Flora,
Thank you for your input. Your background in chemistry gives you a different perspective than most, and a wide range of insight is one of the reasons I enjoy this forum.
I would like to address your thoughts on the matter, and would like to start by saying that I can find no fault in any of your reasoning.
I think the reference to gray iron implies that it is not recycled, but you are correct. That is not a safe assumption.
The issue of carry over of the recycled iron from previous pours did not even occur to me. Again, a valid point.
I don't think that being described as decorative implies that something is not intended for use. Many cast iron items from the past were very functional, as well as being elaborately decorated.
Lodge tests not only for purity, but also to allow the right mix of recycled materials from different sources, to ensure consistent composition of the iron they use. I think that the reason the testing was not done in the past for iron used in cookware has a lot to do with the fact that most of it came from freshly mined ore. That, and also I'm sure that nobody gave it much thought. I know I never thought about it much until very recently.
I'm still not convinced that I should stop using my pizza pan, but you have given me a lot to think about. I thank you for that.
I thought I should post the part of the newsletter that we have been referring to, for the benefit of future readers who may only see a dead link above.