DDT Linked to Preterm Births

Pesticide may have led to 'unknown epidemic' in U.S. in 1960s, says large-scale study

THURSDAY, July 12, 2001 (HealthDayNews) -- Exposure to DDT during pregnancy appears to increase the risk of premature delivery and low-weight-for-date babies, federal epidemiologists report.

But that risk is only one factor that needs to be weighed in decisions by developing countries to continue using DDT against mosquitoes that transmit malaria, says Dr. Matthew P. Longnecker, a physician and epidemiologist with the National Institute of Environmental Health Sciences. He is the lead author of a report in the July 14 issue of The Lancet.

Malaria is a threat to hundreds of millions of people across the globe and causes at least 2 million deaths a year. DDT, banned or restricted in the United States and other industrialized countries in the 1970s, is still widely used for mosquito control in malaria-infested areas. Alternative sprays are much more expensive and more likely to induce resistance.

The new study looked at blood samples collected from the mothers of thousands of children born between 1959 and 1966, when DDT was still being fully used in the United States. The samples came from blood serum that is still stored by the U. S. Collaborative Perinatal Project, a program run by the government and 12 universities.

Longnecker and his colleagues studied levels of DDE, the breakdown product of DDT, in the blood serum of the mothers of 2,380 children.

Of those children, 361 were born before the 37th week of pregnancy and 221 were in the lowest 10 percent of weight for each week of pregnancy. The researchers say that they found elevated levels of DDE in all the mothers of these infants. The incidence of premature birth and low birth weight was directly associated with higher levels of DDE in the blood, the report says.

The United States "may have had an epidemic of preterm births that we are just now discovering," Longnecker says in a statement. Preterm births are considered a major factor in infant mortality.

The results were not surprising, because small studies done two decades ago reported a similar association, Longnecker says. Having those findings confirmed by this large-scale study indicates a need to look for other possible toxic effects of DDT, he adds.

"Other reproductive effects would be an interesting thing to study," Longnecker says. One recent paper reported an association between DDT exposure and fetal loss in China, he says, and the subject is "quite an active area of investigation."

In theory, he says, "it would be a good idea to phase out the use of DDT" for mosquito control. But in real life, decisions must be made "for a given area, considering the given resources available."

And, Longnecker adds, "I would like to see someone else confirm my findings before making decisions."

But most evidence supports the continuing use of DDT, according to the medical director of the American Council on Science and Health, a nonprofit group in New York.

"Its effectiveness has been proven over decades," Dr. Gilbert Ross says. "Even the putative increase in preterm births is far outweighed by the benefits of this chemical."

Overall, Ross says, use of DDT for malaria control "carries very slight risks and benefits millions of people each year."

What To Do

Longnecker sees some possible risks "for a young woman who is not yet married and who spends some time in a country like India and could possibly get higher blood levels of DDT." But he quickly adds, "more studies reporting the same thing would be helpful before coming down with heavy-handed advice."

Detailed information about malaria worldwide and guidance for travelers is available from the Malaria Foundation International. To learn more about what's around you, check into the National Institute of Environmental Health Sciences.

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