Air quality objectives
4.—(1) The air quality objective, in respect of a substance specified in column 1 of the Table in the Schedule to these Regulations shall be to restrict the level at which that substance is present in the air to the level set out in the corresponding entry relative to that substance in column 2 of that Table, by no later than the date set out in the corresponding entry relative to that substance and that objective in column 3 of that Table.
(2) The achievement or likely achievement of an air quality objective prescribed by paragraph (1) above shall be determined by reference to the quality of air at locations–
(a)which are situated outside of buildings or other natural or man-made structures; and
(b)where members of the public are regularly present.