Good morning, Bill. If you look at their Canadian website, you'll find their response about boiling in bags, which they do not recommend. Oddly, they don't mention anything about "boiling" on the US site. Could it be that the bags are manufactured differently in the US than in Canada? Or, perhaps the molecules break down differently when the bags are boiled rather than microwaved? I guess the best way to find out would be to write the Ziploc US company.
Can I boil in ZiplocŪ Brand bags?
No. ZiplocŪ Brand bags are not designed to withstand the extreme heat of boiling.
It also says, not to be used in microwave ovens:
Can ZiplocŪ Brand bags be used in the microwave?
ZiplocŪ Brand Sandwich Bags and Snack Bags are not designed to be used in the microwave. ZiplocŪ Brand Storage Bags may be used for microwave reheating; ZiplocŪ Brand Freezer Bags may be used for microwave heating and defrosting. (Don't use ZiplocŪ Brand Freezer or Storage Bags to microwave food on high.) When defrosting or reheating, always open the zipper 2.5 cm to vent. Be careful when reheating foods that are high in fat or sugar content (bacon, pastries), because these foods reheat very quickly and may exceed the softening point of the bags.
http://www.ziploc.ca/ziploc_questions.asp
P.S. The info about not boiling in bags which I posted originally did not come from a "Send this to everyone you know" email message. I am very aware of the potential for misinformation in these emails. I actually searched for the information when I became personally concerned after seeing this Ziploc Omelet recipe being posted on several other Forums. The information came from
www.about.com, which I thought was pretty reliable. There are other places on the web that have this information too - namely, Ziploc Canada FAQ's.