(Beyond Pesticides, December 6, 2010) A new study finds that exposure to dioxin in the womb can affect female reproduction for generations, reducing fertility and increasing the chance for premature delivery. Scientists from the Women’s Reproductive Health Research Center at Vanderbilt University School of Medicine examined the effects of a specific variety of dioxin on female mice and found that subsequent generations of the mice exposed to dioxin are at risk. The study, entitled â€śDevelopmental exposure to TCDD reduces fertility and negatively affects pregnancy outcomes across multiple generations,â€ť was published in the journal Reproductive Toxicology.
Dioxin refers to a family of chemicals linked to cancer, endocrine disruption, weakened immune systems and reproductive problems. They are persistent organic pollutants that bioaccumulate in humans and other animals, especially in fatty tissue, meaning that concentrations of dioxin in the body generally increase with age. So, even in very low doses, dioxins can cause health problems.
Scientists in this study specifically looked at the variety of dioxin that is considered the most toxic, known as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD is a well-known contaminant of the herbicide 2,4-D, which was originally a part of the deadly chemical weapon Agent Orange. As such, TCDD is still found in soil samples from Central Vietnam in levels that are 200 times what is considered â€śacceptable” to the U.S. Environmental Protection Agency (EPA).
The mice in the study were exposed either once, twice or three times to 10 micrograms of TCDD per kilogram (10 parts per billion). The fertility rates of these mice and their offspring were compared to that of unexposed mice. For the single exposure, pregnant female mice were fed the chemical on day 15.5 of pregnancy to expose the fetus. For animals treated twice, some of the females that were exposed in the womb were fed the chemical right before puberty at four weeks. For mice that were exposed three times, the females exposed in the womb and at four weeks were also fed the chemical at nine weeks, or right after puberty. Researchers then mated the exposed females at 10-12 weeks with normal male mice. If the females became pregnant, some of their female offspring were bred with normal males at age 10-12 weeks. This was repeated for four generations.
Researchers found that mice exposed to 10 micrograms per kilogram of TCDD while in the womb had reduced fertility rates. Only 44% of these mice were able to get pregnant and many of the pregnancies that did come to term were prematurely delivered with a high mortality rate. This pattern was repeated in subsequent generations (the â€śgranddaughterâ€ť and â€śgreat-granddaughterâ€ť mice, if you will).
Not surprisingly, results were much bleaker for those mice that were exposed twice or three times. Only about 66% of the mice that were exposed twice became pregnant and only 29% of their female offspring could conceive, with effects repeating for three more generations. None of the mice that were exposed three times could conceive, compared to all of the unexposed control mice reproductive outcomes.
Source: Environmental Health News