DDT link to premature births

DDT is effective in controlling malaria

Women exposed to DDT, the insecticide effective in controlling malaria, may be more likely to have premature births.

American scientists found that the insecticide increases the risk of pregnant women having their babies before 37 weeks of gestation.

DDT was banned or restricted in industrialised countries in the 1970s but in many countries it is still used to control malaria spreading mosquitoes.

Scientists have long suspected a link between premature births and DDT, but only through small and inconclusive studies.

We have to be concerned about what might be happening in those 25 countries where DDT is still used

Matthew Longnecker

But this latest study of DDT use in the US during the 1960s found strong evidence of a link.

And although levels in the US and industrialised countries are now low enough, there are fears about the health of babies born to pregnant women in the 25 countries still using the chemical.

Matthew Longnecker, lead author on the study, said: "DDT levels in the US are now low and likely not causing any harm.

"But we have to be concerned about what might be happening in those 25 countries where DDT is still used. Also, looking back on earlier decades in the US, we may have had an epidemic of pre-term birth that we are just now discovering.

The findings of our study strongly suggest that DDT use increases pre-term birth, which is a major contributor to infant mortality

Matthew Longnecker

"The findings of our study strongly suggest that DDT use increases pre-term birth, which is a major contributor to infant mortality.

"If this association is causal, it should be included in any assessment of the costs and benefits of insect control using DDT."

The study, published in The Lancet, was carried out by scientists at the National Institute of Environmental Health Sciences, the National Institute of Child Health and Human Development, the University of North Carolina and the Centres for Disease Control and Prevention.

They found elevated levels of DDT's breakdown product DDE, in the stored blood of mothers recorded as giving birth to low birth weight infants.

The scientists studied the blood serums of the mothers of thousands of children born between 1959 and 1966.

A sample group of 2,380 revealed that 351 had been born pre-term and 221 weighed less than most babies of their age.

The mothers of the affected infants had higher levels of DDE in their blood, indicating a high exposure.

Malarial controls

Dr Longnecker said that there were other malarial controls which were more expensive, but less toxic and less persistent and he is now working with epidemiologists in Mexico to see if women in malarial areas exposed to DDT have the same problems.

Professor Chris Curtis, of the medical entomology department at the London School of Hygiene and Tropical Medicine, told BBC News Online that DDT had proved to be a very effective way of controlling malaria.

He said that in South Africa the insecticide had been used to control the disease for 50 years until the 1990s, when the environmental lobby succeeded in persuading the authorities to switch to pyrethroids.

However, within five years malaria had built up resistance to the new compounds to such an extent that DDT was re-introduced.

Professor Curtis said: "There have been so many scares over DDT over the years and most turn out to be pretty unconvincing.

"DDT was used on a huge scale in agriculture in the US in the 1960s. The amount used against malaria is far, far less."