Issue 1, April 20, 2015

Glyphosate and Cancer and Why It's Still Recommended for Weed Control

Recently the IARC (International Agency for Research on Cancer) designated glyphosate as a "possible carcinogen." In sharp contrast, other reviewing bodies, including the U.S. EPA have determined that it is not a carcinogen.  Still, much damage has been done by misleading or alarming headlines and questions are being asked. 

There has been no shortage of news stories, emails, blog posts, and discussions on social media about the topic.  After reading and hearing much about this, my initial concerns have been put to rest. 

The IARC based their determination off of previous studies which have likely been reviewed by the EPA.  There was no new research done by the IARC.  Glyphosate is still registered for use by the EPA and Illinois Department of Agriculture. 

The IARC made their determination after reviewing glyphosate and several other chemicals for only one week.  Reviews of glyphosate in the United States and other countries have taken up to 5 years.

The IARC made their determination based on potential hazard rather than actual risk of harm.  The rates were much higher than what product labels allow.  What happened to "the dose makes the poison"?  Anything at a high enough dose can cause harm.  Estrogen at a high enough dose can cause cancer. 

The "Risk Bites" videos are great at explaining toxicology in an easy to understand yet entertaining manner.   The creators use animation to explain what it means when something could "probably cause cancer".  Here they have tackled the "glyphosate is a carcinogen" topic and put it into perspective. Remember, the dose makes the poison.

Glyphosate is a well-studied herbicide.  Many studies have made the news.  Many studies have been proven to be flawed.  Just as we've seen with medical issues, corrective reports are often deemed less newsworthy than the original eye-catching headline.  At that point, the damage has been done.

Glyphosate is loved by many and hated by many.  Many of the haters include those who are against GMO crops.  Glyphosate is widely used for weed control in both corn and soybean crops that have been genetically modified to tolerate the use of this herbicide.  Today, glyphosate is sold and distributed by many companies.  However, it was originally developed by Monsanto.  Therefore, glyphosate is a popular target by those who march against Monsanto and other forms of "big" or conventional agriculture. 

Sometimes good, solid science is twisted and misrepresented by these anti-GMO groups.  As Kevin Folta of University of Florida Horticultural Sciences describes in his article, imagery is matched with conclusions that clearly do not match the research findings.  These memes are then posted to social media.  It's a wildfire that can't be put out.  Perhaps you saw this headline posted on your Facebook page, "Glyphosate causes endocrine disruption in human placental cells at levels allowed in U.S. drinking water."

In short, given the lack of any new evidence that would steer us otherwise, we and other weed control professionals across the country will still continue to recommend glyphosate as it is a widely used and effective weed killer – not only in genetically modified corn and soybeans, but also in orchards, forests, wetlands, landscapes, etc.  Overall, it is inexpensive and works very well in many situations.  We are committed to safety, yet we are also committed to helping both professionals and land/home owners win their battles against invasive, habitat-destroying, yield-robbing weeds.  If credible science proves otherwise, we will appropriately revise our recommendations.  Of course in most situations, there are other herbicides and weed control methods you can choose from.  Glyphosate is not the only option.  

Users of products which contain glyphosate or any pesticide for that matter should carefully read and follow all label directions.  The label will provide guidance on what clothing or personal protective equipment should be worn so that exposure and therefore the overall hazard associated with using the chemical is reduced.   For applicators, reducing exposure by covering up the skin reduces the hazard.   

Recommended Reading

Glyphosate and Cancer:  What does the data say? By Wyoming weed scientist, Andrew Kniss.  This is long but very thorough in looking at the data.  He offers a much longer list of suggested links than this one.  And he takes the issue seriously as he works with glyphosate and other pesticides regularly.

Henry Miller's article in Forbes:

Is Glyphosate Dangerous? – A list of associated links by the Genetic Literacy Project:

Glyphosate Technical Fact Sheet by the National Pesticide Information Center:

Basic Information about Glyphosate in Drinking Water:

Agricultural Health Study:
"A prospective study of cancer and other health outcomes in a cohort of licensed pesticide applicators and their spouses from Iowa and North Carolina. The AHS began in 1993 with the goal of answering important questions about how agricultural, lifestyle and genetic factors affect the health of farming populations. The study is a collaborative effort involving investigators from National Cancer Institute, the National Institute of Environmental Health Sciences, the Environmental Protection Agency, and the National Institute for Occupational Safety and Health."

A Method to Measure the Environmental Impact of Pesticides - Joseph Kovach and his colleagues have found a standardized way to compare differences in pesticides in terms of their relative dangers to humans and the environment.  An Environmental Impact Quotient (EIQ) is then assigned to a pesticide.  These values can be used to compare pesticides and pest management programs to determine which is likely to have lower environmental impact.  A table of herbicides is provided.  These values can change over time, but at press time, glyphosate has an EIQ of 15.33.  Most of the herbicides listed have higher values, but the lower the number, the lower potential for impact.  Learn more at:

(Michelle Wiesbrook)

Michelle Wiesbrook

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