Just read an interesting article about the chemicals used in making plastic containers and the "plastic Codes" explained.
To summarize the article, there are codes 1 thru 7 on a plastic container. Safe codes are 1,2,4,5. Avoid codes are 3,6,7.
Here's a link to the article which contains some good information:
http://health.yahoo.net/articles/wom...container-safe
Safety First!