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Statement on the findings in recent studies investigating sub-lethal effects in bees of some neonicotinoids in consideration of the uses currently authorised in Europe
The European Food Safety Authority was requested to perform a comparison between the doses of several neonicotinoids tested in the studies from Henry et al. (honeybees, thiamethoxam) and Whitehorn et al., (bumblebees, imidacloprid) published in Science (2012) with exposure of bees, following the actual use of these neonicotinoids. A third study investigating sub-lethal effects on honeybees for clothianidin and imidacloprid was also considered (Schneider et al., 2012). Data of uses authorised in EU and data on residues in pollen and nectar were collected to compare the actual exposure of bees with the investigated doses. The residue data were limited and available only for some crops; therefore, the extrapolation to other crops was not considered appropriate. In the studies on honeybees, the highest residue levels of thiamethoxam, clothianidin and imidacloprid in nectar were compared with the actual concentrations tested. The results indicated that the tested concentrations were higher than the concentrations found in nectar. The residue intake was estimated using different exposure scenarios. The results indicated that the doses tested in these publications were lower for clothianidin and for thiamethoxam than the estimated exposure. For imidacloprid the doses tested were higher in all the scenarios. In the studies on honeybees, the total amount of active substance was consumed by honeybees within a relatively short period instead of being not administrated over a longer period i.e a day. In the study on bumblebees the tested concentrations were in the range of the highest residues of imidacloprid in pollen and nectar. However, the relevance of the exposure period in the study is unknown. The comparison between the doses tested in the studies with the actual doses with the exposure of bees was considered feasible only for the seed treatment uses to maize, sunflower, oilseed rape and alfalfa. Further data would be necessary before drawing a definite conclusion on the behavioural effects regarding sub-lethal exposure of foragers exposed to actual doses of neonicotinoids
© European Food Safety Authority, 2012
Following a request from the European Commission, EFSA performed a comparison between the doses of several neonicotinoids tested in the studies from Henry et al. (honeybees, thiamethoxam) and Whitehorn et al., (bumblebees, imidacloprid) (Science, 2012) with potential exposure of bees following actual use of neonicotinoids. In these studies, the authors suggested that field-realistic levels of neonicotinoids thiamethoxam and imidacloprid might have a considerable effect on colony stability and survival of honeybees and bumblebees. A third study investigating similar effects on honeybees for clothianidin and imidacloprid was also considered (Schneider et al., 2012).
To compare the actual exposure of bees to residues arising from the EU authorised uses with doses investigated in the published research, EFSA collected data on the products and their uses authorised in the Member States (GAP tables), as well as information on the uses considered representative for the active substance approvals (review reports). The available residue data in pollen and nectar, as provided to the Member States by the applicants, were also collected in order to define the extent of the contamination of these feed items resulting from the authorised uses.
A comparison was made between the EU representative uses, as reported in the review reports of the active substances, the uses authorised in the Member States, and the application rates investigated in the residue studies. Overall, the available residue data in nectar and pollen were limited and available only for seed treatments of maize (only pollen), oilseed rape, Phacelia, alfalfa and sunflower; therefore the extrapolation to crops, other than those mentioned above, was not considered appropriate.
The available highest residue levels of thiamethoxam, clothianidin and imidacloprid in nectar were compared with the actual concentrations tested on honeybees by Henry et al. and Schneider et al. and the results of the comparison indicated that the tested concentrations were higher than the concentrations found in nectar. When the residue intake was estimated using different exposure scenarios, the results indicated that the doses tested by Schneider et al. for imidacloprid were higher than the potential estimated exposure. However, the doses tested for clothianidin by Schneider et al. and for thiamethoxam by Henry et al. were lower than the potential estimated exposure in some scenarios. These results indicate that sub-lethal effects following the use of these active substances could not be fully excluded in worst case situations. However, it should be noted that there are several uncertainties regarding these results, therefore, they should be considered with caution. In particular, in the studies from Henry et al and Schneider et al. bees consumed the total amount of active substance within a relatively short period and not administered over a longer period i.e. a day. Depending on the substance properties and how fast the substance can be metabolised by the bees, this method of exposure could have lead to more severe effects than what may occur when bees are foraging.
The concentrations tested on bumblebees by Whitehorn et al. were in the range of the maximum exposure residues of imidacloprid in pollen and nectar. However, it is uncertain as to what extent the exposure situation in the study is representative to field conditions since bumblebees would need to forage for two weeks exclusively on imidacloprid-treated crops in order to be exposed to the same extent as in the study. Further consideration would be necessary to understand whether this situation may occur in intensive monoculture landscapes.
The results of the published studies were considered unlikely to be of relevance for other neonicotinoids (i.e. acetamiprid and thiacloprid).
Overall, before drawing definite conclusions on the behavioural effects regarding sub-lethal exposure of foragers exposed to actual doses of neonicotinoids it would be necessary to repeat the experiments performed in the studies with other exposure levels or in other situations.
Neonicotinoids, sub-lethal effects, honeybees, bumblebees, exposure, nectar