Studies from pesticide manufacturers Bayer and Syngenta, which provide further evidence of neonicotinoid pesticides harmful effects on bees, have been obtained by Greenpeace.

Greenpeace published details of studies, intended to find a ‘safe level’ of exposure to neonicotinoids on Thursday. They were never peer reviewed or published, but were obtained by the environment campaign group via a Freedom of Information Request.

The studies can’t be published in full, due to commercial confidentiality rules, but Greenpeace campaigners said they show that high concentrations of two neonicotinoids harm bees, and that the data could have been of use to independent scientists studying bee health. Agchem companies have blamed climate change, habitat loss and disease for declines in the numbers of bees and other insect pollinators, but maintain that - when used correctly - their products don’t have a notable effect.

The studies on Bayer’s clothianidin and Syngenta’s thiamethoxam products showed high doses of both chemicals caused serious harm to honey bee colonies, and less marked effects were noted at lower levels (concentrations of 50 parts per billion and 40ppb respectively - still higher than levels usually seen in fields).

Prof Dave Goulson, a bumblebee ecology specialist who has conducted work on neonicotinoids at the University of Sussex told the Guardian, “Given all the debate about this subject, it is hard to see why the companies don’t make these kinds of studies available. It does seem a little shady to do this kind of field study - the very studies the companies say are the most important ones - and then not tell people what they find.”

The studies were conducted in the USA, and scientists noted the companies used a method which they have previously criticised when used in previous studies for being ‘unrealistic’, in which bees live in fields but are fed sucrose solution laced with neonicotinoids. Both companies said the design of the studies was agreed to by the US Environmental Protection Agency.

Greenpeace published details of the research as a warning, as the UK government is set to draw up its own policy on agricultural chemicals in light of the Brexit vote. In the run up to the EU Commission’s partial ban on certain neonicotinoids three years ago, the UK government lobbied against restrictions and even published its own neonitocinoid study, which was not peer reviewed but was instead released straight onto the internet. The study was subsequently panned as ’flawed’ and deemed inadmissible as evidence by EU health watchdog EFSA.

The green group has called for greater transparency from companies who wield a significant amount of influence, and have been putting pressure on regulators in the US and Europe to lift restrictions on their products.

A Bayer spokesperson said one of the company’s research scientists was set to make the findings of its study public at an upcoming entomology conference in Florida.

Responding to a request for comment, Bayer spokesperson Utz Klages told Farming Online “The study conducted in North Carolina is an artificial feeding study that intentionally exaggerates the exposure potential because it is designed to calculate a “no-effect” concentration for clothianidin. Although the colony was artificially provided with a spiked sugar solution, the bees were allowed to forage freely in the environment, so there is less stress (which can be a contributing variable) than if they were completely confined to cages.
 
“It is important to note that this protocol was developed jointly by Bayer and the EPA several years ago and it is now being applied to other compounds. Based on these results, we believe the data support the establishment of a no-effect concentration of 20 ppb for clothianidin, which is consistent to that of other neonicotinoids.”

The Bayer spokesperson said one of the company’s research scientists was set to make the findings of its study public at an upcoming entomology conference in Florida.

A Syngenta spokesperson said, “The EPA asked us to do this study and agreed the methodology. A sucrose based mechanism was used on the basis that it was required to expose bees artificially to Thiamethoxam to determine what actual level of residue would exert a toxic effect. There were transient effects observed and the reported No Adverse Effect Level (NOAEL) for this study was 50 ppb (parts per billion). It is accepted that residues of Thiamethoxam in pollen and nectar from seed treated crops are in the single ppb level. So this reported NOAEL of 50 ppb indicates that honey bee colonies are at low risk from exposure to Thiamethoxam in pollen and nectar of seed treated crops.

“This research is already in the process of being published in a forthcoming journal and is clearly already publicly available through the Freedom Of Information process in the United States.”