Revision of water quality standards for imidacloprid RIVM proposes to lower the water quality standard for the pesticide imidacloprid from 67 to 8.3 nanogram per liter. Recent research shows that effects of imidacloprid on water organisms become apparent at lower concentrations than expected. Problematic substance Imidacloprid is a neonicotinoid insectide with a widespread use in agriculture, but it is also authorised for household uses such as ant or fly control. Neonicotinoids receive a lot of attention because of the presumed relationship with bee health decline. The European Commission decided last year to restrict the use of imidacloprid in a large number of crops. Imidacloprid is also known as a problematic substance from the viewpoint of water quality. It is ranked high in the top-10 of substances that exceed water quality standards for surface water in the Netherlands. Sensitive aquatic organisms The current water quality standards were set in 2008. A large number of studies on the effects of imidacloprid on water organisms have been published since then. Recent research shows that mayflies are particularly sensitive. The new data show that the current standard is under protective for mayflies and probably also for other insect groups. Therefore, RIVM evaluated the available data and concludes that an eight-fold lower standard for long-term exposure in freshwater is needed. The standard for short-term peak exposure of 0.2 microgram per liter can be maintained. Lower concentrations are feasible In January 2014, the Dutch board for the authorisation of plant protection products and biocides (Ctgb) restricted the use of imidacloprid. Treatment of discharge water from greenhouses is compulsory and further measures should be taken to reduce drift from treated fields to nearby surface waters. These measures will lead to lower emissions of imidacloprid to surface water and increase the chance that the new water quality standards will be met.