Glyphosate is a widely used herbicide that controls broad-leaved weeds and grasses and is used in the production of various fruits, grains, nuts, and vegetables. It works by inhibiting an enzyme that regulates the synthesis of aromatic amino acids needed for plant growth. Since the late 1970s, glyphosate has been used in low-till and no-till farming, helping to retain soil moisture and reduce soil erosion. The development of genetically engineered glyphosate-resistant crops in 1996 dramatically increased the herbicide’s use in agriculture. Concerns about the effects of glyphosate on the environment and human health have led to extensive safety reevaluation.

What is glyphosate used for?

Glyphosate is a nonselective herbicide effective in controlling broad-leaved weeds and grasses in various settings, including agriculture, bare-ground weed control, and aquatic environments. Its introduction significantly boosted no-till farming by enabling timely crop establishment, improving yields, retaining soil moisture, and reducing soil erosion. Glyphosate's herbicidal action inhibits the EPSP synthase enzyme, disrupting aromatic amino acid synthesis required for plant growth. While most plants are susceptible, some have developed resistance through mechanisms like genetic mutation. Concerns about its environmental and health impacts have led to extensive reevaluation and restrictions in some areas.

How does glyphosate kill weeds?

Glyphosate is a widely used herbicide effective in controlling grasses and broad-leaved weeds in various settings, including agriculture, orchards, vineyards, and aquatic environments. Glyphosate's herbicidal action comes from its ability to inhibit an enzyme called EPSP synthase, which is critical in the shikimic acid pathway. This pathway is responsible for producing aromatic amino acids like phenylalanine, tryptophan, and tyrosine, which are essential for protein synthesis and overall plant growth. By disrupting this process, glyphosate prevents plants from producing the necessary amino acids and proteins, leading to toxic effects and ultimately plant death.

What concerns do people have about glyphosate's use?

People have voiced concerns regarding the use of glyphosate , a widely used herbicide, due to its potential impacts on the environment and human health. These concerns include: * A 2015 report by the World Health Organization (WHO) International Agency for Research on Cancer (IARC) determined that glyphosate is "probably carcinogenic". * The development of glyphosate-resistant crops has led to a rise in the use of herbicides, which can be harmful to pollinating insects and other wildlife. * Glyphosate may pose health risks to humans who consume traces of the herbicide on genetically modified (GM) crops. * The use of glyphosate can reduce weed diversity, which in turn reduces habitat and food for other important species. * Gene flow from plants engineered for glyphosate resistance to wild plants is a cause of concern for the environment and human health.

How is glyphosate's impact on the environment studied and regulated?

Glyphosate's environmental impact is studied and regulated through continuous evaluation and monitoring of its effects on non-target plants, ecological risks, and potential impacts on human health. Mitigation measures, such as changes in product labeling, help minimize risks like spray drift and herbicide resistance. The EPA concluded that glyphosate poses a low risk to human health when used as directed. However, concerns and perceived risks have led some countries and cities to restrict or ban its use. Monitoring programs also track pesticide levels in water and soil to understand how these chemicals move and accumulate in the environment.

glyphosate

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Two large containers of Roundup weed and grass killer with sprayer wands are displayed on a store shelf, labeled as ready-to-use glyphosate-based herbicide.

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Also called:: N-(phosphonomethyl)glycine

Related Topics:: Herbicide; Roundup

On the Web:: National Center for Biotechnology Information - PubMed Central - Overview of human health effects related to glyphosate exposure (Oct. 16, 2026)

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glyphosate

herbicide

Also known as: N-(phosphonomethyl)glycine

Written by

Kara Rogers

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Britannica Editors

Last updated

Oct. 16, 2026 •History

Discovery and development

Can Roundup Cause Cancer? Glyphosate is highly effective at managing weeds—but is that all it does?

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Glyphosate was initially synthesized in 1950 during a search for novel pharmaceutical compounds carried out by chemist Henri Martin at the Swiss company Cilag. The compound was set aside, however, owing to a lack of evidence for pharmaceutical potential. In the 1960s, following the acquisition of Cilag by the American company Aldrich Chemical, glyphosate was added to the Aldrich Library of Rare Chemicals. This led to its rediscovery and, in 1970, its resynthesis by chemists Phil Hamm and John Franz, who were working for the American company Monsanto; their work resulted in the identification of the herbicidal activity of glyphosate. In 1974 Monsanto introduced Roundup, the first glyphosate-based herbicide; Roundup quickly became a leading herbicide product worldwide.

