A monograph () recently published online by the International Agency for Research on Cancer (IARC) classifies the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) as possibly carcinogenic to humans. The monograph discusses “inadequate evidence” of 2,4-D’s carcinogenicity in humans, but “limited evidence” in experimental animals. IARC assigned 2,4-D to Group 2B, , based on epidemiological and experimental evidence of carcinogenicity and mechanistic and other relevant data for the chemical. Explanations of IARC’s categories are available on the agency's .

According to the monograph, workers can be exposed to 2,4-D from product manufacturing and agricultural use, and from forestry, right-of-way, and turf or lawn applications. IARC notes that other populations may be indirectly exposed to the herbicide as a result of “take-home” and “drift” exposures. While dermal absorption and inhalation are the typical routes of occupational exposure for 2,4-D, the monograph states that some incidental ingestion may also occur.

IARC monographs identify and evaluate environmental factors that can increase carcinogenic risks to humans. Learn more on IARC’s .