Exposure to the pesticide DDT may cause harm to the child while still in the womb, says a study. DDT or dichloro-diphenyl-trichlor-oethane was developed as the first of the modern insecticides early in World War II. It was banned in the US and Britain in the 1970s, but it is still used in some countries to kill malaria-carrying mosquitoes. Earlier studies have found it to be linked to premature births and low birth weight. Now Brenda Eskenazi and other researchers at the University of California, Berkeley, found that children exposed to DDT while in the womb also experience development problems, reported the online edition of BBC News.

DDT, an organochlorine, persists in the environment long after use, accumulating in the food chain and in fatty tissues of animals and humans. Over time, it degrades into DDE and DDD, metabolites of DDT, which have similar chemical and physical properties.

Thirty-three years after its use was banned in the US, DDT is still detectable in about five to 10 per cent of people, while DDE is detectable in nearly everyone. The researchers measured the levels of DDT and one of its breakdown products, DDE, in the blood of 360 pregnant women, the majority of whom were born in Mexico where agricultural use of the chemical was only banned in 2000.

The researchers tested the mental and physical skills of the women's babies at six, 12 and 24 months using established tests to measure the children's development. For each tenfold increase in DDT levels measured in the mother, the team found a corresponding two to three-point decrease in the children's mental development scores at 12 and 24 months.

Children with the highest DDT exposures in the womb were associated with a seven to 10-point decrease in test scores, compared to the lowest exposures, the researchers say

When the children's physical skills were measured, there were two-point decreases in children's scores at six and 12 months for each tenfold increase in DDT levels in the mothers. Similar, but weaker effects, were linked to DDE exposure.

The team also found that the longer babies were breastfed for, the better they scored on the developmental tests, even though they would have been exposed to DDT through the milk.