Glyphosate, the pesticide facing scientists

Glyphosate, the pesticide facing scientists

The massive use of glyphosate, created by the Monsanto / Bayer company, has not stopped confronting countries, scientists, and environmental and health authorities since the 1990s. Why is there no unified position against the most widely used herbicide in the world?

"France will no longer use glyphosate from 2021." This was one of the electoral promises of French President Emmanuel Macrona early in his term. However, the proposal ended up fading: the country cannot ensure 100% replacement of the herbicide in French agricultural fields in the coming years.

France cannot ensure 100% herbicide replacement in French agricultural fields in the coming years

"This decision has been canceled because glyphosate is necessary in today's agricultural systems," says Robin Mesnage, toxicologist in the department of Molecular and Medical Genetics at King's College London and an expert on this compound to Sinc.

But although glyphosate does not disappear, for now, from French crops, it does from gardens. Since January 2019, the French courts have succeeded in prohibiting the sale and use to individuals - and not to farmers - of a version of this herbicide, Roundup Pro 360.

“It is a formulation with a known high risk surfactant chemical agent”, details Charles Benbrook, researcher at the University of Newscastle (UK).

Glyphosate was first marketed in the 1970s under the name Roundup, whose patent was held by Monsanto until 2000, the American multinational specializing in agrochemicals and biotechnology for agriculture, acquired by Bayer in 2018. Without However, the dependence on this herbicide is due to a massive use from the 90s.

In Spain, hundreds of products authorized for agriculture, forestry, gardening and domestic application contain glyphosate

Since then 8.6 billion kilograms of glyphosate have spread over millions of hectares around the world. In Spain, hundreds of products authorized for agriculture, forestry, gardening and domestic application contain glyphosate.

This compound was discovered by the chemist Henri Martin, who in 1950 worked in a pharmacological company. Finding no applications, the molecule was sold to other companies in search of possible uses. It was John E. Franz, an organic chemist at Monsanto, who found the key and identified its herbicidal activity in 1970.

Now the pesticide works by eliminating herbs and shrubs and has shown great efficacy in genetically modified crops, in sugar cane crops - to increase the concentration of sucrose - and in city streets and sidewalks to eradicate weeds.

“It was used for the first time in the mid-1970s, but at that time its use was not very widespread or controversial. It was not until the late 1990s, with its application in transgenic crops, that its use skyrocketed, ”explains Benbrook.

Since then, glyphosate has only sowed discord and some concern between a sector of the scientific community and environmental groups. According to these, the pesticide penetrates the soil, seeps into the water, its residues remain in the crops and reaches our organisms.

Cancer risk

"Now its use is controversial because it is by far the most widely used pesticide in the world, and it can be found almost everywhere: in you and me, and in most of the people we know," warns Benbrook.

In 1993, both the United States Environmental Protection Agency (EPA) and the World Health Organization (WHO) classified this type of herbicide as low toxicity. Subsequent analyzes confirmed this in 2000: under current and expected conditions of use there was no risk to human health with Roundup.

After decades of use, the herbicide was finally listed in 2015 as probably carcinogenic to humans

However, in March 2015 the WHO considered the herbicide "probably carcinogenic". In the more than 1,000 studies reviewed by the International Agency for Research on Cancer (IARC), there is limited evidence of glyphosate's association with some types of cancer in the most exposed people, such as farmers. ; but there is sufficient evidence that it produces tumors in laboratory animals.

After decades of use, the herbicide was classified in IARC group 2A. Despite everything, this decision was not decisive for its use and sparked a public debate: the verdict was against the position of the European Union (EU).

To justify and authorize the use of the pesticide in the EU, the European Food Safety Authority (EFSA) produced the most comprehensive scientific report to date on the risk assessment of glyphosate, including the IARC analysis. and other public and industry works of the last 40 years.

The conclusion was that glyphosate did not show "carcinogenic or mutagenic properties, and that it had no toxic effect on fertility, reproduction or embryonic development." In December 2017, the European Commission gave the green light to continue using it for another five years.

