A buffer strip of at least three metres must be established for agricultural activities along watercourses. In addition, the creation and maintenance of permanent grassland and pastureland permanently vegetated is encouraged to minimise the use of pesticides and fertilisers. Luxembourg has six stations - three rural and three urban - for permanent measurement and recording of ground-level ozone concentrations. Replaced by the Directive 2008/50/EC. This holds for washed vegetables for human consumption (threshold of 3 pg WHO-TEQ/g dry matter) and for unwashed vegetables for use as animal feed (threshold of 0.85 pg WHO-TEQ/g dry matter), 1 pg = 10“12 gram, World Health Organisation-Toxic Equivalent Quantity (WHO-TEQ).