Monsanto Company created and marketed Roundup® herbicide and its active ingredient glyphosate in the 1970s. It became the most-used herbicide in the world, sprayed on farms, home gardens and forests. Monsanto claims the weed killer is safe. But, in 2015 the World Health Organization (WHO)'s International Agency for Research on Cancer (IARC) determined glyphosate "probably" causes cancer in humans.
Roundup® is a brand name weed killer made with the active ingredient glyphosate. Missouri-based Monsanto Company discovered glyphosate’s potential as an herbicide in the early 1970s and immediately began marketing Roundup® in 1974. Until the patent ran out in 2000, Monsanto was the only producer of glyphosate-based herbicides.
The multinational agricultural biotechnology corporation brings in billions each year. It made about $13.5 billion in revenue, according to the company’s 2016 annual report.
Monsanto has long maintained glyphosate and Roundup® products are safe. But since the 1980s, government agencies and studies linked Monsanto’s popular weed killer to cancer. In 2015, the World Health Organization (WHO)’s International Agency for Research on Cancer (IARC) classified glyphosate as a Group 2A agent. Group 2A agents “probably cause cancer.”
Some Roundup® lawsuits claim, “Monsanto knew that glyphosate could pose significant risks to human health, including a risk of causing cancer.”
How is Roundup® Used?
Glyphosate works by blocking proteins plants need to grow and eventually killing them. Plants absorb Roundup® through the roots and circulate it to growing roots and leaves. Within hours, the plant stops growing, and several days later the plant begins to die. Roundup® contains 41 percent glyphosate and 59 percent of “other ingredients” not named on the label.
In the U.S., commercial farms use 300 million pounds of glyphosate each year. In fact, agricultural companies use glyphosate on the majority of all corn, soy and cotton crops in the U.S.
Roundup® is known as the second most widely used lawn and garden weed killer in the U.S. Monsanto promoted the product as an easy-to-use, effective way to rid lawns of poison ivy, dandelions, kudzu and other lawn weeds. It remains a popular choice for home gardeners.
In order to make glyphosate easier for farmers to use, Monsanto created genetically engineered Roundup Ready® seeds. These plants withstand the effects of Roundup® so farmers can spray entire fields without damaging their crops. This made glyphosate even more popular for commercial farms. More than 160 countries use it, with more than 1.4 billion pounds used each year.
Monsanto manufactures the most glyphosate-containing products. But other companies that make these herbicides include Dow AgroSciences, Du Pont, Cenex and Land O’ Lakes, Zeneca and Platte. In addition to Roundup®, Monsanto makes several other products that contain glyphosate, including:
- Fallow Master®
- Roundup Pro®
- Roundup Ultra®
Side Effects of Roundup® and Glyphosate
Exposure to Roundup® may cause some skin, eye and respiratory irritation. Ingesting it in large amounts may cause serious symptoms in adults, including death. According to the product’s label, it is harmful if swallowed or inhaled. Some studies link glyphosate to other health risks in humans, including hormone disruption and antibiotic resistance. A few studies also link Roundup® to cancer, including non-Hodgkin’s lymphoma.
Side effects of Roundup® exposure include:
- Skin irritation
- Nasal discomfort
- Unpleasant taste in mouth
- Irritation of throat
- Eye injury
Side effects of ingesting Roundup® include:
- Kidney damage
- Liver damage
- Respiratory distress
- Pulmonary edema
- Heart arrhythmia
One 2015 study in mBio, a journal of the American Society for Microbiology found a link between glyphosate and antibiotic resistance. In the study, researchers exposed samples of Escherichia coli and Salmonella enterica to three herbicides, including glyphosate. E. coli became more tolerant to antibiotics when combined with glyphosate.
“Increasingly common chemicals used in agriculture, domestic gardens, and public places can induce a multiple-antibiotic resistance phenotype in potential pathogens,” wrote study author Brigitta Kurenbach and colleagues. “The combination of high use of both herbicides and antibiotics in proximity to farm animals and important insects, such as honeybees, might also compromise their therapeutic effects and drive greater use of antibiotics.”
Another 2015 study conducted by Australian researchers found Roundup® killed cells responsible for producing progesterone in women at levels allowed in Australia’s drinking water — 1 mg/L. This is only slightly higher than the U.S. Environmental Protection Agency’s limit of .7 mg/L.
The study published by Fiona Young and colleagues in Integrative Pharmacology, Toxicology and Genotoxicology observed progesterone producing cells called JAr cells in a lab. Researchers added Roundup® and glyphosate alone to the cells. They observed more cells died when exposed to Roundup® than glyphosate alone.
In 2009, a team of French researchers from the University of Caen led by molecular biologist Gilles-Eric Seralini studied the effects of polyethoxylated tallowamine, or POEA, on human cells. POEA is another ingredient in Roundup® which helps glyphosate penetrate plants. The research team suspected Roundup might cause pregnancy problems including low birth weight, abnormal fetal development and miscarriage, Scientific American reported.
Roundup® and Glyphosate Cancer
One of the first links to Roundup® and cancer came from the U.S. Environmental Protection Agency in 1985. Members of the EPA’s Toxicology Branch classified glyphosate as a “Category C oncogene.” This meant it was a cancer-causing, non-food product.
But, after the EPA reevaluated the studies, it reversed its ruling in 1991. According to the agency, its findings of tumors in lab mice were statistically insignificant. After WHO and IARC found links to cancer in 2015, the EPA said it would reevaluate its data again.
The IARC evaluated publicly available human and animal studies before classifying glyphosate as a Group 2A agent that “probably” causes cancer.
“For the herbicide glyphosate, there was limited evidence of carcinogenicity in humans for non-Hodgkin lymphoma,” the IARC said in its monograph. “The evidence in humans is from studies of exposures, mostly agricultural, in the USA, Canada, and Sweden published since 2001. In addition, there is convincing evidence that glyphosate also can cause cancer in laboratory animals.”
While IARC found some evidence of NHL in humans, it stated “there is sufficient evidence of carcinogenicity in experimental animals.”
In addition, the chemical caused DNA and chromosomal damage in human cells, the IARC found. One study found people who lived near spray areas of glyphosate showed evidence of chromosomal damage in blood tests.
Lymphoma cancers possibly linked to Roundup® include:
- B-Cell Lymphoma
- Burkitt Lymphoma
- Central Nervous System Lymphoma
- Chronic Lymphocytic Leukemia
- Follicular Lymphoma
- Mantle Cell Lymphoma
- Marginal Zone B-Cell Lymphoma
- Small Lymphocytic Lymphoma
Glyphosate in Food and Environment
Because of its widespread use, traces of glyphosate are in a number of common foods, including eggs, coffee creamer, oats, wheat and honey. Crops sprayed with Roundup® feed cows, pigs and chickens.
The U.S. government doesn’t test for glyphosate in food, human blood or tissues, so there is no reliable data on human exposure. But, a 2014 report in The Journal of the American Water Resources Association on glyphosate found glyphosate in the majority of rivers, ditches, streams and wastewater in 38 states and 70 percent of rainwater samples.
People who are at most risk for exposure are those who work around glyphosate or live near farms.
People who were exposed to Roundup® and developed non-Hodgins’s lymphoma or related cancer claim Monsanto knew the risk for decades, but failed to warn the public. According to lawsuits, Monsanto falsely claimed Roundup® was safe and glyphosate herbicides “create no unreasonable risks to human health or to the environment.”
Those most at risk used Roundup® while working in fields or farms for several years. So far, there have been no lawsuits filed by casual users of the herbicide.