Per- and polyfluorinated alkyl substances (PFAS) are used in numerous industrial processes, but also in consumer products, e.g. in impregnation sprays, as a coating in food packaging (pizza boxes, dishes made from plant fibers, parchment paper) and sportswear, in ski wax and in cosmetic products. The major problem with PFAS is the combination of toxicity and extreme persistence. PFAS damage the liver and kidneys, the thyroid gland, the fat metabolism, the immune system and other bodily functions; they can also cause cancer. A total of around 1000 PFAS are currently on the market in the EU. They have been in use for decades and have led to widespread contamination of soil, groundwater, drinking water and food; they are present in rain worldwide and also in the bodies of billions of people. They do not degrade in the environment, which is why they are also known as "forever chemicals". How did this problem come about and what can be done about it?