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The wheat harvest in Britain is in full swing, much of it will go into tasty, crisp loaves or toast on shelves at local bakers’ and supermarkets. We may see the combines roll, but what many of us won’t be aware of is the glyphosate application a week or two before the harvest. Why would anyone apply a weed killer right before harvest? The explanation can be found on the Agriculture and Horticulture Development Board’s (AHDB) website[1]: “In cereals, glyphosate applications can reduce green material (…) and improve harvest efficiency and grain storage. (…) Although glyphosate residues have sometimes been found in bread samples, these are well below the Maximum Residue Levels (MRLs), according to information published by the UK Expert Committee on Pesticide Residues in Food.”
MRL, ADI, NOAEL…
Unfortunately, this alphabet soup is rather important. For our food to be safe, a Maximum Residue Level, MRL is defined for chemicals such as glyphosate. The level is meant to ensure that we do not exceed the ADI, the Acceptable Daily Intake of any pesticide. It is well below the NOAEL, the No Observed Adverse Effect level.
Herbicide producers such as Bayer-Monsanto argue that with these thresholds in place, and with glyphosate applied according to label instructions, products such as its Roundup weed killer are safe. And yet… in 2015 the International Agency for the Research of Cancer, IARC, classified glyphosate as “probably carcinogenic to humans”, and in the US, tens of thousands of cancer sufferers allege that Roundup caused their illness and they are suing Bayer-Monsanto. “As of May 2025, Monsanto has reached settlement agreements in nearly 100,000 Roundup lawsuits, paying approximately $11 billion”, says the Lawsuit Information Centre[2]. Over 67,000 cases are still pending.
Bayer-Monsanto have done their utmost to discredit the IARC finding, arguing that in the US, the EPA (Environmental Protection Agency) has licensed glyphosate with no need for a warning label. However, for their assessment, the EPA relied on feed studies on rats which were exposed to a daily dose of glyphosate for between 28 to 30 days. Not only did Monsanto conduct most of those studies, a rat lives on average for about two years, which means that the three months studies covered only a fraction of their average life span.
International study delivers real world data: glyphosate causes cancer
What if, like humans, rats were exposed to glyphosate throughout their lives? Scientists from the US and Europe cooperated in a multi-year study and the results were recently published in the peer reviewed journal Environmental Health[3]. In July, PAN UK (Pesticide Action Network) organised a webinar[4] with Dr Michael Antoniou, Professor in Molecular Genetics in the Department of Medical & Molecular Genetics at King’s College, London, who explained the study and its findings.
Into the weeds and our gut microbiome
Glyphosate affects the metabolism of plants[5] and microbes, among them the beneficial bacteria in our gut, such as Lactobacillus and Bifidobacterium. These are the bacteria we try to feed by drinking probiotics, because we now know how important a functioning gut microbiome is, for our health and our mood: the bacteria in the gut microbiome interact directly with our brain.
The effect of glyphosate on plants and microbes is the same: they die.
Glyphosate is the active ingredient in weed killers such as Roundup, but all commercially available weed killers contain other ingredients that make glyphosate more effective and the product easier to use. The rats in the study were therefore split into three treatment groups: one received ‘pure’ glyphosate, the other two were subjected to commercially available formulas.
Each treatment group was split into sub-groups which reached one of the following doses: 0.5 mg/kg body weight/day, the ADI for the EU and UK, 5mg, considered acceptable in the US and most other countries, or 50mg (NOAEL) which still supposedly produces no observable adverse effect.
Middle aged rats, ill or dying
The rats in the treatment groups received a daily dose through their mums before they were born and then for two years, i.e. throughout their lives or until they died.
“We observed early onset and early mortality for a number of rare malignant cancers, including leukemia, liver, ovary and nervous system tumors. Notably, approximately half of the deaths from leukemia seen in the glyphosate and GBHs (glyphosate based herbicides) treatment groups occurred at less than one year of age, comparable to less than 35-40 years of age in humans”, writes one of the lead scientists, Dr. Daniele Mandrioli, Director of the Cesare Maltoni Cancer Research Center in Italy.
Not in my sandwich!
Environmental groups like PAN have demanded a glyphosate ban for years. “Minimally, as a precaution, glyphosate ADI must be drastically reduced”, concluded Michael Antoniou at the end of the webinar.
Given the enormous financial and lobbying power of agrochemical companies like Bayer Monsanto a ban is unlikely to happen soon.
There is no way of knowing how much glyphosate residue any of the fruit, vegetables or bread we eat contain. It’s impossible to test every batch for chemical residues, the best we have are estimates based on spot checks. PAN annually publishes the ‘Dirty Dozen’, a list of the most contaminated foods. It’s a helpful guideline and can be found on the website: https://www.pan-uk.org/dirty-dozen/
With bread, checking production standards can help. Wildfarmed is a supply chain brand for flour from grains grown in regenerative agricultural systems. Bread under the Wildfarmed label is on sale at outlets such as Waitrose, M&S and soon at Tesco, too. In a recent article, Farmers Weekly[6] listed the standards for production which include: “Insecticides, herbicides and fungicides are not permitted to be applied to the growing crop”. According to the company this includes a ban on pre-harvest glyphosate use.
Gail’s Bakery guarantees that from September all flour they use will be organic or from grains that have not been treated with glyphosate before harvest.
There are likely other food producers who work to the same standard, but if you haven’t got the time to contact the company to make sure, there is still one safe option: Buy organic, whenever you can!
[1] https://ahdb.org.uk/knowledge-library/pre-harvest-glyphosate-best-practice-in-cereals
[2] https://www.lawsuit-information-center.com/roundup-lawsuit.html
[3] : https://glyphosatestudy.org/uncategorized/international-study-reveals-glyphosate-weed-killers-cause-multiple-types-of-cancer
[4] https://youtu.be/RbOmX4n2xw0
[5] Glyphosate inhibits the EPSP synthase, an enzyme in the shikimate pathway which means that vital proteins can’t be built. Humans don’t have a shikimate pathway, but our gut microbes do! For more details see the youtube link.
[6] https://www.fwi.co.uk/arable/crop-selection/market-opportunities/wildfarmed-expands-into-oats-and-barley-markets
Marianne Landzettel is a journalist writing and blogging about food, farming and agricultural policies in the UK, the US, continental Europe and South Asia. She worked for the BBC World Service and German Public Radio for close to 30 years. Follow her on X at @M_Landzettel and m.landzettel on Instagram
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