Three pesticides that have been heavily used in both agricultural and non-agricultural applications have been linked to cancer.
The International Agency for Research on Cancer (IARC) evaluated the carcinogenicity of the insecticides lindane and DDT and the herbicide 2,4-D. An IARC working group of 26 experts from 13 countries classified the insecticide lindane as carcinogenic to humans, giving it the highest Group 1 risk rating.
The experts, who published their findings online on 22 June 2015 in The Lancet Oncology, concluded there was sufficient evidence in humans for the carcinogenicity of lindane for non-Hodgkin lymphoma (NHL). The IARC group noted that large epidemiological studies of agricultural exposures in the USA and Canada showed a 60 per cent increased risk of NHL in those exposed to lindane.
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.
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.
Lindane – which was used in agriculture, wood preservatives, disinfectant ‘fog’ bombs, and lice and scabies treatments – and DDT are no longer approved for use in the UK. However, workers with historic exposures may still be at risk of developing related cancers. And DDT is still used in control of insect-borne diseases like malaria.
Use of the herbicide 2,4-D is still allowed in the UK. It has found favour with local authorities for weed control on pavements and in parks and other public areas.
- Dana Loomis and others. Carcinogenicity of lindane, DDT, and 2,4-dichlorophenoxyacetic acid, The Lancet Oncology, published online 22 June 2015.