The Directive, which must be brought into force by Member States by February 2007, sets "target values" for four air pollutants - arsenic, cadmium, nickel and benzo-a-pyrene as an indicator for total polyaromatic hydrocarbons - and some general measures on mercury in air.
In particular, any industrial emission sources contributing to exceedances of the target values need not employ measures going beyond "best available techniques" as defined by the Directive on integrated pollution prevention and control, if they are covered by that Directive.
Monitoring requirements will vary, depending on existing air quality. Measuring levels of each pollutant is mandatory in areas where the upper assessment threshold is exceeded, but can be combined with modelling where concentrations fall between the upper and lower thresholds. Modelling or estimation techniques will suffice where concentrations are below the lower threshold.
The Directive lays down reference methods for sampling and analysis, rules for the use of assessment thresholds and criteria for determining the number of air sampling points. Monitoring requirements are also laid down for PAHs other than BaP and for mercury.
The Directive is to be reviewed by 2010, when the scope for further emission reductions and "the possible merit in introducing limit values" to reduce health risks will be considered.