Glyphosate Toxicology: Human Health Risks

Glyphosate Toxicology: Human Health Risks

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By Jorge Kaczewer

This article reviews the risks that this substance entails for human health (toxicity, carcinogenic and reproductive effects, mutagenic action and food contamination), while warning about the weaknesses in the national systems that regulate biosecurity .

The most commercialized herbicides in the Argentine Republic incorporate glyphosate into their formula, because some transgenic crops, such as soybeans for example, are genetically manipulated to develop resistance to this chemical substance. This article reviews the risks that this substance entails for human health (toxicity, carcinogenic and reproductive effects, mutagenic action and food contamination), while warning about the weaknesses in the national systems that regulate biosecurity .

Glyphosate and compound herbicides:

Argentines will have to face during the next decades the consequences of having made glyphosate the most widely sold and used herbicide in the country. Recent toxicological studies conducted by independent scientific institutions seem to indicate that glyphosate has been erroneously classified as "toxicologically benign", both at a health and environmental level. Thus, glyphosate-based herbicides can be highly toxic to animals and humans. Toxicity studies revealed adverse effects in all standardized categories of laboratory toxicological tests at most of the doses tested: subacute toxicity (lesions in salivary glands), chronic toxicity (gastric inflammation), genetic damage (in human blood cells), disorders reproductive (decreased sperm count in rats; increased frequency of sperm abnormalities in rabbits), and carcinogenesis (increased frequency of liver tumors in male rats and thyroid cancer in females).

At an eco-toxic-epidemiological level, the situation is aggravated not only because few laboratories in the world have the equipment and techniques necessary to evaluate the impacts of glyphosate on human health and the environment. Also because those who initially conducted the toxicological studies officially required for the registration and approval of this herbicide in the United States have been prosecuted for the crime of fraudulent practices such as routine falsification of data and omission of reports on countless deaths of rats. and guinea pigs, falsification of studies by altering annotations of laboratory records and manual manipulation of scientific equipment so that it provides false results. This means that the existing information regarding the residual concentration of glyphosate in food and the environment may not only be unreliable, it is also extremely scarce.

Faced with the imminent universalization of a pesticide treatment system based on a single substance whose toxicological and ecological impacts seem not to have been evaluated with sufficient depth and rigor, the urgency of multiplying locally medium and long-term toxicological studies and dosages is evident. and bio-tests in waters and soils of our Pampean region, not only with respect to the active principle and the product as it goes on sale, but also with respect to each of the adjuvants.

Glyphosate, N- (phosphonomethyl) glycine, is a non-selective, broad-spectrum herbicide used to kill undesirable weeds (annual and perennial grasses, broadleaf grasses, and woody species) in agricultural, forestry, and landscape environments. The use of herbicides had evolved towards increasingly selective substances in order to avoid the damage they cause to the entire biota. However, due to the progressive cost of its research and development, the mass consumption of this non-selective herbicide created in the 1960s was returned.

Glyphosate exerts its herbicidal action through the inhibition of an enzyme, enol-pyruvyl-shikimate-phosphate-synthetase (EPSPS), thus preventing plants from making three essential aromatic amino acids for their growth and survival. Because the metabolic pathway for shikimic acid does not exist in animals, the acute toxicity of glyphosate is low. Glyphosate may interfere with some enzyme functions in animals, but symptoms of poisoning only occur at very high doses. However, products that contain glyphosate also contain other compounds that can be toxic.

Every pesticide product contains, in addition to the "active" ingredient, other substances whose function is to facilitate its handling or increase its effectiveness. In general, these ingredients, misleadingly called "inert", are not specified on product labels. In the case of glyphosate herbicides, many "inert" ingredients have been identified. To help glyphosate penetrate plant tissues, most of their commercial formulas include a surfactant chemical. Therefore, the toxicological characteristics of market products are different from glyphosate alone. The most commonly used herbicidal formulation (Round-Up) contains polyoxyethylene amine surfactant (POEA), related glyphosate organic acids, isopropylamine, and water.

The following list of inert ingredients identified in different commercial glyphosate-based formulas is accompanied by a classic description of their acute toxicity symptoms. The effects of each substance correspond, in some cases, to symptoms verified in the laboratory through toxicological tests at high doses. Most symptoms were compiled from reports prepared by the manufacturers of the different formulas.

· Ammonium sulfate: Eye irritation, nausea, diarrhea, respiratory allergic reactions. Irreversible eye damage in prolonged exposure.

· Benzisothiazolone: ​​eczema, skin irritation, allergic photoreaction in sensitive individuals.

· 3-iodo-2-propynylbutylcarbamate: Severe eye irritation, increased frequency of miscarriage, skin allergy.

