I don't use cast iron pans because I believe they're less toxic, but because they make a damn fine crusty steak or fried potatoes.

And I use teflon pans to stir-fry or steam veggies and chicken, or to make fried eggs, just because they're more convenient.

To be honest, I don't really care all that much about potential toxiticity in cooking equipment. That wasn't really my hypothesis to begin with, I was just sharing my love for cast iron pans :-)