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SUNDAY NOV 25, 2007 (Foodconsumer.org) -- Prenatal exposure to arsenic in contaminated water caused gene expression change that may lead to cancer and other disease later in life, according to Massachusetts Institute of technology researchers.
The MIT researchers developed a method for screening populations to detect signs of arsenic contamination, according to a report published in the Nov. 23 issue of PLoS Genetics (published by the Public Library of Science).
For the study, the researchers followed up 32 mothers and their children in a province of Thailand that experienced heavy arsenic contamination from tin mining.
Although the high levels encountered in the study were found in Thailand, similar levels of arsenic are also found in many other regions including the US Southwest, according to the study.
The study led by Mathuros Ruchirawat, the Chulabhorn Research Institute (CRI) in Thailand, and Leona D. Samson, professor of MIT and colleagues analyzed blood that had been collected from umbilical cords at birth. Motherís toenail clippings were also analyzed for arsenic exposure during their pregnancy.
In babies who were prenatally exposed to arsenic, a set of 450 genes had been turned on or off because of the exposure, meaning these genes were either more active or less active than those in babies whose mothers were not exposed.
"We were looking to see whether we could have figured out that these babies were exposed in utero" just by using the gene expression screening on the stored blood samples, Samson said. "The answer was a resounding yes."
The team said a set of 11 genes in the blood could be used to reliably determine whether babies had been born to mothers exposed to arsenic during pregnancy.
The researchers said the affected genes are mostly associated with inflammation, which can lead to increased risk of cancer.
It remains unclear, however, how long the effect of arsenic on the cancer risk would last or the risk could be modified by other factors. "We will be testing whether these gene expression changes have persisted in these children," Rebecca C. Fry, first author of the study and a research scientist at MIT.
Although this is the first time such a response to prenatal arsenic exposure has been found in humans, it is not entirely unexpected, Samson explained. This is so 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."