Exposure to arsenic—sometimes known as the “king of poisons”—and lead—potentially responsible for the madness of Van Gogh—can be fatal. So a wave of concern has spread across social media following a study that revealed tampons contain arsenic, lead, and other heavy meals. But how worried do we actually need to be?

In the new study, researchers analyzed the levels of 16 metals in 30 tampons from 14 different brands. They found 12 of those metals, including toxic ones, in all products tested. “We found lead, for example, in 100 percent of the tampons we tested,” says lead author Jenni Shearston, an environmental epidemiologist at the University of California Berkeley. 

Despite tampons being on the market in the U.S. for more than 90 years, the study authors think this is the first time anyone has tested them for heavy metals. Shearston attributes this to the historical taboo around menstruation. “If we don’t talk about periods or menstrual products, then we may not ask important scientific questions too,” she says.

Here’s what lead, arsenic, cadmium, and other contaminants in tampons might mean for your health—and other common ways you might not know you’re being exposed.

The king of poisons

In Victorian times, arsenic was in everything from clothes and wallpaper to candles and fake flowers, but it was eventually phased out of use after doctors realized exposure was killing people.