The latest study linking dichloro diphenyl dicloro- ethylene (DDT) to human health damage was published in the July edition of the Journal of the American Academy of Pediatrics.
Lead author Brenda Eskenazi, from the University of California, and five other researchers said they had found a drop of up to 10 points in mental development index scores in children with the highest levels of exposure to DDT.
Babies whose mothers had higher DDT levels developed more slowly, physically and mentally than those whose mothers had low DDT levels. The study involved 360 children born to Mexican migrant farmworkers living in the Salinas Valley in California, where thousands of kilograms of several organophosphate chemicals are sprayed on to crops like lettuce, broccoli and grapes.
However, most of the children in Eskenazi's study are believed to have been exposed to DDT while they were growing in their mothers' wombs because the pesticide has been banned officially in the United States since the early 1970s, while the ban on DDT in neighbouring Mexico took effect in 2000.
The most noticeable effects of brain development delays were among infants aged 1 to 2.
Based on the findings of her study, Eskenazi warned: Countries considering the use of DDT should weigh its benefit in eradicating malaria against the negative associations found in this first report on DDT and human neuro- development.
Other recent studies by South Africa researcher Tiaan de Jager have also linked DDT to lower sperm counts in a group of men in the Mexican province of Chiapas.
Although the use of DDT is banned in most parts of the world, South Africa and some other developing countries have decided to keep using it as an emergency measure to control the spread of malaria.
Two years ago, the South African Medical Research Council reported that there had been a dramatic 96% drop in malaria cases since DDT spray (and other strategies) was re-introduced to control malarial mosquitoes, particularly the highly-resistant Anopheles funestus strain.
Nevertheless, the national Health Department has remained under pressure from some researchers to investigate alternative control options which do not rely on DDT.
Health Department spokes-man Solly Mabotha had not responded late yesterday to questions about the implications of the Eskenazi study for South Africa's malaria control strategy.
Rural mothers have DDT in breast milk - study
In Utero Exposure to Dichlorodiphenyltrichloroethane (DDT) and Dichlorodiphenyldichloroethylene (DDE) and Neurodevelopment Among Young Mexican American Children. Journal of the American Academy of Paediatrics
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Hitting malaria where it hurts: household and community responses in Africa, id 21 Health, August 2006, insights health, Issue 9