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<\/p>\nYou may have heard, or maybe not, that the EU are debating the continued licensing of glyphosate weed killers.\u00a0 There are conflicting studies and arguments between various authorities about the safety of glyphosate based weed killers, the best known being Roundup by Monsanto.\u00a0 Monsanto developed Roundup in the 70\u2019s and until 2000 had a patent.\u00a0 Now of course there are many similar formulations on the market.\u00a0 Regardless of the arguments between scientists advising the World Health Organisation (WHO) and European Food Safety Authority (EFSA) about whether or not glyphosate can be classed as possibly carcinogenic in humans, I was concerned about ANY use of weed killers around produce I have to eat.<\/p>\n
<\/p>\n
At recent General Committee meetings, I had reason to be discussing the affects of using Roundup on spare allotments to control weeds and the future use of the plots by tenants who wished to grow organically.\u00a0 The mantra that was chorused by most of the committee was the usual.\u00a0 \u2018..it is perfectly safe, as soon as it touches the soil it breaks down and is harmless\u2026\u2019<\/p>\n
When it was reported that a prospective tenant did NOT want their new plot sprayed, there was a condescending aside that \u2018\u2026.people should learn their chemistry\u2026\u2019<\/p>\n
Not wanting to let this go and realising that most allotmenteers do not have the time to trawl through scientific papers and studies to find out the details (assuming of course that they can understand the underlying terminology, science and analysis, required) I decided to investigate a bit and summarise some of the information.<\/p>\n
\u2026And it turns out that the \u2018slash and burn\u2019 style gardeners that promote the use of glyphosate are sort of right\u2026\u2026but are also, at the same time, very wrong, are badly informed and guilty of parroting the same line probably given out originally by Monsanto et al.<\/p>\n
Glyphosate works by interfering with a key enzyme (EPSPS) which in turn prevents synthesis of some key amino acids, effectively shutting down a plants growth and killing it.\u00a0 It is absorbed mainly through the leaves and growing parts above ground and also minimally through the roots.\u00a0 EPSPS is only found in plants and some microbes.<\/p>\n
When it gets into the soil (as it will, due to the method of spraying and run-off , etc) it is indeed broken down by microbial action.\u00a0 But the simplistic statement that as soon as it touches the soil it breaks down and is safe is at best a fundamental misunderstanding of the process and at worst deliberate disinformation.<\/p>\n
Firstly, the rate at which it breaks down is very variable.\u00a0 It depends on both the soil type and climate.(and the availability of sufficient microbes).\u00a0 The persistence in soil is given as a \u2018half-life\u2019.\u00a0 This is the length of time taken for half the glyphosate present in the soil to be degraded.\u00a0 The half-life can vary from 2 up to 200 days.\u00a0 An assumed average in the field is around 45 days.\u00a0 (Note that this is not the length of time to degrade all the glyphosate.\u00a0 It could persist for months in significant amounts)\u00a0 Glyphosate bonds readily to soil and this makes it difficult for microbes to get at it, but also means it could later be reabsorbed by plants.\u00a0 Tests published in a fact sheet by the National Pesticide Information Centre in the USA showed residues of glyphosate in lettuces, carrots and barley up to one year after treatment of the soil with glyphosate weed killer.\u00a0 And another point.\u00a0 The committee were discussing Roundup as a control until a plot was taken.\u00a0 This could involve multiple applications over the same ground over a one to two year period.<\/p>\n
Glyphosate on it\u2019s own has been shown to have little harmful effect on humans at low levels of exposure.\u00a0 There are arguments over links to non-Hodgkin lymphoma and other cancers among operators exposed to higher doses.\u00a0 This led to the recent classification of glyphosate by the World Health Organisation as \u2018probably carcinogenic in humans\u2019.<\/p>\n
The glyphosate in soil is broken down by microbial action into aminomethylphosphonic acid (AMPA)\u00a0 This can persist in the soil for long periods of time (longer than glyphosate).\u00a0 AMPA is then broken down over time into final products such as formaldehyde, ammonium (the cation NH4+ , which is itself toxic to plants) phosphate and CO2.\u00a0 You may be pleased to know that AMPA is considered to be no more toxic than glyphosate itself (interpret that as you wish).<\/p>\n
In other studies glyphosate does affect microbes that use the enzyme EPSPS, including some beneficial gut flora normally found in humans.\u00a0 It has also been shown to affect the growth of some species of earthworms and some amphibians.<\/p>\n
And don\u2019t forget the bees.\u00a0 Published scientific studies have shown detrimental affects on honey bee navigation and learning after exposure to sub-lethal doses of glyphosate on farms.\u00a0 As bees do make it back to the hive they then carry trace amounts back to the colony which are fed to the next generation (and put in the honey that is then fed to humans).\u00a0 The overall effect could be to degrade the ability of the colony to forage and threatening colony survival.<\/p>\n
Note that the majority of studies on toxicity, etc are just for glyphosate alone.\u00a0 Commercially it is formulated with many other ingredients, some or all of which could have an effect on the user, the environment or the consumer.\u00a0 Most notable is the use of various surfactants (think washing up liquid) to help the product wet the foliage and increase absorption.<\/p>\n
Interestingly, Roundup is formulated with a surfactant called polyethoxylated tallow amine (POEA) presumed to be made from tallow (a mixture of fats from the fatty tissue of cattle and sheep) and so is not exactly good news for vegetarians and vegans.<\/p>\n
So while it is an invaluable product to use to control weeds in the urban environment or eradicate some very bad invasive species, totally safe on your vegetable plot it is not.\u00a0 Unless you wish to deliberately feed your children traces of various chemicals as a long term experiment.<\/p>\n
Maybe some members of the committee need to read up a little more on chemistry \u2026.and possibly biology.<\/p>\n","protected":false},"excerpt":{"rendered":"
You may have heard, or maybe not, that the EU are debating the continued licensing of glyphosate weed killers.\u00a0 There are conflicting studies and arguments between various authorities about the safety of glyphosate based weed killers, the best known being Roundup by Monsanto.\u00a0 Monsanto developed Roundup in the 70\u2019s and until 2000 had a patent.\u00a0 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32],"tags":[],"class_list":["post-624","post","type-post","status-publish","format-standard","hentry","category-ontheplot"],"_links":{"self":[{"href":"https:\/\/our-shed.co.uk\/balgablog\/wp-json\/wp\/v2\/posts\/624","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/our-shed.co.uk\/balgablog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/our-shed.co.uk\/balgablog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/our-shed.co.uk\/balgablog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/our-shed.co.uk\/balgablog\/wp-json\/wp\/v2\/comments?post=624"}],"version-history":[{"count":3,"href":"https:\/\/our-shed.co.uk\/balgablog\/wp-json\/wp\/v2\/posts\/624\/revisions"}],"predecessor-version":[{"id":628,"href":"https:\/\/our-shed.co.uk\/balgablog\/wp-json\/wp\/v2\/posts\/624\/revisions\/628"}],"wp:attachment":[{"href":"https:\/\/our-shed.co.uk\/balgablog\/wp-json\/wp\/v2\/media?parent=624"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/our-shed.co.uk\/balgablog\/wp-json\/wp\/v2\/categories?post=624"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/our-shed.co.uk\/balgablog\/wp-json\/wp\/v2\/tags?post=624"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}