Chemicals can turn genes on and off; new tests needed, scientists say.

A National Academies workshop examined the evidence of epigenetic effects and considered whether the thousands of chemicals in use today should be tested for them. Some pollutants and chemicals don't kill cells or mutate DNA. Instead, they may be more subtle, muting genes or turning them on at the wrong time, which can lead to diseases that are passed on for generations. Asthma in New York City children exposed to traffic exhaust is an example, experts say.

By Bette Hileman
Environmental Health News

Each of us starts life with a particular set of genes, 20,000 to 25,000 of them. Now scientists are amassing a growing body of evidence that pollutants and chemicals might be altering those genes—not by mutating them, but by sending subtle signals that silence them or switch them on at the wrong times.

Last week, several dozen researchers and experts convened by the National Academies tackled this complicated topic, called epigenetics, at a two-day workshop in Washington, D.C. They discussed new findings that suggest chemicals in our environment and in our food can alter genes, leaving people vulnerable to a variety of diseases and disorders, including diabetes, asthma, cancer and obesity. They also considered whether regulatory agencies and industry should start testing the thousands of chemicals in use today for these effects.

“There is little doubt these epigenetic effects are important. The next question is how we test for effects," said William H. Farland, professor of environmental and radiological health sciences at Colorado State University. "We don’t need to abandon current approaches to chemical testing. When testing chemicals in animals, we may just need to add some new endpoints."

Exposure to gene-altering substances, particularly in the womb and shortly after birth, “can lead to increased susceptibility to disease,” said Linda S. Birnbaum, who was named director of the National Institute of Environmental Health Sciences and of the National Toxicology Program in December. “The susceptibility persists long after the exposure is gone, even decades later. Glands, organs, and systems can be permanently altered.”


Animal studies indicate that some environmental chemicals cause epigenetic changes that trigger breast and prostate cancer, obesity, diabetes, heart disease, asthma, Alzheimer’s, Parkinson’s disease and learning disabilities, she said. And some new human studies are now adding to the evidence.

“There is a huge potential impact from these exposures, partly because the changes may be inherited across generations. You may be affected by what your mother and “There is a huge potential impact from these exposures, partly because the changes may be inherited across generations. You may be affected by what your mother and grandmother were exposed to during pregnancy.” Linda Birnbaum, Director, National Institute of Environmental Health Sciences
grandmother were exposed to during pregnancy,” Birnbaum said

What a pregnant mother eats and the chemicals she is exposed to can affect her offspring without causing mutations in the DNA, the experts said. Instead, such exposures can disrupt the way that genes behave, according to both animal and human studies. These changes, in turn, can be passed on to the next generations.

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