12.—(1) The Welsh Ministers must install sampling points in accordance with the criteria set out in Sections I, II and IV of Annex III to Directive 2004/107/EC for the assessment of arsenic, cadmium, nickel and benzo(a)pyrene.
(2) The Welsh Ministers must ensure that monitoring sites for polycylic aromatic hydrocarbons other than benzo(a)pyrene—
(a)are located together with sampling points for benzo(a)pyrene,
(b)are located in accordance with the criteria set out in Sections I to III of Annex III to Directive 2004/107/EC, and
(c)are selected so that geographical variations and long-term trends in the concentrations of polycyclic aromatic hydrocarbons can be identified.
(3) The Welsh Ministers must ensure that—
(a)at least one background sampling point is installed to provide indicative measurements for the purposes of paragraph (6) of regulation 11,
(b)such background sampling points are located in accordance with the criteria set out in Sections I to III of Annex III to Directive 2004/107/EC, and
(c)such background sampling points are selected so that geographical variations and long-term trends in the concentrations and total deposition rates of the relevant pollutants can be identified.