1(1)Where in pursuance of any such arrangements entered into by a water authority or statutory water company before 20th December 1984 as have effect immediately before the coming into force of this Act as arrangements entered into by a water undertaker—
(a)a scheme for increasing the fluoride content of water supplied by the authority or company in any part of England and Wales was in operation immediately before that date; or
(b)work had been begun by the authority or company before that date for enabling such a scheme to be brought into operation,
that water undertaker may, while the conditions mentioned in sub-paragraph (2) below are satisfied, operate the scheme.
(2)The conditions referred to in sub-paragraph (1) above are that the arrangements require—
(a)fluoridation to be effected only by the addition of one or more of the compounds of fluorine mentioned in subsection (4) of section 87 of this Act; and
(b)the concentrations of fluoride in the water supplied to consumers to be maintained, so far as reasonably practicable, at one milligram per litre.