Glyphosate, the primary ingredient in Roundup, is a possible carcinogen. Should we limit this chemical in the foods we eat? Should it be kept away from our lawns, farms, and public spaces like playgrounds and municipal parks and golf courses?

We’re talking about the most successful herbicidal chemical of all time, so limits to its use could have an effect on several industries and hundreds of millions of people.

roundup label
“Weed and Grass Killer… Rainproof… Visible results in three hours… Keep out of reach of children…” From a bottle of Roundup

What’s glyphosate?

Herbicides, including natural and organic herbicides, are necessary for farming. But the most potent ones quickly kill or mutate living plant cells and limit biodiversity. Meanwhile, genetically modified (GM) crops, specifically designed in many cases to accept high doses of herbicides and still live, may contain their own cocktail of “complex… transgenes that can come from bacterial, viral, fish, plant and other sources,” interacting in the digestive and endocrine systems with natural gut bacteria and animal organs in ways that may be harmful. So glyphosate is present in the honey of bees, is interacting with bacteria in your gut, and bleeds into the water you drink and the breast milk infants digest.

There are reasons to be concerned about glyphosate, and there are additional chemicals in products like Roundup that may be even more toxic than glyphosate. If you don’t like this widely used herbicide, you can do something about it. 

Is glyphosate bad for you? 

The Center for Food Safety describes the World Health Organization’s International Agency for Research on Cancer as the world’s leading, unbiased source of research on the subject, and this organization stated in 2015 that glyphosate is “probably carcinogenic in humans.”

Studies with more nuanced conclusions concede that glyphosate does not yet have a conclusive risk in small doses, and even studies of larger doses in mice and rats provide results that are either ambiguous or not always replicated.  But there is evidence that Monsanto researchers themselves have discovered links between Roundup and cancers (including a 1984 study showing elevated kidney cancers in Roundup-fed mice). And they’ve worked to actively weaken conclusions in studies weighing the chemical risks of their herbicide. Meanwhile, many academic articles warn that these chemicals contaminate our drinking water and soil longer and more thoroughly than has been previously recognized, that human exposure is rising, and that more sanguine estimates of tolerant daily intakes are based on outdated science. 300 million pounds of glyphosate employed every year may eventually take a more severe toll on biodiversity, and on us.

Europe Works to Ban It

Glyphosate is more restricted in Europe than elsewhere. The European Chemicals Agency classifies glyphosate as causing serious eye damage on contact, and toxic to aquatic life. UK and Irish authorities state caution against glyphosate especially when used as a pre-harvest treatment to dry out crops.  This process makes crops easier to harvest but can provoke more prevalent chemical residues in food.  Ireland also admonishes public authorities to “pay particular attention” to the use of glyphosate in “public parks and gardens, playgrounds, school grounds, healthcare facilities and sports and recreation ground” even though the presence of this product in food might be more disconcerting.  France’s environmental minister Nicolas Hulot likens the fight against glyphosate to a necessary war.  And its use has been severely restricted in Belgium, the Netherlands, and France.  Even in Germany, where the powerful Bayer Company bought Monsanto (producer of Roundup), agricultural officials like Svenja Shulze and Julia Kloeckner have worked to end or restrict the use of glyphosate.  A complete list of countries that had “said no to glyphosate” by 2018 is here

The European Union also severely restricts the production of genetically modified crops for anything but research – although these crops can be imported in animal feed.  Russia also bans GM crops.  So this may limit glyphosate use by limiting the production of crops genetically engineered to withstand high doses.  The list of dozens of countries restricting the use of GM crops is growing.

Canada and the US Say Keep Roundup Despite Risks

In 2017 and early in 2019, the Canadian health bureau Health Canada decided to let glyphosate continue to be sold in more than 130 Canadian crops, despite objections from many groups including Ecojustice, Équiterre, David Suzuki Foundation, and Environmental Defence.  These groups fear the potential risks to human health and the environment posed by glyphosate, and protest that this decision was not based on independent research but rather reviews of research.  Many of those reviews of research were conducted by or with the help of Monsanto scientists.  Denise Di Santo, a Canadian working locally in the Seattle area on watershed management and stormwater project planning, views this as “an unfortunate and ill-guided decision that will not only negatively affect our soil, water, and food supply, but our health, habitat, and ecosystems as a whole.” 

