Does Roundup Weed Killer Cause Cancer?


You may have seen the TV commercials featuring the Roundup Sharpshooter, a suburban cowboy taking on the weeds. And there may even be a tub of glyphosate (Roundup) on a shelf in your basement or garage.

If you’re in agriculture, you’ve probably known about Roundup for years, and maybe you even grow “Roundup-ready” varieties of corn or soybeans – genetically modified organisms, or GMOs, that defy the herbicidal effects of this weed killer.

Why not? Such use of glyphosate with GMOs has been billed as less harsh on the environment and has been supported by the Centers for Science in the Public interest.

Emerging Concern about Glyphosate

Just in time for spring in the United States, we are starting to hear reports that glyphosate (in Roundup weed killer and other products) may cause cancer. Glyphosate has been used for 40 years, mind you.

The International Agency for Research on Cancer (IARC), working under the World Health Organization (WHO), recently classified glyphosate as “probably carcinogenic.”  The IARC also said there was “limited evidence” that glyphosate was carcinogenic in humans for non-Hodgkin’s lymphoma. The evidence came from studies of exposure in the US, Canada, and Sweden that were published since 2001 and were mostly agricultural exposures.

Monsanto, the world’s largest seed company -- and producer of Roundup -- said the data did not support the conclusions and asked the WHO to hold an urgent meeting to explain the findings.

Philip Miller, Monsanto’s vice-president of global regulatory affairs, has been quoted by Reuters News Service as saying, “We don’t know how IARC could reach a conclusion that is such a dramatic departure from the conclusion reached by all regulatory agencies around the globe.”

Regulatory statements seem somewhat equivocal when it comes to the risk of cancer and are much more robust in describing acceptable levels of glyphosate in the drinking water.

According to the Wall Street Journal:

  • EPA concluded in a 2012 study that glyphosate meets safety standards for human health when used in keeping with its label.
  • EPA is currently conducting a scheduled review of glyphosate in conjunction with Canadian regulators.
  • The Center for Science in the Public Interest, a nonprofit customer advocacy group, said the IARC finding “should be taken seriously by the EPA, farmers and industry.”

According to the United States EPA:

  • “There is inadequate evidence to state whether or not glyphosate has the potential to cause cancer from a lifetime exposure in drinking water.”
  • Acute exposure to glyphosate potentially cause the following health effects: At levels above the maximum contaminant level in drinking water (MCL): congestion of the lungs; increased breathing rate.
  • “Drinking water levels which are considered "safe" for short-term exposures: For a 10-kg (22 lb.) child consuming 1 liter of water per day, up to a ten-day exposure to 20 mg/L or up to a 7-year exposure to 1 mg/L.”
  • Maximum contaminant level: 0.7 mg/L
  • Chronic exposure: Glyphosate has the potential to cause the following health effects from long-term exposures at levels above the MCL: kidney damage, reproductive effects.
  • The EPA’s 2012 assessment of glyphosate concluded that it met the statutory safety standards and that the chemical could “continue to be used without unreasonable risks to people or the environment.”

Bottom Line

  1. Don’t sprinkle herbicides over your breakfast cereal.
  2. Always follow all cautions and warnings from manufacturers of products known or suspected to be harmful to humans.
  3. Watch for more helpful statements to come from science, industry and our regulatory agencies.


Technical Factsheet on: GLYPHOSATE Accessed March 2015.​

Monsanto Bites Back at Glyphosate Findings.

Roundup weedkiller 'probably' causes cancer, says WHO study. Accessed March 2005.

Monsanto weed killer can 'probably' cause cancer: World Health Organization. Accessed March 2015.

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