· Isobutane: nausea, nervous system depression, dyspnea.

· Methyl pyrrolidinone: Severe eye irritation. Abortion and low birth weight in laboratory animals.

· Pelargonic acid: Severe skin and eye irritation, respiratory tract irritation.

· Polyoxyethylene-amine (POEA): Ocular ulceration, skin lesions (erythema, inflammation, exudation, ulceration), nausea, diarrhea.

· Potassium hydroxide: Irreversible eye damage, deep skin ulceration, severe ulceration of the digestive tract, severe irritation of the respiratory tract.

· Sodium sulfite: Severe eye and skin irritation concomitant with vomiting and diarrhea, skin allergy, severe allergic reactions.

· Sorbic acid: Skin irritation, nausea, vomiting, chemical pneumonitis, angina, allergic reactions.

· Isopropylamine: Extremely caustic substance of mucous membranes and upper respiratory tract tissues. Lacrimation, coryza, laryngitis, headache, nausea.

Toxicity and undesirable effects:

Acute toxicity: The Environmental Protection Agency (EPA) has already reclassified pesticides containing glyphosate as class II, highly toxic, for being irritating to the eyes. The World Health Organization, however, describes more serious effects; in several studies with rabbits, he rated them as "strongly" or "extremely" irritating. The active ingredient (glyphosate) is classified as extremely toxic (category I).

Formulas containing glyphosate produce greater acute toxicity than glyphosate alone. The amount of Round-Up (glyphosate + POEA) required to kill rats is three times less than that of pure gifosate. Regarding the forms of exposure, the toxicity of both presentations (pure glyphosate, compound formulas) is greater in cases of dermal and inhalation exposure (occupational exposure) than in cases of ingestion.

In humans, symptoms of poisoning include skin and eye irritations, nausea and dizziness, pulmonary edema, drop in blood pressure, allergic reactions, abdominal pain, massive loss of gastrointestinal fluid, vomiting, loss of consciousness, destruction of red blood cells, electrocardiograms abnormalities and kidney damage or failure.

Occupational accidents with agrochemicals are frequent throughout the world. According to a recent study conducted by the World Health Organization, of a global annual total of 250 million occupational accidents, 335,000 were fatal accidents. 170,000 of these deaths occurred in the agricultural sector, resulting in a fatal accident rate twice that of any other activity.

Since occupational exposure to high doses of these substances is common, the applicators of the product to the crops should be protected in a special way instead of continuing to insist the producing companies in their argument regarding the low toxicity of glyphosate.

Studies by independent scientists have shown that glyphosate has been mistakenly described as "toxicologically benign." A review of glyphosate toxicology conducted by a North American team of independent scientists, the Northwest Coalition for Alternatives to Pesticides (NCAP), identified adverse effects in all standard categories of toxicology studies (subchronic, chronic, carcinogenic, mutagenic, and reproductive). The findings of the NCAP were questioned by arguing that these effects were verified because the protocol standard requires finding adverse effects at the highest dose studied. However, a study on glyphosate published in November 1998 by Caroline Cox, editor of the Journal of Pesticide Reform, describes adverse effects that did not result from this requirement: all were found at lower doses than the highest dose studied.

On the other hand, toxicological studies on glyphosate officially required for registration and approval have been associated with fraudulent practices. In 1976, an audit carried out by the EPA discovered serious errors and deficiencies in studies conducted by one of the most important North American laboratories involved in the toxicological determination of pesticides prior to their official registration. The EPA publicly accused Industrial Biotest Laboratories (IBT), a laboratory that conducted 30 studies on glyphosate and commercial glyphosate-based formulas (among these, 11 of the 19 studies conducted regarding its chronic toxicity), of routine falsification of data and omission of reports of countless rat and guinea pig deaths. The EPA reported the episode with a 7-year delay (1983) and little media coverage. However, reports from the US Congressional Government Operations Committee and summaries from the EPA's Office of Pesticides and Toxic Substances confirm in detail the fraudulence and poor scientific quality of the IBT studies.

In addition, the EPA denounced in 1991 that Craven Laboratories, a company that conducted determinations for 262 pesticide manufacturing companies, had falsified studies, resorting to "tricks" such as falsifying annotations of laboratory records and manually manipulating scientific equipment to produce results. false. Studies on round-up residues in potatoes, grapes and beets were part of the questioned tests. In 1992, the owner of Craven Laboratories and three of his employees were found guilty in 20 different criminal cases. The owner was sentenced to 5 years in prison and a fine of $ 50,000; the fine for Craven Laboratories was $ 15.5 million. Although the toxicological studies of glyphosate identified as fraudulent have already been superseded, these facts cast a shadow of doubt on the totality of the official pesticide registration procedures.

