Per- and polyfluoroalkyl compounds, abbreviated PFAS, are compounds that are widely used in industry and consumer products due to their unique properties. They are present in polymer synthesis, in fire-fighting foams and as additives to improve the properties of food packaging, make-up and textiles. Their persistence and long half-life pose a significant risk to human health. Regulatory institutions are studying the effects of these chemicals on the environment and on humans and have already phased out the use of perfluorooctane sulfonic acid (PFOS) and perfluorooctanecarboxylic acid (PFOA), but many other PFASs can also cause harmful effects. The aim of this master thesis was to review the occurrence of PFASs in the natural environment worldwide and to identify which PFASs cause the most adverse effects on humans and animals. We focused on adverse effects identified in in vivo and in vitro studies. A systematic literature review of two databases, PubMed and Science Direct, was used to collect the articles. The information suitable for the review was selected from the retrieved articles according to the PRISMA methodology. Potential sources of exposure to the compounds we have investigated include consumer products, dust and indoor air, water and sediment, and wastewater and sewage sludge. Across continents, surveys have shown the presence of PFASs in indoor air, soil and water. PFOS and PFOA are commonly present in dust and air, with higher levels in urbanised areas. In Europe and North America, PFOA and PFOS are the most commonly found, while in Asia there is a more marked shift towards alternative short-chain PFASs (e.g. 6:2 fluorotelomer sulfonate (6:2 FTS), potassium salt of 6:2 fluorotelomer sulfonate (F-53B)). Areas where aqueous film-forming firefighting foams, abbreviated AFFF, are used show the highest levels of contamination. The consumer products with the highest PFAS content are ski waxes. In our review of human incidence studies, we have mainly extracted data on PFAS levels in the blood of populations from the literature. The most frequently detected compounds in human blood were PFOA, PFOS, perfluorohexanesulfonic acid (PFHxS) and perfluorononanoic acid (PFNA). Occupationally exposed people around the world have higher levels of PFAS compared to the general population. In the in vitro studies reviewed, PFOA, PFOS, PFHxS, PFNA and PFDA in particular have shown effects on estrogen and androgen receptors and on the thyroid hormone system. The in vivo animal studies reviewed show mainly effects on the liver, the endocrine system and the development of offspring. In the human biomonitoring studies reviewed, inconsistent results were found. But a non-negligible impact on thyroid hormones, prenatal development, lactation and on fertility and sex hormones has been
demonstrated. Many questions remain about the impact on the immune system and on neurodevelopment, particularly in children.
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