The uncertainty of averaging a time series of measurements and its use in environmental legislation

This paper assesses the problem of the calculation of an averaging uncertainty for measurements in the framework of the European Air Quality Directives. Current environmental legislation establishes maximum uncertainties associated with a defined period of measurements. The difficulties of an ‘a priori’ determination of uncertainty contributions associated with both the averaging of measurements and an incomplete time series are discussed. The definition of an overall uncertainty, which includes budget contributions from the afore-mentioned factors, is not helpful as a regulatory parameter for quality. Alternatively, it should be used as additional information to associate with the average measurement value. This should be taken into consideration in future revisions of the European ambient air quality legislation.