Subchronic toxicity: In medium-term studies in rats, glyphosate produced microscopic lesions of the salivary glands throughout the entire dose spectrum tested. There was also an increase in two liver enzymes, a decrease in normal weight gain, diarrhea and an increase in blood levels of potassium and phosphorus.

Chronic Toxicity: Long-term animal studies show glyphosate to be toxic. At high doses in rats (900-1,200 mg / kg / day), a decrease in body weight was observed in females, a higher incidence of cataracts and lens degeneration, and a greater liver weight in males. At low doses (400 mg / kg / day), inflammation of the stomach mucous membrane occurred in both sexes. Studies in mice with high doses (around 4,800 mg / kg / day) showed weight loss, excessive growth, subsequent death of liver cells and chronic kidney inflammation in males; in females, excessive growth of kidney cells. At low doses (814 mg / kg / day), excessive cell division was found in the urinary bladder.

Carcinogenic Effects: Publicly available scientific studies were all conducted by or for their manufacturers. The EPA initially classified glyphosate as class "D" (not classifiable as a human carcinogen). Later, in the early 1990s, he placed it in class "C" (Possible human carcinogen). It is currently classified as Group E (evidence of non-carcinogenesis in humans) in the absence of evidence according to available information. However, the controversy regarding the carcinogenic potential of glyphosate still continues.

In successive studies carried out since 1979, it was found: Increase in interstitial testicular tumors in male rats at the highest dose tested (30 mg / kg / day), increase in the frequency of thyroid cancer in females; dose-related increases in the frequency of a rare kidney tumor; Increase in the number of pancreatic and liver tumors in male rats. The EPA did not associate any of these tumors with glyphosate: they considered that the statistics were not significant, that it was not possible to define thyroid tumors as cancer, that there was no dose-related trend, or that there was no progression to malignancy.

Doubts about the carcinogenic potential of glyphosate persist, because this ingredient contains the pollutant N-nitrous glyphosate (NNG) at 0.1 ppm or less, or this compound can be formed in the environment by combining with nitrate (present in human saliva or fertilizers), and most N-nitroso compounds are known to be carcinogenic. Additionally, in the case of Round-up, POEA surfactant is contaminated with 1-4 dioxane, which has caused cancer in animals and liver and kidney damage in humans. Formaldehyde, another known carcinogen, is also produced during the breakdown of glyphosate.

A recent study, published in the Journal of American Cancer Society by eminent Swedish oncologists, revealed a clear link between glyphosate and non-Hodgkin's lymphoma (NHL), a form of cancer. The researchers argue that exposure to the herbicide increases the risks of contracting NHL and, given the increasing increase in its worldwide use (in 1998, 112,000 tons) since this study was carried out, there is an urgent need for new epidemiological studies. The finding was based on a population case control / study conducted in Sweden between 1987 and 1990. Its authors concluded that "exposure to the herbicide increases the risk of NHL." The increase in the incidence of this cancer detected in the last decades in Western countries, is now also being seen in many other countries. According to the American Cancer Society, this increase reached, since 1970, the alarming figure of 80%.

On the other hand, in a report published on August 1 of this year in the online newsletter of the Institute of Science in Society of England, Professor Joe Cummins reveals that the recent health alert regarding the presence of toxic acrylamide in cooked food is related causally with glyphosate, the herbicide that is tolerated by the most widespread transgenic crops, such as Round-Up Ready soybeans.

Acrylamide is the building block for the construction of the polyacrylamide polymer, a material well known in molecular biology laboratories for its use as a matrix gel to break down DNA fragments in sequence analysis and protein identification, processes that are carried out under the influence of electric fields. Worldwide, polyacrylamide is used in water purification to flocculate organic matter in suspension. Recently, the World Health Organization convened a closed-door meeting to examine the finding of significantly high levels of acrylamide in cooked vegetables. The finding had a massive impact because acrylamide is a potent neural toxicant in humans and also affects male reproductive function and causes birth defects and cancer in animals. The press reports of that Organization revealed that the discovery of acrylamide was surprising and deduced that the contamination arose probably due to the cooking of the vegetables.

Strangely, the World Health Organization newsletter did not mention the fact that polyacrylamide is a recognized additive in commercial herbicide products (25-30% solutions), added to reduce spray drift and act as a surfactant. Glyphosate-based herbicides from Monsanto (for example, Round-Up) are of particular concern, as the herbicide interacts with the polymer. Experimentation showed that heat and light contribute to the release of acrylamide from polyacrylamide, and glyphosate was found to influence the solubility of polyacrylamide, which is why great care was advised when mixing these two substances.

