According to research on the internet, there are no components of steel that will leach out, burn out, gas off, or any other term I could think of at the time that would cause a health problem from normal blacksmith use. Applied coatings, such as paint, galvanizing, powder coatings, various chemicals, etc, are a very different matter and care should be taken when removing or applying these coatings. Using 4340 steel as an example (Element Weight % C 0.38-0.43 Mn 0.60-0.80 P 0.035 (max) S 0.04 (max) Si 0.15-0.30 Cr 0.70-0.90 Ni 1.65-2.00 Mo 0.20-0.30 ); the chromium, molydenum, nickel, etc, will not "come out of" the steel and therefore do not pose a health hazard as a component of the steel. Commercial steel suppliers can provide uncoated steel of various grades so one does not have to worry about using steel itself.