Leaching chemicals. Here's an article I found after a quick google search, http://myplasticfreelife.com/2011/04/bpa-free-does-not-mean-safe-most-plastics-leach-

Leaching chemicals. Here's an article I found after a quick google search, http://myplasticfreelife.com/2011/04/bpa-free-does-not-mean-safe-most-plastics-leach-hormone-disrupting-chemicals/ http://myplasticfreelife.com/2011/04/bpa-free-does-not-mean-... It doesn't mention heat, but I presume leaching increases with heat.