IARC Declares 2,4-D Possibly Carcinogenic

In a move that was expected by the industry, the International Agency for Research on Cancer (IARC), the specialized cancer agency of the World Health Organization, declared 2,4-D as “possibly carcinogenic to humans.” The IARC also evaluated the carcinogenicity of the insecticides gamma-hexachlorocyclohexane (lindane) and dichlorodiphenyltrichloroethane (DDT).

According to the IARC, “the herbicide 2,4-D was classified as possibly carcinogenic to humans (Group 2B), based on inadequate evidence in humans and limited evidence in experimental animals. There is strong evidence that 2,4-D induces oxidative stress, a mechanism that can operate in humans, and moderate evidence that 2,4-D causes immunosuppression, based on in vivo and in vitro studies. However, epidemiological studies did not find strong or consistent increases in risk of NHL or other cancers in relation to 2,4-D exposure.”

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(Read CropLife International President & CEO Howard Minigh’s assessment of the IARC here.)

Since its introduction in 1945, 2,4-D has been widely used to control weeds in agriculture, forestry, and urban and residential settings. Occupational exposures to 2,4-D can occur during manufacturing and application, and the general population can be exposed through food, water, dust, or residential application, and during spraying.

The insecticide DDT was classified as probably carcinogenic to humans (Group 2A), based on sufficient evidence that DDT causes cancer in experimental animals and limited evidence of its carcinogenicity in humans. Lindane has been used extensively for insect control, including in agriculture and for treatment of human lice and scabies. High exposures have occurred among agricultural workers and pesticide applicators; however, the use of lindane is now banned or restricted in most countries. Large epidemiological studies of agricultural exposures in the USA and Canada showed a 60% increased risk of NHL in those exposed to lindane.

Read the IARC release here.