’s use as a paint stripper, the Food and Drug Administration allows its use in decaffination.

“Methylene chloride works as a solvent. It binds to the caffeine in coffee so that it can essentially be discarded,” says STAT’s Nick Florko. “The process actually isn’t that different from how paint stripper is used to remove paint.”

In the case of paint stipper, the EPA banned methylene chloride because consumers were directly exposed to it. But with decaf, people using the product aren’t breathing in the chemical, Florko explains.

The cancer risk for decaf drinkers is has been reported to be very low since the beans are roasted at a high temperature after the chemical is used. In the 1980s, the FDA found that the risk of cancer for people who drink multiple cups of decaf per day is one in a million, Florko says.

“That estimate does have some flaws, namely the fact that it assumes a cup of decaf is about five ounces, which is pretty small,” he says. “That’s less than half the size of a tall Starbucks cup.

More recent studies have shown methylene chloride causes cancer in lab animals. Consumer groups cite a 1950s law that says the FDA can’t approve food additives that are shown to cause cancer in people or animals, Florko says.

Consumer groups argue that companies can use other methods to decaffeinate coffee. Some chains including Peet’s Coffee and Caribou Coffee use the Swiss water method, which entails soaking coffee beans in water and filtering out the caffeine.

A group of coffee makers against banning methylene chloride recently wrote the FDA saying, “true coffee aficionados in blind tastings” prefer coffee decaffeinated with the chemical, Florko says, “which is a pretty funny claim if you consider the fact that we’re talking about coffee here that’s essentially rinsed in paint thinner.”

The small FDA office in charge of reevaluating existing food additives has acknowledged its limited resources to respond to these pending petitions, Florko says.

“Time will tell,” he says.

Gabrielle Healy produced and edited this interview for broadcast with Peter O’Dowd. Allison Hagan adapted it for the web.

This article was originally published on WBUR.org.

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