I can understand your concern W-Stewart. But the concern about contaminants doesn't go away with new cast iron. The cast iron from China has been known to be made from used materials or scrap iron. From old engine blocks, etc. Any impurities would be considered in the iron itself. It's probably generally considered to be purified by the remelting process I suppose. But if lead or other toxic metals are present I would think it probably isn't.
Older cast iron was made from virgin materials it was also a finer casting/s and less porous so the experts say. It is evident by visual inspection. I don't classify myself as an expert, chemist, metallurgist though.
With used CI. If it was used for melting lead you can tell and it won't go away with cleaning methods. Even electrolysis. It would be like removing plating. You wouldn't be able to get it all out and you will also see it after seasoning especially.
Any thing else, solvents etc wouldn't penetrate into the metal itself. The process for cleaning by using a lye bath, or electrolysis and then seasoning at 400 degrees would most likely remove anything from the surface/pores.
Trying to cook with a piece of cast iron that has been used with solvents or cleaners like you mention would also smell/smoke like heck if you try to use it. It would also taint the food (it would taste awful) to the point you could tell right away.
I personally won't and don't cook in anything I by until it goes through that cleaning process mentioned above. And I cook in everything I own which is a fare number of pieces and I'm not dead yet
Certainly trust your own concern and just buy new and leave it for the collectors
Trust your own judgment of course and do what you think is safe. To each his own.
