But there isn't lead or other heavy metal in the cast iron itself. If there are heavy metals, they are found in the glazing, so the best thing to do is buy pure cast iron, not glazed cast iron. The same goes for ceramics, but you can't really buy ceramics without glazing, because the ceramic itself is porous - I personally replaced all ceramics with glass and stainless.
Just as a single data point, all our kitchenware today is:
glass, borosilicate glass, pyrex(the US made ones are not borosilicate),
stainless, titanium, cast iron (that we season ourselves),
wood (but not bamboo -- too much glue in there), silicone (for mats and mittens).
Stainless does have problems leeching nickel (and sometimes chromium), especially after being cleaned by an abrasive, or cooking acidic foods, which is common. This happens to an extent to cause allergic reactions in people.
Also silicone products are commonly mixed with plastic fillers that have the same issues as normal plastics. Pure platinum cured silicone products are premium products and somewhat rare.
It's very hard to stay away from everything that is bad for you...We do use some stainless pots for cooking, because really there is no 100% good alternative: cast iron pots are waay too heavy, ceramic can contain heavy metals in the glazing, glass can explode if not handled properly...and there isn't a pot-like glass option anyway (something you need for a soup or stew).
Our cutlery and cooking utensils are stainless, but when possible we use plain wood spoons (not the kind that is glued).
Is there a good alternative to stainless for these things? let me know.
I am aware of silicone issues, it's usually not in contact with our food.
I assume titanium is better than stainless as far as leaching goes? With a quick search I could find titanium pots (actual titanium, not coated) up to 5L. I have a few on hand for backpacking, but I've never thought of using them for routine cooking... but this thread has got me thinking. I use cast iron for most purposes, but not for sauces or soups.
Just as a single data point, all our kitchenware today is:
glass, borosilicate glass, pyrex(the US made ones are not borosilicate),
stainless, titanium, cast iron (that we season ourselves),
wood (but not bamboo -- too much glue in there), silicone (for mats and mittens).
Almost no plastic anywhere.