DDT exposure in womb tied to hypertension
Women who were exposed in the womb to a pesticide that pervaded the United States until it was banned four decades ago were found in a new study to have an increased risk of developing high blood pressure before age 50.
The pesticide, known as DDT, was widely used for insect control nationwide starting in the 1940s. It was banned in 1972 when scientific evidence showed it was a likely carcinogen that damages the liver, the nervous system and the reproductive system.
Millions of Americans breathed it in during the three decades when the chemical compound was in use. Today, the adult daughters of women who were pregnant at the time are at greater risk for hypertension, according to researchers from UC Davis and the Public Health Institute in Berkeley, among other institutions.
Their study was published Tuesday in the journal Environmental Health Perspectives.
Past research shows that adults with high levels of DDT in their system are likely to develop hypertension, but the authors of the study said theirs was the first to trace that link back to the womb.
Insights into health
They said they hoped their findings would shed light on a condition that puts an estimated 68 million U.S. adults at risk for heart disease and stroke - and on the health dangers of an insecticide that is still widely used to combat malaria in Africa and Asia.
"The people who were in their moms' wombs cannot change their exposures," said Barbara Cohn, the study's senior author and an epidemiologist at the Public Health Institute in Oakland. "But what we can do to protect our health is, honestly, to understand that there's a possibility that there are things in our environment that we cannot control and could harm us and our children that we need to stay informed (about).
"We need to think really hard about the introduction or use of any chemical in our lives, and really decide we really need it before we use it."
The findings are part of a larger study of 15,000 Bay Area women who gave samples of their serum during their pregnancies from 1959 to 1967. The project, called the Child Health and Development Studies, is examining long-term environmental exposures in generations of women.
Cohn said she hoped to study DDT's effects on men at a future date.
For the latest study, researchers quizzed 567 daughters of the women in the original study about their health. All were in their 30s and 40s when the survey took place from 2005 to 2008. About 110 women said they had been diagnosed with hypertension, and 70 of them said they were taking medicine for the condition.
Daughters who were in the womb when their mothers tested for high levels of DDT were much likelier to be taking medicine for hypertension than those whose mothers showed lower levels of DDT, according to the study.
There was also a link, though less strong, between mothers with high levels of DDT and daughters who reported having high blood pressure but were not taking medicine at the moment. This was possibly because self-reported diagnoses can be inaccurate, researchers said.
These trends were clear, researchers said, even when they accounted for traditional risk factors, such as age, birth weight, body size and onset of menopause.
Even though DDT is banned, it remains a risk because it lodges in the soil and food chain and dissolves very slowly, said David Jacobs, a public health professor at the University of Minnesota and a pesticides expert who was not part of the study. He noted that exposure to DDT has also been linked to diabetes.
DDT still in use
"What you have is some toxic compounds that were toxic at much lower doses than people thought at the time they were using them, are banned and are persisting in the environment and the body," he said. "This article ... is amplifying that conclusion."
It is unclear exactly how DDT acts in the body to lead to hypertension, but a UC Davis scientist plans to examine this in experiments on mice.
Global health experts are concerned that DDT is being sprayed inside homes in developing countries to kill malaria-carrying mosquitoes. Cohn said she hopes her study serves as a warning of how this pesticide in particular, and chemicals in general, can manifest in poor health in future generations.
"Opening the idea to a very early exposure being something that leads to a ... midlife occurrence is exciting, because maybe we can prevent it," she said. "It would be really nice to prevent it - not just medicate it, not just treat it."