By Jean Clavelle, Farm & Food Care Saskatchewan
Glyphosate is a herbicide — a type of pest control product used to kill plants. It is the active ingredient in the now infamous chemical Roundup, and is one of the most used agricultural chemicals worldwide.
Google glyphosate, originally released as the product Roundup, and you’re faced with results like ‘horrific’ “new evidence about the damage Roundup causes” and “Roundup chemicals are lethal.” One quick search and I can understand why society might have concerns about the pervasive use of glyphosate in agriculture. Reading these statements does lead us to question: is Roundup poisoning us?
Let’s examine the science.
A small amount (think: pop can) is mixed into a tank of water on the back of a special machine called a sprayer. Farmers use these machines to spray the mixture onto the weeds over a large area (that one pop can treats an area nearly the size of a football field) where it is absorbed by the plant. Once inside the plant, glyphosate binds to an enzyme (EPSP synthase), preventing it from building essential amino acids that a plant needs to live and grow. With this enzyme disabled, plants die. Now, the really interesting thing is that EPSP synthase is found only in plants and bacteria; humans and animals do not use this process.
Remember that Google search which told us glyphosate is one of the most toxic chemicals around? Not so. The general standard for acute (short term) toxicity is a value called an LD50. This refers to the median lethal dose, the amount of a chemical needed to cause death in 50% of the animals it is tested on. An LD50 is one way to measure the relative short-term poisoning potential of a compound. The lower the number the more toxic it is. For example, the LD50 of sodium bicarbonate (baking soda, a common ingredient in baking) is 4220 mg/kg; table salt 3000 mg/kg; caffeine (as in our precious morning coffee) is 192 mg/kg; and nicotine (cigarettes) is 50 mg/kg.
So where does glyphosate fit? Glyphosate has an LD50 of 5600 mg/kg. Yes. It is less toxic than baking soda, table salt, and coffee.
Our entire world is comprised of chemicals. Water, salt, and vinegar are chemicals, and even our bodies can be considered walking, talking chemical bags.
You’ve probably heard the old adage of toxicologists “the dose makes the poison”. Even those regular household compounds like salt, vinegar or yes, even water can be toxic if ingested in high enough doses. When glyphosate is used as it is intended, just like salt, vinegar, and water, it has minimal toxicity to humans and animals because the amount used is small.
But how do we know we are not consuming high levels of pesticides? Health Canada scientists review the data from over 250 separate studies before they approve a pesticide for sale or use in Canada. As part of this extensive review before a chemical is approved for sale, they identify the amount of a pesticide that a person could be exposed to without any adverse health effects. These levels are then compared to the maximum amount of residue that might be found on crops after use of the pesticide (a value known as the Maximum Residue Limit or MRL) in order to ensure that consumers are never exposed to an amount that could pose a risk to health. Indeed, MRLs are typically 100-1000 times below levels that are still considered safe.
Thanks to the MRLs established by Health Canada, based on science, we can be confident that if small amounts of glyphosate are ingested through exposure in our food system, we know they won’t be at toxic enough levels to cause damage, even if they are consumed every day over a life time.
I should probably also mention that it is not just Health Canada that has assessed the science around glyphosate. Most other major regulatory organizations around the world, including the European Food Safety Authority, the World Health Organization, and the U.S.’s Environmental Protection Agency, have also reviewed data on glyphosate (available here).
Glyphosate is easily and relatively quickly broken down in the environment. It does not bioaccumulate, meaning it does not build up in the bodies of fish and wildlife (read an example of mercury bioaccumulation here). And finally, it is excreted by our bodies if ingested. Their overwhelming consensus? When glyphosate is used according to label directions, it poses minimal risk to people, wildlife, and the environment.
We need to evaluate claims on the basis of overall weight of scientific evidence behind it. The stronger the weight of evidence, the more confidence we can have in the scientific findings. Glyphosate has been investigated by many scientists from around the world, in hundreds and hundreds of studies (again, available here) all of which have determined that, when it is used as it is intended, it is safe for people, for animals, and our environment.
Being a science geek, I follow facts. And the evidence tells me glyphosate is not the problem a cursory Google search might suggest. If you would like to know how glyphosate is used, the label (which is a legal document authorized by the Pest Control Products Act) can be found here. And if you still have questions, we want to hear them.
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