Are glyphosate herbicides safe?

Summary

Roundup and other glyphosate herbicide formulations have never been tested or assessed for long-term safety for regulatory purposes. Only the isolated ingredient glyphosate alone was tested – by the same companies that manufacture the chemical and profit from its regulatory authorization. But even the industry tests on glyphosate alone revealed toxic effects. Independent studies in animals and human cells, and some human epidemiological studies, indicate that glyphosate and Roundup have toxic effects. These include disruption of hormonal systems and beneficial gut bacteria, damage to DNA, birth defects, cancer, and neurotoxicity.

The agrochemical lobby often claims that glyphosate has low toxicity to animals, including humans.1 The “Glyphosate Facts” website of the Glyphosate Task Force, a group of chemical companies that manufacture and sell glyphosate herbicides, claims that “numerous health assessments conducted by public authorities over the past 40 years have consistently concluded that glyphosate does not pose any unacceptable risk to human health.”2

But this claim is misleading. The “health assessments” are indeed conducted by public authorities, but these agencies only assess industry studies, commissioned or carried out by the very same companies that are applying to gain regulatory authorization for their products.

Many of these studies are decades old and follow outdated protocols designed 50-100 years ago to assess risks from acute exposures to gross poisons.3 4 They are unsuited to revealing risks from low exposures over a long period, which is the type of exposure that most of us are subjected to.5 The industry studies themselves are kept secret under commercial confidentiality rules and cannot be examined by the public or independent scientists.3 4

In contrast, numerous studies carried out by scientists independent of the industry show that glyphosate, the presumed active ingredient of Roundup, is toxic. Moreover, commercial glyphosate herbicide formulations like Roundup contain extra added ingredients (adjuvants) and are more toxic than glyphosate alone. Therefore assurances of the safety of glyphosate do not apply to the complete formulations; they are chemically and biologically different substances (see “Roundup is more toxic than glyphosate”).

Toxic effects of glyphosate and Roundup include disruption of hormonal systems and beneficial gut bacteria, damage to DNA, developmental and reproductive toxicity, birth defects, cancer, and neurotoxicity.

Roundup and other glyphosate herbicide formulations have never been tested or assessed for long-term safety for regulatory purposes. Only glyphosate alone was tested – by the very same companies that manufacture the chemical and profit from its regulatory authorisation. But even the industry tests on glyphosate alone revealed toxic effects, including malformations.3 4

The shikimic acid pathway

One of the ways that glyphosate kills plants is by blocking a metabolic pathway (the shikimic acid pathway), which is essential for the growth of plants but does not exist in humans and other animals. It does this by inhibiting an enzyme, the EPSPS enzyme. This enzyme is responsible for catalyzing a reaction in plant cells that is necessary for the synthesis of amino acids that the plant needs to grow.

Claims that glyphosate is safe are based on the fact that while the shikimic acid pathway is present in plants, it is not present in humans or animals.

However, scientific studies find that glyphosate and Roundup do have toxic effects on animals, including humans. This shows that the toxic effects of these chemicals are not restricted to the shikimate pathway in plants but also affect other metabolic pathways that are present in humans and animals.

Indeed, some research studies have gone so far as to identify some of the pathways through which glyphosate and Roundup have toxic effects on animals and on human cells tested in vitro (laboratory studies not performed on living animals). Those pathways include:

  • Endocrine (hormone) disruption,6 7 8 9 which has been described as “hormone hacking”. Endocrine disruption can lead to serious disease, including birth defects, cancer, and reproductive and developmental problems
  • Interference with the retinoic acid signalling pathway, which can lead to birth defects10
  • Negative effects on gut bacteria, causing the growth of disease-causing bacteria like those that cause botulism11 and Salmonella and E. coli poisoning.12

It is not justified to claim safety for glyphosate and Roundup on the basis that one of the ways in which it kills plants does not apply to humans and animals. We say “one of the ways” because some scientists believe the real way glyphosate kills plants is by depressing their defence system, so that they die of infection from the pathogenic organisms present in all soil (see “Glyphosate herbicides cause plant diseases”).

References

  1. Industry Task Force on Glyphosate. What is glyphosate? Glyphosate Facts. 2013. Available at: http://www.glyphosate.eu/glyphosate-basics/what-glyphosate.
  2. Glyphosate Task Force. Does glyphosate pose risks to human health? Glyphosate Facts. 2013. Available at: http://www.glyphosate.eu/answers-key-questions/does-glyphosate-pose-risks-human-health.
  3. Antoniou M, Habib MEM, Howard CV, et al. Teratogenic effects of glyphosate-based herbicides: Divergence of regulatory decisions from scientific evidence. J Env Anal Toxicol. 2012;S4:006. doi:10.4172/2161-0525.S4-006.
  4. Antoniou M, Habib M, Howard CV, et al. Roundup and Birth Defects: Is the Public Being Kept in the Dark? Earth Open Source; 2011. Available at: http://bit.ly/IP2FWH.
  5. Vandenberg LN, Colborn T, Hayes TB, et al. Hormones and endocrine-disrupting chemicals: Low-dose effects and nonmonotonic dose responses. Endocr Rev. 2012;33(3):378-455. doi:10.1210/er.2011-1050.
  6. Séralini G-E, Clair E, Mesnage R, et al. Republished study: long-term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize. Environ Sci Eur. 2014;26(1):14. doi:10.1186/s12302-014-0014-5.
  7. Romano RM, Romano MA, Bernardi MM, Furtado PV, Oliveira CA. Prepubertal exposure to commercial formulation of the herbicide Glyphosate alters testosterone levels and testicular morphology. Arch Toxicol. 2010;84:309-317.
  8. Gasnier C, Dumont C, Benachour N, Clair E, Chagnon MC, Séralini GE. Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines. Toxicology. 2009;262:184-91. doi:10.1016/j.tox.2009.06.006.
  9. Thongprakaisang S, Thiantanawat A, Rangkadilok N, Suriyo T, Satayavivad J. Glyphosate induces human breast cancer cells growth via estrogen receptors. Food Chem Toxicol. 2013. doi:10.1016/j.fct.2013.05.057.
  10. Paganelli A, Gnazzo V, Acosta H, López SL, Carrasco AE. Glyphosate-based herbicides produce teratogenic effects on vertebrates by impairing retinoic acid signaling. Chem Res Toxicol. 2010;23:1586–1595. doi:10.1021/tx1001749.
  11. Krüger M, Shehata AA, Schrödl W, Rodloff A. Glyphosate suppresses the antagonistic effect of Enterococcus spp. on Clostridium botulinum. Anaerobe. 2013;20:74–78.
  12. Shehata AA, Schrodl W, Aldin AA, Hafez HM, Kruger M. The effect of glyphosate on potential pathogens and beneficial members of poultry microbiota in vitro. Curr Microbiol. 2012. doi:10.1007/s00284-012-0277-2.

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