Pesticides made by some of Europe's agrichemical giants can have a negative effect on the health of honeybees, according to the Continent's top food safety agency.

Draft findings from the European Food Safety Authority feed into a long-running, heated and so far inconclusive debate into why Europe's bee populations are in decline.

The EU will vote as soon as next week on whether to extend a ban on three chemicals — known as neonicotinoids — which are accused of crippling insects’ nervous systems and decimating bee colonies. Earlier this year the issue gained so much attention that European Commission President Jean-Claude Juncker said he was "the best-known friend of the bees in Luxembourg" and that he would do everything in his power to prevent further decline.

EFSA has been looking at data on neonicotinoids since 2015, though the vast majority of the data on the risks posed by the substances was deemed inconclusive. But according to draft documents seen by POLITICO, one of the substances — imidacloprid, which is manufactured by Germany's Bayer — could pose a danger to bees.

Farmers across the EU argue the pesticide ban has backfired, causing their crops to be devoured by bugs such as flea beetles and wireworms.

"The data for honeybee colony strength clearly indicate a tendency for a negative deviation from the [scientific] control, suggesting that exposure to imidacloprid can have a negative effect on honeybee colonies," states one of the documents, which are drafts and subject to change. The agency said two other substances — Syngenta's thiamethoxam and Bayer's clothianidin — posed a "small to negligible negative" effect on honeybee colonies.

"The data for honeybee colony strength, in general, appears to indicate a small to negligible negative deviation [from the scientific control]. However, owing to the high level of biological variability observed both within the studies and across studies and the low reliability of the endpoints, it is considered that this can only be considered as a tentative indication," the review states in the case of clothianidin.

EFSA was also at the heart of a debate over the safety of the herbicide glyphosate, which it deemed to be safe despite widespread claims from environmentalists that some of the science the agency used was not declared as being commissioned by Monsanto, the weedkiller's main producer. And another agency linked the glyphosate to cancer.

(Mostly) banned

The EU imposed a partial ban on three neonicotinoids in 2013 following EFSA findings that their use contributes to bee deaths. The ban made sure that neonicotinoid pesticides were prohibited for use on crops deemed to be attractive to bees and on cereals. Some uses in greenhouses and on winter crops were permitted pending submission of additional data. EFSA has since reviewed more than 750 individual studies.

Even after assessing the data for winter crops, EFSA does not seem to be any nearer to determining how dangerous the pesticides are.

For instance, in the case of thiamethoxam, "the available data do not offer a picture of clear effects." For clothianidin use during the winter, EFSA said the data offer only a "tentative indication" of its "negligible" effects on bees. For imidacloprid, EFSA drew more negative conclusions, stating that "the data for honeybee colony strength after overwintering indicates a clear tendency for a negative deviation with a dose-response pattern."

The EFSA findings are hardly likely to aid policymakers in determining whether to extend the ban on the three pesticides. Health experts from EU countries will meet in Brussels as part of the European Commission's Standing Committee on Plants, Animals, Food and Feed on December 12 and may vote to extend the ban, although that isn't yet certain. The Commission needs a majority of countries to favor extending the ban to implement its proposal.

Earlier this year, POLITICO reported that several EU member countries were flouting the ban by using loopholes in EU law that grant exceptions to farmers and pesticide producers, allowing them to use neonicotinoids should yields fall too quickly as a result of not being able to use the chemicals.

Farmers across the EU — from sunflower growers in Bulgaria to oilseed rape growers in the U.K. — argue the pesticide ban has backfired, causing their crops to be devoured by bugs such as flea beetles and wireworms. What's more, the agricultural lobby Copa Cogeca in Brussels says that in many cases, the ban has forced farmers to turn to even more potent forms of pest control.

Environmentalists, however, point out that official data show yields for oilseed rape across the EU have gone up since the 2013 ban came in. For example, in both 2015 and 2017 good yields were achieved above the five-year average. Production levels for oilseed rape have also increased with levels reaching 34.8 million tons in 2017, higher than the five-year average.

“We remain convinced of the evidence showing that neonicotinoids do not pose an unacceptable risk to bees" — Utz Klages, Bayer

An EFSA spokesperson said the agency does not comment on documents it has not publicly released. The spokesperson added that the "assessments are currently with member state experts for consultation and will be finalized in February 2018 as recently announced."

Syngenta declined to comment on the documents. But Bayer fired back by criticizing EFSA's forthcoming review. The company said that EFSA's findings are not valid because they are based on the agency's so-called Bee Guidance Document, which provides rules on how to assess the potential risks to honeybees, bumblebees and solitary bees from the use of pesticides.

The pesticide industry complains that the document is outdated and that its pesticide substance does not result in harm to honeybee colonies when applied correctly and using proper pest management techniques.

“From our point of view, to ensure a just assessment of the three neonicotinoids, it is of pivotal importance that the current draft Guidance Document be reviewed and approved before any decisions concerning future restrictions are taken on its basis,” Bayer’s head of external communications, Utz Klages, said in an email.

Klages also said a study from earlier this year looking into the substances imidacloprid, clothianidin and thiamethoxam discovered seed treatments do not result in harm to honeybee colonies when applied correctly.

“We remain convinced of the evidence showing that neonicotinoids do not pose an unacceptable risk to bees when applied responsibly and properly in accordance with the label instructions,” he said.

Martin Dermine, pollinators project coordinator for the Pesticide Action Network Europe, which opposes the use of neonicotinoids, said the EFSA findings were in line with work carried out by the agency in 2012.

"Despite the high biological variability, EFSA is able, in many cases, to identify clear trends," he said. "In our view, the draft reports confirm that the available science confirms the European Commission's proposal to ban these three insecticides from open fields."