Phthalates, which are in products made of PVC plastics (like the pipes) which includes childrens toys but are also found in tons of other things like cosmetics, deodorants, and fragranced products.

Bisphenol A (BPA) is the other major offender. Many companies are at least removing from baby bottles and teethers now.

http://en.wikipedia.org/wiki/Bisphenol_A

http://en.wikipedia.org/wiki/Phthalate