Glyphosate is the active ingredient in many weedkillers, including Monsanto’s Roundup – used in farming, public places like parks, streets and schools and also by people in their gardens. It is the world’s most widely sold weedkiller.

How is glyphosate getting into our bread?

Glyphosate is one of three pesticides regularly found in routine testing of British bread, appearing in over 60% of wholemeal bread samples tested by the Defra committee on Pesticide Residues in Food.

Many farmers routinely use Roundup and other herbicides to clear their fields of weeds before crops emerge in the spring. But what’s more alarming is they’re also using glyphosate on crops shortly before they are harvested, in order to desiccate (dry out) the plants and make them easier to harvest.

Glyphosate kills parts of the crop that haven’t ripened evenly, and dries the crop. This allows Combine harvesters to move more quickly and cover more ground during harvest, and may reduce drying costs. But applying glyphosate so close to harvest makes the likelihood of finding residues in food even higher.

Glyphosate and human health – the research

Concerns about the dangers of glyphosate to human health have been around for years. There have long been concerns that glyphosate is a hormone disrupter which can cause cancerous tumours, birth defects, and other developmental disorders. If this is the case, as some scientists argue, there is no safe lower level for human consumption.

The chemical companies and the food industry claim the level of glyphosate in food poses no danger to the British public. But recent World Health Organisation (WHO) findings and the chemical cocktail often found in bread sold in the UK bring this into serious question. The amount of glyphosate in bread may sit well below the level deemed unsafe by the EU, but this level has not been re-examined since the WHO’s ‘probable carcinogen’ ruling.

The safety regulators in the UK and EU only look at glyphosate on its own, often referring to unpublished industry studies that aren’t publicly available and have never passed peer review or been exposed to expert critique. But in the real world, glyphosate is always mixed with other chemicals to make sure the glyphosate sticks to and penetrates the plants it’s sprayed on. The International Agency for Research on Cancer (IARC) panel looked at what farmers are actually using.

Reviewing published, peer reviewed research and scientific studies, the Agency examined data on the impact of commercially available glyphosate-based herbicides, like Roundup, to determine that it is “probably carcinogenic to humans“.

Can UK farmers use less glyphosate?

The chemical companies encourage wheat farmers to use glyphosate not only as a weedkiller but also as a pre-harvest desiccant (i.e., a drying agent). But even the industry-funded Agriculture and Horticulture Development Board advises farmers that there is no advantage—and some risk—in using glyphosate this way:

  • “Trials in England and Scotland showed no advantage – in terms of grain and straw moisture content, harvest efficiency or grain quality – where weed-free wheat crops were treated.”
  • “Serious yield losses can occur when much of the grain is well above 30% moisture content. This highlights the potential risk of using pre-harvest glyphosate to ‘even up’ harvesting. Residues are likely to be higher if glyphosate is applied to such moist grain.”

In March 2015, the International Agency for Research on Cancer (part of the World Health Organisation), published a report in which glyphosate was identified as a ‘probable carcinogen’ to humans.

There is a maximum residue level (MRL) set for glyphosate, and the residues found in bread do fall below the current MRL; however this level has not been reviewed since the IARC’s announcement.

About the IARC Report

The IARCs decision was made by 17 scientists led by Aaron Blair—an internationally renowned epidemiologist who spent thirty years at the National Cancer Institute, and the author of more than 450 scientific papers.

How did IARC reach this decision?

Three types of data were reviewed: epidemiological studies on humans who had been repeatedly exposed to glyphosate; lab tests on animals; and “mechanistic” analyses, which analyse how a compound can actually cause cancer in our bodies. The animal studies “found excesses of rare tumours”. This was supported by the human studies, which showed “a strong link between people who used or were around glyphosate, and an increased risk of non-Hodgkin’s lymphoma” [1].

Why not a ‘definite’ carcinogen?

