by Marty Fisher, EMGV
I think I was in high school when RoundUp first burst on the gardening scene. I hate to admit it, but that was four decades ago. I remember how excited my mother was to spray it on that hateful Bermuda grass and watch it shrivel and die—really DIE! It seemed like a miracle, and we wondered if it were too good to be true.
Glyphosate, the active ingredient in RoundUp and other herbicides, has been extensively tested in laboratory animals and humans over the years and repeatedly found to be safe—or as safe as a human-engineered chemical introduced into the natural environment can be. It is a non-selective, broad-spectrum herbicide. When applied to actively growing plants, it is absorbed into the tissues and disrupts vital biochemical processes. Annuals begin to wilt and die in two to four days, while perennials can take seven to 10 days to die.
Glyphosate’s widespread appeal is based on its effectiveness, its low toxicity, and the fact that it has a low risk of leaching into groundwater. It is absorbed onto soil particles, where it stays in place and is gradually broken down into carbon dioxide.
Agricultural use of glyphosate greatly increased when food crops were genetically modified to make them immune to it. This enabled farmers to spray entire fields without fear of damaging their crops, and, understandably, led to concerns about glyphosate’s proliferation in the environment.
A Cancer Risk?
The latest controversy over glyphosate started in 2015, when the International Agency for Research on Cancer (IARC) an arm of the World Health Organization (WHO), released a report concluding that glyphosate is a Group 2a carcinogen—meaning it “probably causes” cancer in humans.
The Group 2a classification prompted mass litigation in the United States against Monsanto Corporation, the manufacturer of RoundUp, by people claiming glyphosate gave them cancer. A number of countries have now banned or restricted the sale or use of glyphosate-based herbicides.
In California, environmental officials sought to require cancer warning labels on food products containing traces of glyphosate, but this move was recently barred by a federal judge. The ruling leaves glyphosate on the state’s Proposition 65 list as “a chemical known to the state of California to cause cancer,” but bars anyone from enforcing a requirement to warn consumers about its presence in food. Major agricultural industry groups have sued California, alleging that a warning label on food would violate First Amendment free speech protections by compelling retailers to post “false, misleading, and highly controversial statements” on their products.
The IARC study has been called “an outlier” by scientists in Europe and the United States, because glyphosate has been studied so rigorously for so long. The IARC study is the only study to have declared it a “probable carcinogen.”
A review of the IARC study by Reuters News concluded that significant revisions were made to a draft of the study before it was published. The revisions concerned animal studies, specifically the omission of conclusions by multiple scientists that there were no links between glyphosate and cancer in laboratory animals.
In 2016, a joint United Nations and WHO panel reviewed the potential for glyphosate in food to cause cancer in people. It concluded the herbicide was “unlikely to pose a carcinogenic risk to humans.” Both the U.S. Environmental Protection Agency (EPA) and the European Food Safety Authority and the European Chemicals Agency have also assessed glyphosate and ruled it safe for humans and the environment.
A Miracle, with Caveats
For home gardeners, who constantly battle increasingly prevalent, highly invasive weeds, glyphosate truly does have the impact of a small miracle. It can eliminate in minutes what would have taken hours to remove by hand. Some weed infestations pose a risk to human health, native plants and wildlife habitat, and ornamental plantings. In these cases, glyphosate-based products are a reasonable and highly effective solution.
They should be used as a weapon of last resort, and as part of an integrated pest management (IPM) strategy. IPM helps solve pest problems while minimizing risks to people and the environment. An ecosystem-based strategy, it focuses on long-term prevention and management through biological control, habitat manipulation, modification of cultural practices, and the use of resistant plant varieties.
As with any herbicide or pesticide, take appropriate precautions when using glyphosate. These include wearing protective clothing to cover all exposed skin, a breathing mask and goggles or glasses, and removable shoe covers. Never spray on a windy day, as spray may drift onto desirable plants and water surfaces. Follow manufacturer’s directions carefully.
Resources for More Information on Glyphosate
Where is Glyphosate Banned?
Reuters: U.S. EPA says Glyphosate Not Likely to be Carcinogenic to People
Gyphosate Use and Cancer Incidence in the Agricultural Health Study, NCI Journal, November 2017
National Pesticide Information Center, Glyphosate Fact Sheet
Killing Weeds in the Garden with Glyphosate, Michigan State University Extension
Safety Update from the EPA on April 30, 2019