I have a neighbor/friend who recently asked me if I knew how to stop our neighborhood landscaping crew from spraying Roundup in the common areas. She didn’t know that I blog about agriculture issues, nor did she know I used to work for Monsanto. I told her my position and asked her why she had concerns. It boiled down to all the things that people think about Roundup: it’s bad for the environment, and it’s possibly carcinogenic. She suggested we look for an alternative that is unquestionably safe. During this conversation another friend of mine piped up and admitted that, “I don’t really know much about Roundup, I’ve just heard it’s bad.” Then a few weeks later I was helping out in the school garden at my children’s elementary school when I heard one of the adults tell the kids that “pesticides are bad.”
Pesticides are incredibly useful, but that’s not what the public thinks. So today I’m going to talk about the most commonly used herbicide in the world: Roundup. This post is really meant for the lay-person, so if you’re looking for in-depth analysis, you’re probably not going to find it, but I will provide links throughout on where you can find more information.
This is a long post because there’s so much to cover, so I’ll summarize up front. I’m going to talk about
- What Roundup is: a broad-spectrum herbicide containing glyphosate as its active ingredient.
- How it’s used: to kill weeds in agricultural, forestry, and industrial settings as well as around the neighborhood.
- What Roundup Ready is: crops that have been bioengineered to tolerate Roundup so just the weeds die and the crop survives.
- Why it’s beneficial: (for crops) reduction in tillage which results in less run-off, better soil, and carbon sequestration.
- Alternatives to Roundup: more harmful or less effective herbicides or less-efficient, energy intensive options.
- Is it safe: yes.
- Does it cause cancer: no.
- Do farmers douse fields: no, or use it too much: it’s complicated, and super weeds: they’re not that super after all.
The bottom line is that you shouldn’t be concerned about Roundup. If you don’t want to use it in your yard, don’t. But as far as herbicides go, Roundup has a long, safe history and is a useful tool for farmers. It’s not the end-all-be-all of agriculture, but it’s an extremely valuable agricultural tool.
What is Roundup? (for the non-scientist)
Roundup contains the active ingredient glyphosate, which is a non-selective, systemic herbicide. Throughout this post I’ll use the two terms interchangeably, but Roundup is a brand name for glyphosate like Tylenol is a brand name for acetaminophen. There are dozens of other herbicide brands that also contain glyphosate, but Roundup is the most well known. An herbicide is something that kills weeds (for clarity: pesticide is the umbrella term that includes herbicides, insecticides, fungicides, etc.) Non-selective means that it doesn’t just work on one kind of weed (like just broad-leaf weeds or just grasses), it works on virtually all plants. In contrast, selective herbicides (like Dicamba) are likely what you’ve seen advertised to use on your lawn to kill dandelions and clover – it doesn’t kill grass, only broadleaf weeds. Don’t spray a non-selective herbicide like Roundup on your dandelions, it will kill the dandelions but it will also kill your grass. Systemic means that it doesn’t just damage the sprayed leaves of the plant; it gets inside the plant and disrupts the functions that keep it alive. Compare this to vinegar, which is a contact herbicide (non-systemic) and will only damage the part of the plant that gets sprayed with vinegar, but the weed isn’t dead, just damaged and it might come back. Systemic herbicides are very effective because it’s less important that you completely cover the plant, just a little will do the trick.
If you want to know more, there’s plenty of information out there about how glyphosate actually works in the plants (it inhibits specific enzymes only found in plants and blocks the shikimic acid pathway.) Here’s a good video on how glyphosate works. And here’s a good detailed overview of the mode of action (warning: very sciencey).
How is Roundup used?
In non-agricultural settings like your yard and neighborhood, Roundup is really effective in places where you don’t want anything to grow: cracks in pavement, along rock borders, in mulched areas in your flower bed. It’s what landscape crews are probably spraying in hard-to-mow spots like under fences and around trees. It’s also commonly used by state transportation departments to manage roadside vegetation instead of mowing which creates emissions and is labor-intensive. It is also used by parks departments to get rid of noxious weeds like poison ivy and invasive weeds like blackberry, and along railroads or power line corridors to prevent weeds and trees from causing disruptions.
In agricultural settings, Roundup is used to increase cropping efficiency. Weeds compete with crops for resources like sunlight, water, space and nutrients. Weeds that get a stronghold will out-compete crops by shading them from the sun and stealing valuable nutrients. In the end, not treating for weeds means farmers make less money and get far less production out of every acre, and it means we need more acreage to feed the same number of people and wastes resources like water on something we can’t eat.
