Roundup Weed Killer | Uses, Safety & Cancer Risk (2024)

Roundup is the brand name for an herbicide containing the active ingredient glyphosate. Glyphosate is a nonselective weed killer, meaning it can kill most plants on contact within days or weeks. Agricultural workers often apply glyphosate by spray to large areas of crops.

As of June 2023, Roundup with glyphosate was still available in retail stores and online. However, Bayer, the current manufacturer, has said it may begin removing glyphosate from its consumer products within the year. Bayer will base its decision to remove glyphosate from Roundup on reviews by the U.S. Environmental Protection Agency and state counterparts.

In June 2023, Bayer agreed to pay $6.9 million to resolve claims by the New York attorney general that the company misled consumers. The claims say Bayer promoted Roundup as an environmentally safe product. The settlement also requires Bayer to stop advertising Roundup containing glyphosate as safe and nontoxic.

Roundup was initially developed for large-scale farming operations but is now available in home and garden versions and has become a popular household pesticide. Glyphosate is the most widely used pesticide in global agriculture, and glyphosate-based products are the second-most widely used home and garden weed killers.

In 2015, a United Nations agency listed glyphosate as “probably carcinogenic,” spurring controversy over whether a link exists between Roundup and cancer. Courts and regulatory agencies have had conflicting reactions to the claim. In 2017, the EPA issued a draft report concluding that glyphosate, the main ingredient in Roundup, is safe and “not likely” to cause cancer in humans. The agency is still reviewing data on the herbicide to determine whether it can increase the risk of cancer or other serious illnesses when used as suggested.

Roundup use peaked between 2004 and 2014, accounting for two-thirds of its use since its launch in 1974. The EPA estimated that by 2016, Roundup use had reached between 280 million and 290 million pounds per year. Glyphosate use exploded exponentially in 1996 when Monsanto introduced “Roundup Ready” crops. The genetically modified seeds were immune to glyphosate’s effects.

Previously, farmers had applied Roundup before their crops emerged from the ground or after harvest to kill lingering weeds. The new seed technology let farmers use glyphosate even as their crops were growing. As a result, farmers used as much as triple the amount of glyphosate.

There are risks associated with Roundup use because of its active ingredient, glyphosate, but governing bodies have not officially classified the chemical as a carcinogen. The World Health Organization and the U.S. Environmental Protection Agency disagree on the safety of Roundup. The EPA classifies Roundup as “safe for use,” but the International Agency for Cancer Research, an arm of the World Health Organization, classifies glyphosate as a “probable human carcinogen.” Roundup products continue to be sold without a cancer risk warning label.

Research on Roundup and cancer is still evolving, but studies show some evidence that exposure to high levels of glyphosate may increase the risk of developing non-Hodgkin lymphoma among people exposed to the chemical over long periods of time. Research also shows that long-term high level glyphosate exposure may impact the developing fetus in pregnant women and that glyphosate damage to gut bacteria may negatively impact the growing brains of young children. Effects of Roundup exposure can be mild or severe, depending on the length and amount of exposure.

Key Facts

Although glyphosate doesn’t stay in the air very long, it can remain in the soil for months depending on climate, soil pH and other factors. When glyphosate breaks down, it contaminates soil and water. Researchers at McGill University showed that even bodies of water exposed to moderate amounts of glyphosate had less diversity over time, negatively impacting that ecosystem. Glyphosate is also highly toxic to some water animals, particularly invertebrates.

Research shows that the other components of glyphosate-containing herbicides, like surfactants, can also have a negative environmental impact. Glyphosate and the components in Roundup can impact the environment by affecting the growth of soil microorganisms, in some cases causing an increase in microorganisms that can be dangerous to humans and animals.

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In some cases, courts have determined that Roundup exposure led to cancer and have awarded millions of dollars to individual parties. Most often, research linked these cases to long-term workplace exposure over decades. Large multidistrict Roundup suits that bring hundreds of separate lawsuits together under one judge have led to settlements of billions of dollars, and many are still ongoing.

Short-term acute exposure to glyphosate requires medical attention. Acute exposure to glyphosate can irritate the eyes, nasal passages, throat and lungs and cause breathing issues.

Roundup alternatives don’t contain glyphosate. Most ready-made products contain acetic acid, vinegar or plant-based oils and soaps. These formulas can rapidly kill weeds by damaging the leaf cuticle and causing cell leakage. Like Roundup, these products kill plants on contact and can only be applied directly to weeds.

Roundup alternatives such as corn gluten meal and iron-based herbicides may only work under specific conditions. Manual weed control methods, such as mulching, can effectively control young weeds, and boiling water poured over adult plants will deter growth. Integrated weed management systems that combine approaches work best as Roundup alternatives.

Roundup alternatives include:

The University of Maryland Extension Service says most alternatives are not as effective as glyphosate. It recommends using alternative herbicides with other gardening practices such as soil health and irrigation methods.

Natural does not always mean safe. Most vinegar and natural-oil herbicide alternatives are more toxic to human skin than glyphosate or other synthetic pesticides. People should avoid inhaling these alternatives and getting them on their skin or in their eyes.

Roundup alternatives can have downsides for plant use as well. Acid-, iron- and soap-based alternatives damage the outer layers of a plant and, like Roundup, will damage any plant they come in contact with.