We should definitely disallow cutting of any stainless steel, which causes dangerous hexavalent chromium dust. For those of you with the blank stares, hex chromium is the pollutant linked to dozens of cancer cases in the Erin Brokovich movie, a dramatized account of an infamous case where PG&E wound up paying out a third of a billion dollars in damages.
We should probably ban any galvanized metals as well. Zinc fumes are nasty. Nickel in stainless steel is a concern as well. So is the cadmium and manganese in some grades of steel.