It’s important here to point out a very big difference between managing weeds in your yard which is primarily for aesthetic reasons and managing weeds on a farm which is entirely for efficiency reasons. The downside to weeds in your yard is looking at a weedy yard. Yes, it looks untidy and it might even decrease the value of your house and your neighborhood, but it’s not a huge problem. Not managing weeds on a farm is a big deal and not really an option. Even organic farmers who aren’t allowed to use synthetic herbicides have to manage weeds or suffer unsustainable yield losses.
What’s Roundup Ready and Why is it Beneficial?
One of the reasons that Roundup is so popular among farmers (aside from the fact that it’s a highly effective and extremely safe herbicide) is because of the development of Roundup Ready crops. In 1996 Monsanto introduced glyphosate-tolerant “Roundup Ready” soybeans, the first major GM crop that was bioengineered to survive applications of Roundup. Soybeans were quickly followed by Roundup Ready cotton, canola, corn, and later, sugar beets. For farmers this meant that they could go from spraying many different herbicides in an attempt to get effective weed control, to only spraying primarily one herbicide. It offered farmers simplicity and flexibility. Not surprisingly, Roundup Ready crops were rapidly adopted by farmers. In fact, the technology is said to be the most rapidly adopted technology in the history of US agriculture. Today, 90 percent or more of all soybeans, corn, cotton, canola and sugar beets grown in the US are Roundup Ready.
This is what a no-till field looks like. Last season they grew fescue. They harvest the fescue, spray Roundup, and plant peas right into that fescue residue on the field. (Photo courtesy of Kathy Hadley)
Roundup Ready crops (and the use of Roundup in agriculture generally) has also contributed to the adoption of no-till and conservation-till methods which help reduce soil erosion and water runoff and increase organic matter and nutrients in the soil. Importantly, no-till also sequesters carbon in the soil and reduces the amount of fuel consumed because farmers don’t have to drive machinery over their fields as many times, thereby reducing agriculture’s carbon footprint. It’s estimated that in 2013 alone, biotech crops reduced carbon emissions equivalent to taking 12.4 million cars off the road for one year; no-till and conservation-till methods helped contribute to that figure. The use of herbicides like Roundup allows farmers to kill weeds without tilling (literally digging and turning over the ground to mechanically destroy weeds). Roundup is perfectly matched to no-till agriculture because it removes essentially all existing weeds before planting, and has no residual toxicity to crops that emerge later. No-till has become increasingly popular in conventional farming as it saves time, money and fuel, sequesters carbon, water, and maintains soil structure.
Alternatives to Roundup
Let’s pretend that activists managed to get Roundup banned like they claim it should be. It’s naive to think that farmers would stop using herbicides to manage weeds, because as I already mentioned, weed control is critical to successful crop production. Likely it would mean that conventional farmers would use a different herbicide (or combination of herbicides). When Roundup was introduced, it displaced other more dangerous herbicides like alachlor which is more toxic than glyphosate, considered to be likely carcinogenic at high doses, and poses potential chronic toxicity concerns or MCPA which is much more toxic than glyphosate. Because of this and its bioaccumulation issues, MCPA is a restricted use pesticide in the US. Pesticides have come a really long way in the last few decades in terms of safety, which is great news, but as I’ll talk more about below, Roundup is one of those really safe herbicides. Taking it out of the toolbox would not result in the use of less herbicide or the use of a safer alternative.
I took this picture at a Costco in California.
“But, Sara, what about an organic approach? I saw on Pinterest that you can use a combination of vinegar, salt and dish soap for a chemical-free and more effective alternative to Roundup!” First of all, who says these mixtures are organic? “Organic” means the USDA program for non-chemical pest control and fertility enhancement. It does not mean you can spray anything you can whip up in your garage. The vinegar / salt / soap mixture is not chemical-free or great for the soil. Vinegar contains the chemical acetic acid, and salt (sodium chloride) sticks around for a really long time in the soil and can make it difficult to grow anything at all for a long time (think salt flats). Soap is also a chemical, and interestingly, commonly used in synthetic pesticides as a surfactant. Just because you are more familiar with those chemicals, does not make them safer alternatives. Acetic acid is more toxic than glyphosate. Does that make vinegar scary? No. It just means glyphosate is pretty darn safe. Andrew Kniss actually did a great analysis of that home-made herbicide and concluded that, “The acetic acid in the homemade mixture is nearly 10 times more lethal than the glyphosate in the Eliminate mixture. And this doesn’t include the salt.” And, as mentioned, these home-made mixtures are non-systemic and merely destroy sprayed foliage. In addition, pesticides are regulated and approved by EPA and state authorities, and you may not spray non-approved non-labeled mixtures for pest control on food crops.
