In recent years, polyfluorinated chemicals (PFCs) have increasingly been used as surfactants in various industry- and consumer products, because of their unique properties as repellents of dirt, water and oils. The most well-known PFCs are perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and their derivatives belonging to the group of perfluoroalkylated substances. The PFCs are very persistent in the environment, and some of them have been discovered as global pollutants of air, water, soil and wildlife and even found in remote polar areas. Bioaccumulation occurs also in humans, and everybody in our society has traces of these PFCs in their blood and internal organs such as the liver, kidneys, spleen, gall bladder and testes. In the blood, PFOS and PFOA are bound to serum proteins. The acute toxicity of the polyfluorinated substances is moderate but some substances can induce peroxisome proliferation in rat livers and may change the fluidity of cell membranes. Some of these PFCs, such as PFOS and PFOA, are potential developmental toxicants and are suspected endocrine disruptors with effects on sex hormone levels resulting in lower testosterone levels and higher oestradiol level. Other PFCs have oestrogenic effects in cell cultures. The industrial production of PFOS and its derivatives stopped in 2000, and the European Union has banned most uses from the summer of 2008. However, hundreds of related chemicals: homologues with shorter or longer alkyl chain, PFOA and telomers, which potentially may degrade to perfluoroalkanoic (carboxylic) acids, are not regulated.