[Tool Time]

Cast iron seems relatively safe among the alternatives. It does leach some iron into the food, but it's the same type of iron you get from natural foods, and it's unlikely that you'll consume so much additional iron from the cookware to be a problem. A figure I often see for the safe upper limit for daily iron intake is ~45mg. Your cast iron pot generally will only leach a few milligrams of iron into the food at worst. Also note that new, unseasoned cast iron cookware will leach more iron compared to seasoned cookware.

I would advise avoiding anything with teflon.