1 groundwater quality standard: an environmental quality standard, expressed as the concentration of a particular pollutant, group of pollutants or indicator of pollution in groundwater, which should not be exceeded in order to protect human health and the environment;

2 background level: the concentration of a substance or the value of an indicator in a body of groundwater corresponding to no or only very minor anthropogenic alterations to undisturbed conditions;

3 threshold value: a groundwater quality standard for all pollutants, groups of pollutants and indicators of pollution for which it has been established, in accordance with the analysis of characteristics under Article 60 of the Decree of 18 July 2003 concerning the integral water policy, that bodies of groundwater or groups of bodies of groundwater run the risk of not achieving a good chemical status of the groundwater.