Recent use of DDT in malaria control in Kenya has lead to high and extensive contamination of soils, according to a team of Chinese researchers.
The researchers, most affiliated to the Chinese Academy of Sciences and the Sino-Africa Joint Research Center based in Nairobi, have reported unhealthy levels of soil contamination with DDT and the agricultural chemical endosulfan.
Soil samples collected from malaria areas especially in the western highlands showed high levels of contamination from more than 26 types of pesticides.
DDTs and endosulfan were the dominant in that order and further analysis showed the source being recent use of DDT in malaria control programmes.
The team published the results in a February issue of the journal Environmental Pollution and is clear that the contamination in the soil presents a significant threat to human health.
Last year the World Health Organisation’s International Agency for Research on Cancer said DDT, or dichlorodiphenyltrichloroethane, probably causes cancer, with scientific evidence linking it to non-Hodgkin lymphoma, testicular and liver cancers.
Endosulfan widely used by tea, fruit vegetable and grain farmers for control of a variety of pests has been linked to serious human health consequences and plans are underway to phase it out by the end of this year.
Kenya banned the use of DDT for agriculture use in 1986 but around 2010 there was a huge campaign to bring it back for malaria control.
Then the agriculture sector had opposed DDT use, arguing it could find its way in food crops and threaten the country’s horticulture export market estimated at $355 million annually.
But now Kenya may be exploiting the WHO option allowing a group of high malaria countries a limited use of DDT in mosquito control.
A recent Dispatch, Volume 21, Number 12—December 2015 by the US Centers for Disease Control and Prevention – Nairobi, shows DDT is one of the chemicals being used for mosquito control in Kenya.
“In Kenya, current policy on indoor residual spraying use of insecticides is limited to pyrethroids and DDT,” says the Dispatch.
The Dispatch cites a study carried out by researchers from the Kenya Medical Research Institute, Kenyatta University, Kenya, Masinde Muliro University of Science and Technology, Kenya, and University of California, US, and funded by the US National Institutes of Health.
Ironically Kenyans may be poisoning themselves for no gain because the extensive study described in the dispatch indicates DDT is no longer killing mosquitoes since they have developed resistance.
“We conducted standard insecticide susceptibility testing across western Kenya and found that the Anopheles gambiae mosquito has acquired high resistance to pyrethroids and DDT.”