What is known about the glyphosate herbicide?
Glyphosate is a broad-spectrum herbicide developed in 1950 and registered in 1974. It is a popular pesticide for its efficiency in killing weeds at low cost and for its rapid absorption by plants. It is commonly used in crops and in urban areas and gardens in some countries. Glyphosate is currently the most widely used herbicide worldwide with more than $ 5 billion in sales in 2011.
Glyphosate is the active ingredient of more than 750 herbicides, made of around 36-48% of it. Glyphosate is never used without its adjuvants, which are considered inert diluents because they are not directly responsible for the pesticide activity. They act improving the glyphosate action, on herbicide adhesion on the plant surface or facilitating penetration into plant cell walls.
The list of adjuvants is not publicly accessible and each manufacturer has a different formulation. That means the real composition of the herbicides based on glyphosate is not known.
Considered a safe herbicide for many years since it acts to inhibit an enzyme found only in plants glyphosate has aroused doubts about the evidence of this safety. It has been observed a greater exposure to the product in the last decades and the action of it combined with the adjuvants may potentialize effects not found alone. In addition it has been used as a crop desiccant to accelerate the natural drying of grains, which may lead to an increasing level in glyphosate residue in the products.
The exposure of glyphosate to soil and water is inevitable during the spraying. The half-lives of both glyphosate and its major bioactive metabolite AMPA (aminomethylphosphonic acid) can be length ranging between 1 to 150 days in soil, determined by the combination of biochemical properties of soil and diversity and microbial activity of soil. In humans, the elimination is via renal.
There is a rising concern about prolonged exposure in its toxicity, environmental effects and in the health of animals and humans.
In general, most studies are laboratory, in vitro or in vivo, and there is a lack of epidemiological and long-term studies of the exposure to glyphosate and its relation to diseases.
In diet exposure the Joint Meeting on Pesticides Residues concluded that it would be unlikely to determine risk of cancer in humans from glyphosate exposure by this route. FAO/WHO recommends maximum daily exposure of 1mg / kg (weight) of glyphosate and AMPA via diet.
In fish has been found an association between glyphosate and alterations in the reproductive development and in the induction of oxidative stress by enzymatic inhibition, which can induce DNA damage.
In rats is suggested damage in liver, kidneys and heart.
About cancer, in 2015 the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) classified glyphosate as probably carcinogenic substance to humans, with limited evidence in humans but sufficient evidence from animal research. Studies on glyphosate and herbicides based on glyphosate were included here.
In 2016, the European Food Safety Authority (EFSA) published different conclusions from IARC, stating that glyphosate is unlikely to be carcinogenic to humans. This publication included studies using glyphosate alone.
All of this evidenced the presence of conflicts of interest in studies and in regulation of glyphosate (some of the researches was supported by the manufacturing companies) and it could influence the integrity of decision-making.
And since then there are many studies published with divergent results. Sometimes is found a relationship with non-Hodgkin's lymphoma and other types of cancer, sometimes this relation doesn’t exist. Endocrine changes are observed in some research but not in other analyzes. And what do we really know? Almost nothing!
Vandenberg LN, Blumberg B, Antoniou MN, et al. Is it time to reassess current safety standards for glyphosate-based herbicides? J Epidemiol Community Health 2017;71:613–618.
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Araújo JSA, Delgado IF, Paumgartten FJR. Glyphosate and adverse pregnancy outcomes, a systematic review of observational studies. BMC Public Health. 2016; 16:472.
Changa ET, Delzella E. Systematic review and meta-analysis of glyphosate exposure and risk of lymphohematopoietic cancers. Journal of Environmental Science and Health. 2016.
Rodrigues LM, Oliveira R, Abe FR, Brito LB, Moura DS, Valadares MC et al. Ecotoxicological assessment of glyphosate-based herbicides: effects on different organisms. Environmental Toxicology and Chemistry 2017
Tarazona JV, Court-Marques D, Tiramani M, Reich H, Pfeil R, Istace F et al. Glyphosate toxicity and carcinogenicity: a review of the scientific basis of the European Union assessment and its differences with IARC. Arch Toxicol. 2017
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Gary M. Williams, Marilyn Aardema, John Acquavella, Sir Colin Berry, David Brusick, Michele M. Burns, Joao Lauro Viana de Camargo, David Garabrant, Helmut A. Greim, Larry D. Kier, David J. Kirkland, Gary Marsh, Keith R. Solomon, Tom Sorahan, Ashley Roberts & Douglas L. Weed. A review of the carcinogenic potential of glyphosate by four independent expert panels and comparison to the IARC assessment, Critical Reviews in Toxicology. 2016.