Toxicological effects of poly- and perfluoroalkyl chemicals: Aspect of species difference

<p>Poly- and perfluoroalkyl substances (PFAS) are chemicals that are used in various industrial processes and final products as water-, and oil-repellent, fire-extinguisher. Once PFAS was emitted to environment, these are not degraded due to their chemical and biological stabilities, distributed globally, and found in all environmental media; air, water, soil, sediment. Very low levels of PFAA were found in human, plants and wildlife, globally. PKPD of PFAS were studied widely in experimental animals and in vitro and revealed their target; liver, thyroid hormones, serum lipids, reproduction and development, and immune system. Almost of these studies were addressed to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), and studies on other PFAS were limited. Information of epidemiologic studies were increasing past decade, and revealed increased risk of high blood pressure, kidney or testicular cancer, increased cholesterol level, decreased vaccine response in children. The discrepancy between animal studies and epidemiologic studies are partially due to species difference. For example, Plasma elimination half-lives of PFOA and PFAS were 10 days and 30 days, respectively in male rats, whereas approximately 3 years and 6 years in human, respectively. Recently, transporters that responsible for reabsorption and elimination of PFOA and related chemicals. The species difference in these transporters are partially due to plasma half-lives. Target molecule identification in vitro and animal studies and following studies on species difference are useful for estimating human risk. In epidemiologic studies, plasma levels of PFAS in human were very low whereas relatively high dose were applied in almost animal studies. These differences are to be considered.</p>