Field Research
North Dakota researchers are exploring
whether exposure to pesticides
affects
children's learning and development
Jan Gunderson had good reason to suspect that the chemicals farmers sprayed on their fields might make children more prone to learning disabilities. Having worked as a librarian and teacher in Northwood in rural, eastern North Dakota, she noticed an increasing number of children diagnosed with conditions such as dyslexia, central auditory processing disorder, attention deficit disorder and hyperactivity during her nine years with the school district.
“When we would go to conferences, they would say that the average in the nation [of children diagnosed with such disorders] was less than 10 percent. In our district, we were up to 15 percent, and you wondered why,” she says.
That wasn’t the only reason Gunderson suspected a possible connection between pesticide exposure and brain development. Her own son, now 16, was diagnosed when he was 9 with central auditory processing disorder, an inability to discriminate, recognize, or comprehend what is heard even though hearing and intelligence are normal.
“At the time he was an infant, we were living on farmland,” says Gunderson, who is now circulation manager for the library at the UND School of Medicine and Health Sciences in Grand Forks.
Stories such as Gunderson’s inspired a team of researchers from across the university to discuss the need to study the possible connections between health and pesticide exposure. Among that group are Patricia Moulton, Ph.D., (B.S. ’97, M.A. ’99, Ph.D. ’02), an assistant professor in the School of Medicine and Health Sciences Center for Rural Health, and Tom Petros, Ph.D., a professor of psychology.
After searching the literature, they were surprised at how little research had been done on pesticide exposure and development. A number of correlations were drawn, Petros says. “They speculate that an increase in developmental disorders over the last couple of decades is in some degree due to pesticides.” But there was little that offered concrete evidence.
The two researchers decided to design their own study to determine if there is a connection.
A Ready-Made Sample
Families such as the Gundersons, who live in the Red River Valley area of eastern North Dakota and western Minnesota, are in a unique position to help scientists tease out possible connections between the chemicals in pesticides and health and development. Farming is the No. 1 occupation in the area, and in order to increase their yields, farmers use a variety of insecticides, herbicides, and fungicides.
With that in mind, Moulton and Petros applied for and received a two-year, $100,000 grant from the National Institute of Environmental Health Sciences. Their plan was to obtain measures of (or biomarkers for) pesticide exposure in blood and urine of area children and compare those results with cognitive test results.
During the summers of 2003 and 2004, the researchers tested 128 Red River Valley children between the ages of 7 and 12 years—ages when exposure to chemicals poses a great risk to brain development.
“Any alterations in these processes can lead to deficits in cognitive and motor capabilities,” Moulton says.
Half of the children tested lived at least a mile from a farm or active agricultural field; the other half, which included Gunderson’s daughter, Abby, now 13, who has no academic difficulties, lived on or next to a farm. (Gunderson says their current home in Thompson, ND, about 10 miles south of Grand Forks, is surrounded on three sides by farmland that is sprayed with pesticides.) The researchers tested blood and urine samples from each of the children for 18 pesticides, and for elevated cholinesterase levels, another marker for pesticide exposure.
The children were then given tests of intelligence, reading, and
listening comprehension, and memory and attention, as well as tests that measured simple reaction time, choice reaction time, and tracking of a target on a computer screen. In addition, the parents were given intelligence quotient (IQ) tests and evaluated for socioeconomic status.
A Small-but-Significant Difference
Although Moulton and Petros are still comparing the data about the type and amount of chemicals present in the children’s blood and urine from the Centers for Disease Control and Prevention, they have made one discovery: that the kids living on or near a farm scored an average of five points lower on IQ tests than the
children who did not.
“The IQ scores were still in the normal range, but there was a significant difference,” Petros says. He adds that even when correcting for the IQ and socioeconomic status of the parents, the differences remained.
The researchers expect to have their final results this summer.
Gunderson, who is careful about not running the air conditioning and keeping pets inside when the neighbors are crop-dusting, hopes the study will start to explain why so many children in the area, including her son, have been diagnosed with learning disabilities. “I can’t go back in time and take away that disability,” she says. “But if I can, I’d like to prevent another parent from having to fight the battles we’ve had to fight.”
This article by Kim Kiser originally appeared in the
March 2006 issue of Minnesota Medicine.
© 2006 Minnesota Medical Association.
It is reprinted in North Dakota Medicine and www.ndmedicine.org
with permission.
return to top
|
