Study is the latest evidence that glyphosate herbicides are so pervasive that residues can be found in foods not produced by farmers using glyphosate.
As U.S. regulators continue to dance around the issue of testing foods for residues of glyphosate weed killers, government scientists in Canada have found the pesticide in 197 of 200 samples of honey they examined.
The authors of the study, all of whom work for Agri-Food Laboratories at the Alberta Ministry of Agriculture and Forestry, said the prevalence of glyphosate residues in honey samples - 98.5 percent - was higher than what was reported in several similar studies done over the last five years in other countries.
Glyphosate is the world's most widely used herbicide and is the active ingredient in Roundup brands as well as hundreds of others sold around the world for agriculture and other purposes. Use has grown dramatically over the last 25 years and consumers have become concerned about residues of the herbicide in their food.
The data provides fresh evidence that glyphosate herbicides are so pervasive in the environment that residues can be found even in a food that is not produced by farmers using glyphosate. The researchers noted in their report that they ran into delays trying to calibrate their testing equipment "due to difficulties encountered in obtaining a honey sample which did not contain traces of glyphosate."
Bees pick up traces of pesticides as they move from plant to plant, unintentionally transferring residues from crops or weeds sprayed with glyphosate back to their hives.
In a different study, researchers on the Hawaiian island of Kauai took honey directly from 59 bee hives and found glyphosate residues in 27 percent of them. The Hawaiian researchers said bee hives located near farming areas as well as golf courses where glyphosate is used had higher concentrations of the pesticide.
The Canadian report also comes amid growing evidence that glyphosate herbicides can cause cancer, specifically non-Hodgkin's lymphoma. On Tuesday a jury in San Francisco unanimously found that Roundup, a glyphosate-based herbicide made popular by chemical manufacturer Monsanto Co., use was a "substantial factor" in causing non-Hodgkin's lymphoma in a California man. That echoed a similar unanimous jury verdict handed down in August in a separate case in which a cancer victim also alleged his disease was due to exposure to Monsanto's glyphosate-based herbicides.
Both verdicts came after plaintiffs' lawyers presented evidence of multiple studies showing the cancer-causing potential of glyphosate herbicides, including one published last month in a journal whose editor is a senior scientist at the U.S. Environmental Protection Agency (EPA).
The Canadians' decision to examine honey samples for glyphosate comes after a similar look at honey samples by a U.S. Food and Drug Administration chemist in 2017. That FDA scientist found all 28 honey samples he looked at had traces of glyphosate, with 61 percent of the samples having enough glyphosate to be measured. The other samples had residues of the herbicide too slight to measure.
Credit: Mike Mozart/flickr
The Canadian report, published in a journal called Food Additives & Contaminants: Part A, said that glyphosate is currently an active ingredient in 181 herbicides registered for use in Canada and its widespread use has made it commonly found in the environment.
The study authors pointed out that Canada, like the United States, does not have a legal standard for how much of the herbicide is considered safe in honey. Regulators in different countries set what are referred to as "maximum residue limits" (MRLs) and tell consumers their food is safe if pesticide residues remain below the MRLs. In Europe, the MRL for glyphosate in honey is 0.05 mg/kg, also expressed as 50 μg/kg.
The Canadian study authors said that all of the levels they found were below the European limit, though the highest was just barely within the legal limit. Because the residues did not exceed the MRL, they said, "the risk to consumer health appears to be quite low based on the residues detected."
Several of the residue levels found by the FDA scientist in U.S. honey were above that so-called safe level that applies in the European Union. But the FDA, like the U.S. Department of Agriculture (USDA) and EPA, assert that as long as pesticide residues are below the legal MRLs, they are not harmful.
Many scientists do not agree that MRLs actually are protective of public health, however.
"People think the standards are protective of public health but they are not," Dr. Philip Landrigan, director of the Global Public Health Program at Boston College, told EHN. "The optimal amount" of pesticide residues in food is "zero," he said. "Remember, many of the people eating honey are children."
A team of Harvard scientists published a commentary in October stating that more research about potential links between disease and consumption of pesticide residues is "urgently needed" as more than 90 percent of the U.S. population has pesticide residues in their urine and blood.
The United States has fallen behind Europe, Canada and other countries in testing foods for residues of glyphosate. Though both the FDA and the USDA annually test thousands of food samples for pesticide residues and report the data in reports, both agencies have not included glyphosate in their yearly testing programs.
In fact, the honey test data gathered by the FDA chemist was never published by the FDA and was not included in the agency's first-ever glyphosate testing data that was released late last year as part of the annual test data report.
The USDA has similarly balked at testing foods for glyphosate residues for decades. The agency planned to start limited testing in 2017 but dropped the plan with little explanation only a couple of months before testing was to have started.
Legislative push for testing
Amid all the concerns about glyphosate and residues in food, U.S. Rep Rosa DeLauro of Connecticut this month introduced a measure called the "Keep Food Safe From Glyphosate Act." The bill would require the USDA to routinely test food samples for glyphosate residues.
The bill would also ban the spraying of glyphosate as a desiccant on oats. The practice is employed by some farmers to dry their oats before harvesting. It makes harvest more efficient but leaves higher residues on finished oat-based foods.
Monsanto, now a unit of Bayer AG, has marketed glyphosate for use on oats as a desiccant for years, and the company also has successfully convinced the EPA to raise the MRL for glyphosate residues allowed in oat products. In 1993, for example, the EPA had a tolerance for glyphosate in oats at 0.1 parts per million (ppm) but in 1996 Monsanto asked EPA to raise the tolerance to 20 ppm and the EPA did as asked. In 2008, at Monsanto's suggestion, the EPA again looked to raise the tolerance for glyphosate in oats, this time to 30 ppm.
In her bill, DeLauro is looking to slash the MRL for glyphosate residues in oats to 0.1 ppm.
Canadian farmers are among the world's top producers of oats, and desiccation with glyphosate has been a common practice there.
Health Canada has rejected concerns about glyphosate safety, saying: "No pesticide regulatory authority in the world currently considers glyphosate to be a cancer risk to humans at the levels at which humans are currently exposed."
In addition to testing for glyphosate residues, the Canadian scientists also tested for residues of glyphosate's main degradation product, a metabolite called aminomethylphosphonic acid (AMPA). Like glyphosate, AMPA has long been considered to have low toxicity. AMPA was detected in 198 of the 200 samples up to a concentration of 50.1 μg/kg.
"The contribution of glyphosate and AMPA residues present in the ambient environment to contamination of plant nectar and subsequently honey itself is further complicated by the variations in the levels of these compounds in environmental matrices such as soil and surface water," the scientists said in their report.
The scientists also looked for residues of the weed killer glufosinate and found residues of that herbicide in 125 of 200 samples, with the maximum concentration detected being 33 μg/kg.
Glufosinate is the active ingredient in BASF's Liberty herbicide.
Carey Gillam is a journalist and author, and a public interest researcher for US Right to Know, a not-for-profit food industry research group.