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 spray their fields with the herbicide. They also found that birth defects peaked during the same months indicating a close correlation. Read more.