A study that looked at blood samples from pregnant women during the 1960s has found that their granddaughters are at higher risk for breast cancer.
(CN) — In the first report on the health effects of the infamous insecticide DDT over three generations, exposure of the chemical has been linked to two breast cancer risk factors in granddaughters.
In an article published Wednesday in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research, a study by Public Health Institute’s Child Health and Development Studies (CHDS) and the University of California at Davis showed that the higher levels of DDT a grandmother had in her blood during pregnancy, the higher likelihood that her granddaughter would be overweight and have early onset menstruation.
Both obesity and an early start to menstruation are risk factors for developing breast cancer and diseases like diabetes and high blood pressure.
DDT, developed in the 1940s to combat insect-born diseases like malaria and typhus, was banned in the United States in 1972 and is a known endocrine disrupter, interfering with hormones and development.
The CHDS study on DDT exposure in pregnant women began in 1959, collecting blood samples from 20,000 expectant mothers in the San Francisco Bay Area during the 60s, a time of heavy DDT use.
Researchers were able to contact a number of the children of those women, now in their 50s, and their own daughters now in their 20s.
According to the article, this was to “examine associations of environmental chemical levels with health outcomes in 3 generations: founding generation of women exposed during pregnancy, the offspring generation exposed in utero during development, and the grandchild generation exposed in the egg.”
New information was collected during phone interviews and in-home visits with 365 granddaughters of the original participants to measure their body mass index, or BMI, and time of first menstruation.
The third generation in the study is currently too young to assess occurrences of breast cancer, although previous studies have linked DDT exposure to breast cancer development in the second generation.
The researchers said that BMI rose across the three generations while the age when menstruation started fell, consistent with international patterns.
However, when they factored in DDT levels in the grandmothers’ blood during pregnancy, they found that the granddaughters were two to three times more likely to be obese and two times as likely to menstruate before age 11, “presenting a consistent pattern of associations that support the concept that in egg exposure to o,p’-DDT has potential for altering risk of breast cancer across generations.”
According to the article, this means that DDT exposure while pregnant reached not only the fetus, but the ovarian follicles inside the fetus, which end up as eggs and eventual granddaughters.
“We already know that it’s nearly impossible to avoid exposures to many common environmental chemicals that are endocrine disruptors. Now our study shows for the first time in people that environmental chemicals like DDT may also pose health threats to our grandchildren,” said Barbara Cohn, director of CHDS and senior author of the study, in a statement.
Cohn added, “In combination with our ongoing studies of DDT effects in the grandmother’s and mother’s generations, our work suggests we should take precautionary action on the use of other endocrine disrupting chemicals, given their potential to affect generations to come in ways we cannot anticipate today.”