DDT’s Toxic Impact Spans Generations

Birth Defects

The impact of DDT exposure spans generations.

Toxicologists, molecular biologists and epidemiologists at UC Davis and the Public Health Institute in Oakland have now confirmed that the granddaughters of women who were exposed to DDT, or dichlorodiphenyltrichloroethane, during pregnancy throughout the 1950s and 1960s also suffer from significant health threats: Higher rates of obesity and menstrual periods that start before age 11.

The scientists told the Los Angeles Times that those factors could put those young women at greater risk of breast cancer — as well as high blood pressure, diabetes and other diseases.

The pesticide was banned in the 1970s after breast cancer was discovered in women exposed to the hormone-disrupting chemical in the 1950s and 1960s. Many of their daughters, who had been exposed in the womb, also suffered from breast cancer. Researchers over the years have also linked DDT exposure to obesity, birth defects, reduced fertility and testicular cancer in the sons of those exposed, according to the study published in the journal Cancer Epidemiology, Biomarkers & Prevention.

“This is further evidence that not only is a pregnant woman and her baby vulnerable to the chemicals that she’s exposed to — but so is her future grandchild,” said Barbara Cohn, director of the Public Health Institute’s Child Health and Development Studies, a multigenerational research project in California that has followed more than 15,000 pregnant women and their families since 1959.

“This is something that people had always thought was possible,” she told the LA Times, “but there had never been a human study to support the existence of that link.”

More than 60 years ago, in what the LA Times described as the heyday of DDT, a team of scientists had the foresight to start collecting blood samples from more than 15,000 pregnant women at the Kaiser Permanente hospital in Oakland. At every trimester and also shortly after birth, each woman provided a sample that was studied and carefully archived.

Researchers tested the blood for DDT and continued to follow up. They stayed in touch with the women’s daughters, who had been exposed to DDT in the womb, and then with their granddaughters, the LA Times said. After years of research, they found that women heavily exposed to DDT during childhood are five times as likely to develop breast cancer. A mother’s DDT exposure during pregnancy, or immediately after birth, is linked to an increased risk of breast cancer for their daughter. Their daughters are also more likely to experience delays in getting pregnant.

In this most recent study, the research team found that the risk of obesity in the granddaughters — who are now in their 20s and 30s — was two to three times greater than women whose grandmothers had little DDT in their blood during pregnancy. These granddaughters were also twice as likely to have much earlier menstrual periods — another indicator of increased health risks later in life.

This generational exposure is likely related to the reproductive system, Cohn told the LA Times. Since a female is born with all her eggs, a granddaughter is technically also exposed to DDT if her mother was exposed in the womb.

“Even though we banned that stuff more than 40 years ago, people now walking the earth — the granddaughters of those who were pregnant — were exposed,” Cohn said.

She wondered to the LA Times if the increasing rates of childhood cancer, diabetes and other health problems affecting young people today are also connected to chemical usage in the past. “It’s the full meaning of what a ‘forever chemical’ is — in some ways, that makes every chemical potentially ‘forever’ if it has the potential to do this.”

Developed in 1939, DDT was first used during World War II to clear South Pacific islands of malaria-causing insects for U.S. troops. Its inventor was awarded the Nobel Prize. When DDT became available for civilian use in 1945, only a few people expressed concerns. As a result, it was widely used for insect control in crop and livestock production, institutions, homes and gardens, according to the Centers for Disease Control.

The publication in 1962 of Rachel Carson’s “Silent Spring,” exposed the hazards of DDT and prompted widespread public concern over the dangers of pesticide use. Carson described how DDT entered the food chain and accumulated in the fatty tissues of animals and humans, and caused cancer and genetic damage. Carson wrote that DDT and other pesticides had irrevocably harmed animals and had contaminated the world’s food supply.

Pregnant women exposed to the insecticide DDT are much more likely to give birth prematurely or to full-term but low birth weight babies, according to a 1997 study. Although DDT is now banned in the developed world, it is still widely used elsewhere to combat malaria, particularly in Africa.

“One of the reasons this finding is important is there are not any generally accepted adverse health effects of exposure to DDT or its metabolite, DDE, in humans,” researcher Matthew Longnecker of the US National Institute of Environmental Health Sciences in North Carolina told New Scientist in 2001.

Longnecker analyzed data on 2,380 babies born in the U.S. in the 1960s when DDT was still widely used. He also measured the concentration of DDE in blood samples taken from the mothers during pregnancy. His team found that the risk of premature birth or low birth weight rose with increasing concentrations of blood DDE. A high blood DDE concentration was more strongly linked to prematurity than maternal smoking.

As a third-generation female to be part of a major DDT study, Akilah Shahid told the LA Times that her family has faced health problems, including her grandmother, who fought cancer three times. Shahid herself struggles with her weight and wonders about the lasting effects of DDT.

“How many times have we talked about climate change and things that we need to do better for our children and grandchildren? This is more proof that hello, what we do today is going to affect people way forward,” she said.

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