Environmental quality standards for priority and priority hazardous substances are determined by Directive 2008/105/EC. Environmental standards are set as the annual average permitted content of these substances in water, which ensure protection against long-term exposure, and as the maximum permitted content in water, which prevent acute consequences of pollution (arso.gov.si, 2010).
The European Union has set quality standards for groundwater for nitrates (50 mg NO3/l), individual pesticides, their relevant degradation products (0.1 µg/l) and for the sum of pesticides (0.5 µg/l) (Directive 2006/118 /EC of the European Parliament and the Council of December 12, 2006 on the protection of groundwater from pollution and deterioration and Regulation on the state of groundwater, 2009) (arso.gov.si, 2010).