Duties in relation to long-term objectives for ozone
20.—(1) The Scottish Ministers must ensure that all necessary measures not entailing disproportionate costs are taken to attain the long-term objectives for ozone set out in Schedule 4.
(2) Measures taken pursuant to paragraph (1) must be consistent with the programme referred to in regulation 18(5) and any air quality plan prepared and implemented in accordance with regulation 24(3).
(3) In zones where the long-term objectives for ozone have been attained, the Scottish Ministers must, insofar as factors including meteorological conditions and the transboundary nature of ozone pollution permit—
(a)ensure that they continue to be met;
(b)maintain the best ambient air quality compatible with sustainable development; and
(c)maintain a high level of protection for the environment and human health.