The controversy of plagiarism

But how could such a comprehensive report show disagreement with the largest cancer research body? Given the suspicion that the evaluation carried out in part by the Federal Institute for Risk Assessment (BfR) of Germany had been prepared by the Glyphosate Task Force (GTF) - a consortium of companies in favor of the renewal of the European glyphosate registry - , a group of parliamentarians with different political affiliations commissioned a detailed analysis of the EFSA report.

Stephan Weber, plagiarism expert, writer and professor at the University of Vienna (Austria) and Helmut Burtscher-Schaden, biochemist, PEST Committee expert and member of the GLOBAL 2000 organization in Austria, were in charge of evaluating it. His conclusion, presented last January, was that much of the work was the result of plagiarism or cut-outs.

According to the authors, plagiarism was discovered exclusively in the chapters that dealt with the evaluation of published studies on glyphosate-related health risks. In these chapters, 50.1% of the content was identified as plagiarism - including entire paragraphs and full pages of text, while 22.7% was short-paste. In total, plagiarism represents 72.8%.

Despite controversies over the document that allowed the renewal of glyphosate use in Europe, scientists doubt that this report can be reconsidered. "Nothing is certain yet," Mesnage confesses to Sinc.

The indisputable thing is that the use of this pesticide continues to increase. For Charles Benbrook, knowing these data is very useful to study its impact on the environment and health.

According to a study published in 2016 inEnvironmental Sciences Europe, in the United States, more than 1.6 billion kilograms of the active ingredient have been applied in 30 years, which represents 19% of the global use of the herbicide, estimated at more than 8.6 billion kilograms. Two-thirds of the total volume used in the US and 72% of the world volume have been spread over the last 10 years, the work emphasizes.

“On a global scale, the use of glyphosate has increased 15-fold since the so-calledRoundup Ready, which allowed the introduction of genetically modified glyphosate-tolerant crops in 1996, ”says Benbrook in his study. Farmers sprayed enough glyphosate to apply 0.53 kg per hectare to all crops in the world. No other pesticide has even come close to heavy use levels for glyphosate, and it won't.

There is no clear scientific evidence

Despite everything, there are no studies that show that this amount of herbicide affects the environment and human health. However, many scientists are concerned. In 2016, the magazineEnvironmental Health published a statement of concerns from a group of scientists about the heavy use of glyphosate.

The team of American, Canadian and British researchers claimed that this pesticide pollutes drinking water sources, rainfall and the air, especially in agricultural regions. Also, the half-life of glyphosate in water and soil is longer than previously recognized.

The researchers also claimed that human exposures are increasing and that regulatory estimates of tolerable daily intakes for glyphosate in the US and the European Union are based on outdated data.

However, "no study has found direct toxic effects of glyphosate on human health at ambient levels," ditch Robin Mesnage. "There are doubts about the risks for this reason," adds the expert.

Several studies have tried to show how commercial glyphosate formulations could be implicated in the development of non-Hodgkin's lymphomas, a cancer of the lymphatic tissue, or in multiple myeloma, a cancer of the bone marrow. One of these works, published in the magazineCritical Reviews in Toxicology, reviewed 11 studies on both types of cancer.

The research "found no evidence of an association between glyphosate and non-Hodgkin lymphomas," say the authors, led by the University of New Mexico in the US In the case of multiple myeloma, "the data was too sparse to allow an informed causal judgment. "Added the scientists, who found no support in the epidemiological literature for a causal association between glyphosate and these cancers.

More recently, another study also found no statistical association between cancer and glyphosate use. However, when exposure to the pesticide increased, there was an increased risk of acute myeloid leukemia, but researchers need more research to confirm this.

For Robin Mesnage, the main problem is that the commercial formulations of glyphosate present a different toxicity with respect to the active principle of the herbicide itself. "Adequately controlled longitudinal (throughout life) studies on the carcinogenic effect of glyphosate and its commercial formulations should be carried out to determine the consequences of this pesticide", concludes the expert.

Video: Glyphosate: How to sell an Incredibly Dangerous Pesticide (September 2021).