The evidence seems to indicate precisely that acrylamide is released by environmental polyacrylamide, the main source of which is found in glyphosate-based herbicidal formulas. Cooking vegetables that have been exposed to glyphosate used in herbicide-tolerant transgenic crops, or used during soil preparation in conventional crops would result in additional acrylamide release. The situation is worsened by the fact that, in the US, polyacrylamide-type additives are considered a "trade secret" and information on the composition of herbicidal formulations is not publicly available.

Mutagenic action: None of the mutagenesis studies required for glyphosate registration have shown mutagenic action. But the results are different when studies are done with commercial glyphosate-based formulas: in laboratory studies with various organisms, Round-Up and Pondmaster (another formulation) were found to increase the frequency of lethal sex-linked recessive mutations in the fruit fly; Round-Up at high doses showed an increase in the frequency of sister chromatid exchange in human lymphocytes and was weakly mutagenic in Salmonella. DNA damage was also reported in laboratory tests with mouse tissues and organs.

Reproductive Effects: In laboratory tests with rats and rabbits, glyphosate affected the quality of semen and the number of sperm. According to the EPA, continued exposures to residues in water in concentrations greater than 0.7 mg / L can cause reproductive effects in humans.

Food contamination: The weight of current scientific evidence makes it possible to assert that the incidence and severity of various types of cancer, congenital malformations and neurological disorders would be much lower if the population were not exposed to pesticides through diet, water and habitat.

In any country whose preventive health system prides itself on really caring for the health of the population, the maximum limits for pesticide residues in food are strictly monitored. The objective of this control is to ensure that residue levels are kept as low as possible, recognizing that certain sectors of the population, such as children and the elderly, may have increased susceptibility and noting that any pesticide can be used simultaneously in more than one crop. Studies conducted by the EPA to assess the magnitude of non-occupational exposure to pesticides among the general population, conclude that dietary exposure is the route that generates the greatest impact.

Dietary exposure occurs through the consumption of domestic and imported foods containing pesticide residues and the ingestion of contaminated drinking water. Most experts argue that pesticide residues in the diet pose a very modest risk to the average individual. The term "average" means an adult person, in reasonable health, who eats a reasonably appropriate diet, and who does not have a genetic, health, or environmental predisposition or unusual risk factors that increase their vulnerability to disease. This definition corresponds to approximately two thirds of the population. For the other third, pesticide residues in the diet increase the risk of suffering from various health problems.

Until the advent of glyphosate-tolerant transgenic crops, the maximum limit for residual glyphosate in soybeans set in the US and Europe was 0.1 milligrams per kilogram. But beginning in 1996, these countries raised it to 20 mg / kg, an increase of 200 times the previous limit. This increase is due to the fact that glyphosate producing companies are requesting permits to approve the presence of higher concentrations of glyphosate in foods derived from transgenic crops. Monsanto, for example, has already been authorized for a triple increase in transgenic soy in Europe and the US (from 6 ppm to 20 ppm).

These traces of glyphosate and its metabolites in transgenic soy are also present in foods made from legumes. Glyphosate residue testing is complex and expensive, which is why it is not routinely performed by the government in the United States (and never performed in Argentina). But there is research showing that glyphosate can be absorbed by plants and concentrated in the parts that are used for food. For example, after application, glyphosate has been found in strawberries, blueberries, raspberries, lettuce, carrots, and barley. According to the World Health Organization, its use before the wheat harvest to dry the grain results in "significant residues" in the grain; the bran contains residues in concentrations 2 to 4 times higher than the grain


An additional risk to human health posed by the use of this type of glyphosate-based herbicide deserves to be examined: our society has not developed any policy or apparatus to effectively restrict the competitive biotech race, or to properly regulate or guide its products. towards safer or more productive courses. This deficiency is also related to the lack of scientific criteria in decision-making and in the establishment of standards in the biosafety regulation. It is the health risk resulting from the strategy implemented by the transgenesis industry (based on genetic engineering) to minimize the public's fears of the various risks analyzed here and quickly get people used to eating transgenic foods, a strategy that in Argentina today is materialized in the form of a plan called "Solidarity Soy".

Along with food aid from huge servings of processed soy such as milanesa, hamburger, meatball, noodle, raviol, milk, yogurt, and "soy" cheese, now nearly 17 million impoverished and hungry Argentines will also receive their massive dose of glyphosate. …. The industry's relentless business strategy allows us to anticipate how it envisions its path to a prosperous future…. at the cost of the health of millions of people not even yet informed of the existence of this type of product.


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* Dr. Jorge Kaczewer
National University of Buenos Aires

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