Glyphosate Under the Gun — World Health Organization Weighs In

Thyroid Cancer Incidence Rate


The Lancet Oncology, the world’s premier scientific journal for cancer studies, recently published a paper by the World Health Organization’s International Agency for Research on Cancer (IARC) that has classified glyphosate (the active ingredient in Roundup) as a “probable carcinogenic,” outlining several scientific studies showing that it causes a range of cancers including non-Hodgkin’s lymphoma, renal cancers, skin cancers and pancreatic cancer.

Seventeen independent experts, with no conflicts of interest, from 11 countries met in March at the IARC headquarters in France to assess the carcinogenicity of tetrachlorvinphos, parathion, malathion, diazinon and glyphosate. All of these chemicals were given classifications for their ability to cause cancer based on published peerreviewed scientific studies.

Glyphosate, the most common herbicide in the world, was given the second highest classification of 2A. IARC has five classifications for the carcinogenicity of substances:

  • Group 1: Carcinogenic to humans
  • Group 2A: Probably carcinogenic to humans
  • Group 2B: Possibly carcinogenic to humans
  • Group 3: Unclassifiable as to carcinogenicity in humans
  • Group 4: Probably not carcinogenic to humans


Group 1 is for substances like tobacco, alcohol and benzene, cases where numerous scientific studies show that they cause cancer in humans. Only around 100 substances of more than 900 studied have been placed in this category.

Group 2A is for substances where there is sufficient evidence of causing cancer in animals and limited studies in humans. According to IARC the 2A classification was because of “strong mechanistic evidence; for malathion and glyphosate, the mechanistic evidence provided independent support of the 2A classification based on evidence of carcinogenicity in humans and experimental animals.”

There are other scientific studies linking glyphosate to breast cancer, thyroid cancer and liver cancers. Several animal and human studies have shown that glyphosate can cause cell damage, gene mutations and chromosomal aberrations. These types of genetic damage can be the precursors of cancer. A study published in 2004 found that glyphosate-based herbicides caused cell-cycle dysregulation. According to the researchers, “Cellcycle dysregulation is a hallmark of tumor cells and human cancers. Failure in the cell-cycle checkpoints leads to genomic instability and subsequent development of cancers from the initial affected cell.” The researchers tested several glyphosate-based pesticides and found that all of them caused cell-cycle dysregulation.

A case-controlled study published in March 1999 by Swedish scientists Lennart Hardell and Mikael Eriksson showed that non-Hodgkin’s lymphoma (NHL) is linked to exposure to a range of pesticides and herbicides, including glyphosate.

Research published in the peer-reviewed scientific journal Food and Chemical Toxicology in 2013 found that glyphosate at residue levels commonly found in people caused a five- to thirteenfold increase in the multiplication of estrogen-sensitive human breast cancer cells. This is a significant study as around 80 percent of breast cancers are estrogen-sensitive. Combined with the study showing that glyphosate causes cell-cycle dysregulation, it means that if precancerous damage causes an estrogen-sensitive breast tumor to develop, the cancer will rapidly multiply.

A peer-reviewed study into glyphosate and human health by Swanson et al. (I am one of the co-authors) found strong statistical correlations between the rapid increase in glyphosate and GMO crops and 22 diseases in the United States, including cancers of the liver, kidney, bladder/urinary system and thyroid. Researchers also found correlations between pancreatic cancer incidence and deaths from acute myeloid leukemia.

Glyphosate use has increased dramatically since the introduction of Roundup Ready GMO crops. Since the introduction of GE seeds in 1996, the amount of glyphosate used on crops in the United States has increased from 27 million pounds in 1996 to 250 million pounds in 2009. Dr. Charles Benbrook, research professor at the Center for Sustaining Agriculture and Natural Resources, Washington State University, showed that there was a 527 million pound (239 million kilogram) increase in herbicide use in the United States between 1996 and 2011.

