In March 2013 a new study was published by the UK Food and Environment Research Agency (FERA) investigating the effects of neonicotinoid seed treatments on bumble bee (Bombus terrestris) colonies under field conditions (March, 2013; Thompson et al.). The study investigated effects on bumble bee colonies placed in the vicinity of crops treated with neonicotinoids. The authors concluded that the study did not show conclusively that exposure to neonicotinoids, used within a normal agricultural setting, had a major effect on bumble bees colonies.
The European Food Safety Authority (EFSA) was requested by the European Commission to clarify whether this new study had an impact on the risk assessment for bees provided in the EFSA Conclusions on the three neonicotinoids clothianidin, thiamethoxam and imidacloprid (EFSA Journal 2013;11(1):3066; EFSA Journal 2013;11(1):3067; EFSA Journal 2013;11(1):3068).
To address the request from the European Commission, EFSA performed an evaluation of the study by Thompson et al. (2013) by taking into account the study report and the additional raw data submitted by the study authors upon request from EFSA. EFSA performed an in-depth assessment of the study, particularly focusing on the statistical methodology used.
Furthermore, the routes and level of exposure in Thompson et al. (2013) in relation to those assessed in the EFSA Conclusions on the three neonicotinoids clothianidin, thiamethoxam and imidacloprid were considered. Finally, the suitability of field studies performed with bumble bees for understanding the risk to honey bees and solitary bees was discussed.
EFSA identified several weaknesses of the study design and in particular the lack of an unexposed control, and uncontrolled covariates. In addition, EFSA noted that the route and level of exposure in the Thompson et al. (2013) study was not adequate to address the risks to honey bees for the authorised uses as indicated in the EFSA Conclusions. EFSA also considered that field studies performed with bumble bees cannot be used to understand the risk for honey bees and solitary bees.
Overall, EFSA considered that the study is not adequate to understand the effects of exposure of neonicotinoid residues on bumble bee colonies. EFSA also concluded that the study by Thompson et al. (2013) does not change the conclusions of the risk assessment previously drawn for thiamethoxam, clothianidin and imidacloprid in the EFSA Conclusions published in January 2013 (EFSA 2013a, EFSA 2013b and EFSA 2013c).