Glyphosate was discovered by a Swiss pharmaceutical chemist in 1950. Monsanto researchers later determined that glyphosate had herbicidal effects, and it was patented under the commercial name Roundup. It was first approved in the U.S. in 1974.

Monsanto’s patent for glyphosate expired in 2000, and it “is now marketed by over 40 companies under an assortment of trade names.” Since the 1980s, it has one of the world’s most-used herbicides for large-scale agriculture and residential homes and gardens.

How Glyphosate Works

According to the National Pesticide Information Center, “Glyphosate is a non-selective herbicide, meaning it will kill most plants. It prevents the plants from making certain proteins that are needed for plant growth. Glyphosate stops a specific enzyme pathway, the shikimic acid pathway. The shikimic acid pathway is necessary for plants and some microorganisms.


Why Roundup Is So Popular

A 2011 report by the EPA determined that glyphosate, an herbicide, is the No. 1 pesticide active ingredient used in the agricultural market sector (180-185 million pounds applied in 2007, the most recent year for EPA data), and ranks No. 2 in use in the industry/commercial/government market sector (13-15 million pounds annually) and the home and garden market sector (5-8 million pounds annually).

Glyphosate’s most common use is as the active ingredient in Roundup, Monsanto’s extraordinarily successful product.  Because Monsanto had the original patent on glyphosate, the company had a head start in marketing its use and solidifying Roundup’s market position before the patent experience in 2000.

Spray containers of Roundup Ready-to-Use Weed & Grass Killer III sold for consumer use advertise “Visible Results in 3 Hours.” The containers also note the simple benefits of Roundup: “Spray the leaves to kill the root” and “Glyphosate targets an enzyme found in plants but not in people or pets.” In short, Roundup takes a lot of the work out of eliminating weeds, and Monsanto assures that it hurts only weeds, not animals or humans. The Roundup container (with illustrations featuring dandelions as the weedy enemy) suggests spraying it on “fence lines, driveways and walkways, around trees, flower beds.”

Since 1996, Monsanto has used Roundup as part of a larger business using genetically modified seeds for corn, soybeans, sugar beets, cotton, canola, and other crops that are glyphosate resistant. Thus, Roundup can be sprayed on entire fields once weeds emerge, ideally killing all plant life except for the crops grown from Monsanto’s patented Roundup Ready seeds. In 2015, Monsanto generated $15 billion in annual revenues. Their pesticide business contributes to about 31 percent of Monsanto’s revenues, and also supports their patented seed business, which is the largest segment of Monsanto’s revenues.

Monsanto attests to the safety of glyphosate in all of its corporate reports. For example, they note: “Like all pesticides, glyphosate is routinely reviewed by regulatory authorities to ensure it can be used safely. In the U.S., that’s the job of the Environmental Protection Agency (EPA), and like other regulatory authorities around the world, the EPA’s process is comprehensive and based on the best available science…When it comes to safety assessments, no other pesticide has been more extensively tested than glyphosate. In evaluations spanning four decades, the overwhelming conclusion of experts worldwide, including the EPA, has been that glyphosate can be used safely according to label instructions.”

An important point, though, is that Monsanto is much less likely to discuss the safety of its Roundup formulations; i.e., is Roundup, which is a mixture of glyphosate and a number of other “adjuvant” ingredients – some disclosed on the label, some not – safe? Historically, the EPA tested only for glyphosate safety, not the safety of the other Roundup ingredients, nor their interactions with glyphosate and the other ingredients. Increasingly, academic and independent researchers are looking at the safety of Roundup and its adjuvants.

In its 43-page report (Adrienne Held, James Hudson, Larry Martin, and William Reeves, Benefits and Safety of Glyphosate, July 2016,, Monsanto spends about ½ page addressing the safety of one class of adjuvants, surfactants, which aid in the absorption of the herbicide into plant leaves. (See section 3.5.8, pages 30-31.)

What’s in Roundup

There are several formulations to Roundup. For example, the residential use Roundup Ready-to-Use Weed & Grass Killer III lists the following ingredients:

Active Ingredients
 Glyphosate, isopropylamine salt..............2%
 Pelargonic acid and related fatty acids......2%
 OTHER INGREDIENTS.........................96.0%

The more concentrated Roundup POWERMAX II lists these ingredients:

Active Ingredients:
 Glyphosate, N-(phosphonomethyl)glycine,
 in the form of its potassium salt ........48.8%
 OTHER INGREDIENTS:........................51.2%



Dandelion photo by Dan Zen