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From September 7, 2006                                                                                                        

Study Finds DDT is Linked to Developmental Delays in Children
(Beyond Pesticides, September 7, 2006) A new study, Utero Exposure to Dichlorodiphenyltrichloroethane (DDT) and Dichlorodiphenyldichloroethylene (DDE) and Neurodevelopment Among Young Mexican American Children, finds DDT accumulation in a woman's tissues can be transmitted to her developing fetus across the placenta and is associated with developmental delays in the young child.

The study, led by a team of researchers at the University of California, Berkeley (UC Berkley), is the first to examine the effects of maternal levels of DDT, rather than its breakdown products, on child neurodevelopment – that is, the development of mental and physical skills. At a time when health authorities around the world are considering increasing use of this pesticide to combat malaria, the study is one of the first to suggest that DDT may be harmful to child development. The study provides important health information for decision makers, said Doctor Brenda Eskenazi, Ph.D., the study's lead author and professor of epidemiology and maternal and child health at UC Berkeley's School of Public Health.

Dr. Eskenazi said, "People need to consider this data if they are going to continue using DDT or reintroduce it in countries where it's been banned." Dr. Eskenazi continued, "Given the impact of malaria on child health, I'm not saying that we shouldn't use it. But if we do, we need to think of ways to protect women and children."
Though DDT is banned in most countries, particularly industrialized ones, because of its harmful effects on the environment, it is still manufactured and sold by India and China to other developing countries. DDT has also become increasingly associated with childhood developmental problems.

In another study, entitled Contamination of the Water Environment in Malaria Endemic Areas of KwaZulu-Natal, South Africa, by Agricultural Insecticides, findings show that mothers tested in South Africa’s rural areas have pesticides, including DDT, in their breast milk. According to that study, women were found to have as high as 77 times, and infants 12 times, the World Health Organization’s acceptable limit of the pesticide (See Daily News).

In the UC Berkley study, Dr. Eskenazi and her team measured blood levels of DDT and one of its breakdown products, DDE, in 360 pregnant women. Then they tested the mental and physical skills of the women's babies at six, 12 and 24 months using tests known as the Bayley Scales of Infant Development, a well-known method for developmental assessment of young children.

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. No decrease was found at six months. The highest in utero DDT exposures were associated with a seven- to 10-point decrease in Bayley mental scores, compared to the lowest exposure levels.

In the physical skills evaluations – known as psychomotor testing – there were two-point decreases in children's scores at six and 12 months for each tenfold increase in DDT levels in the mothers. No decrease was found at 24 months.

When the effects of DDE on development were evaluated, the team found associations that were similar to those for DDT, but not as strong.

Other findings, reported earlier by the team, include that the mothers' levels of DDT and DDE did not affect the length of their pregnancies or their infants' birth weights.

In its analysis of the data, the team took into account many factors, including the mother's age and number of years she had lived in the United States, income, education, marital and work status, the child's gender, duration of breastfeeding and the quality of the home environment for young children.

Although small decreases on the Bayley tests may not be apparent in individual children, Dr. Eskenazi said, the findings of decreased scores are relevant for populations. (The Bayley test is designed so that the average score is 100 and scores below 85 indicate a possible developmental delay.)

According to Dr. Eskenazi, "If you had a whole population with a downward shift like this, you'd be seeing more kids with developmental problems.” The team hopes to be able to follow these children until they reach school age to determine whether the effects of DDT exposure persist. Dr. Eskenazi continued, "We need to know what's happening further down the road. What's critical is to find out whether these levels of exposure are affecting a child's ability to perform academically and to function in society."

The mothers in the DDT study are participants in a long-term UC Berkeley project called the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS). The project is designed to examine the effects of pesticides and other environmental factors on the health of pregnant Latina women and their children living in California's Salinas Valley, one of the most intensely farmed regions in the world.

Ninety percent of the women in the study were born in Mexico, where DDT was widely used in agriculture during the 1970s. Its use gradually declined there until 2000, when a full ban went into effect. As a result, levels of DDT in most women in the CHAMACOS study are considerably higher than those of the general population in the United States, where domestic use of DDT was discontinued in 1972.

For more information contact Sarah Yang: scyang@berkeley.edu, 510-643-7741, University of California – Berkeley.