“That is a profound observation,” Benninghoff said.
Third generation female rats also showed an increase in ovarian disease, which is consistent with previous studies.
For male rats, kidney disease was significantly higher in the third generation rats whose ancestors were exposed to dioxin, the first time such a finding has been reported. Twenty-seven percent of the third generation male rats had signs of kidney damage, compared to about 9 percent of the control group.
Third generation female rats also had a higher incidence of multiple diseases or abnormalities per rat.
Complicating matters, the rats directly exposed to dioxin had different disease profiles than later generations, so “one cannot necessarily predict possible disease outcomes in future generations by observing individuals that were directly exposed,” Benninghoff said.
Sperm from the great-grandkids – the first generation without direct dioxin exposure – had telltale modifications in gene expression in 50 regions of DNA as a result of their ancestors’ dioxin exposure, Skinner said. These regions can be used as “biomarkers for ancestral exposures and disease,” he said. That means researchers could use these regions as a road map to trace dioxin exposure through generations.
The study focused on TCDD, but Skinner speculated that all dioxins would behave the same way, but that remains to be studied.
Other environmental chemicals also have transgenerational effects in lab animals, including BPA, phthalates, the pesticides permethrins, vinclozolin and methoxychlor and the insect repellent DEET.
The American Chemistry Council, which represents chemical companies, did not return a request for comment.
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.