Skip to Content
No Fees Unless We Win 855-948-5098

Researchers Find Probability that Roundup Causes Cancer

Female researcher looking through microscope

Monsanto herbicide Roundup [glyphosate] is the most widely used herbicide in the U.S. for decades, Monsanto has marketed Roundup as safe and non-toxic. However, growing evidence is calling the herbicide’s safety into question—it is probable, according to the World Health Organization (WHO), that exposure to Roundup causes cancer.

Those who work in agriculture or live near fields where Roundup is sprayed are at risk for a number of health issues related to glyphosate exposure, including cancer. If you have been diagnosed with cancer after being exposed to Roundup and would like to speak with an experienced personal injury attorney about filing a Roundup lawsuit, please fill out this contact form or call (855) 948-5098 for a free, no-obligation case consultation.

Why is it ‘Probable’ That Roundup Causes Cancer?

Cancer is caused by mutations (or changes) to the DNA within cells. The DNA inside a cell is bundled with a large number of individual genes, which contain instructions that tell a cell what functions to perform, as well as how to grow and divide. When these instructions have errors, the cell can stop functioning normally, which may allow the cell to become cancerous.

Gene mutations can instruct a healthy cell to:

  • Grow rapidly. Gene mutations can inform the cell to grow and divide at a faster rate, which in turn creates more cells with this same mutation.
  • Allow unmitigated cell growth. Normal cells have tumor suppressor genes that tell cells to stop growing in order to ensure that your body maintains the right number of each type of cell. Cancer cells lack this control. Mutations in tumor suppressor genes can cause cancer cells to grow and accumulate.
  • Make mistakes when repairing DNA errors. DNA repair genes scan for DNA cell errors and make corrections. Mutations in DNA repair genes can allow some errors to go uncorrected, which can then lead to cells becoming cancerous.

For most people, gene mutations happen after birth, most often the result of smoking, radiation, viruses, or exposure to carcinogenic chemicals. A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in the cause of cancer.

In March of 2015, the World Health Organization’s cancer research arm (International Agency for Research on Cancer) came out with a report that classified glyphosate—the active ingredient in Monsanto Roundup—as a “probable carcinogen.” Professor Christopher Portier, one of the co-authors of the WHO study, reiterated the findings by saying glyphosate “is definitely genotoxic. There is no doubt in my mind.”

It is “probable” that Roundup causes cancer because the IARC examined studies that found glyphosate to be genotoxic (genotoxicity refers to the property of chemical agents that damages genetic information within a cell). DNA damage or DNA strand breaks can cause gene mutations, and as we have seen, gene mutations may allow a cell to become cancerous.

Roundup studies have also shown that exposure to glyphosate can result in oxidative stress, which is believed to be involved in the development of cancer. When the IARC examined a potential link between glyphosate and oxidative stress, researchers found strong evidence that glyphosate can induce oxidative stress. This finding could be an important mechanism by which Roundup causes cancer.

Roundup and Breast Cancer

A study conducted by researchers from the Center of Excellence on Environmental Health and Toxicology, Ministry of Education, and The Chulabhorn Graduate Institute in Thailand found that Roundup causes cancer. According to the study published in the journal Food and Chemical Toxicology, glyphosate promotes the growth of breast cancer cells at minute concentrations.

The Thai in-vitro study human cells showed that glyphosate induced the growth of human breast cancer cells via estrogen receptors. Even at low, environmentally relevant doses, glyphosate exposure was found to stimulate estrogenic activity. The study pointed to an additive estrogenic effect between glyphosate and genistein, which is a phytoestrogen in soybeans. Researchers say this additive effect needs further study.

This study is worrisome, as Roundup and other herbicides with glyphosate serving as an active ingredient are widely used in soybean farming. According to the U.S. Department of Agriculture Economic Research Service, the amount of soybean acreage sprayed with glyphosate (either by itself or in conjunction with other herbicides) increased from 25 percent in 1996 to more than 90 percent in 2006 to 2012.

