Is Roundup Dangerous?

Roundup Weed Killer on store shelf

Is Roundup dangerous? Or is it safe?

You’ve likely heard of Roundup either because it’s a popular, inexpensive, effective herbicide or because recent safety concerns have developed, and its use is becoming a hotly debated topic. So which is it? Dangerous or safe?  Let’s look at the facts.

In this article:

What is Roundup?

Roundup is a widely known and used herbicide intended to eliminate weeds in lawns, gardens, and crop fields. It was first developed in the 1970s by Monsanto and later acquired by Bayer AG in 2018. 

There may be several active ingredients in Roundup, but the key active ingredient is glyphosate, a non-selective metabolic inhibitor. This means that glyphosate blocks key parts of the metabolic system in plants, causing them to die. It successfully kills all plants it comes in contact with, including weeds, grass, and flowers.

Monsanto developed a line of genetically engineered Roundup Ready seeds designed to withstand glyphosate herbicide application. Many of our food products are grown from these seeds, including soybeans.

Notable Exception: There are some Roundup products that do not contain glyphosate.

Does Roundup Exposure Cause Long-Term Health Risks?

The long-term health risks of Roundup and glyphosate herbicide use is hotly debated. There are many studies that suggest there are long-term effects, while others have determined that there are no long-term effects. Let’s take a closer look.

Evidence That Suggests Roundup may Have Long-Term Health Risks

An article published by Interdisciplinary Toxicology, then by the NIH, suggests a link between glyphosate and Celiac disease and other gut problems. This study showed that “Fish exposed to glyphosate develop digestive problems that are reminiscent of celiac disease.”

A study published by Surgical Neurology International, then the NIH, determined that cows fed genetically modified Roundup Ready feed showed a severe depletion of manganese. Why is that significant? Manganese deficiency is linked to multiple health problems, including:

  • Alzheimer’s disease
  • Autism
  • Depression
  • Anxiety syndrome
  • Parkinson’s disease
  • Osteoporosis and osteomalacia
  • Infertility
  • Birth defects
  • Prion diseases

Evidence That Suggests Roundup may not Have Long-Term Health Risks

According to an article originally published by Regulatory Toxicology and Pharmacology (RTP), then by the National Institutes of Health (NIH), “Several regulatory agencies and scientific institutions worldwide have concluded that there is no indication of any human health concern.” This article also notes that no glyphosate bioaccumulates (becomes concentrated inside the bodies of living things) in any animal tissue.

In 2020, the U.S. Environmental Protection Agency (EPA) reevaluated the information available and found “that there are no risks of concern to human health when glyphosate is used in accordance with its current label.”

Is Roundup a Human Carcinogen?

Does Roundup cause cancer? There isn’t a simple answer to this question. 

Evidence That Suggests Roundup may be a Human Carcinogen

In 2015, the World Health Organization’s International Agency (WHO) and International Agency for Research on Cancer (IARC) classified glyphosate as “probably carcinogenic to humans.” They based this declaration on multiple studies, including several animal studies and studies of farmers who work with the herbicide.

A University of Washington study showed an increased risk for some cancers, including non-Hodgkin Lymphoma (NHL), by as much as 40 percent.

In January of 2019, France determined regulators did not properly assess health risks and banned Roundup 360 based on the research from the IARC.

Evidence That Suggests Roundup may not be a Human Carcinogen

However, another study reported that “Glyphosate exposure was not associated with cancer incidence overall or with most of the cancer subtypes we studied.” On the other hand, they found that “There was a suggested association with multiple myeloma incidence that should be followed up as more cases occur in the [Agricultural Health Study].”

Furthermore, an additional review found “no consistent pattern of positive associations indicating a causal relationship between total cancer (in adults or children) or any site-specific cancer and exposure to glyphosate.” However, critics note that there is a financial tie between some of the authors of this review and Monsanto, the creator of both glyphosate and Roundup.

The U.S. Environmental Protection Agency (EPA) conducted another review in January of 2020 and released the following findings:

  • “No risks of concern to human health from [the] current uses of glyphosate”
  • “No indication that children are more sensitive to glyphosate”
  • “No evidence that glyphosate causes cancer in humans”

The EPA publicly disagrees with the IARC findings and says their research was more thorough. They cite examples like “IARC only considered eight animal carcinogenicity studies while EPA used 15 acceptable carcinogenicity studies.”

Is Roundup Bad for the Environment?

Like most concerns regarding Roundup, there is no undeniable conclusive evidence that it’s bad for the environment. Yet, many have significant concerns for land and aquatic plants.

One NIH review found that “glyphosate and its metabolites can possibly persist in soil, water, and plant tissues in certain conditions. Research suggests that glyphosate may reach groundwater, surface water, and several other nontarget sites through processes such as leaching and surface runoff.”

Further, another study from McGill University noted evidence of glyphosate leaching into rivers and surrounding environments and reported “[a] significant loss of biodiversity in [freshwater] communities contaminated with glyphosate.”

Are There Lawsuits Against Roundup?

Yes. There have been many lawsuits filed against Bayer AG. U.S. News and World Report released an article in June 2022 that states “Last year, Bayer set aside 4.5 billion dollars to deal with the claims that glyphosate, the weed-killing ingredient in Roundup, causes non-Hodgkin lymphoma, a type of cancer. The company had previously taken a charge of nearly 10 billion dollars for earlier rounds of litigation.” 

