BPA (Bisphenol-A)

BPA acts like a hormone and is therefore also affective in very small doses - which means there is no safe limit of BPA in a product - zero amount of BPA is the only safe way.

Extract from Wikipedia:

Known to be estrogenic since the mid 1930s, concerns about the use of bisphenol A in consumer products were regularly reported in the news media in 2008 after several governments issued reports questioning its safety, thus prompting some retailers to remove products containing it from their shelves. A 2010 report from the United States Food and Drug Administration (FDA) raised further concerns regarding exposure of fetuses, infants, and young children.

From the "Slow Death by Rubber Duck Website":

“The Wall St. Journal insults the intelligence of concerned parents and scientists who know it is dangerous for children's health to use products such as baby bottles and sippy cups made from plastic containing BPA. Hundreds of recent studies have linked BPA to human ailments as varied as prostate and breast cancer and heart disease. In our tests, documented in the book, our BPA levels rose 7.5 times over 48 hours after eating and drinking from microwaveable BPA plastic containers. The chemical reached levels in our urine that many recent studies have found to have a biological effect. And infants, who are often exposed to BPA leaching from both the plastic in their baby bottles and the lining of infant formula cans, have far greater exposure to chemicals relative to their body weight and nutritional intake.”