Hi Debbie - This rumor has been around for a long time - either link onto this : snopes.com: Microwaving Plastic Releases Cancer-Causing Agents OR go to SNOPES yourself and check out what they have to say (type in under "Search" for dioxins and plastic containers or something similar). For the most part, it isn't true, but we have stopped microwaving anything in plastic or drinking from plastic glasses anyway. Common sense prevails, esp. after you read what this site has to say. I BELIEVE you can also pull up some information from Johns Hopkins on this information too. Hope this helps. Warmly, JaneP.