WASHINGTON, June 24, 2015 –The International Agency for Research on Cancer (IARC), an arm of the World Health Organization, classified the herbicide 2,4-D as “possibly carcinogenic to humans” this week, a rating seized upon by GMO labeling campaigns, but downplayed by industry and agricultural groups who say the classification sounds much worse than it actually is.

The IARC Working Group placed 2,4-D in its group 2B, alongside other reviewed substances including aloe vera, coffee and pickled vegetables. GMO Answers, a portal run by agricultural companies for consumers, put together a chart of some substances or activities IARC has placed in category 2B since 1979. Among them are talc-based body powder and carpentry. See below. 


IARC said its decision was based on “limited evidence in experimental animals,” and “inadequate evidence in humans.” The classification was made by a working group of 26 experts from 13 countries, the agency said.

2,4-D, a widely used herbicide that controls broadleaf weeds, has been registered in the United States since 1948.

James Bus, a senior managing scientist at Exponent Engineering and Scientific Consulting, said in an article that exposure and dosage are critical when determining if a substance is a human carcinogen.

“IARC acknowledges that if exposure were factored into the equation, a different result could be reached,” Bus said in a post on GMO Answers. The agency looks at whether something “could potentially” cause cancer, but not whether it “will or is likely to” cause cancer in real-world use, he noted.

The U.S. Environmental Protection Agency has determined in its reviews of the chemical that 2,4-D is “not likely to be carcinogenic to humans.” 

EPA reviewed 2,4-D comprehensively in 2005, again in 2012 and in 2014 when it evaluated a new product from Dow AgroSciences called Enlist Duo, which combines 2,4-D and the herbicide glyphosate. The agency approved Enlist Duo for commercial use in 15 states.

EPA concluded that the herbicide meets safety standards for the public, agricultural workers and endangered species. The product contains what EPA described as a “new, lower volatility pesticide formulation” that uses the choline salt of 2,4-D.

IARC also recently reviewed glyphosate, and categorized the widely used herbicide as riskier than 2,4-D, in group 2A —“probably carcinogenic to humans.”

EPA previously concluded that glyphosate does not pose a risk to human health if used according to the label, but is conducting a re-registration review of the product. Food safety and environmental groups are asking EPA to “strongly weigh” IARC’s glyphosate analysis in its upcoming review.

Julie Goodman, an epidemiologist, board certified toxicologist and consultant to the 2,4-D Research Task Force, said during a media call Tuesday that she does not believe IARC’s classification of 2,4-D should have any influence on EPA or any other regulatory body.

“IARC classifies substances based on their hazards but that is not the whole picture,” she said. “[The IARC review] is a hazard assessment; not a risk assessment.”

“You need exposure information in real-world situations to see if people are actually at risk,” Goodman said, adding that 90 regulatory agencies around the world -- including EPA, Health Canada, the European Food Safety Authority and the World Health Organization – have determined there is no risk of cancer from 2,4-D. The WHO assessment is independent of IARC.

Meanwhile, the Just Label It campaign issued a statement Tuesday that says IARC’s decision to classify 2,4-D as a possible human carcinogen “means that both active ingredients in Dow AgroSciences’ Enlist Duo herbicide for GMO crops are human cancer risks.”

The group, which advocates for mandatory labeling of any food made with genetically modified crops, said EPA’s decision to approve Enlist Duo means “that millions of Americans will be exposed to herbicides with known human health hazards in coming years.”

Gary Hirshberg, chairman of the Just Label It campaign and chairman and co-founder of Stonyfield Farm, added, “Unless GMO products are labeled, consumers have no way to know if ingredients in the food they buy were grown in a way that promoted use of these herbicides.”

In the House of Representatives, the Energy and Commerce Committee and Agriculture Committee are currently reviewing legislation sponsored by Rep. Mike Pompeo, R-Kan., that would pre-empt state laws requiring mandatory GMO food labeling.

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