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Regulators in the United States and Canada are making a formal review of the safety of glyphosate, the key ingredient in herbicides that have revolutionized row crop farming over the last 30 years.

The Problem with Roundup May Be the Additives, Not the Active Ingredient

Critics of this active ingredient in Roundup herbicide cite the spread of herbicide-resistant superweeds and the possibility of causing infertility and cancer, while Monsanto and other makers of herbicides argue that their products protect the soil.

Until the 1970's, weeding crops depended on manual labor or carefully timed cultivation of fields. One of the major problems with getting rid of weeds with farm machines has always been that what gets rid of weeds can also get rid of crops. It's only possible to plow away the weeds when crops are small, and many soils are easily compacted if they are too wet or impossible to till if they are too dry. Even as late as 1980, even in the USA, it was not unusual for farmers to hire laborers to clear fields of weeds that could reduce food yields by 50 per cent or more.

The introduction of the glyphosate herbicide Roundup in 1974 dramatically changed the way farmers weed their fields. Synthesized from the amino acid glycine, glyphosate herbicides kill many kinds of tender plants by interfering with an enzyme they use to make the amino acids phenylalanine, tryptophan, and tyrosine. Mammals (including humans) do not have this enzyme, getting their phenylalanine, tryptophan, and tyrosine from food, so they are unaffected by the main active ingredient in the product.

The herbicide can be sprayed on fields before seed crops emerge from the ground to kill young weeds, preventing the need to plow the soil. This conserves the soil, fuel, and the farmer's time. The machines used to spray crops are far less expensive than the machines used to plow the ground to get rid of weeds. Agricultural scientists took the use of glyphosate a step further by genetically engineering many crops that are resistant to the herbicide, so the fields can be sprayed a second or third time even after the food plants have emerged from the ground.

The US Food and Drug Administration, the European Commission Health and Consumer Protection Directorate, and the United Nations World Health Organization have all concluded that glyphosate does not cause cancer in humans. Bacteria in the soil quickly degrade glyphosate, depending on soil temperature. Fifty percent of glyphosate sprayed on the soil will break down in just three days in hot and muggy Texas, although fifty percent of glyphosate may remain on the forest floor in Sweden for as long as two years.

In the form of Roundup and competing products, glyphosate is used around the world with very few reports of toxic exposure, usually by people who immersed a hand or foot directly into a barrel of the product! So why should regulators in the US and Canada take a second look at glyphosate safety? There are three good reasons.
  1. Although the active ingredient in Roundup and similar glyphosate herbicides does not cause cancer, it is often combined with the herbicide diquat, which does. Most brands of glyphosate herbicide sold in the US and Canada do not contain diquat, but brands sold in the UK often do. In laboratory studies, low concentrations of diquat have even been used as a kind of chemotherapy, but higher concentrations are carcinogenic.
  2. The preservative in these herbicides, Proxel (benzisothiazolin-3-one), can cause burns and irritation of eyes and skin.
  3. Weed sprays are formulated with various kinds of surfactants to make sure the active chemical, which is only a tiny percentage of the total amount of liquid sprayed on plants, is evenly distributed. There are at least five different surfactants used in glyphosate sprays, and their effects are not completely predictable.
While diquat does cause cancer, it's not included in the bestselling Monsanto product and it's not used in North America. The US Food and Drug Administration has already concluded that glyphosate does not cause cancer. So why are regulators taking a second look at Roundup?
Continue reading after recommendations

  • Bolognesi C, Carrasquilla G, Volpi S, Solomon KR, Marshall EJ.Biomonitoring of genotoxic risk in agricultural workers from five colombian regions: association to occupational exposure to glyphosate. J Toxicol Environ Health A. 2009,72(15-16):986-97.
  • Hokanson R, Fudge R, Chowdhary R, Busbee D. Alteration of estrogen-regulated gene expression in human cells induced by the agricultural and horticultural herbicide glyphosate. Hum Exp Toxicol. 2007 Sep,26(9):747-52.
  • Photo courtesy by TJ Martins on Flickr: