(1)The Secretary of State may by regulations amend—
(a)any provision of the Alkali Act or the Clean Air Acts 1956 and 1968 ; or
(b)any provision of an instrument made or having effect under any of those Acts,
by substituting an amount expressed in metric units for an amount not so expressed.
(2)Any amendments made in pursuance of the preceding subsection shall be such as to preserve the effect of the provisions mentioned in that subsection except to such extent as in the opinion of the Secretary of State is necessary to obtain amounts expressed in convenient and suitable terms.