Glyphosate: harmful or harmless?

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Over the last 2 weeks, the herbicide glyphosate has again been in the news.

On 12th August, a San Francisco jury ruled that glyphosate had caused a former groundskeeper’s terminal cancer and ordered the manufacturer Monsanto to pay him $289m in compensation.

In the subsequent media frenzy, there has been much debate about whether glyphosate is harmful or safe for use in agriculture.

It’s hard to find a simple answer to the question because many competing interests are involved.  Even the World Health Organisation (WHO) has been accused of allegedly falsifying one of its major documents on the issue – more below.

I’m not a scientist.  Before the last fortnight, my knowledge of glyphosate was pretty sketchy to say the least.  Being aware of the media reports, but also a little sceptical of the universal farmers’ opinion that glyphosate is harmless to people and soil, I decided to try doing my own research.  Not an easy task!

After many hours and late nights of trawling the internet for research papers, news articles and reports from international health organisations, I gathered enough information to get the broad picture and form an opinion.

So here it is:

From my understanding, and as far as we know at the moment, glyphosate seems pretty safe. But there seem to be areas of research that haven’t yet been undertaken, which probably should be.

Here is my explanation for that conclusion.

What is glyphosate?

Glyphosate is a broad-spectrum (non-specific) herbicide, used widely in agriculture and gardening.  It was introduced in 1974 and was rapidly accepted because of its relative safety in comparison to other weedkillers.

It’s absorbed by leaves and transported to the plant’s growing points, including the roots. It works on a biological system found only in plants – not in animals – and stops the production of an essential plant enzyme.  This kills the plant within a few days.

Once it reaches the soil, glyphosate is inactivated almost immediately.  One of  its advantages is that new crops can be sown within a few days of treating the weeds.

Many articles talk only about ‘Roundup’.  This was the original product introduced by Monsanto, but there are now hundreds of different glyphosate products manufactured by many companies worldwide.

How is glyphosate used?

  • Here in the UK, one of the main uses of glyphosate is on stubble fields after the harvest, when the weeds left behind are just beginning to grow.  Treatment with glyphosate means the weeds are eliminated before the next crop is sown in the field.
Stubble field with weeds pre-treatment 3
One of glyphosate’s main uses in the UK – eliminating newly-growing weeds like this after the harvest, before sowing the next crop
  • By killing the weeds immediately before planting the next crop, they don’t have time to become a problem.  Consequently, the farmer doesn’t have to till (plough or harrow) the land as much.  Minimum-till (‘min-till’) techniques are now becoming widely adopted – less ploughing means that there is less leakage of greenhouse gases such as CO2 and nitrous oxide into the atmosphere. (You can find interesting stuff about keeping carbon in the soil here.)  Min-till also makes the soil healthier as it’s not constantly being compacted by heavy farm machinery.
  • In the UK, glyphosate is also used before harvesting certain crops, e.g. oilseed rape, to stop the ripe plants from growing .  As the crop is already ripe, glyphosate is not absorbed by the seeds.
  • In Britain, glyphosate is not used on actively-growing crops as it would kill them.
  • In the US, genetically modified (GM) crops designed to be resistant to glyphosate have been widely planted, so it can be sprayed onto crops without killing them.  No GM crops are grown in the UK.

Problems with glyphosate

There has been some concern that glyphosate may cause cancer, particularly for people who use it in their work.  So far, there doesn’t appear to be conclusive evidence for this, and the research is contradictory (see below).

Much of the research into this field has been done on glyphosate alone, but there is a suggestion from some researchers that added ‘inert’ chemicals in commercial products may make it more harmful.  Further research on this has been recommended.

Because glyphosate can be used on crops genetically-modified to resist it, it appears that where these crops are grown, particularly in the US, more of it is being used than is necessary.

There is some concern that, because it is used so widely, weeds may become resistant to glyphosate, which means it may not work in the future.

Controversy in the WHO and EU

In the last few years, there has been controversy over official reviews of the cancer risk posed by glyphosate.

In March 2015, the International Agency for Research on Cancer (IARC), an arm of the World Health Organisation (WHO), stated that glyphosate is probably carcinogenic to humans.

However, in November the same year, the European Food Standards Agency (EFSA) and the European Chemicals Agency (ECHA) disagreed with this finding, stating that glyphosate is unlikely to cause a carcinogenic hazard to humans.  This prompted Dr Chris Portier, an expert on environmental health data relating to cancer, to write to the president of the European Commission to complain that EFSA and ECHA had not carried out the reviews correctly.  The heads of the two organisations wrote a letter in reply, explaining why their research was robust.

In September last year, after the EU re-authorised the use of glyphosate, EFSA was again  accused of carrying out the review incorrectly.  It published a statement defending its methods and findings, also suggesting the criticism was part of an ‘orchestrated campaign to discredit the scientific process behind the EU assessment of glyphosate.’

In other words, EFSA claimed its findings didn’t ‘fit’ the widely accepted belief that glyphosate causes cancer. The EFSA website carries a video explanation of the process involved in reviewing pesticides.

Even more surprising was the allegation by Reuters news agency last November that the 2015 IARC report had been significantly changed from its original draft.  The report shows evidence that the first draft of the document had originally stated that glyphosate is unlikely to be carcinogenic.  The journalist alleged that 10 changes had been made to the draft document, including ‘the removal of multiple scientists’ conclusions that their studies had found no link between glyphosate and cancer in laboratory animals.’

Other research

Just a sample of the research out there.

A toxicology study looking at reasons for the different interpretations of cancer risk between the IARC and EFSA.  It recommended that research should be carried out into other chemicals present in commercial glyphosate formulations, (e.g ‘Roundup’ and ‘Touchdown’). Some studies have shown different results between commercial products and glyphosate alone, which could mean that the added chemicals make it more harmful. These chemicals include surfactants that help to spread the herbicide evenly.

This line of further research has also been suggested by other studies.

A study published in a German food safety and consumer protection journal concluded that evidence from urine samples showed no health concerns for food consumers, or for workers who applied glyphosate.

The Agricultural Health Study, a huge 20-year ongoing study of American farming families, (89,000 people, all licensed pesticide applicators), looks at the incidence of cancers and other diseases related to pesticide and herbicide use.  In May this year, it reported that there was no association between glyphosate and any ‘solid tumours’ (cancers) including non-Hodgkins lymphoma; however there was an increased risk of acute myeloid leukaemia in workers with the highest glyphosate exposure, although this wasn’t statistically significant.

What would happen to farming if glyphosate was banned?

  • Farmers would have severe problems trying to control pervasive weeds like couch grass and black grass. These weeds compete with the crop, reducing the yield.
  • More ploughing and cultivating of land would be needed to kill the weeds.  The result would be an increased release of greenhouse gases, more diesel used and greater damage to soil.
  • Farmers would have to use greater quantities of selective (hormone) weedkillers instead, which are sprayed directly onto the growing crop.
  • Planting of winter crops may not be possible, due to longer weed-killing processes.  Spring crops yield less grain.
  • Elimination of weeds would be more expensive.  This could put up food prices.

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We will need to produce more food in the future to feed the increasing global population.

Glyphosate is an extremely useful tool in modern-day farming which can help to achieve this.  It encourages better farming techniques which help to protect soil and reduce greenhouse gases entering the atmosphere.  Without it, farmers would have to spend a lot of time cultivating the soil and would possibly need to use other chemicals on crops.

However, there are questions that need to be answered.  For instance, are commercial formulations containing other chemicals more harmful than glyphosate by itself?

I don’t think this topic will be disappearing any time soon.

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