The World Health Organization (WHO) has classified a “widely used” herbicide as a “probable” carcinogen; 2,4-dichlopenoxyacetic acid (2,4-D) is also a key ingredient in a new product being developed by Dow Chemical. The classification was made by WHO’s International Agency for Research on Cancer (IARC).

This piece, written by staff, appeared in both Reuters and Guardian Environment. 


The IARC announced that it decided to classify 2,4-D as “possibly carcinogenic to humans”. That is a step below a more definitive classification: “probably carcinogenic.” However, it’s also two steps above the “probably not carcinogenic” category. The herbicide has been used since 1945.

Environmental and consumer groups have been waiting for IARC’s findings; they are advocating with U.S. regulators to “tightly restrict” the herbicide’s use. Farm groups and others defend the herbicide as an “important agent in food production that does not need more restrictions.”

IARC findings don’t have regulatory power, but they can (and do) influence regulators, lawmakers…and the public. In March, the IARC announced it found that the herbicide glyphosate (the key ingredient in Monsanto’s widely used Roundup product) was “probably carcinogenic to humans.”


Dow AgroSciences, a unit of Dow Chemical Co, has had a particular interest in IARC’s review. The company is using both glyphosate and 2,4-D in a herbicide it calls Enlist Duo that received US approval last year. Enlist Duo is designed to be used with genetically engineered, herbicide-tolerant crops developed by Dow.

Dow had no comment on the IARC classification but the company has said 2,4-D is a safe and valuable tool for agriculture.


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