In the US, the Environmental Protection Agency has disregarded substantial scientific evidence of genotoxicity (destructive to a cell’s genetic materials) associated with weed killing products such as Roundup.  The EPA’s lax regulatory decisions are viewed very critically by Charles Benbrook, a former executive director of the National Academy of Sciences board on Agriculture, by Emanuela Taioli, an epidemiologist at Icahn School of Medicine at Mount Sinai in New York, and many others.  Mainstream news reports have highlighted the importance of industry-funded studies in EPA analyses and also the industry sources for around 30 percent of the EPA’s budget.  Scientists argue the EPA research under President Trump in particular has “a whack-a-mole quality to it. Throughout, the [EPA] authors included data sets suggesting that glyphosate could cause cancer, only to knock them down.” California has worked to label glyphosate as a “chemical known in the state of California to cause cancer,” but a judge has blocked  anyone from enforcing a requirement to warn consumers about the presence of the herbicide in any product.

Studies in the US suggest, in addition to cancer, glyphosate and herbicides containing it may have other negative health effects on humans, for example, shortening pregnancies.  Some research warns of correlations between the use of glyphosate or production of GM crops designed to withstand glyphosate, and very wide-ranging health problems including hypertension, stroke, diabetes, obesity, senile dementias, and several types of cancer.  In the US, there are 9,300 U.S. lawsuits over Roundup’s safety in state and federal courts across the country, including most prominently that of Dewayne Johnson, a retired groundskeeper, who was initially awarded $289 million in damages for his non-Hodgkins lymphoma in a case that Monsanto’s parent company has appealed.

What Can You Do About It?

The easiest things you can do to limit glyphosate in your own life: 

  • Try to avoid foods that are not organic, including especially foods with heavy spraying of this herbicide or high residues such as soybeans and oats.  You can stay away from brands like Cheerios, Doritos, Oreos, and Stacy’s Pita Chips where levels are “alarming”.  Another list of breakfast foods and granola snacks containing high levels of glyphosate is found here. For soybeans in your food, organic tofu and soy products are proven to have less glyphosate than GM versions, which frequently contain levels of herbicide that Monsanto itself characterizes as “extreme”.  When you buy vegetable oils for frying, or products containing diverse vegetable oils, you can check if you are consuming large quantities of soybean oil; in one product or another this accounts for 61 percent of America’s vegetable oil consumption. More than 90 percent of it is GM soy with higher glyphosate content.
  • Don’t put chemical herbicides on your own lawn and plants, even if they may be a lazy man’s way to kill weeds.  Some natural herbicides, like vinegar, may be effective against several types of weeds.  It is also possible that you can let your lawn become a more diverse ecosystem, or weed by hand while also aerating the soil and perhaps planting more of what you like.  It need not be a uniform green color, and recreational activities like backyard vegetable gardening need not be free of mild exercise, like hand weeding.  Advice on organic gardening can be found on our webpages or here and here.
Look for organic, non-gmo, and (rare for now) glyphosate-free labels when buying soy products, oat products, and other groceries; photo by the author
  • Tell local park and recreation services that you are nervous about any park use of this possible carcinogen.  Locally in Seattle, Round Up is sprayed in parks and on public property, for example, at Alki Beach.  An excellent article on local parks that limit the use of glyphosate (but it is occasionally used anyway) was published with a map in the Seattle Times.  Parents and children might enjoy more confident visits at University Playground, Meridian Playground, and Alki Playground which are on a “pesticide-free” list (also with lower herbicide use). Parks with access to tidelands or wetlands that enjoy more limited spraying include Magnolia Tidelands Park and West Montlake Park.  If you’d like this list expanded, you can write to Seattle parks at and tell them you don’t want herbicides (or pesticides) in public places, or go straight to the top and write to or call Mayor Jenny Durkan ( 206-684-4000).  You can give the same message to King County Parks at

Should we avoid glyphosate even where it’s legal? Cancer is the big killer in my family, and for me the answer is yes.

Article featured photo, “Chosen Foods with Glyphosate-free Certification,” by Paul Karmel 2019