It is hereby expressly declared that it is the intent of the Congress to supersede any and all laws of the States and units of local government insofar as they may now or hereafter provide for a requirement, prohibition, or standard relating to the lead span in paints or other similar surface-coating materials which differs from the provisions of this chapter or regulations issued pursuant to this chapter. Any law, regulation, or ordinance purporting to establish such different requirement, prohibition, or standard shall be null and void.