Dioxins, a group of chemical compounds, are environmental pollutants of the highest order--they’re present in industrial waste, accumulate in animal fatty tissue throughout the food chain, and can cause prostate cancer, respiratory cancers, type II diabetes, Hodgkin’s disease, non-Hodgkin’s lymphoma, Parkinson’s disease, and more. And as one recent study has shown, their insidious effects can possibly be passed on through the generations to the great-grandchildren of people who have been exposed.
The transgenerational effect with dioxin was first shown in a study by researchers at Vanderbilt University-- "Developmental dioxin exposure of either parent is associated with an increased risk of preterm birth in adult mice." In the study, the offspring of mice exposed to dioxin were shown to have reproductive problems. A study published this week in PLOS One,“Dioxin (TCDD) Induces Epigenetic Transgenerational Inheritance of Adult Onset Disease and Sperm Epimutations”,takes the research a step further, showing that the transgenerational effect effect extends to rats, and goes beyond reproductive issues.
The most recent study, which comes from researchers at Washington State University, exposed gestating female rats to dioxin and then tracked adult-onset disease in subsequent generations. The result: the F1 and F3 generations (the rats’ children and great-grandchildren, essentially) had higher incidences of disease, including polycystic ovarian syndrome in the F1 generation and kidney disease in the F3 generation.
"What this shows is that it’s not just the individual that’s directly exposed to dioxin," explains Michael Skinner, one of the authors of the study. "It’s a transgenerational phenomenon."
Government agencies have made efforts in recent years to cut down on human dioxin exposure, but contamination from industrial accidents that happened decades ago lives on because of the chemical compound’s long half life. One recent study suggested, for example, that breast cancer rates in the Great Lakes Bay Region are high because of dioxins leaked into the nearby Tittabawassee River in the 1930s through the 1970s. In some places, dioxin-filled seafood and meat is a concern--over 90% of human dioxin exposure comes from food.
This phenomenon--of toxic chemical effects being passed down through the generations--has been shown in several different environmental compounds, including some pesticides and plastics. The good news is that this most recent study might make it possible down the line to test humans for dioxin exposure in previous generations.
"There’s an epigenetic marker in sperm induced by dioxin. We can use this biomarker for [detection of] exposure.We might be able to in the future do an analysis to see if your ancestors were exposed to dioxin, and if so it might imply certain diseases that you’re susceptible to get as you get older," says Skinner.
In the future, Skinner and his colleagues hope to do tests on human populations with known exposure to dioxin. An accident in the 1970s at a chemical plant in Sevesin, Italy exposed the local population to dioxin; now, grandchildren of the originally exposed are being born. "There’s a potential for generational studies," says Skinner.