DDT linked to developmental delays in babiesJul 7, 2006 | AP
The study by scientists at UC Berkeley measured levels of various pesticides in 360 pregnant women who recently emigrated from Mexico to the Salinas Valley and tested the mental and motor skills of their U.S.-born infants and toddlers. The mental tests measure the children's ability to learn and think, including memory and problem-solving skills.
For every tenfold rise in DDT exposure, the children's scores on mental tests dropped 2 to 3 points. Their motor skills were also reduced. In the most severe cases, the highest DDT doses were associated with a 7- to 10-point drop in the mental scores of 2-year-old children compared with those who were not exposed.
The researchers tested the women for other pesticides, but only DDT was connected to neurological effects. It was not known whether the effects found in the toddlers will persist. The UC Berkeley team plans to study the same children until they enter school.
"This suggests that DDT has effects that no one thought to test back when it was in use," said Walter Rogan, an epidemiologist with the National Institute of Environmental Health Sciences. He was not involved in the study, published in the journal Pediatrics.
DDT was banned in the United States in 1972. The Salinas Valley women had very high exposures, eight times higher than average levels in the U.S. population reported recently by the Centers for Disease Control and Prevention. Researchers say they were probably exposed in Mexico, because most of them had lived in the United States for less than five years.
Mexico allowed the use of DDT on farms until 1995 and for mosquito control until 2000.
The study is part of a federally funded UC Berkeley project that assesses whether agricultural chemicals in the heavily farmed Salinas Valley are harming children.
The study's findings have particular relevance to the current debate on the use of DDT in Africa to combat Malaria.
"The take-home message is that this is not an entirely benign compound even though the great advantages of its use when you're saving lives with effective malarial control are very important," Rogan said.