RoundUp Glyphosate Weed Killer May Produce a Bacteria-Killing Antibiotic Effect in the Human Gut

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Driving down a grid road in central Saskatchewan, a machine that looks like a giant insect approaches me in a cloud of dust. The cab, hanging 8 feet above the road, is suspended by tires at least 6 feet tall, with wing-like appendages folded along each side. Should I drive around it or under it?

It is harvest season, and the high-clearance sprayer is on its way to desiccate a field. Desiccation may be the most widespread farming practice you’ve never heard of. Farmers desiccate by applying herbicide to their crops; this kills all the plants at the same time, making them uniformly dry and easier to cut. In essence, desiccation speeds up plant aging. Before desiccation, crops would have to dry out naturally at the end of the season. Today, there are examples of desiccation being applied to every type of conventional crop in Canada, the United States, and the United Kingdom.¹ Chances are that most of what you ate today was harvested using a desiccant, but you’d never know.

Mike Shewchuk jumps down from his swather as I pull into his farmyard. He is a young farmer whose blond brush cut and a robust stride would have not been out of place 50 years ago. Along with his dad, uncles, and brother, he farms 15,000 acres an hour outside of Saskatoon, Saskatchewan. They recently received a century farm award, for having continuously farmed the land since the early 1900s.

He is in the middle of a cut, and asks if I would mind riding with him as we talk. I climb up beside him on a small fold-down seat.

Swathers are giant lawn mowers farmers use to cut crops. The cut plants are left to dry on the ground before combining. It can be tricky knowing when to cut. If you start too early, you’ll get too many green seeds. Depending on the crop, that might lead to early germination (wheat) or self-combustion (canola). But if you wait too long, you may be scraping your seeds off the ground after the snow melts.

I doubt that I’ll be able to tell which fields had been desiccated. But the shriveled, brown peas are in stark relief to the green fields around it.

Swathing is quickly going out of fashion, as most farmers desiccate to ripen their crops. One of the big agro-chemical companies even has a marketing campaign with the hashtag #sellyourswather, encouraging farmers to desiccate and ditch swathing altogether. I asked Mike why he hadn’t sold his swather yet.

He laughs. “We’re not desiccating canola, and canola is paying the bills right now.”

For many farmers, that is changing. Until recently, farmers did not desiccate canola because it “shattered” the seedpods, shedding the seeds in soil. But breeders have been busy: In 2017, five new varieties of shatter-resistant canola were released in Canada. That will make desiccation viable for Canada’s second-most common crop, and accelerate a trend that began around 10 years ago, when desiccation started to become popular.

Not coincidentally, it was also around then that herbicide use spiked. When you sit down to eat dinner today, there will probably be desiccant in your food.

There are thousands of ways to kill a weed. You can starve it, bleach it, mess with its proteins. You can feed it fake hormones. You can force it to make acid so that it disintegrates from within. There are more than 400 licensed weed killers, or herbicides, in Ontario alone. And we love to use them. Canadians used more than 58,000 tons in 2014, compared with only 21,000 tons in 1994. Our landscape, and our crops, have never been so saturated.

Our thirst for herbicides is partly due to GMOs like RoundupReady corn, soy, and canola. These herbicide-tolerant crops came on the market in the late 1990s, and changed the farming landscape by making it possible to control weeds by using herbicides on crops still in the field.

Herbicide resistance explains part of the increase in herbicide use around the world over the past decades. If you blast a weed with herbicide, eventually its cells become resistant. Farmers are left with fields of weeds they can’t kill. This is what happens in people, with antibiotic resistant bugs. Faced with resistant weeds, farmers double down, spraying even more and using multiple herbicides. But desiccation accounts for a significant part of the growth in herbicide use. It’s impossible to say precisely how much, because stats are tracked for herbicide use by crop—not by usage type.

In theory, anything that kills a plant can desiccate a crop, but farmers can only use herbicides that are licensed as desiccants. In practice, there are only a few that are regularly used.

Glyphosate is increasingly used as, or with, desiccants. It’s sold under the trade name RoundUp, and is the most commonly used herbicide in the world, as well as the most commonly used desiccant. In 1974, global use of glyphosate was 3,200 tons per year. It is expected to reach 1 million tons per year by 2020.¹ In the U.S., the rate of growth has been accelerating. Between 1995 and 2004, glyphosate use grew by 356 percent. Between 2005 and 2014, it grew by 637 percent.²

Glyphosate works by interrupting protein synthesis in plants, rendering them unable to photosynthesize. It is also considered relatively safe for humans. But in 2015 the World Health Organization (WHO) declared it a possible carcinogen, on the basis of an independent survey of the scientific literature. Outrage from governments and industry around the world fueled a reanalysis by the Food and Agriculture Organization of the United Nations and WHO, which concluded in 2016 that it was “unlikely to pose a carcinogenic risk to humans through diet.”

Industry, and farmers, breathed a sigh of relief. The reports analyzed, however, did not consider the increase in exposure to glyphosate via desiccation. This practice has dramatically increased the dissemination of glyphosate into the environment, and into us.

There have been no explicit tests of the effect of desiccation on our microbiome.

I asked Sheri Roberts, a crop specialist with Agriculture and Agrifood Canada in Moose Jaw, Saskatchewan, whether she thought desiccation was safe. She was reluctant to make the call, but said she wished it was not so commonly used. “The timing’s really tight,” she said. “If you don’t get it just right, that herbicide ends up in the grain.” If farmers apply a non-contact herbicide (like glyphosate) too early, it will be taken up by the growing plant and end up inside the seed. Non-contact herbicides are taken up by the living plant and incorporated into still growing tissues, while contact herbicides kill the tissues they touch.

A 2015 study by the Canadian Food Inspection Agency found glyphosate in 30 percent of 3,200 food products.³ Similar studies have found glyphosate exceeding maximum residue limits (or MRLs) in Cheerios, beer, and wine.^4,5 MRLs are the allowable concentration of herbicides on food crops. Health Canada and the Environmental Protection Agency (EPA) come up with MRLs by feeding rats or dogs herbicide until an effect is observed. The figures are important for trade: If countries have different MRLs, shipments can be rejected. In 2011, the European Union rejected a shipment of Canadian lentils because MRLs were 40 times the EU limit. Alternatively, countries can use MRLs to negotiate a lower price, or raise their MRLs in response to industry pressure.

According to the EPA, between 1993 and 2015, glyphosate MRLs increased by 100 percent to 1,000 percent in the U.S., depending on the crop. Desiccation has changed the game: Because we are using more herbicides, herbicide residues and MRLs have also gone up.  Countries can use MRLs as a bartering tool to negotiate lower prices, and will raise their MRLs in response to pressure. Monsanto and other manufacturers of glyphosate have requested increases in MRLs, and been granted many of them.²

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