A study by the Journal of the Endocrine Society has found that greater exposure to polyphenrophic substances (PFAS), a group of man-made chemicals found in everyday products, may negatively impact the development of children. The study measured four types of these substances in children's blood, first at birth, then at age 3, 8, and 12. The findings add to a growing body of evidence that these chemicals may interfere with development in ways that won't be fully known until adulthood.