More and More Boys Born With Deformed Genitals -- What's to Blame?

A third problem is what some scientists have coined the "cocktail effect," which postulates that individual chemicals are often not nearly as dangerous as a combination of chemicals. Studies are being conducted on the effects of various chemicals when found together, pointing to a further complication in what is already a complex, and at times confounding, science. Some researchers fear we not only carry many EDCs in our bodies, but we are exposed to new ones almost daily through our food, personal products, water and even air.

Epigenetics
One bright light at the end of the tunnel is a discovery in the field of genetics. In the past 10 years, scientists have demonstrated that epigenetic switches and markers that lie along the length of the double helix of a cell can be "dimmed" or turned off — and on. Unlike the chromosomes that make up 50 percent of our DNA, these protein molecules carry the epigenetic marks and information that regulate how a gene expresses itself.

Randy Jirtle, a professor of radiation oncology at Duke University, was one of the first researchers to delve into this realm. In a study with postdoctoral student Robert Waterland published in 2003, Jirtle found that when pregnant mice carrying the agouti gene (that made them more prone to cancer and diabetes, as well as ravenous and yellow) were fed a diet rich in methyl donors (small chemical clusters that can attach to a gene and turn it off), their offspring were slender, brown and not susceptible to cancer or diabetes. Chemical clusters in the methyl donors are found in many foods, including onions, garlic and beets, and in food supplements often given to pregnant women.

DNA methylation is important because it involves adding a methyl group to particular bases in the DNA sequence that can interfere with chemical signals, effectively silencing the gene.

Since that study, scientists have been able to show that the epigenome is sensitive to many environmental factors, including exposure to toxins and even behavioral factors such as nurturing — and that changes in genes can be passed from one generation to the next, without a change in the gene sequence.

Jirtle exhibited the patience and communication skills inherent in a good teacher in a recent interview with Miller-McCune. He described the difference between the genome and epigenome in this way: "I always think of the genome as comparable to the hardware of your computer and the epigenome as the software that tells that computer when, where and how to work. That's why you can have one set of genetic information in your cell, but you'll have some cells that give rise to skin cells, liver cells, eye cells. That's because they're programmed differently. It's the same thing as the same computer running Word, Excel and Photoshop."

In the case of the agouti mice, methylation was reversed, altering the epigenome without changing the DNA. Thus, Jirtle and Waterland were able to demonstrate that genetic alteration can occur through programming of the epigenome. In a more recent study Jirtle and others showed that bisphenol-A in mice caused DNA methylation, which altered the epigenome. As interesting, and obviously, promising, is the finding that these epigenetic switches can be reversed, in the case of these mice, by dietary supplements.

Jirtle said recent breakthroughs in the mapping of the epigenome (which is different for each species) will play a role in determining what EDCs might be affecting species and when. "The problem with altering these programs very early is that every cell in your body now has that inappropriate information," he said, "so they're altering the programming, which can increase susceptibility to cancer, neurological disorders, the kinds of things potentially that are being seen in these deer (referring to Hoy's findings). All of that stuff could be happening because you're altering the programming by these endocrine-disrupting agents."

He said recent findings in epigenetics will likely bring the studies of toxicology and genetics closer together, adding that to date "the focus at the National Toxicology Program has been on whether a compound causes mutations to the genome - changing the computer rather than altering the software." He said it's important that scientists research epigenetic change, which he believes is linked to susceptibility to many diseases that researchers have assumed are the result of genome mutation.