Regulation 5 Zones and agglomerations
(1)
The National Assembly must, for the purposes of this Part, divide the territory of Wales into zones.
(2)
A zone is to be classified as an agglomeration for the purposes of this Part where—
(a)
it comprises a population in excess of 250,000 inhabitants; or
(b)
in any other case, it has a population density per km2 for which the National Assembly considers that such a classification is justified.
(3)
The National Assembly may establish different zones for different pollutants where it considers it appropriate.