Maintenance of air quality standards
10.—(1) This regulation applies in respect of each zone in which—
(a)concentrations of one or more Group A pollutants are below the relevant limit values;
(b)concentrations of one or more Group B pollutants are below the relevant target values; or
(c)concentrations of ozone meet the long-term objectives.
(2) Where sub-paragraphs (a) or (b) of paragraph (1) apply, the Secretary of State shall in respect of each pollutant meeting the conditions set out in those sub-paragraphs—
(a)maintain compliance with the relevant limit values or target values; and
(b)endeavour to maintain the lowest concentration which he considers to be compatible with sustainable development.
(3) Where paragraph (1)(c) applies, the Secretary of State shall—
(a)in so far as the transboundary nature of ozone pollution, meteorological conditions and any other similar factors permit, ensure that concentrations are kept at or below the long-term objectives; and
(b)maintain through proportionate measures the lowest concentrations which he considers to be compatible with sustainable development and a high level of protection for the environment and human health.