By SUSAN BLOWER

WASHINGTON D.C. — Commodity groups are concerned that 2,4-D, a common herbicide, will be classified as a "probable carcinogen" by the International Agency for Research on Cancer (IARC) in coming weeks.

Strong media coverage ensued after IARC, a subsidiary of the U.N. World Health Organization, reclassified glyphosate as a "probable carcinogen" earlier this year. Now, according to media reports, an upcoming review of 2,4-D will identify it as another potential carcinogen.

"Like anyone who creates something, farmers need tools to produce a safe and healthy crop. ... These two substances play an especially important role in corn and soybean farming as they allow us to manage weeds in a sustainable way," said leaders of the National Corn Growers Assoc. (NCGA) and American Soybean Assoc. (ASA) in a statement last week.

A March Against Monsanto, maker of RoundUp, a trade name for glyphosate, took place in 240 U.S. cities two weekends ago, the Huffington Post reported.

Consumer confusion is the main concern of the NCGA and ASA. In addition, they charge that the IARC’s classification system is misleading and based on select studies.

"Glyphosate – and now 2,4-D – are in Class 2-A, in which the IARC also placed coffee, hair salons and working the night shift. Our biggest concern is that this causes a lot of fear, stress and confusion for the public. Cancer is a weighty word," said Cathryn Wojcicki, NCGA communications manager.

The 2A designation as a "probable carcinogen" does not mean that the chemical is likely to cause cancer, said Fred Whitford, a pesticide specialist with Purdue Extension. "If it was, we’d be seeing cancer all over the place. In fact, cancer rates are going down," Whitford told Farm World.

The IARC process is not a risk assessment and evaluates only the potential for a compound to cause cancer, but not the likelihood, said Alan Boobis, professor of biochemical pharmacology at Imperial College London, reported sciencemediacentre.org

The pesticides in question are used widely on driveways and yards to kill weeds. Farmers are not at an increased risk, Whitford said. If farmers wear gloves and long sleeves when using pesticides, he said they will reduce their exposure to almost zero.

"The key here is to understand that this is a controversy on paper. Our farmers need to appreciate that in using fuel, pesticides, any chemical, that they need to give it respect. Wear gloves to reduce exposure. Then they don’t have to worry about controversies," Whitford said.

Exposure to potential toxins is the important factor. Gasoline, for example, contains benzene, which is a known carcinogen, Whitford said, but because the gas nozzles limit our exposure, it is not a worry for most people.

Whitford said that glyphosate and 2,4-D are two of the most widely used products and most-studied chemicals, and he would be "shocked" if glyphosate were found to cause cancer after 50 years of use.

Even so, he said that farmers and consumers should keep an open mind when new studies come out.

"Any report is worth considering from any group that is an international body," Whitford said. "Generally, scientists argue until there is a consensus. The EPA will look at the recommendations from this international group to see if there is merit."

Whitford believes that the EPA, which has to date approved the use of both pesticides, will use science-based methods to evaluate the data.

While there are mathematical associations in some studies between 2,4-D and cancer, it is not verified by real-world cases, Whitford said.

The ASA and NCGA also believe that dicamba and other crop protection tools will be similarly reclassified by the IARC in coming weeks or months. 2,4-D has been in use since 1945 and dicamba since 1967.

"The IARC doesn’t take into account the way the materials are used. 2,4-D and glyphosate have been used for years by farmers, who use them as directed and prescribed on the label," said Patrick Delaney, ASA communications manager.

"Nearly every regulatory body has reviewed these chemicals and confirmed their safety," Delaney said. "Of the hundreds of items reviewed by IARC, only one was classified as non-carcinogenic: a nylon compound. Their methodology is difficult to understand.

Noting there was little evidence found by the United Kingdom Committee for Cancer Carcinogenicity, Boobis said that establishing a link between pesticide use in ag workers and cancer is difficult.

"Ag workers, the most commonly studied group, are almost never exposed to just a single pesticide, and it is very difficult to establish cause and effect," Boobis said.

"These conclusions of the IARC are important and should be taken into account when evaluating these pesticides, but we must also take into account how the pesticides are used in the real world. In my view, this report is not a cause for undue alarm," Boobis said of the glyphosate report last March in sciencemediacentre.org