Magneto is way over-powered, even for a mutant. With the given relation between electricity and magnetism, what could be possible? here is already study work on biomagnetism, we know the nervous system is electric and the blood contains iron, so there is iron moving in an electric field. Assuming at least twice the iron content found in normal blood, and a change in physiology to have eel strength (500v DC or such) nervous system, how close could one get?
I did not tag this hard-science because I do not need a numeric answer, but I would like to see supporting details for any answer given.
EDIT: I am aiming for the ability to attract iron and repel magnets. Such an ability when used on iron could only attract, and you would need loadstone or something with fixed poles before you could get repulsion.