What about other organic alternatives? The thing is there aren’t many organic herbicides. There are some (yes, organic farmers DO SPRAY PESTICIDES) like clove oil and citrus oils which are approved in the USDA program, but they are primarily contact herbicides (non-systemic) and require higher doses to be effective. There are other methods like mulches and flooding, and mechanical methods discussed below, but even the organic farmer in Tomorrow’s Table confessed that weeds are really a weak spot in organic farming. Maybe you could make it work on a small organic farm, but it’s just not feasible on a large scale. Not to mention it’s a less efficient use of resources.
What about mowing, hoeing, weed-whipping or just pulling them out by hand? Sure, you can do that to avoid spraying anything at all. Easy peasy. OK, get your gardening gloves on and head out to weed 500 acres, which is a small farm in the Midwest. That’s about 500 football fields worth of mowing or weed whipping with a gas-powered device, all the while consuming fossil fuels and spewing exhaust. Or you could hire a group of people to remove weeds out in the sun (a known carcinogen) using man-power (and possibly contributing to sore backs and arthritis.) In fact, as I’ve discussed before, in 1975 the use of the short-handled hoe was banned to prevent worker injury and in 2004 California banned hand-weeding to prevent back injury (except organic producers are exempt because without the use of hand-weeding, they’re pretty much at the mercy of weeds). Consider that US farming covers slightly less than 1 billion acres, with perhaps a third of that considered prime crop growing land. The entire US population working all summer could not effectively hand weed US crop production acres. And what fraction would be willing to try?
Now, if you want to avoid spraying anything in your yard or neighborhood, it’s totally doable. Like I said, there’s a big difference between managing weeds in agriculture and managing them in your backyard. All you have to do is not mind looking at weeds and convince all your neighbors they don’t mind either. Or you can try to mobilize a group of neighbors to regularly weed your neighborhood’s common spaces in their free time. Considering that most of my neighborhood relies on hired landscape crews to mow and maintain their own small (less than a quarter acre) lots, I’m doubtful that’ll work. But, you can try.
Safety of Roundup
Roundup is an extremely safe herbicide. In fact, it’s 25 times less toxic than caffeine (from LD50 levels based on oral ingestion in rats.) Like I said in the very first section, glyphosate only works in plants and bacteria, not in animals. Glyphosate is not well-absorbed in animals, it doesn’t accumulate in tissues and is excreted largely unchanged. From an environmental perspective, glyphosate binds very tightly to the soil so it doesn’t contaminate ground water and is broken down by microbes in the soil so it doesn’t persist or migrate in the environment.
Glyphosate has been used safely for more than 40 years, and it’s the most widely used and most comprehensively evaluated herbicide. There are more than 800 studies demonstrating its safety. The US Environmental Protection Agency classifies glyphosate as “practically non-toxic,” and there are a whole slew of regulatory bodies around the world that have come to the same conclusion. I’ve written extensively before on how regulatory bodies determine which pesticides are approved and how much is safe to use, and this blog post concludes that based on those figures you could eat 62 pounds of produce every day and still come in 100 times lower than the no-effect level. Monsanto recently said you could eat 900 pounds of fruits or vegetables every day for the rest of your life without worrying about any health problems from glyphosate residue.
Yes, you can find plenty of stuff on the internet that contradicts what I’ve just said. Activists will point to (debunked) studies that claim glyphosate causes everything from autism to Parkinson’s. The regulatory bodies that make these safety determinations have access to the same studies that you can find on the internet and many more that are proprietary. If the majority of the global scientific community didn’t think those studies were good enough to reverse their conclusions, neither should you.
But, I Read in the News Lately That Roundup Causes Cancer.
Nope, Roundup does not cause cancer. You might think you read that because last March a division of the WHO called the International Agency for Research on Cancer (IARC) categorized Roundup as class 2A, probably carcinogenic. What does that mean? Well, importantly, IARC does hazard identification, not risk assessment. That means they’re looking for potential, not likelihood; they’re not required to take real-world exposure situations into account. There was no new study done, IARC looked at the same existing body of research that EPA and all other global regulatory bodies have access to, but really only expressly considered publicly available information. After IARC’s announcement, EPA stood by their conclusion, saying the research, “does not provide evidence to show that glyphosate causes cancer, and it does not warrant any change in EPA’s cancer classification for glyphosate.” EPA’s not the only one who disagrees with them, either. Not surprisingly, Monsanto disagrees as do lots of other scientists in the field. Additionally, the European Food Safety Authority just announced earlier this month that they again looked at the evidence and concluded Roundup is unlikely to cause cancer in humans and recommended increasing the safe limit for consumption.
