(Beyond Pesticides, February 10, 2009) Living near farms that use the weed killer atrazine increases the risk of a rare birth defect, according to a study presented February 5, 2010 at the annual meeting of the Society for Maternal-Fetal Medicine in Chicago.
Gastroschisis, a rare birth defect in which an infant’s intestines stick out of the body through a defect on one side of the umbilical cord, affects 1 in 5000 babies born in the U.S. each year. Babies with this condition have problems with movement and absorption in the gut, because the unprotected intestine is exposed to irritating amniotic fluid. Surgery is required to repair this defect. The rate of gastroschisis has risen 2- to 4-fold over the last three decades, especially in areas where agriculture is the primary industry, according to Sarah Waller, PhD, of the University of Washington, Seattle, and colleagues.
Dr. Waller’s team studied the potential link between atrazine and the birth defect because, as they note in their conference abstract, “During the last 10 years, the highest percentage per population of gastroschisis 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. The researchers looked at more than 4,400 birth certificates from 1987-2006 – including more than 800 cases of gastroschisis, and the U.S. Geological Survey databases of agricultural spraying between 2001 and 2006.
The researchers found that the closer a mother lived to a site of high surface water contamination with atrazine the more likely she was to deliver an infant with gastroschisis. The birth defect occurs more often among infants who live less than 15 miles from one of these sites, and it occurs more often among babies conceived between March and May, when agricultural pesticide use is common.
Dr. Waller’s group is not the first to report a link between gastroschisis-like birth defects and surface water atrazine levels. In 2007, Indiana researchers reported in the Journal of Pediatric Surgery that in their state, where rates of such birth defects are also very high, atrazine levels were significantly linked with the rate of gastroschisis and other defects. Another study, published last year in Acta Paediatrica, found similar results for the general rate of birth defects in the U.S. population. Atrazine, that study found, upped the risk of nine birth defects in babies born to mothers who conceived between April and July, when surface water levels of the pesticide are highest. Another study also found that atrazine triggers the release of stress hormones leading researchers to believe that this may explain how the popular weed killer produces some of its harmful reproductive effects.
As the most commonly detected pesticide in rivers, streams and wells, an estimated 76.4 million pounds of atrazine is applied in the U.S. annually. It has a tendency to persist in soils and move with water, making it a common water contaminant. Research found that intersex frogs are more common in suburban areas than agricultural areas. Another study suggests it as a possible cause for male infertility.
In October 2009, EPA announced that it will launch a new comprehensive evaluation of the pesticide atrazine to determine its effects on humans this fall. In EPA’s own words, “At the end of this process, the agency will decide whether to revise its current risk assessment of the pesticide and whether new restrictions are necessary to better protect public health.” Agency staff will evaluate the pesticide’s potential cancer and non-cancer effects on humans. Included in this new evaluation will be the most recent studies on atrazine and its potential association with birth defects, low birth weight, and premature births. The decision to review atrazine follows recent scrutiny and findings that the current EPA regulation of atrazine in water is inadequate.