Researchers at Washington State University say the pesticide DDT makes the grandchildren of exposed people more susceptible to weight gain. While many people have a genetic predisposition to obesity, new research suggests that the use of a controversial pesticide may make us more susceptible to it, as well as other diseases. Michael Skinner, founder of the Center for Reproductive Biology at Washington State University, says widespread exposure to the pesticide dichlorodiphenyltrichloroethane (DDT) in the 1950s continues to affect the health of humans today. Previous research has linked DDT to increased rates of diabetes, developmental problems, reproductive harm, miscarriages, and certain cancers. In the 1970s, it was also shown to have impacted bald eagle and peregrine falcon populations.

Studying the Effects of DDT Generations Later In a new study published in the journal BMC Medicine, Skinner tested how exposure to DDT affected pregnant rats. But while the rates of obesity showed no difference in the first or second generations of rat offspring, in the third generation half of the rats were obese. “Interestingly, in the first generation, we didn’t see any obesity. We saw many diseases, but not obesity. It took three generations to ramp up,” Skinner said. “What this ancestral exposure does is increase a person’s susceptibility for obesity. This is probably the case with most diseases.” The process is called transgenerational epigenetic inheritance. While DDT doesn’t mutate genes, exposure to it during key points in development—namely when sex organs are forming in the womb—can affect which genes are expressed. “This doesn’t promote the disease, but it increases the susceptibility to develop a disease,” Skinner said. During the 1950s, the U.S. obesity rate was below three percent. Now, more than one third of Americans are considered obese, according to the U.S. Centers for Disease Control and Prevention .

The Upside of Epigenetic Inheritance Trangenerational epigenetic inheritance essentially means that what our grandparents were exposed to during their lifetimes can affect us today. Knowing how this mechanism works, Skinner says, means that looking at epigenetic biomarkers early in a person’s life can help determine what diseases they might face later. “That’s call preventative medicine,” Skinner said. “We’ve never been able to do preventative medicine in the past because we’ve never had these kinds of biomarkers.” Previously, Skinner’s lab tested the epigenetic effects of other environmental toxins, including plastics, fungicides, and other pesticides besides DDT. “The reason we did this one was because around four years ago the World Health Organization and the Gates Foundation pushed to remove the ban on DDT so they could use it for malaria treatment, mainly in Africa,” he said.