Last updated March 6, 2017 at 3:10 pm
Science Update is a monthly written series from Dr Paul Willis tackling some of the controversial topics in the public and aims to provide the current research behind these subjects.
Have you ever heard of glyphosate? Perhaps not, but you might have seen Roundup, Weedmaster Duo or Zero on the shelf at Bunnings. With over 500 products containing this chemical registered for use, it is the most widely used herbicide in Australia.
There is a lot of misinformation concerning its use, so here’s an update on the science behind the dangers of glyphosate.
Glyphosate is a broad-spectrum herbicide which is particularly effective against annual broadleaf weeds and grasses that compete with crops. Technically, it is a type of phosphonate, one of the organophosphorus compounds (organic compounds containing phosphorus).
Confusion over the safety of glyphosate was sown over the last couple of years when two different agencies of The World Health Organisation released two seemingly contradictory reports.
In 2015, the International Agency for Research on Cancer (IARC) released a report in which they concluded that glyphosate is probably carcinogenic to humans and they placed it into Group 2A of probable carcinogens. This groups also contains a long list of chemicals including ‘lead compounds’ as well as mixtures such as wood fire smoke, red meat and bitumen, all thought to probably cause cancer in humans.
Early this year, a panel of experts from The Food and Agriculture Organisation of the United Nations (FAO) and WHO put out a report on pesticide residues in food concluding that glyphosate is unlikely to be genotoxic in anticipated dietary exposures. In other words, the amount of glyphosate people are likely to eat once it is in the food chain is unlikely to have any effect on their genes.
This contradiction has been explored by the Australian Pesticides and Veterinary Medicines Authority.This group are responsible for assessing the risk and possible threats of chemicals. They conclude that products that contain glyphosate are safe to use within the practices recommended by the manufacturer. They agreed that, as a residue in food, the amount of glyphosate people are likely to consume poses no significant risk to them.
Resolution of the contradiction revolves around the observation that the chances of glyphosate causing cancer are related to dose and it is only in very high doses – above natural consumption levels – that this problem arises. Lower doses of the kind that most people will be exposed to are considered safe.
So just how toxic is glyphosate?
Measuring toxicity is a tricky business because there are many variables such as dose, means of admission and so on. The Australian Pesticides and Veterinary Medicines Authority, conclude that glyphosate is a low-risk active constituent in herbicide products but its toxicity is of concern in aqueous environments like creeks and rivers.
The toxicity of glyphosate is explored in some detail in an article that compares it to some natural herbicide recipes found online. Most of these natural recipes are mixtures of vinegar (acetic acid) and salt. The startling conclusion is that glyphosate is less toxic than vinegar and salt is more toxic than glyphosate when taken orally.
Based on the number of salt and vinegar chips I’ve consumed, it’s reasonable to assume that glyphosate is unlikely to cause harm based on average human consumption levels.