The problem under consideration

In July 1980 the European Commission issued a Directive on drinking-water quality (80/778/EEC) setting a maximum admissible concentration for 71 distinct parameters. One of the most strictly regulated substances in the directive was the set of chemical pesticides. The European Commission adopted a ‘practically zero’ level of permissible contamination for these substances. The limit for any individual pesticide product was set at the trace level of 0.1 μg/l; a ‘cocktail’ standard for the allowed aggregate level of contamination by all chemical pesticides was set at 0.5 μg/l. These were levels of chemical contamination that were only just detectable under then-existing monitoring technologies. The Commission's standard was intended as a clear and unequivocal pronouncment against the accumulation of chemicals within the drinking water of the EEC.

Despite this pronouncement against chemical accumulation, pesticides have been accumulating in groundwater over the past 15 years to such an extent that several substances have breached the allowed concentration in groundwater in many of the agricultural districts across the European Union (EU) (see, generally, Bergman and Pugh, 1994). This is important because two-thirds of the EU citizenry continue to acquire their drinking-water supplies from untreated groundwater, i.e. directly from the aquifers underlying their communities. In adopting its tough stance against chemical accumulation, it had been the object of the European Commission to stimulate a comprehensive strategy of pesticide management (based on agricultural, land use and pesticide management). However, the continued accumulation of pesticides in European groundwater supplies placed the EU in the position of choosing between two poor options: either the relaxation of its earlier drinking-water quality directive or the costly treatment of groundwater prior to delivery to consumers.