Uses, mechanism of action, and resistance

Glyphosate has played a central role in agriculture since its introduction. In the late 1970s and ’80s, for example, it gave impetus to low-till and no-till farming, allowing for more timely crop establishment and improved crop yields; these approaches further aided the retention of soil moisture and helped reduce soil erosion, particularly in arid and semiarid environments. Beginning in 1996 with the development of genetically engineered glyphosate-resistant crops, the herbicide’s use in agriculture increased dramatically; such engineered crops include varieties of canola (rapeseed), corn, cotton, and soybeans. Other uses of glyphosate are focused on bare-ground weed control, such as in orchards and vineyards, in fallow fields, along fence lines, and on lawns and gardens. It is also often used to control weeds in aquatic environments, particularly cattails (Typha), reed canary grass (Phalaris arundinacea), purple loosestrife (Lythrum salicaria), and common reed (Phragmites), which grow near water and are considered invasive in many areas.

The herbicidal actions of glyphosate result from its inhibition of an enzyme known as EPSP synthase, which regulates the synthesis of the aromatic amino acids via the so-called shikimic acid pathway. Aromatic amino acids include phenylalanine, tryptophan, and tyrosine, which are necessary for the synthesis of proteins involved in plant growth. Glyphosate further disrupts the synthesis of nonaromatic amino acids via additional mechanisms and causes the accumulation of shikimate, a substrate of EPSP synthase. Thus, inhibition of EPSP synthase prevents plants from producing amino acids and proteins required for growth and has other toxic effects. These actions are nonselective in terms of plant species, and therefore glyphosate is toxic to most plants following contact with foliage.

Some species of plants are naturally tolerant to glyphosate; examples include field horsetail (Equisetum arvense), yellow nutsedge (Cyperus esculentus), and wild buckwheat (Fallopia convolvulus). In other instances plants develop resistance to glyphosate after repeated exposure. Glyphosate resistance has been documented in at least several dozen species of plants worldwide. The mechanisms underlying resistance vary; examples include genetic mutation that leads to overexpression of EPSP synthase, mutation that prevents herbicide interaction with EPSP synthase, and mutation that results in decreased herbicide uptake and retention. Plants that have been engineered to resist glyphosate carry a gene that encodes a version of EPSP synthase from bacteria that is insensitive to glyphosate. Gene flow from plants engineered for glyphosate resistance to wild plants can occur via pollen and seed and is a cause of concern for the environment and human health.

Environmental and health impacts

Concerns about impacts to the environment and human health resulted in extensive reevaluation of the chemical’s safety and use. Many concerns about human health stemmed from a 2015 report by the World Health Organization (WHO) International Agency for Research on Cancer (IARC), which concluded that glyphosate is “probably carcinogenic.” In 2020, following extensive evaluation by the U.S. Environmental Protection Agency (EPA), the risk to human health from glyphosate was concluded to be very low, with no likely threat of cancer when products were used according to manufacturer’s instructions. Nonetheless, in the 2010s numerous lawsuits claiming that Roundup caused cancer were filed against Monsanto. In 2018 the German chemical and pharmaceutical company Bayer acquired Monsanto; shortly thereafter the first Roundup lawsuit was decided in favour of the plaintiff. In 2020 Bayer agreed to pay more than $10 billion to settle claims regarding Roundup.

Risks to nontarget plants from glyphosate use, particularly through spray drift, are well documented. Mitigation measures to minimize such risks have included changes in product labeling to more clearly explain the management of spray drift and ways to prevent herbicide resistance. Analysis of other ecological risks, including impacts to monarch butterfly habitat, outcrossing from engineered plants, and potential actions as an endocrine disruptor, is ongoing. Despite a lack of scientific evidence to support claims against glyphosate use, the perceived risks and potential impacts to human health, including yet unknown effects on reproduction and neurological function—in addition to environmental risks—have led some countries and cities to ban or otherwise restrict the use of glyphosate.

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