To put IARC’s classification into perspective, other things in the same “probably carcinogenic” 2A category include working as a hairdresser or night-shift worker, acrylamide which shows up in coffee beans and French fries, and red meat. The category one step above, carcinogenic to humans, includes alcoholic beverages, outdoor air pollution, working as a painter, exposure to the sun and wood dust. IARC is also the same organization that just classified processed meat as carcinogenic, indicating that from their cancer-causing perspective, consumption of hot dogs are more dangerous than exposure to Roundup.
Ok, even so, why wouldn’t I want to avoid something that even some scientists think may cause cancer? (I’m going to assume if you feel that way, you’re also going to avoid all the things I listed above, like sun exposure, alcohol, bacon and exhaust fumes: you should be consistent, after all.) I get that, but it’s also important to note that even if we agree IARC’s classification is consistent with the science (of which I’m personally not convinced), the committee themselves noted that the hazard is really for agriculture applicators, not consumers. They’re not talking about residue on your food, or spraying your rock border, they’re talking about farmers who are applying Roundup on a large scale. Even for those farmers the risk is low, because federal regulations mandate how and when to apply, and what precautions should be taken when applying pesticides.
What About Super Weeds and the Increase in Herbicide Use?
Graphic courtesy of Nurse Loves Farmer
I hear the term “dousing” used a lot when people refer to farmers and pesticides, particularly Roundup. “They’re just dumping that stuff on we have proof because now all these weeds are resistant to Roundup!” First, the dousing: Nurse Loves Farmer did a great post on how inaccurate that term is and pointed out that typically farmers use about the equivalent of a can of soda of Roundup on an acre of crops. Remember, an acre is about the size of a football field. Additionally, farmers don’t want to spray pesticides if they don’t have to. It’s expensive and a waste of their time. I was blown away at the advanced technology I saw when I rode in a sprayer – it is so precise that the boom (the arm on the machine that sprays the pesticide) uses GPS guidance and will turn off if it passes over a portion of the field it knows has already been sprayed. Would you mow your lawn twice in the same day? No. Farmer’s don’t spray pesticide if they don’t need to.
Next: has the use of herbicide gone up? One of the claims about GMOs is that they would reduce pesticide application. That’s definitely true for insect-resistant crops, but it’s trickier for herbicide-tolerant crops. In reality, the use of Roundup alone has increased as a result of GMOs that are immune to its effects. This is intuitive, and I already touched on it – a farmer who switched from conventional to Roundup Ready corn used to spray three or four different herbicides and now only sprays one. Lots of farmers adopted this approach, and the use of Roundup went up. That’s actually a good thing, because as we already discussed, Roundup is a safer herbicide than many it replaced. Total use of herbicide is also trending down, but more importantly, the move to safer herbicides means the environmental impact of herbicide use has gone down.
What about super weeds? The term super weed refers to weeds that have become resistant to an herbicide, in the same way that some bacteria are now resistant to antibiotics. This is not new and certainly not unique to Roundup. In fact, there are many other herbicides with greater resistance issues than Roundup (including the ALS-inhibitors used to treat the sunflowers that Chipotle switched to because they claimed Roundup Ready crops created too many superweeds). Roundup is the most widely used herbicide and (according to the International Survey of Herbicide Resistant Weeds) there are seven herbicides with more resistant weed species.
That being said, there are good ways to manage resistant weeds. They’re not super at all; you can still get rid of them with another herbicide, or by physically pulling them up or tillage. Farmers are starting to use combinations of herbicides to prevent resistance, and seed companies like Monsanto are developing crops engineered to withstand multiple herbicides in an effort to help stem resistance. Over-reliance on one particular herbicide leads to resistance because it increases the selection pressure for weeds that have naturally developed resistance. It’s like always using the same antibiotic over and over to treat an illness. Not using the right amount of an herbicide can also increase the chances of developing resistance, just like when your doctor tells you to use an antibiotic for a whole week but you stop after three days because you feel better. Roundup resistant weeds have taught us a good lesson about over-reliance and following proper usage rates, but it’s not a fundamental problem with Roundup: it’s more about how the herbicide has been used.
In summary, don’t be afraid of Roundup and don’t sign petitions to ban it because that won’t solve anything. If you don’t like Monsanto, that’s an entirely different issue (Monsanto’s not the only company that sells glyphosate, anyway). If you want to pull weeds by hand, go for it – I weed my own garden (mostly) by hand because it’s small, I enjoy it, and sometimes I’m too lazy to walk to the garage and get the sprayer. But know the facts: Roundup isn’t evil, it’s a very thoroughly tested, efficient and effective herbicide with a long history of safe use and it’s a tremendous tool that enables farmers to farm sustainably and efficiently.