A series of synthetic chemicals widely used in household products, food packaging and clothing have a significant effect on the development of frogs, even at low doses, according to a Purdue University study.Per/polyfluoroalkyl substances (PFASs) are man-made chemicals used to make products stain resistant, waterproof and nonstick, and are present in foams used to fight fires. A U.S. Centers for Disease Control and Prevention (CDC) study from 2007 showed that some PFASs were present in 98 percent of blood samples collected from American adults and children for the National Health and Nutrition Examination Survey. According to the CDC, scientific studies on the impact of PFASs on human health are inconclusive.