For those of you who may be new to CIC the below attached video will for sure let you know what to not do with your cast iron. As you can see the molds use for his project are all "cooking" cast iron pieces. When we speak of lead in our pans this is most likely how it gets there, and when you see pans that are "off color" reddish looking, be cautious that it probably was someone's piece of cast iron that was used (not for cooking).
https://www.youtube.com/watch?v=pAe7SqHbKtM
https://www.youtube.com/watch?v=pAe7SqHbKtM