19.—(1) Northern Ireland departments shall ensure that all necessary measures not entailing disproportionate costs are taken to ensure that concentrations of PM2.5, ozone, arsenic, cadmium, nickel and benzo(a)pyrene do not exceed the target values in Schedule 3.
(2) Northern Ireland departments shall draw up a list of all zones where the target values for arsenic, cadmium, nickel or benzo(a)pyrene are met, and in relation to those zones shall maintain the levels of those pollutants below those target values and shall endeavour to achieve the best ambient air quality compatible with sustainable development.
(3) Northern Ireland departments shall draw up a list of all zones where the target value for arsenic, cadmium, nickel or benzo(a)pyrene is exceeded, and in relation to those zones, shall identify the areas where those values are exceeded and the relevant sources of pollutants.
(4) In relation to the zones to which paragraph (3) applies, the measures in paragraph (1) shall be directed at the predominant sources of emission which have been identified, and where applicable will entail the application of best available techniques in accordance with Directive 2008/1/EC(1) of the European Parliament and of the Council concerning integrated pollution, prevention and control.
OJ No L 24, 29.1.2008, p.4, as amended by Directive 2009/31/EC (OJ No L 140, 5.6.2009, p.114)