How Safe Is Roundup?

Roundup Weed Killer
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Roundup, made by Monsanto, is the most popular weed killer in the world, used by agricultural corporations and weekend gardeners alike. Though it's been around since the 1970s, questions about the safety of Roundup continue to swirl around the herbicide.

The active ingredient in Roundup is a chemical compound called glyphosate, which works by preventing the plant from making proteins that are necessary for plant growth. As a non-selective herbicide, Roundup will kill most plants, except for genetically modified crops that are designed to resist the weed killer.

Roundup also contains ingredients that are listed as inert or inactive ingredients, meaning that they are not herbicides. One of these, polyethoxylated tallowamine, or POEA, has come under scrutiny since there is some evidence that it may not be safe for humans or other animals.

The Safety Profile of Roundup

In use for almost 40 years, Roundup appears to have a better safety profile than many other pesticides. Glyphosate, used in several herbicides manufactured by companies other than Monsanto, has been the subject of dozens of studies that have consistently confirmed its overall safety.

Critics, however, charge that many of these studies have been funded by herbicide manufacturers including Monsanto. Industry-funded studies, of course, can hardly be called impartial.


Glyphosate has been linked in some studies to birth defects, reproductive disorders, miscarriages, and non-Hodgkin's lymphoma, or NHL, a type of cancer. There is also some research that has linked the herbicide's so-called "inert ingredient" POEA to the death of human embryonic, placental, and umbilical cord cells.

POEA is a detergent-like surfactant that helps Roundup work by making it more "soapy" so it can better coat the leaves and stems of plants.

As reported in Scientific American: "'This clearly confirms that the [inert ingredients] in Roundup formulations are not inert,' wrote the study authors from France’s University of Caen. 'Moreover, the proprietary mixtures available on the market could cause cell damage and even death [at the] residual levels' found on Roundup-treated crops."

A Safer, Natural Weed Killer

So ... is Roundup safe? Unfortunately, the best answer available today is "maybe." Until there's more data proving that Roundup—and not just its active ingredient glyphosate—is safe for humans, animals, and the environment, it's important to remember that the herbicide is irrefutably a toxin. It does, after all, kill plants, and should always be used cautiously and according to its instructions, if it's used at all.

The EPA, through its Office of Pesticide Programs, is expected to conduct a review of Roundup by 2015 to determine if its use should be restricted, or if the herbicide should continue to be available on the market.

In the meantime, there are safer alternatives for household weed killers. Vinegar, for example, is a relatively safe herbicide that effectively kills weeds. Because of its acidic nature—vinegar contains acetic acid—it's good for weed control in yards, gardens, driveways, and sidewalks.

Other commercially available, "natural" weed killers might be a safer alternative to Roundup. In all cases, read and follow the instructions carefully, since "natural" does not always mean "safe."