Pesticides from the EU First and Second Watch Lists in the Water Environment

The contamination of water with pesticides used in agriculture and urban areas is a priority issue that is currently of global concern. In 2015, the European Union (EU) published the first Watch List (1st WL), which showed the necessity for Union-wide monitoring of ten organic substances/groups of substances in the field of water policy. The list includes, among other items, eight pesticides: five neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam), and methiocarb, oxadiazon, and tri-allate. In 2018 the EU published the second Watch List, which repealed the 1st WL. In this list, among other changes, one pesticide (metaflumizone) was added, and two (oxadiazon and tri-allate) were removed. This review summarizes the current state of knowledge on the reported occurrence and concentrations of these pesticides in surface and groundwaters and in effluents from wastewater treatment plants derived from 73 studies in 21 countries worldwide. Imidacloprid, acetamiprid and thiamethoxam were the most frequently found pesticides due to their widespread use, while metaflumizone, methiocarb, oxadiazon, and tri-allate are less studied pesticides whose occurrence in water is also poorly reported. More investigation is needed to assess the occurrence and impact of these pesticides on the aquatic environment worldwide in the context of water supply and human security.