Studies Suggest Monsanto Had Prior Knowledge That Roundup Causes Cancer

As far back as the 1980s, Roundup studies have shown that despite the low overall mortality rate from serious health conditions, such as heart disease and cancer, farmworkers in the United States and around the world appear to have higher rates for developing non-Hodgkin lymphoma, leukemia, multiple myeloma, Hodgkin’s disease and various forms of cancer when compared to the general population. The strongest link between farmworkers and various forms of cancer is Roundup [glyphosate], and numerous studies have found it likely that Roundup causes cancer.

In 1993, the National Cancer Institute started a prospective cohort study in North Carolina and Iowa on farmers and agricultural workers (those most likely to be exposed to pesticides) to answer the question of whether or not Roundup causes cancer. The study subjects were identified when they applied for a pesticide applicator license or went through pesticide application training.

This study, which was conducted over the span of a decade (between 1993 and 2003) concluded:

“Current medical research suggests that while farmers are generally healthier than the general U.S. population, they may have higher rates of some cancers, including leukemia, myeloma, non-Hodgkin lymphoma, and cancers of the lip, stomach, skin, brain, and prostate.”

In 1995, Caroline Cox of the Northwest Coalition for Alternatives to Pesticides published a glyphosate review showing that most if not all of the herbicide’s toxic effects had already been discovered in a series of animal studies. Feeding glyphosate to animals for a period of three months resulted in reduced weight gain, diarrhea, and salivary gland lesion, according to one of the studies. Feeding glyphosate to animals during the course of a lifetime led to excess growth and death of liver cells and an increase in the frequency of thyroid, pancreas, and liver tumors, among other health issues.
Cox wrote in 1995 that the carcinogenic potential for glyphosate had been controversial since the first lifetime feeding studies concluded in the early 1980s. The first study, conducted between 1979 and 1981, found an increase in testicular interstitial tumors in male rats receiving the highest dosage (30 mg/kg of body weight per day), while researchers observed an increase in thyroid cancer among female rats.

In the second study that culminated in 1983, researchers found dose-related increases in instances of a rare kidney tumor among male mice. Another study conducted between 1988 and 1990 found an increase in the frequency of liver and pancreatic tumors among male rats, along with the same increased frequency of thyroid cancer among female rats that had previously been reported in an earlier study.

After looking at the available data from these and other studies, the Environmental Protection Agency (EPA) said the increased incidence of tumors in the above studies were “not considered compound-related.” In 1991, the EPA concluded that glyphosate should be classified as a Group E oncogen, which means there is no evidence that Roundup causes cancer in humans. This classification was based on “available evidence at the time of evaluation and should not be interpreted as a definitive conclusion that the agent will not be a carcinogen under any circumstances.”

Perhaps the worst part of the EPA’s classification is that in 2013, the agency set new standards allowing for drastic increases in the amount of glyphosate allowed. In crops like flax, soybeans, and canola, the standard doubled from 20 ppm to 40 ppm. In food crops, the standard increased 30-fold from 200 ppm to 6,000 ppm.

It remains to be seen whether the EPA will change its stance on glyphosate in the wake of the WHO study. Carissa Cyran, chemical review manager for the EPA’s Office of Pesticide Programs, has said the agency plans to address the glyphosate issue in the very near future.

Lawsuits Allege Roundup Causes Cancer

In response to Monsanto’s deception, more and more farmers, agricultural workers and those who live near farmland are making the decision to file a Roundup lawsuit, alleging that Roundup causes cancer. If you would like more information on filing a Roundup lawsuit, please get in touch with a Baum Hedlund Aristei & Goldman personal injury attorney today by calling (855) 948-5098 for a free, no-obligation case consultation.

Related Articles:



  • Please enter your first name.
  • Please enter your last name.
  • Please enter your phone number.
    This isn't a valid phone number.
  • Please enter your email address.
    This isn't a valid email address.
  • Please enter your city.
  • Please enter your state.
  • Please make a selection.
  • Please make a selection.
  • Please enter a message.