RIVM proposes that the water quality standard for the insecticide imidacloprid be reduced by a factor of eight. New research has shown that the harmful effects of imidacloprid on aquatic organisms occur at lower concentrations than expected.

Imidacloprid is an insecticide used on a large scale in agriculture. It is also used in and outside homes, for example in ant bait and flea treatments. Recent research has shown that mayflies are particularly sensitive to imidacloprid. These insects lay their eggs in surface water.

Problematic substance

Imidacloprid is detected frequently in surface water, and in The Netherlands it is high on the list of the top 10 substances that exceed standards. Since the current standards for imidacloprid in surface water were drawn up in 2008, a lot of new studies into the effects of imidacloprid on aquatic organisms have been published. RIVM has therefore evaluated the available data and concludes that the standard for long-term exposure should be reduced from 67 to 8.3 nanograms per litre of surface water. The standard for short-term peak exposure of 0.2 micrograms per litre remains unchanged.

The group of substances to which imidacloprid belongs (neonicotinoids) is attracting a lot of attention because of the presumed link to bee deaths. For this reason the European Commission decided at the end of last year to restrict the use of imidacloprid in the cultivation of a lot of crops.

Lower concentrations are feasible

In January 2014 the Board for the Authorisation of Plant Protection Products and Biocides (Ctgb) imposed additional restrictions on the use of imidacloprid. The waste water from greenhouses has to be treated and when crops are sprayed in fields the insecticide must not drift into nearby water. These measures ensure that less imidacloprid gets into the surface water, which increases the chances of compliance with the new standard.