According to lead scientist Aaron Blair, there were good grounds to conclude this [2]. But one of the many human studies did not find a link between people who use glyphosate and the emergence of cancers, so this category was not chosen. Time will tell: The picture may become clearer as more studies are done, as it did in the case of benzene – now universally acknowledged as carcinogenic.

Is glyphosate dangerous below current regulatory limits?

Pesticide industry representatives have implied that, as IARC only evaluates hazards, not the risks associated with exposure, their conclusion only applies to extreme levels well above current regulatory limits. But IARC has identified a totally new hazard – carcinogenicity – and this raises new questions about what level is safe; both the EU and US risk assessments were done before this new hazard was found.

The industry’s claim ignores the fact that the studies IARC examined included low levels of glyphosate exposure. Current regulatory limits need urgent re-assessing.

Glyphosate herbicide operators

IARC found that the studies which showed the clearest link between glyphosate and cancers in humans concerned operators using glyphosate herbicides. This seriously calls into question the safety of farmers and workers who regularly use glyphosate products in their jobs.

New studies that support IARC’s conclusion

Alongside the concerns laid out by IARC, two new studies suggest that the daily consumption of very low levels of glyphosate may indeed pose a health risk. According to UK government data, the average level of glyphosate found in bread is around 0.2mg in up to a third of bread. Given the average amount of bread eaten daily and the average bodyweight of a UK adult, the average person therefore consumes around 78ng of glyphosate per kg body weight every day. This is nearly 20 times the level found to cause liver and kidney damage in one of the recent animal studies (only 4ng per kg body weight per day) [3].

Damage to gene functions leading to organ damage

Research animals were given Round-up, Monsanto’s patented glyphosate based product, on a daily basis, at a dose equivalent to half the levels permitted in drinking water in the European Union—thousands of times below the regulatory set safety limits of glyphosate alone. The study concluded:

“A distinct and consistent alteration in the pattern of gene expression was found in both the liver and kidneys of the Roundup treatment group … these alterations in gene function were consistent with fibrosis (scarring), necrosis (areas of dead tissue), phospholipidosis (disturbed fat metabolism) and damage to mitochondria (the centres of respiration in cells)” [4].

Liver and kidney damage at ultra-low environmental doses

A review of regulatory reports and published literature found around 30 studies that indicate glyphosate-based herbicides have toxic effects below regulatory limits. This included studies performed by chemical companies on their own products, and studies looking at the impact of Roundup at a concentration of 0.1 parts per billion, with a glyphosate concentration half that allowed in drinking water by the European Union. The researchers concluded:

“Our results suggest that chronic exposure to a GBH [Glyphosate-based herbicide] in an established laboratory animal toxicity model system at an ultra-low, environmental dose can result in liver and kidney damage with potential significant health implications for animal and human populations”[5].

Why did IARC reach a different conclusion to US and EU regulatory bodies?

Regulatory bodies frequently only look at studies undertaken by the pesticide companies themselves. Because these studies are commercially confidential, they are not subject to the normal scientific process of peer review and open publication in the scientific literature, and they are not available for public scrutiny. Importantly, all regulatory bodies, including in the EU, only consider scientific research on the effects of the pure chemical – in this case glyphosate – rather the final product mixtures that farmers, gardeners and many others actually use. By contrast, the IARC reviewed only publically available peer-reviewed studies, and this included studies of actual glyphosate based products like Round-up, as used by those most at risk. Despite what pesticide industry representatives claim, this makes IARC’s results far more relevant when assessing real risk.

What’s the difference between pure glyphosate & glyphosate herbicide products?

Glyphosate as a pure chemical is very rarely used as a herbicide. Instead, it is mixed with other chemicals, known as adjuvants. These improve the efficacy of products – for example easing spraying or ensuring the product sticks to the plant. These mixtures may interact to have an adverse combined effect. Furthermore, whilst these adjuvants are considered ‘inert’, research has shown that some are, themselves, toxic. However, as they are not named by the chemical company as the main ingredient, they are not subject to the same safety testing. Research has shown that glyphosate with adjuvants may be many times more toxic than glyphosate alone [6].


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