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The two-year study, published online in the British Journal of Urology International, was conducted among 3,310 boys born to women from the Limpopo province where DDT spraying was carried out in high-risk areas to control malaria between 1995 and 2003.
The study found that women who stayed at home in sprayed villages, rather than leaving the house at times to work or study, had a 41% higher chance of giving birth to a boy with urogenital birth defects (UGBD), such as missing testicles or problems with their urethra or penis.
The authors suggest that this is because they spent more time in homes where domestic DDT-based sprays are still commonly used to kill the mosquitoes that cause malaria, even in areas where organised mass spraying no longer takes place.
Chemical build-up
“If women are exposed to DDT, either through their diet or through the environment they live in, this can cause the chemical to build up in their body” explains lead author Professor Riana Bornman from the University's Department of Urology.
“DDT can cross the placenta and be present in breast milk and studies have shown that the residual concentration in the baby's umbilical cord are very similar to those in maternal blood."
The study
The study compared boys born to women in the 109 villages that were sprayed, with those born to women from the 97 villages that were not.
This showed that 357 of the boys included in the study – just under 11% – had UGBDs.
“It has been estimated that if DDT exposure were to cease completely, it would still take ten to 20 years for an individual who had been exposed to the chemical to be clear of it," said Bornman in the article.
"Our study was carried out on boys born between 2004 and 2006, five to nine years after official records showed that their mothers had been exposed to spraying."
Bornman said records were not kept before 1995 in the Limpopo Province, but it is reasonable to assume that DDT was being used before that date to combat malaria.
DDT banned
Although most countries have now banned the use of DDT, certain endemic malarial areas still use indoor residual spraying with DDT to decrease the incidence and spread of the disease.
Bornman said a number of other factors, like smoking and drinking and the mother's age, were taken into account to rule out possible causes of the birth defects.
Bornman said all authorities should ensure that the general public, including those living under indoor residual spraying conditions, are aware of the possible health risks. - (Sapa, October 2009)
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