Many plaintiffs claim they received a cancer diagnosis after using Roundup. Even though Bayer AG maintains that there is no cancer risk, they said they “would replace glyphosate in Roundup for residential use beginning in 2023.”

How to Apply Roundup Safely

When homeowners apply Roundup themselves, it’s important to follow the directions carefully. Follow these tips:

  • Wait for a clear, dry, windless day. Moisture can dilute the product, making it less effective. Wind can spread the herbicide to areas not intended for application.
  • Wear proper safety clothing. Wear long sleeves, rubber gloves, and rain boots to prevent Roundup from coming in contact with your skin.
  • Carefully read product directions when preparing the solution. As a general rule, use 3-6 ounces of Roundup for every gallon of water.

Avoid inhaling the product or getting it on your skin or in your eyes. Wash your hands immediately after use, and don’t touch the product when it’s still wet. 

A few potential health risks from direct contact include:

  • Irritated skin, nose, eyes, and throat
  • Increased saliva and mouth burns or pain, if swallowed
  • Nausea, diarrhea, and vomiting
  • If intentionally ingested, it can lead to death

What are some Roundup Alternatives?

If you’re looking for a Roundup alternative, Consumer Notice suggests these alternatives:

  • Homemade solution: A half-gallon of vinegar, half cup of salt, and 2 tablespoons of dish soap. This solution is effective against annual weeds, but not as effective against perennial weeds (weeds that return year after year).
  • Mulch: With 2-3 inches of mulch, weeds do not receive the sunlight they need and are smothered under the weight. However, the most persistent weeds may still break through.
  • Iron-based herbicides: Several iron-based weed killers have been approved by the EPA and are most effective against broadleaf weeds, which absorb iron easier than grass and die from oxidation within hours.
  • Organic herbicides: These typically include natural oils and acids which are most effective against weeds that have already sprouted. They tend to be less effective against perennial weeds.
  • Manual removal: The most effective way to remove weeds is to dig them up manually. Unfortunately, it’s also the most time-consuming.

If you’d like more information on how to control weeds, check out our complete Guide to Weed Control in Your Yard.

FAQ About Roundup

Do all Roundup Products Contain Glyphosate?

It’s important to note that while glyphosate was invented by Monsanto and is contained in many Roundup products, there are versions of Roundup that contain a different active ingredient — penoxsulam, a relatively new herbicide.

Penoxsulam is becoming popular, especially among farmers, but it’s still being researched. While penoxsulam’s EPA Pesticide Fact Sheet shows it’s safe for humans, a peer review by the European Food Safety Authority shows risks for pets and crop retention of the chemical.

Is Roundup Dangerous When Dry?

No. When Roundup is dry, it’s safe for humans and pets. Just be sure that it’s 100 percent dry as the wet product can be hazardous. However, not everyone agrees.

Is Roundup Dangerous for Dogs?

Manufacturers claim that Roundup is safe for dogs when dry. However, there are some who say no, it’s not safe. 

According to Animal Wellness Magazine, data collected by European poison control centers has shown acute glyphosate poisoning in companion pets, which led to death in some cases. They believe pets were poisoned when they rolled in and ate the sprayed grass. 

Currently, there is a more comprehensive research project being considered at the Health Research Institute Laboratories (HRI). Specifically, they’re measuring the glyphosate in pet urine and working to determine if there is an acceptable daily level of the chemical.

How Much Exposure to Roundup is Dangerous?

When it comes to a safe level of exposure, there isn’t a clear answer. For ethical reasons, researchers can’t conduct experiments that would expose humans to differing levels of glyphosate and must rely on gathering circumstantial data. As mentioned earlier, some studies show a dangerous correlation between Roundup and humans, while others show no notable dangers at all.

However, Paul Mills, a public health professor at the University of California San Diego who has studied glyphosate exposure in humans said, “There is consensus, among non-industry scientists, that there is no safe level of exposure to glyphosate. That is, no level established that comes with no possible harm.”

How Long Does Roundup Stay in the Soil?

Glyphosate can stay in the soil for up to 6 months. This varies widely due to:

• Differences in soil composition

• Glyphosate concentrations

• Temperature

• Rain conditions

• Traffic in the applied area

Is Roundup a Pesticide or a Herbicide?

Roundup is both a pesticide and a herbicide. Pesticides handle a wide range of problems, including insects, fungus, and undesirable plants like weeds. Herbicides are more specific, eliminating unwanted plants. Some take out specific plants, while others, like Roundup, take out all plants.

What if I Have more Questions about Roundup?

You can contact the National Pesticide Information Center. You can get answers regarding glyphosate use, glyphosate residues, pesticide residues, risk assessments, and more.

Hire a Professional

Information about Roundup and pesticide formulations is a lot to digest. Choosing an option and putting it into practice can be a time-consuming headache. Why do it yourself? 

A fast, free quote from an experienced, local professional is just a click away. Whether you’re looking for organic weed control or a more aggressive option, they have you covered.

Main photo credit: Mike Mozart / Flickr / CC BY 2.0

Nicki DeStasi

Nicki DeStasi

Nicki DeStasi is a writer, author, and teacher who grew up in western Massachusetts and currently resides in the Austin area. She enjoys flower and vegetable gardening, reading, cooking, listening to true-crime podcasts, and spending time with her husband, three children, dog, and cat.