Lindane, DDT and herbicide 2,4-D cause cancer, says WHO arm

The insecticide Lindane, once widely used in agriculture and to treat human lice and scabies, causes cancer and has been specifically linked to non-Hodgkin lymphoma, the International Agency for Research on Cancer (IARC), the cancer research arm of the World Health Organisation (WHO), said today.

A widely used farm chemical 2,4-D, a key ingredient in a new herbicide developed by Dow AgroSciences, was also found to be carcinogenic.

The IARC also said that DDT, or dichlorodiphenyltrichloroethane, also probably causes cancer, with scientific evidence linking it to non-Hodgkin lymphoma (NHL), testicular cancer and liver cancer.

After thoroughly reviewing the latest available scientific literature, a working group of 26 experts from 13 countries convened by the IARC monographs programme classified the insecticide Lindane as carcinogenic to humans (Group 1).

IARC said there was sufficient evidence in humans for the carcinogenicity of Lindane for non-Hodgkin lymphoma (NHL).

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. Epidemiological studies found positive associations between exposure to DDT and NHL, testicular cancer, and liver cancer.

There was also strong experimental evidence that DDT can suppress the immune system and disrupt sex hormones.

However, overall there was no association between breast cancer and DDT levels measured in samples of blood or fat.

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.

IARC's findings on 2,4-D have been awaited by environmental and consumer groups that are lobbying US regulators to tightly restrict its use, as well as by farm groups and others that defend 2,4-D as an important agent in food production that does not need more restrictions.

Since its introduction in 1945, 2,4-D has been widely used to control weeds in agriculture, forestry, and urban and residential settings.

In March, IARC said it had found another popular herbicide -glyphosate - was ''probably carcinogenic to humans.'' Glyphosate, the world's most widely used weed killer, is the key ingredient in Monsanto Co's Roundup herbicide and other products.

IARC classifications do not carry regulatory requirements but can influence regulators, lawmakers and the public. Following the glyphosate classification, some companies and government officials moved to limit glyphosate use.

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 U.S. approval last year. Enlist Duo is designed to be used with genetically engineered, herbicide-tolerant crops developed by Dow.

Dow said in a statement that IARC's classification was flawed and was ''inconsistent with government findings in nearly 100 countries'' that have affirmed the safety of 2,4-D when used as labeled.