The main duty imposed on Member States by the Directive is to set up monitoring networks to assess the risk that human exposures to ozone may exceed a specified health protection threshold, and to measure vegetation exposure to ozone in relation to two protection thresholds.
Unlike other EC legislation on air quality, the Directive does not lay down maximum permitted ozone concentrations, but requires official warnings to be given when ozone levels exceed two specific values (ENDS Report 213, pp 34-35 ).
The Directive was due to be brought into force by Member States by 21 March, and this is the date on which the UK's implementing regulations took effect.
The regulations are notable more for changing the way in which EC legislation on air quality is implemented than for anything else. The three earlier air quality Directives - on smoke and sulphur dioxide, lead and nitrogen dioxide - were initially brought into force in the UK by administrative means, and it was only following a threat of legal action from the European Commission that the Government eventually gave them statutory force in 1989.
The Government has learnt its lesson, and the key provisions of the ozone Directive have been transposed word for word into UK law. They place a duty on the Secretaries of State to designate or establish ozone monitoring stations, the number and location of which are to determined in accordance with criteria set out in the Directive. They also oblige them to ensure that a reference method of analysis laid down in the Directive, or an alternative giving equivalent results, is used, and require them to appoint laboratories to evaluate the analytical methods used and to carry out laboratory intercomparisons. The EC requirement for public warnings to be given when ozone levels exceed the two health protection thresholds has also been made a statutory duty.