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expert reaction to EPA’s first of four preliminary risk assessments for insecticides potentially harmful to bees

The US Environmental Protection Agency has released a risk assessment for a specific neonicotinoid which reports that the insecticide may pose a risk to hives. The agency is due to deliver three other such assessments later in the year.

All our previous output on this subject can be seen here.


Dr Christopher Connolly, Reader at Centre for Environmental Change and Human Resilience, University of Dundee, said:

“If the point of this document is to address the possible risk of imidacloprid to the environment and food security, then the statement in their press release that below 25 parts per billion (ppb) is unlikely to have an effect on honeybees is inadequate (even if true). In fact, this should be corrected to ‘unlikely to have an effect over 6 weeks’ as chronic effects to honeybees have been reported for other neonicotinoids (Sandrock 2014), where they cause the reproductive problems seen by beekeepers in the field. Moreover, bees may actually preferentially seek out neonicotinoids (Kessler & Wright 2015) and exposure to imidacloprid is unlikely to be limited to the crop flowering period as it can be translocated to wildflowers, resulting in prolonged exposure (David 2015).

“That other risks (beyond that to honeybees) exist is acknowledged by their comment within the document stating: ‘Therefore, uncertainty exists in extrapolating the risk findings of this assessment to non-Apis bees.’ Uncertainty shouldn’t exist as there is evidence on the effects of much lower levels (2.5-10 ppb) of imidacloprid on bumblebee colonies (Whitehorn 2012, Gill 2012, Moffat 2015), where all three studies identify a negative impact.

“The report then states that for non-Apis bees, that the exposure and effects of imidacloprid are similar to that of honeybees. In which case 25 ppb would be 10 times too high (based on the bumblebee studies). Given their knowledge of these studies, it is then difficult to understand their statement one sentence later: ‘It is also noted that there are limited data on the toxicity of imidacloprid to non-Apis bees.’ especially when it is followed by ‘At the colony level, however, a review of studies published in the open literature suggests that bumble bees may be adversely affected at the colony level at concentrations in sucrose considerably lower than those observed for the honey bee.’ These inconsistencies are confusing and inconsistent.

“Regardless of the inconsistencies, with this knowledge of the bumblebee studies, it is unclear what USEPA believe about their 25 ppb threshold. They say that below this is unlikely to have an effect on honeybees. However, surely the question should be what is the threshold level for environmental safety? I’m sure that Obama cares about other insect pollinators, aquatic life and the entire environment. There’s a lot more to ecosystem stability than the role of honeybees in crop pollination.”


Declared interests

Dr Connolly: “I have no interests to declare beyond working on neonicotinoids.”

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