Is Glyphosate in Weed Killer Linked to Cancer?

What’s the cost of a lush, weed-free lawn? If you’re using a weed killer containing glyphosate, some believe the price may be your health.

Glyphosate is one of the most widely used weed-killing chemicals. The question of whether exposure to it can increase your risk of cancer has been debated by scientists, regulators and the public for years.

So, does spraying those unwanted dandelions put you at risk? The answer isn’t exactly cut and dried. We asked oncologist Dale Shepard, MD, PhD, to help us weed out fact from fiction.

Can glyphosate cause cancer?

Glyphosate is a chemical used to kill weeds and other unwanted plants. It’s been available for weed control since 1974. It’s one of the most common ingredients found in herbicides around the world.

But there’s widespread debate about whether glyphosate increases cancer risk — and the only thing for certain is that there’s no universally agreed-upon answer.

In its most recent assessment in 2017, the U.S. Environmental Protection Agency (EPA) concluded that glyphosate poses no health concerns to children or adults when used as directed. The EPA found that glyphosate “is not likely” to cause cancer in humans.

The EPA expects to update its risk assessment by late 2026. The agency notes that its current determination is consistent with those of other regulatory and advisory bodies around the world, including:

• Canadian Pesticides Regulatory Directorate
• Australian Pesticides and Veterinary Medicines Authority
• European Food Safety Authority
• Food Safety Commission of Japan
• An expert group administered by the Food and Agriculture Organization of the United Nations and the World Health Organization

But other experts and agencies have raised concerns.

In 2015, the International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic to humans.” Some research has focused specifically on a possible association between glyphosate exposure and non-Hodgkin lymphoma (blood cancers).

That disagreement has played out beyond scientific circles, too. Tens of thousands of lawsuits have alleged that glyphosate-containing weed killers caused cancer, eventually leading one agrochemical manufacturer to agree to billions of dollars in settlements.

So, which conclusion should you believe?

“The weed killer story points to interesting disconnects between science, public opinion and court decisions,” Dr. Shepard notes. “There’s really no clear and definitive answer.”

Should you be concerned?

Your level of exposure matters when it comes to glyphosate and cancer risk.

If you use a glyphosate-containing weed killer around your home — or don’t use the product at all — the available evidence suggests you probably don’t have much reason for concern, says Dr. Shepard.

Glyphosate concentrations in products intended for home use are generally low, making toxic exposure less likely if you’re spraying a patch of crabgrass or clover in your yard.

The potential concern is greater for people who regularly work with larger amounts or more concentrated forms of glyphosate. This would include farmers, landscapers and groundskeepers.

How common is glyphosate exposure?

Researchers estimate that most of the U.S. population has recently been exposed to glyphosate. A 2022 study found the chemical in 81% of tested urine samples from children and adults.

Exposure likely occurs by consuming food and water with trace amounts of glyphosate.

But detecting a chemical in your body only means it’s present. It doesn’t necessarily mean that it’s harming you. What these low-level exposures mean for long-term health remains unclear and under study.

Tips to limit health risks from glyphosate

If you use a glyphosate-based or other chemical weed killer, treat it like what it is — a product designed to kill living plants. Dr. Shepard recommends these precautions to reduce risk and exposure when using herbicides:

• Read the label. Follow all instructions and safety warnings, including how much product to use and how to apply it.
• Cover up. Wear gloves and protective glasses and cover exposed skin when applying weed killer. Consider wearing a mask, too, as glyphosate can be present in the air after spraying.
• Watch the weather. Don’t spray on rainy or windy days, when the product may drift or spread beyond the area you’re treating.
• Keep people and pets away. Wait until the treated area is dry before allowing anyone back into the space.

Another option is to skip using chemical weed killers. Old-fashioned weed pulling by hand is one way to limit direct exposure. Other alternatives include using organic weed-suppression products.

Remember this, too: A few dandelions in the yard never hurt anybody.