Except as provided in subsections (b) and (c), whenever a standard established by the Commission under this Act applicable to a household substance is in effect, no State or political subdivision thereof shall have any authority either to establish or continue in effect, with respect to such household substance, any standard for special packaging (and any exemption therefrom and requirement related thereto) which is not identical to the standard established under section 1472 of this title (and any exemption therefrom and requirement related thereto) of this Act.