Each year, about 1 in 5,000 babies born in the U.S. suffers from a birth defect called gastroschisis, in which part of the intestines bulges through a separation in the belly. While still considered rare, this birth defect is on the rise. And researchers are particularly concerned about the high rates of gastroschnisis that occur in agricultural areas. According to a study presented at the annual meeting of the Society for Maternal-Fetal Medicine in Chicago, living near farms that use the weed killer atrazine may up the risk of gastroschisis considerably.

Over the last 30 years, the rate of gastroschisis has risen two- to four-fold. In Washington state, the highest percentage per population of gastroschisis over the last 10 years was in Yakima County, in the eastern part of the state, where agriculture is the primary industry.

Overall, Washington state has about double the national average of gastroschisis cases — an average of 43 cases per year.

In order to understand the reasons behind these increases, researchers at University of Washington, Seattle, analyzed over 4,400 birth certificates from 1987-2006 — including more than 800 cases of gastroschisis — and aU.S. Geological Survey databases of agricultural spraying between 2001 and 2006.

They found that the closer a mother lived to a site of high surface water contamination by atrazine, the more likely she was to deliver an infant with gastroschisis. The highest rates occurred whose mothers lived within 15 miles from one of these sites, and the condition was even more common among babies conceived between March and May, when agricultural spraying is at its peak.

In an interview with Reuters Health, Steven Goldsmith, a spokesperson for atrazine manufacturer Syngenta, disputed the credibility of the study stating, "Through thousands of studies, atrazine has been found again and again to not cause any variety of health effects, including those in this Washington study," Goldsmith said. "Use of atrazine in Washington state is the second lowest amount in the country, and in eastern Washington, so little is used that it barely appears in surface water."

But the University of Washington study was not the first to show a link between atrazine and gastroschisis-like birth defects. In 2007, an Indiana study published in the Journal of Pediatric Surgery found that high rates of these types of birth defects occurred in areas where high atrazine levels were present. Another study, published last year in Acta Paediatrica, found that atrazine increased the risk of nine birth defects in babies born to mothers whose last menstrual period was from April to July — that is, when surface water levels of the pesticide were highest. The U.S. Department of Health and Human Services' Agency for Toxic Substances and Disease Registry has also reported that high levels of the chemical have been shown to cause birth defects in animals.

Atrazine was banned in the European Union in 2004 because of its persistent groundwater contamination, but in the U.S. the chemical remains as persistent as ever. In 2003, the Natural Resources Defense Council asked the U.S. Environmental Protection Agency to restrict the use of atrazine in agriculture, citing numerous health threats. But the EPA declined, finding that the weed killer was not likely to cause cancer in humans.

According to the NRDC, the best ways for families to protect themselves from atrazine is to install a simple activated carbon-based water filter to filter the chemical from household drinking water.

The opinions expressed by MNN Bloggers and those providing comments are theirs alone, and do not reflect the opinions of MNN.com. While we have reviewed their content to make sure it complies with our Terms and Conditions, MNN is not responsible for the accuracy of any of their information.