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.
The Alcoholic Beverages Division reminds businesses they can not serve Moscow Mules in mugs with a copper interior.
You can spot a Moscow Mule cocktail from across the bar by its cheery copper mug, frosted with cold on the outside, filled with ginger beer, vodka and a wedge of lime. Examples of foods with a pH below 6 also include vinegar, fruit juice and wine, according to the notice.
According to health officials the acid in the cocktail can leech out the copper metal and once it's swallowed it can cause stomach pains unpleasant trips to the bathroom, or worse. It's not the actual beverage that makes it so iconic, but the flashy copper mug that is nearly always used to serve it.
Iowa and many other states have adopted the FDA Model Food Code, which bans copper (and copper alloys, such as brass) from coming into direct contact with acidic foods that have a pH below 6.0.
Tropical Showers and Less Wind in the Forecast
We are stuck in this unsettled pattern with higher rain chances thanks to a stationary frontal boundary off to our north. With the incoming storms and warm high temperatures, the increase in humidity may make it feel a little sticky.
Copper is commonly used for kitchenware like pots and pans, but it can be unsafe.
Mugs aren't the only place where copper might be able to leach into acidic foods.
Not all copper mugs, however, are poisonous. "However, copper mugs lined on the interior with another metal, such as nickel or stainless steel, are allowed to be used and are widely available".
Over time, Business Insider says that copper exposure can damage the liver and kidneys.