Officials warn against drinking Moscow mules from copper mugs

Moscow mule lovers beware: The copper mug could create a poisonous cocktail. 

As The Washington Post reported this week, the Iowa Alcoholic Beverages Division released a bulletin late last month warning bartenders and restaurants against serving the popular cocktail in copper mugs, as is traditional. 

Food and Drug Administration (FDA) guidelines - adopted by multiple states, including Iowa - prohibit copper from coming into direct contact with foods like vinegar, fruit juice or wine that have a pH below 6.0.

"The pH of a traditional Moscow Mule is well below 6.0," the ABD said of the drink typically made with lime juice, vodka and ginger beer.

"This means that copper mugs that have a copper interior may not be used with this beverage," according to the ABD.

But if the inside of the copper mug is lined with another metal, like nickel or stainless steel, ABD says that's fine. 

"High concentrations of copper are poisonous and have caused foodborne illness," the official bulletin said. "When copper and copper alloy surfaces contact acidic foods, copper may be leached into the food."