Is Glyphosate Safe?

Sep 13, 2018 | Sustainable Agriculture |

The Dirt:
Glyphosate and its popular product, Roundup, is the most widely used weed killer in the world. Yet, it has come under intense scrutiny lately in the courts, and headlines are claiming there are harmful glyphosate residues in some of our favorite foods including Cheerios. What is glyphosate, why is it used, and what does science say about its safety?
At my home, we struggle with an ongoing battle against goutweed— a Hydra Lernaia of the invasive weed world. If you pull or cut this weed, it will only sprout more roots underground as a survival response. We researched and spoke with weed experts and ended up turning to Roundup, a glyphosate product, to get rid of it. And after three applications this past spring, the weed was finally gone.
At Dirt-to-Dinner, we have researched and written about glyphosate before and concluded it safe for use as directed. But with the enormous judgement against Monsanto, have things changed?

What is glyphosate?

Glyphosate is a broad-spectrum herbicide. That means it kills anything green and growing that it is sprayed on. It is the active ingredient in Roundup, among other herbicides, and is marketed to homeowners and farmers. It is used to kill weeds in lawns, crop fields, vineyards, and orchards. Golf course owners use it to keep the greens and fairways pristine. The National Forestry Foundation uses it for forest management.
Glyphosate is also used in conjunction with herbicide-tolerant seeds for corn, soy, and cotton. So a farmer growing Roundup-ready soybeans, for example, can plant in the early spring then spray the field with glyphosate for weed control, and not kill the soybean seedlings.

Why do farmers use glyphosate?

Glyphosate controls weeds so farmers can realize a better yield on their crops. This can be translated into more plentiful and affordable food.
Glyphosate is used to clear a field for planting. In this case, the farmer doesn’t have to “till” their field to rip out the weeds. Reduced tillage means lower greenhouse gas emissions from not firing up the tractor a countless number of times and means more decomposing matter in the soil which creates a healthy soil. Healthy soil creates strong plants, retains water, and reduces runoff and erosion.

Here is a great video produced by Know Ideas Media explaining why farmers use glyphosate.

How does glyphosate work?

Glyphosate inhibits the activity of an enzyme, called EPSP, which is essential to plant growth. This particular enzyme is not found in humans or animals. Applied to weeds as they are growing, it stops them in their tracks.
Once absorbed, glyphosate travels to the roots, and then is broken down naturally by bacteria and other organisms living in the soil.

How much glyphosate does the average farmer use?

Brian Scott is a soybean, corn and wheat farmer who manages 2,300 acres of land in northwest Indiana. He demonstrates that the amount of glyphosate applied to his crops is less than 2 cans of soda for every acre of land. Canadian farmer Jake Leguee puts in it another way:
“Here’s the thing about spraying a chemical like glyphosate. An acre of land is 43,560 square feet, which is a little smaller than an American football field. On that acre, 360 grams of glyphosate active ingredient is sprayed. Put another way: 2 cans of beer of glyphosate sprayed over an area almost the size of a football field. That’s .015 mL of beer on each square foot – and that includes the solution the glyphosate active ingredient is suspended in. That is an incredibly low concentration. A standard “drop” of water is .05 mL. That’s less than a third of a drop of water!”

Is glyphosate safe to use?

The science says yes. And as farmer Jake Leguee says, “…it has absolutely been the single greatest invention in agricultural history. And it is unequivocally, fantastically safe. It is one of the lowest toxicity herbicides we use on our farm. It is less toxic than alcohol. Less toxic than caffeine.

Pesticides used on conventional and organic crops are highly regulated and undergo rigorous scientific evaluation by the U.S. Environmental Protection Agency. It is through this process that pesticides are safe when used according to the product label.

In the case of glyphosate, The U.S. Environmental Protection Agency (EPA), the National Institutes of Health (NIH), the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) and regulatory authorities throughout the world have reaffirmed that glyphosate is safe to use as directed and does not cause cancer.

What about the findings of glyphosate residues in our food?

Whether farmed conventionally or organically, trace amounts of pesticide residues can find their way into our food system. The question is how much residue is too much? The answer is many, many portions, every day, for the rest of your life!
To understand how much is too much, we need to understand the Acceptable daily intake (ADI).  ADI is a measure of the amount of a specific substance in food or drinking water that can be ingested on a daily basis over a lifetime without an appreciable health risk. The ADI is set with a large margin of safety, usually 100 times the maximum effect seen in the laboratory. The European Union has set an ADI for glyphosate at 0.3 milligrams per kilogram of body weight per day. The U.S. EPA figures are 1.75 milligrams per kilogram of body weight per day.
Cheerios by General Mills and Old Fashioned Oats by Quaker Oats were among the favorite consumer products recently tested for glyphosate residue by the Environmental Working Group (EWG), a consumer advocacy organization supported by many in the organic industry. The group has a history of presenting data to cause unnecessary fear.
Cheerios were a staple breakfast item in this household during my children’s younger years. I wondered about this claim from the EWG that I poisoned my kids.
In the examples below, we use the more conservative European Union Acceptable Daily Intake for glyphosate (0.3 milligrams per kilogram of body weight per day).
The science says… The highest level of glyphosate found in the Environmental Working Group report for Cheerios (serving of 28 grams), was 0.53mg/kg. The highest level of glyphosate found in Quaker Old-Fashioned Oats (serving of 40 grams) was 1.3 mg/kg.
A child weighing 11 pounds would have to eat 29 servings of Quaker Old Fashioned Oats and 101 servings of Cheerios every day over a lifetime.
An older child weighing about 44 pounds would have to eat 115 servings of Quaker Old Fashioned Oats and 404 servings of Cheerios every day over a lifetime.

What about the lawsuit?

The California jury ruled based on their assertion that Monsanto intentionally kept Roundup’s potential risks hidden from the public – it did not link glyphosate with cancer. Monsanto maintains that glyphosate does not cause cancer. Decades of scientific studies have shown the chemical to be safe for human use. (If you would like to read more about this case, read here.)

What are the heribicide alternatives?

Glyphosate was first introduced in the mid-1970s. It replaced a class of much more dangerous herbicides. The chemical profile of glyphosate has a low toxicity to humans and animals and it decomposes in the soil. While there are certainly other chemicals that farmers use, glyphosate is considered the safest and most environmentally friendly.

The Bottom Line: 

Weeds are a challenge for all growers. Glyphosate is just one tool in a farmer’s toolbox for managing crop health. It has helped farmers use fewer herbicides on their crops and improve their yield. Additionally, it has contributed to no-till farming, which benefits the soil, the environment, and sustainable farming practices. Hundreds of studies and regulatory agencies have confirmed its overall safety profile.