Germans’ favorite beers may contain a common herbicide.

Germany is home to one of the world’s oldest food safety laws: the 500-year-old Rheinheitsgebot, or Beer Purity Law, which requires that beer be made only from hops, malt, yeast, and water. German brewers are fiercely proud of this tradition, so much so that in 2013 they lobbied to add the Beer Purity Law to the UNESCO World Heritage list. Today, however, a German environmental group found that the country’s 14 most popular beers contain traces of glyphosate, a primary ingredient in Monsanto’s weed-killing Roundup and other products, at levels well above the 0.1 microgram limit allowed in drinking water. Hasseröder, a beer owned by Anheuser Busch, was most contaminated, containing 29.74 micrograms per liter.