Common herbicide may increase risk of birth defect

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Exposure to a common herbicide may increase the risk of a rare congenital disorder, according to a new study.

Researchers at Baylor College of Medicine found that exposure to atrazine – the most commonly used herbicide in the U.S. – may be linked to an increased risk of choanal atresia.  Atrazine is typically used in corn crops.

Choanal atresia is a disorder where tissue forms and blocks the back of the nasal passage, affecting one or both sides of the nasal airway.  While rare, affecting approximately 1 in 7,000 infants, the condition can be serious because it can impede a baby’s ability to breathe.

Infants with choanal atresia blocking both sides of the airway may suffer breathing failure and require resuscitation on delivery. Doctors typically treat the condition through surgery to remove the obstruction.

Using the Texas Birth Defects Registry, researchers found women who lived in the counties with the highest levels of estimated atrazine application were 80 percent more likely to give birth to a child with choanal atresia or stenosis compared to those who lived in counties with the lowest levels. Choanal stenosis is a less severe form of the disorder.

While the researchers controlled for various socioeconomic and demographic factors, and found no impact on the risk observed, Lupo said areas with higher atrazine application do tend to share certain characteristics.

“If a county has a lot of acreage devoted to farming, and a lot of that acreage is corn crops, it is more likely to have higher atrazine application compared to a county with more urban areas and where corn isn’t grown,” Lupo said.  “…But not all rural counties are characterized by high atrazine application rates.”

Few risk factors for choanal atresia have been identified, but researchers believe chemicals that disrupt the mother’s endocrine system may play a role.

Atrazine is believed to be one of these so-called endocrine disrupters.

“One exposure that tipped in the direction [of atrazine] was maternal use of thyroid medications during pregnancy – there’s a hypothesis that hormones, and in particular, thyroid dysfunction, are related to choanal atresia risk,” Dr. Philip Lupo, an assistant professor in the department of pediatrics at Baylor College of Medicine, told FoxNews.com.  “We know through literature that atrazine is a suspected endocrine disruptor that alters endocrine activity and normal thyroid levels.”

Lupo said atrazine likely affects the endocrine system by mimicking certain hormones in the body, thus blocking their activity and upsetting normal biological processes.

However, while the study’s results were significant, Lupo said more independent studies would need to be done in other areas before making any new policy recommendations.

The study was published in the Journal of Pediatrics.