Two teams of researchers recently had innovative behavioural studies published in the journal Science which suggested that low levels of neonicotinoid pesticides can have significant effects on bee colonies. Following publication of the studies, the European Commission asked EFSA to compare the actual exposure of bees to neonicotinoids – as a result of their use as plant protection products in the EU – with the exposure levels used in the research. The Authority was also asked to determine whether the results can be applied to other neonicotinoids used for seed treatment.
In its statement published today, EFSA concludes for honeybees that the concentrations tested in the published studies are higher than the highest recorded residue levels found in nectar for the neonicotinoids thiamethoxam, clothianidin and imidacloprid. For bumblebees, the doses of imidacloprid tested were in the range of maximum residue levels found in pollen and nectar. The Authority also explains that in order to draw these conclusions it considered a third study that looked at the effects of imidacloprid and clothianidin on honeybees.
In the studies by Henry et al. and Schneider et al. bees consumed the total amount of active substance within a relatively short period rather than over a longer, more realistic, period. Depending on the substance properties and how fast the substance can be metabolised by the bees, this method of exposure could lead to more severe effects than when bees are foraging under realistic field conditions.
Furthermore, it is uncertain to what extent imidacloprid exposure in Whitehorn et al. is representative of field conditions as bumblebees would need to forage for two weeks exclusively on imidacloprid-treated crops to be exposed to the same extent as in the study.
However, before drawing definite conclusions about the behavioural effects of neonicotinoids on forager bees and bee colonies based on actual doses, it would be necessary to repeat the experiments performed in the studies with other exposure levels or in other situations. Additional data would also be required to fully consider the relevance of the new research results to the seed treatment of other crops and to spray uses.
EFSA will continue to work in this area and has recently received a mandate from the European Commission, similar to a request also received from the French competent authority, to provide an in-depth review of the effects of the neonicotinoid active substances thiamethoxam, clothianidin, imidacloprid, acetamiprid and thiacloprid. The review, due to be published in December 2012, will pay particular attention to acute and chronic effects on bee colony survival and development, taking into account the effects on bee larvae as well as bee behaviour. In this context, an assessment of effects of sub-lethal doses on bee survival and behaviour will be further considered.
To compare the actual exposure with the doses used in the published research, EFSA analysed data on plant protection products authorised in the Member States, as well as information on the representative uses considered in the EU’s active substance approval process. Data on pesticide residues in pollen and nectar were also used to assess the extent of contamination of these feed items resulting from authorised use of neonicotinoids. The highest residue levels were then compared with the concentrations and doses used in the published papers.