The findings are based on data from more than 2,500 adults from Bonn and the Dutch municipality of Leiderdorp. Since their invention in the 1950s, more than 10,000 different substances from the category of per- and polyfluorinated alkyl compounds (PFAS) have been developed. Due to their water, fat and dirt-repellent properties, they are used in thousands of products such as cosmetics, dental floss, but also in pan coatings.