Environmentally-Caused Disease Crisis? Pesticide Damage to DNA Found 'Programmed' Into Future Generations
Aug. 16, 2018 11:09AM EST
When Dr. Paul Winchester, a pediatrician, moved to Indiana from Colorado in 2002, he noticed something disturbing—a high number of birth defects. "I was used to the number of birth defects I should see in a community hospital, and I saw many more in Indiana," said Winchester, who is medical director of the Neonatal and Intensive Care Unit at St. Francis Hospital in Indianapolis.
Winchester decided to investigate the reason for the higher numbers of birth defects. His research zeroed in on the herbicide atrazine, one of the most widely used herbicides in the U.S. and the most commonly detected pesticide in U.S. drinking water.
Winchester and several other researchers including Michael Skinner, professor of biology at Washington State University's Center for Reproductive Biology, conducted a study to see if there was a link between atrazine in drinking water and birth defects.
Studies have found that atrazine is an endocrine disruptor, a substance that can alter the human hormonal system. Atrazine was banned by the European Union because of its persistent groundwater contamination.
In their study, Winchester and his team found that concentrations of atrazine in drinking water were highest in May and June when farmers sprayed their fields with the herbicide. They also found that birth defects peaked during the same months indicating a close correlation.
"We plotted water concentrations and birth defects, and they fit like a hat," Winchester said.
Their study, which was funded by the Gerber Foundation, was published in 2017 on PLOS One.
Epigenetic Changes Programmed Into Future Generations
But the most disturbing finding was that atrazine had epigenetic effects. Epigenetics is the theory that environmental factors, such as diet, lifestyle choices and pesticides can impact the health of people who are exposed to them and also their descendants. Human DNA, according to epigenetics, is not unchangeable; it can be altered by such environmental factors. Epigenetic changes can be imprinted on the DNA of a fetus during pregnancy according to Winchester.
Epigenetics is a fairly new concept that is slowly gaining acceptance.
"This is a really important concept that is difficult to teach the public, and when I say the public I include my clinical colleagues," Winchester said.
For the atrazine study, Winchester's team used Skinner's advanced technology to detect epigenetic changes—and resulting negative health impacts—over several generations of rats whose mothers were exposed to atrazine.
Common sense would seem to dictate that fewer negative health outcomes would be seen with subsequent generations. But the study found the opposite: There were more abnormalities and diseases in later generations of rats. The first generation of rats whose mother was exposed to atrazine weighed less than a group of control rats. The second generation weighed less but also had incidences of testicular disease and breast cancer. The third generation suffered the most problems, according to Winchester.
"We waited until the third generation, where no direct exposure (to atrazine) occurred, to ask if these epigenetic effects could be inherited, because there is no mechanism, no exposure, no toxicity that could explain a change in disease rates in the third generation. We found that 50 percent of offspring had multiple diseases, emotional and physical problems, hyperactivity, abnormal sperm, and premature puberty."
In an earlier study, Skinner found that the fungicide vinclozolin also caused inheritable diseases in rats. In all, he tested nearly 20 chemicals and found that all produce epigenetic effects, said Winchester.
"The most alarming (finding) to me is that almost every chemical tested including atrazine reduced fertility in the third generation of offspring."
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