Pests at bay, but what about cancer?

New Delhi, June 27, 2015
A cancer alert has been sounded on insecticides lindane, DDT and herbicide 2,4-D, after their carcinogenicity was evaluated by the International Agency for Research on Cancer – a specialised agency under the World Health Organisation (WHO).

A working group of 26 experts from 13 countries reviewed scientific literature and classified lindane as “carcinogenic to humans.” Evidence was found linking lindane to non-Hodgkin lymphoma (NHL), the WHO said.

DDT was classified as “probably carcinogenic to humans,” as links were found between DDT exposure and NHL, testicular cancer, and liver cancer. DDT could also suppress immune system and disrupt sex hormones, it added.

Herbicide 2,4-D was classified as “possibly carcinogenic to humans.” There was strong evidence that 2,4-D induces oxidative stress (a mechanism that can operate in humans) and moderate evidence that it causes immunosuppression, the note said. Lindane was used extensively for insect control, including in agriculture and the treatment of human lice and scabies. It is now banned or restricted in most countries.

DDT was introduced to control insect-borne diseases during WW-II and used later in agriculture and to eradicate malaria. Though most DDT uses are banned since the 1970s, DDT and its breakdown products are highly persistent and can be found in environment and in animal and human tissues around the world. DDT exposure still occurs, mainly through diet. The remaining and essential use of DDT is in controlling malaria, strictly restricted under the Stockholm Convention.

Introduced in 1945, 2,4-D was used to control weeds in agriculture, forestry, and urban and residential settings. Occupational exposures occur during manufacturing and application, while general exposure is through food, water, dust, residential application etc, the note said.