Quantitative weight of evidence assessment of higher tier studies on the toxicity and risks of neonicotinoids in honeybees. 3. Clothianidin

Abstract

A quantitative weight of evidence (QWoE) methodology was used to assess higher tier studies on the effects of clothianidin (CTD) on honeybees. Assessment endpoints were population size and viability of commercially managed bees and quantity of hive products. A colony-level no-observed-adverse effect concentration (NOAEC) of 25 µg CTD/kg syrup, equivalent to an oral no-observed-adverse effect-dose (NOAED) of 7.3 ng/bee/d for all responses measured. Based on a NOAEC of 19.7 µg/kg pollen, the NOAED for honeybee larvae was 2.4 ng/bee larva/d. For exposures via dust, a no-observed-adverse effect rate of 4 g CTD/ha was used to assess relevance of exposures via deposition of dust. The overall weight of evidence suggested that there is minimal risk to honeybees from exposure to CTD from its use as a seed treatment. For exposures via dust, dust/seed and dust/foliar applications, there were no exposures greater than the NOAED for CTD in nectar and pollen, indicating a de minimis risk to honeybees when the route of exposure was via uptake in plants. Analysis of effect studies in the field indicated a consistent lack of relevant effects, regardless of the way CTD was applied. For exposures via dust, there were no adverse effects because of these applications and there were no exposures greater than the NOAED for CTD in nectar and pollen. The overall weight of evidence based on many studies indicated no adverse effects on colony viability or survival of the colony. Thus, the overall conclusion is that clothianidin, as currently used in good agricultural practices, does not present a significant risk to honeybees at the level of the colony.

The impact of the EU neonicotinoid seed‐dressing ban on oilseed rape production in England

“…reviewed 15 years of research on the hazards of neonicotinoids to bees and showed that although many laboratory studies described lethal and sublethal effects of neonicotinoids on foraging behavior and learning and memory abilities, no effects were observed in field studies at field‐realistic dosages. Quantitative weight of evidence analyses studies have also shown minimal risk to honeybees in the use of imidacloprid, clothianidin and thiamethoxam as seed treatments …”

“…Quantitative weight of evidence analyses studies have also shown minimal risk to honeybees in the use of imidacloprid, clothianidin and thiamethoxam as seed treatments. 24,25 The aim of this study was to assess the impact of the neonicotinoid seed dressing ban on oilseed rape production in England over a 2-year period using a stratified sample of oilseed rape growers. The survey elicited information on changes in production area, damage caused by CSFB and management practices used to alleviate pest damage.…”

Epigenetic Effects of Exposure to Insecticide on Early Differentiation of Mouse Embryonic Stem Cells

“…Neonicotinoids have been widely applied as emerging insecticides, but they carry high risks of neurotoxicity in organisms (Solomon and Stephenson 2017). We selected the popular neonicotinoids ACE and IMI for DNA methylation evaluation.…”

Quantitative weight of evidence assessment of higher tier studies on the toxicity and risks of neonicotinoids in honeybees. 4. Thiamethoxam

“…The methods used to score the papers and reports for quality and relevance and how these scores were used to produce the QWoE diagrams in this paper are also provided in the text and supplemental information in Solomon and Stephenson (2017a). These methods are common to this and two other companion papers (Solomon and Stephenson 2017b;Stephenson and Solomon 2017) and are not discussed in detail here.…”

“…Generally, for a period after planting, TMX is readily available for uptake by plants and once in the plant, it can be translocated from the roots to other parts of the plant via the xylem. TMX is metabolized in plants and the environment to clothianidin, also registered as an insecticide by another company and subjected to a separate QWoE (Solomon and Stephenson 2017b). This factor complicates the characterization of field exposure for risk assessment as there are two possible sources of clothianidin in the environment: direct use as an insecticide and as a breakdown product of TMX.…”