The use of pesticides in agriculture increased rapidly during the second half of the 20th century. A side effect of this increased use is the dispersion of unwanted substances in the environment, including drinking water sources, and sometimes also in food. Several studies on food safety reported mixtures of pesticide residues in food (Jardim & Caldas, 2012; Szpyrka, 2015) and even in mother milk (Ennaceur, Gandoura, & Driss, 2007; Honeycutt & Rowlands, 2014; Liu, Pan, & Li, 2015). The side effects of intensive pesticide application on water quality are well studied, and international monitoring programs of water quality show that pesticides and antibiotics are present in surface and groundwater bodies with changing concentrations over the years (Folch, Carles-Brangarı, & Carrera, 2016; Hildebrandt, Guillamón, Lacorte, Tauler, & Barceló, 2008; Larson, Capel, & Majewski, 1997; Wang et al., 2016).

Within the EU a precautionary boundary is set at (0.1µg/L) for contamination of water sources with pesticides to prevent any harmful effects on humans and the environment. The EU has a strong monitoring program on water safety and before a pesticide is permitted to be used, it is tested and checked on safety by the EFSA (European Food Safety Agency).

However, there is also a debate about the safety of allowed pesticides, with glyphosate as a recent example (Samsel & Seneff, 2013). Safety not only in terms of possible health effect, but also regarding the potential of pesticides to pollute off-site locations including ground and surface waters. For example glyphosate is regarded relatively safe environmentally, but recent investigations indicate possible leaching and toxicity problems with its use (Mesnage & Antoniou, 2017). Even though the use of glyphosate may be considered environmentally neutral, toxicological problems still persist with the additives (surfactants) that are needed for glyphosate to penetrate plant cuticles.

The European Union (EU) has developed a series of directives, guidelines and policies over the last decades to decrease the pollution of drinking water sources, and pollution in general, by pesticides from agriculture, industry and households. The requirements of the EU Drinking Water Directive set an overall minimum quality for drinking water within the EU. The EU Water Framework Directive and the Groundwater Directive require Member States to protect drinking water resources against pesticide pollution in order to ensure production of safe drinking water.

The aforementioned directives have as yet not achieved a consistent level of implementation and effectiveness across all Member States. As a consequence, limits for pesticides (0.1 µg/L) are still exceeded in some areas with vulnerable water resources (Eurostat, 2011). Diffuse pollution of pesticides from agriculture is a main obstacle to meeting the Drinking Water Directive targets.

Soil or field conditions and pesticides characteristics are the main factors defining the potential pollution of drinking water by pesticides. If a pesticides is not transported anywhere after application there is no risk of pollution of drinking water. However, combined with water flow dynamics, infiltration and runoff after rainfall events, transport is often possible. Several reviews on pesticide pathways to ground- and surface water exist (Borggaard & Gimsing, 2008; Flury, 1996; Rittenburg et al., 2015; Tang, Zhu, & Katou, 2012; Vereecken, 2005; Wauchope, 1978). Three main pathways have been identified (Rittenburg et al., 2015);

• leaching to groundwater,
• subsurface flow to surface waters and
• overland runof.

Different soils and climatic conditions influence the most occurring pathways on a field (Borggaard & Gimsing, 2008; Reichenberger, Bach, Skitschak, & Frede, 2007). For example flat peat soils will have a much higher leaching risk than a Mediterranean vineyard on a steep slope, where overland transport is the main transport route. Besides the pathways, the characteristics of the applied pesticide also have a major effect on potential pollution. Main identified characteristics are the solubility, sorbtivity and half-life time of the pesticides (Rittenburg et al., 2015; Wauchope, 1978).These influence the availability for transport to water.

To reduce the transport of pesticides from agricultural fields, and thereby pollution of drinking water, various measures and good agricultural practices have been developed and implemented in practice at farm level in the EU. Reviews focussing on how to reduce pesticide pollution using land management include Fawcett et al. (1994), Krutz et al. (2005), Reichenberger et al. (2007), Alletto et al. (2010), Felsot et al. (2010), Rittenburg et al. (2015) and Vymazal and Brezinova,( 2015). There is a huge diversity within the EU in farming systems, climate, geomorphology, hydrology, soils, education level of farmers, quality of extension services, and type of water supplies, which means that site-specific measures and good practices are required to decrease pesticides pollution of drinking water resources. Coherent site-specific packages of measures are needed. However, the critical success factors that determine the effectiveness of these measures on a site by site basis are not well-known. It has been recognized in several studies and working groups that the environmental directives and the Common Agricultural Policy should be better integrated when focusing on the protection of drinking water resources. The possibility of an integrated risk assessment and risk management by using Water Safety Plans, which was recently included in the Drinking Water Directive, is generally welcomed as a vehicle to become more flexible and proactive. In general, there is a growing consensus that good water governance is an essential prerequisite for water management since multiple actors may contribute to pollution.

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