It may produce adverse effects on human and animal development and reproduction, the immune system and the nervous system and these may occur at very low doses.
They are the proud sponsors of Channel 4's River Cottage series and widely recognised for their commitment to the environment, promoting 'conservation grade' farming where growers must dedicate portions of their land to benefit wildlife.
But Jordans - the leading manufacturer of breakfast cereals and cereal snack bars - is reviewing its farming methods after some of its products were found to contain residues of a controversial herbicide that campaigners say is potentially harmful to human health.
The company has pledged to review its use of glyphosate, a powerful weedkiller, after a pressure group analysed the results of tests carried out by the Government's official Pesticides Residues Monitoring Programme on bread, bakery products, cereal bars and other foodstuffs.
Safe, pure and wholesome?
According to GM Freeze, 100% of the Jordans cereal bars tested were found to contain glyphosate. The group also says that at least 85% of tested products made by Warburtons – the well known bread company – contained traces of the herbicide.
The Government's sampling programme is not exhaustive and is designed to provide only a snapshot of residues in a variety of products at a specific time. Still, the figures speak for themselves.
Of 40 Warburtons products sampled, 34 tested positive for glyphosate. These included Warburtons white, brown and wholemeal loaves, and its crumpets. The products were sold in leading supermarkets including Tesco, Morrisons and Asda.
All five samples of Jordans cereal bars contained the herbicide. they included Jordans cranberry and raspberry, crunchy honey and almond, and red berry varieties, purchased in Sainsburys and Tesco.
The testing was carried out in 2012 but the results were only recently published in full.
Glyphosate linked to health problems
The weedkiller residues were present in small quantities - between 0.1 and 0.8 mg/kg. This is well below the permitted EU maximum residue levels (MRLs) for cereal crops, which currently span 10 - 20 mg/kg.
However scientists have found reasons to be very worried about dietary glyphosate. According to Anthony Samsel and Stephanie Seneff, writing in the Journal Entropy, glyphosate has the effect of inhibiting the action of a key enzyme, cytochrome P450:
"Residues [of glyphosate] are found in the main foods of the Western diet, comprised primarily of sugar, corn, soy and wheat.
"Glyphosate's inhibition of cytochrome P450 (CYP) enzymes is an overlooked component of its toxicity to mammals. CYP enzymes play crucial roles in biology, one of which is to detoxify xenobiotics. Thus, glyphosate enhances the damaging effects of other food borne chemical residues and environmental toxins.
"Negative impact on the body is insidious and manifests slowly over time as inflammation damages cellular systems throughout the body. Here, we show how interference with CYP enzymes acts synergistically with disruption of the biosynthesis of aromatic amino acids by gut bacteria, as well as impairment in serum sulfate transport.
"Consequences are most of the diseases and conditions associated with a Western diet, which include gastrointestinal disorders, obesity, diabetes, heart disease, depression, autism, infertility, cancer and Alzheimer's disease."
The sheer number of positive tests for both companies "raises questions" about the use of glyphosate in their supply chains, say campaigners. They also highlight the absence of any MRL for herbicide levels in the bread and bakery products themselves.
"We are concerned because glyphosate has been implicated as a potential endocrine disruptor", GM Freeze director Helena Paul told The Ecologist.
"This means that it may produce adverse effects on human and animal development and reproduction, the immune system and the nervous system and these may occur at very low doses."
The group says there is a growing body of evidence suggesting the herbicide could be linked to health problems and that there should be a ban on its use on food crops and a review of the MRLs to minimise exposure to consumers.
Environmentalists point to studies which they say found that glyphosate herbicides can be toxic to humans, even at lower doses, affecting both embryonic and placental cells.
"Laboratory tests on rats have highlighted damage to testosterone levels in male offspring, while studies on cell cultures found that glyphosate blocks receptors for male sex hormones, and that it inhibits production of oestrogen", according to Friends of the Earth, which published a report on the issue earlier this year.
And a recent article on The Ecologist highlighted reports from Denmark that the health of pigs was being adversely affected by eating feeds containing elevated - but still legal - levels of glyphosate.
Monsanto: it's harmless!
Manufacturers of glyphosate vigorously dispute such claims. They insist that the herbicide is safe, and accuse campaigners of touting flawed research, or manipulating the findings to suit their own agenda.
