No proof, but there is evidence that polycarbonate baby bottles which contain bisphenol A (BPA) have a "hormone-like" effect on the reproductive system. The CDC has issued cautions and now the Canadian government will be banning this toxic substance.
No proof, but evidence of harm should be sufficient. When our children are exposed to substances which may be toxic or have significant long term side effects we have to act as quickly as possible to eliminate those toxins from our children's lives. Doctors and government agencies which insist that we have to prove harm are being irresponsible: It's the manufacturers' obligation to prove safety.
(I have not asked David Kirby's permission to use his book title in this post.)