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Does Roundup Cause Cancer? (The Answer Isn’t What You Think)

On June 7, 2018, Bayer bought Monsanto for $66 billion. At the time, they didn’t know about the storm they were about to enter. You see, Monsanto’s Roundup weed killer had been in the news for allegedly causing cancer. There were several lawsuits pending in California against Monsanto for this very reason.

Roundup is a glyphosate-based weed killer – and it is the most widely used herbicide in the entire world. Monsanto first introduced Roundup in 1974. Since then, 18.9 billion pounds of glyphosate have been used worldwide, according to a 2016 study.

For almost 50 years, Monsanto insisted that Roundup and other glyphosate-based weed killers are perfectly safe; they do not cause cancer in humans. Monsanto and Bayer spokespeople alike have argued that there is no evidence that glyphosate causes cancer “even at very high doses.”[1]

In 2019, the Environmental Protection Agency (EPA) also said that glyphosate poses no risk to public health “from the current registered uses of glyphosate.”[2]

On the other hand, the International Agency for Research (IARC), a part of the World Health Organization, found that glyphosate was “probably carcinogenic to humans.”

How did the EPA and IARC come to different opinions? It boils down to three reasons.

3 reasons why the EPA and IARC can’t agree on glyphosate’s link to cancer

Number 1:

The EPA and IARC looked at two very different kinds of data and studies. The EPA used unpublished studies paid by companies registered with them. IARC instead examined peer-reviewed studies.

Number 2:

The EPA looked at studies only on glyphosate. In contrast, the IARC used studies that looked at all of the ingredients in herbicide products – not just glyphosate. No herbicide in the world contains only glyphosate; these herbicide products contain a number of other ingredients.

Number 3:

In its study, the EPA analyzed the average person’s exposure to glyphosate in their food. The EPA studies did not consider what happens when people are exposed to large amounts of glyphosate over time.

Many people, such as farmers, gardeners, and groundskeepers, use a lot of glyphosate every day. The IARC study’s data did include studies on glyphosate exposure in food consumption. It also included studies on glyphosate exposure in the workplace.

It all comes down to the studies analyzed

As you can see, the EPA and IARC looked at different studies to reach their conclusions. With these facts in mind, it is no surprise that the EPA and IARC came to polar opposite conclusions.

If you’re interested in the science behind both organizations’ testing methods, Environmental Sciences Europe published a fantastic article on it[3].

In the article, the Environmental Sciences Europe recommends even more testing is needed to determine whether glyphosate products are carcinogenic to humans. Any new studies should consider how glyphosate affects people who use it every day.

In time, we hope that the EPA and the IARC will work together, along with other environmental organizations, to determine how safe Roundup is for us.  


[1] https://theintercept.com/2016/05/17/new-evidence-about-the-dangers-of-monsantos-roundup/

[2] https://www.epa.gov/newsreleases/epa-takes-next-step-review-process-herbicide-glyphosate-reaffirms-no-risk-public-health

[3] https://enveurope.springeropen.com/articles/10.1186/s12302-018-0184-7

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