The EU has set Maximum Acceptable Concentrations (MACs) for pesticides (and another 43 microbiological, physical and chemical contaminants) in drinking water, as part of Council Directive 80/778 "relating to the quality of drinking water intended for human consumption. The MAC for any pesticide is 0.1 ppb and 0.5ppb for total pesticides. The UK manufacturers have been trying to get this altered so that each pesticide has its own MAC. A revised Directive is expected with revised limits of pesticides, in line with guidelines produced by the WHO. Between 1985-87 the limits for pesticides were exceeded about 300 times in the UK, mostly in the south. The triazines, atrazine and simazine, were the most common offenders, and are now under review.

The Council Directive 91/414 "concerning the placing of plant protection products on the market" seeks to harmonise the different approaches to authorisation in different countries and to establish a list of authorised active ingredients. It replaces the previous directive that banned a number of specific substances, such as chlordane. The new Directive allows refusal of a pesticide if it is likely to exceed the drinking water requirements. The EC Committee of the American Chamber of Commerce is "considerably" concerned at this, as "it may lead to loss of many products and less efficient agriculture".