Arrangements under section 87(1) above shall include provision for securing that, so far as reasonably practicable, the concentration of fluoride in the water supplied to premises in the specified area is maintained at the general target concentration of one milligram per litre.

But the arrangements may provide for the concentration in the specified area (or any part of it) to be lower than that if the relevant authority considers that it is not reasonably practicable to achieve the general target concentration in the specified area (or that part of it).

Any such lower concentration must still be as high as is reasonably practicable in the circumstances.

If, in relation to any area (“area A”), an order under section 88A(1) below specifies a general target concentration lower than that for which any arrangements effective there provide (or, by the previous operation of this subsection, are taken to provide), the arrangements shall have effect from the coming into force of the order as if they provided for the general target concentration specified in the order (subject to the operation again of subsections (2) and (3) above).

If the result of the operation of subsection (4) above in relation to arrangements in area A is that in an area adjoining area A (“area B”) it is not reasonably practicable to maintain the concentration of fluoride in the water supplied by virtue of arrangements made in area B with the same water undertaker, the order shall be taken to extend also to area B so far as those arrangements are concerned, and subsection (4) above shall apply accordingly.

An order under section 88A(1) below which in relation to any area specifies a general target concentration higher than that for which any arrangements effective there provide (or are taken to provide by virtue of subsection (4) or (5) above) does not have effect to increase the concentration for which the arrangements provide (or are taken to provide).

In this section, “specified area” means the area specified in arrangements under section 87(1) above.