Key points:
- A recent study in animals found exposure to multiple different toxicants across generations can amplify health problems.
- Rats bred out to a fifth unexposed generation still had a significantly increased incidence of obesity, kidney and prostate diseases—as much as 70%.
- The work is part of a project to identify epigenetic biomarkers for inherited health conditions, including obesity, autism and pre-term birth.
As perhaps one of the most well-known insecticides, DDT gets a lot of attention for its negative effects, and ultimate banning in 1972. But DDT is not the only toxicant humans have been exposed to. DDT may not have persisted beyond 1972, but it lived on in previous generations, while new toxicants arose in newer generations.
And now, researchers at Washington State University have found evidence that multiple toxicant exposures of past human generations likely had a compounded impact on grandchildren and great-grandchildren.
In a new study, published in Environmental Epigenetics, researchers exposed an initial generation of pregnant rats to a common fungicide, then their progeny to jet fuel and the following generation to DDT. When those rats were then bred out to a fifth unexposed generation, the incidence of obesity as well as kidney and prostate diseases was compounded—rising by as much as 70%.
“We looked at multiple-generation exposures because these types of things are going on routinely, and previous research has only looked at single exposures,” said Michael Skinner, a WSU biology professor and the study’s corresponding author. “We found that if multiple generations get different exposures, then eventually there’s an amplification or compounded effect on some diseases.”
Skinner and his colleagues also conducted epigenetic analysis of each generation of the animals, finding that the toxicant exposures shifted their entire epigenetics dramatically. Along with changes to genes themselves, inherited epigenetics which influence gene expression, are considered to have a significant impact on evolution.
“When we made the comparisons with different generations, we did not find a lot of overlap in epigenetics. In other words, every time each generation had a new exposure, it appeared to reprogram the whole epigenome,” Skinner said.
While the study does not exactly mimic what may have happened to human generations, people in the U.S. have potentially been exposed to these particular toxicants at different times. The authors note a likely sequential exposure over human generations might involve an exposure to DDT, which was widely used in the 1950s, then plastics in the 1970s, followed by many modern herbicides still in use today.
This new study is part of work Skinner’s lab is doing to identify epigenetic biomarkers for inherited health conditions, including obesity, autism and pre-term birth.
“We need to know to what degree our past generations activities that have affected us,” Skinner said. “We cannot fix problem, but it's important to know that it happened so that we can try to better treat potential health problems through preventative medicine.”