"Extensive animal and in-vitro (test-tube) data has demonstrated that glyphosate does not cause cancer or tumors, nor is an endocrine disrupter", Thomas Helscher, spokesman for Monsanto - a major supplier of glyphosate products under its 'Roundup' brand - told The Ecologist.
Inconvenient research suppressed?
Last month the prominent peer-reviewed Journal of Food and Chemical Toxicology retracted a controversial scientific paper by Professor Gilles-Eric Seralini, an expert in molecular biology - triggering an international storm of protest and allegations of corporate manipulation.
Seralini's research found that rats fed a diet of GM maize, or exposed to glyphosate, for two years, developed higher levels of cancers and died earlier than controls.
The study had been repeatedly criticised by the agribusiness industry and academics, who said it contained methodological flaws, was scientifically substandard, and its findings sensationalised.
An earlier review by the European Food Safety Authority had also concluded that Seralini's research could not be regarded as scientifically sound because of inadequacies in the design, reporting and analysis of the study.
"The Seralini study does not provide information which calls into question the extensive safety evaluations of glyphosate or Roundup herbicides", insisted Helscher.
However others believe that the research was carried out to an exceptionally high standard and that the paper was only retracted because its findings were inconvenient to corporate interests.
An open letter to Elsevier, the publisher of the Journal, criticising its decision to retract as a "clear violation of the international ethical norms" has so far attracted signatures from 787 scientists and 2,131 non-scientists from 76 countries.
How does the glyphosate enter the food chain?
Glyphosate is used widely on conventional crops in the UK. For example, it is routinely sprayed on arable fields to kill off weeds before crops germinate, and so increase yields.
It is also used for crop 'dessication' - where farmers spray crops with the herbicide just prior to harvesting in order to make combining easier. GM Freeze believes this is most likely cause of the glyphosate found in the 2012 samples.
But glyphosate's use globally is massively on the increase on genetically modified (GM) soya, maize and canola, engineered to be resistant to the chemical. This allows glyphosate to be sprayed on the growing crop - killing the weeds but leaving the crop plants unaffected.
The repeated use of glyphosate on growing crops resistant to glyphosate can also lead to high levels of the herbicide entering the food chain, often in animal feeds.
Jordans and Warburtons 'compare unfavourably'
There is no suggestion of any wrongdoing on the part of Jordans or Warburtons. However campaigners point out the frequency of their positive results compare unfavourably with major competitors.
In the bread category, according to the GM Freeze analysis, less than 15% of Hovis samples tested positive for glyphosate, with 28% of Kingsmill products found to contain residues. Four samples of Tracker bars tested negative, and just one of 11 Nature Valley items contained the chemical.
"The companies should ask questions about the use of glyphosate and other herbicides and pesticides in production, because we can now see how frequently residues of glyphosate appear in food", said Paul.
"Convenience in production is not the only criterion - people need healthy and nutritious food, and companies need to be proactive in protecting consumer interests in health and wellbeing, especially in complex issues where most consumers cannot be expected to be knowledgeable themselves."
'Conservation grade' permits glyphosate
Jordans confirmed that glyphosate is permitted for use on its 'conservation grade' farms and said it is typically used around 8 weeks prior to planting crops. In a statement the company said:
"The results identified within this survey are a fraction (c. 0.5% - 1.5%) of the permitted Maximum Residue Level, or MRL [for cereal crops], and it is important to remember that this level is itself assessed and set by European regulators on the basis of very detailed scientific evidence."
"However, we respect the fact that GM Freeze has gathered detailed information in support of its claims; therefore we have asked internal and external experts to review this, together with known scientific data, and provide us with an assessment of whether we need to adopt a different position."
Jordans: change on the way?
Jordans' statement also said it would be asking the Guild of Conservation Grade Producers to review the GM Freeze research and provide an assessment of whether they believe Jordans needs to make any changes to its crop management protocols as a result.
"Our Head of Technical will also review the available scientific data relating to glyphosate and advise whether he feels that we should be stipulating a Maximum Residue Level lower than that specified currently within relevant legislation. Our newly designated Sustainability Governance Committee will evaluate this information in the New Year."
Paul Murphy, Jordans CEO, earlier said he would request his crop development manager "explore whether it might be possible to gain agreement on the use of an alternative means of crop management other than the use of glyphosate", in a forthcoming annual meeting of Jordan's farm suppliers.
Warburtons: nothing doing
Warburtons declined to respond to The Ecologist's questions.
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