There are numerous studies linking glyphosate to multiple diseases, not just cancer. Some of the most concerning are many studies showing that it causes birth defects, adversely affects a large range of metabolic pathways and causes intestinal diseases such as botulism, salmonella, Crohn’s disease, celiac disease, gluten intolerance and damage to key organs including the kidneys and liver. If you want more information on this, read my book The Myths of Safe Pesticides, which contains examples of scientific studies showing the numerous negative health effects of glyphosate.

According to Reuters, March 24, 2015, Monsanto, the manufacturer of Roundup, is trying to put pressure on IARC to retract its findings on the basis that the scientific studies they used were “invalid.” The company is seriously concerned as banning or restricting glyphosate would result in billions of dollars lost, and they will do everything to discredit this study by the world’s most reputable authority on cancer.

Many in the scientific community feel the only studies that should be invalid are the ones provided by Monsanto, as they present a conflict of interest over the peer-reviewed studies conducted by independent scientists and researchers published in reputable journals.

It is good to see a credible scientific body using these independent scientific studies over the non-peer reviewed “commercial in confidence” studies provided by the manufacturers. Regulators such as the U.S. EPA tend to only use the manufacturers’ studies rather than studies by independent researchers. These studies by the manufacturers are rarely available to the public as they are commercial in confidence. Concerned people in Europe are still fighting to get a copy of Monsanto’s commercial in confidence study that was used by the European Union to increase the minimum risk levels (MRLs) for glyphosate.

Regulators need to use transparent systems based on studies published in open journals because we have a right to know what data is being used to make the decisions on the safety of chemicals, rather than the current closed system that can be seen as collusion between regulators and manufacturers.

Testing of glyphosate is a recent occurrence, and it is still not included in food pesticide residue studies such as the recent one published by the USDA. Glyphosate and its degradation product, aminomethylphosphonic acid (AMPA), have been detected in the air, surface water, soil and sea water. These studies show that glyphosate and AMPA persist in the soil and water, and the amounts detected are increasing over time with increasing agricultural use. Glyphosate was frequently detected in water, rain and air in the Mississippi River basin with concentrations as high as 2.5 μg/L in agricultural areas in Mississippi and Iowa.

Because glyphosate is in air, water and food, humans are likely to be accumulating it in low doses over time. Glyphosate residues of up to 4.4 parts per million (ppm) have been detected in stems, leaves and beans of glyphosate- resistant soy, indicating uptake of the herbicide into plant tissue. Reports from Germany of glyphosate in the urine of dairy cows, rabbits and humans ranged from 10-35 ppm. According to the study, “chronically ill humans had significantly higher glyphosate residues in urine than healthy humans.” Furthermore, glyphosate residue levels in the tissues of the kidneys, liver, lung, spleen, muscles and intestines of the dissected cows were comparable to those found in the urine. This means that glyphosate is not being passed through the urine without affecting the organism and that meat and dairy are an additional source of dietary glyphosate for humans. Glyphosate has been found in human breast milk and is able to cross the placenta and damage human placental cells, raising massive concerns about its effects on the fetus and newborn children — one of the most vulnerable groups to minute levels of chemicals.

The classification of glyphosate with the second highest level of carcinogenicity by IARC means that its widespread use in GMO crops, as a crop desiccant, in orchards, food production, in children’s playgrounds, sidewalks, roadsides and in home gardens needs to stop. It is time this highly dangerous chemical was banned.

Farmer, author and international speaker and organic advocate André Leu is president of International Federation of Organic Agriculture Movements (IFOAM),

This article appears in the May 2015 issue of Acres U.S.A.


“Carcinogenicity of tetrachlorvinphos, parathion, malathion, diazinon, and glyphosate,” Lancet Oncology 2015, published online March 20, 2015

The Myths of Safe Pesticides by André Leu, Acres U.S.A.

Swanson, N.L., Leu, A., Abrahamson, J. and Wallet, B., Genetically engineered crops, glyphosate and the deterioration of health in the United States of America, Journal of Organic Systems, 9(2), 2014



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