A study by British researchers found that undisclosed inert ingredients in certain Roundup weedkiller products are highly toxic to bumblebees.
The study by Royal Holloway, University of London researchers looked at co-formulants found in several Roundup products.
Co-formulants are inert additives that increase the efficiency of the active ingredient in a chemical product.
Inert ingredients are not tested by the U.S. Environmental Protection Agency to the same degree as active ingredients.
The study involved three Roundup products available in the United Kingdom, only two of which contained glyphosate as the active ingredient. They also tested a glyphosate-based weedkiller from a different brand.
Glyphosate has been previously found to destroy the gut bacteria in honeybees and has been linked to a higher risk of certain type of cancer in humans called Non-Hodgkin’s lymphoma.
The researchers directly sprayed the products onto bumblebees and saw what happened over 24 hours.
They found that all the Roundup products, including those without glyphosate, had a high toxicity rate for bumblebees.
The bees had a 94% mortality rate with Roundup Ready-to-use, a 30% mortality rate with Roundup ProActive and a 96% mortality with Roundup No Glyphosate, a product not available in the U.S.
Weedol “did not cause significant mortality,” according to the researchers.
The Center for Biological Diversity, an American environmental advocacy group, said there are 1,102 registered formulations for glyphosate, each with a proprietary mixture of inert ingredients that do not have to be disclosed.
“EPA must begin requiring tests of every pesticide formulation for bee toxicity, divulge the identity of ‘secret’ formulation additives so scientists can study them, and prohibit application of Roundup herbicides to flowering plants when bees might be present and killed,” said Bill Freese, science director at the Center for Food Safety.
The EPA in November found that glyphosate-based products were likely to “adversely affect” 93% of all plants and animals protected under the Endangered Species Act.