Researchers have found that the children of mothers whose water supplies were contaminated with arsenic during their pregnancies harboured gene expression changes that may lead to cancer and other diseases as they grow.
Even when water supplies are cleaned up and the children never experience any direct exposure to the pollutant they may suffer lasting damage.
The study was conducted on 32 mothers and their children in a province of Thailand that experienced heavy arsenic contamination from tin mining.
The team led by Mathuros Ruchirawat, Director of the Laboratory of Environmental Toxicology of the Chulabhorn Research Institute (CRI) in Thailand, Leona D. Samson, Director of MIT's Center for Environmental Health Sciences (CEHS) and Rebecca C. Fry, a research scientist analysed blood that had been collected from umbilical cords at birth.
The exposure of mothers to arsenic during their pregnancy was independently determined by analysing toenail clippings - the most reliable way of detecting past arsenic exposure.
About 450 genes whose expression had been turned on or turned off in babies exposed to arsenic while in the womb were analysed.
They found these genes had either become significantly more active (in most cases) or less active than in unexposed babies.
The first author of the study Rebecca C. Fry said that the change in gene expression found in the exposed children are mostly, which can lead to increased cancer risk.
It's not yet clear how long the changes may last.
"We will be testing whether these gene expression changes have persisted in these children," Fry said.
This is the first time such a response to prenatal arsenic exposure has been found in humans.
"But it is not entirely unexpected, Samson explains, because "in mice, when mothers are transiently exposed to arsenic in the drinking water, their progeny, in their adult life, are much more cancer-prone," Samson added.
The research also studied the possible ways of reversing or mitigating the damage, through dietary changes, nutritional supplements, or drug treatments to counteract the gene expression changes.