The study, led by Joel Kline, M.D., professor of internal medicine in the UI Roy J. and Lucille A. Carver College of Medicine, appears in the June issue of Chest, the peer-reviewed journal of the American College of Chest Physicians (www.chestjournal.org).
"Previous research has shown increased rates of asthma among children living in rural areas of Iowa and the United States," said Kline, who also is deputy director of the Environmental Health Sciences Research Center (EHSRC) in the UI College of Public Health, which helped fund the study. "Given that CAFOs release inflammatory substances that can affect the health of workers at these facilities and the air quality of nearby communities, we were interested in whether there was a connection between CAFOs and increased rates of asthma among kids in rural areas."
Researchers surveyed the parents of kindergarten through fifth-grade students attending two Iowa elementary schools to compare the prevalence of asthma among students. The "study" school was located a half-mile from a CAFO in northeast Iowa; the "control" school was in east-central Iowa, more than 10 miles away from any CAFO (generally classified as a livestock facility that houses more than 3,500 animals). Sixty-one participants responded from the study school, and 248 participants responded from the control school.
Study results indicated a significant difference in the prevalence of physician-diagnosed asthma between the two schools: 12 children (19.7 percent) from the study school located near a CAFO and 18 children (7.3 percent) from the control school. The overall rate of physician-diagnosed asthma reported for Iowa is around 6.7 percent, the study authors noted.
Using the broadest definition of asthma (physician diagnosis, asthma-like symptoms or asthma medication use) the prevalence rate was 24.6 percent at the study school, compared to 11.7 percent at the control school.
Although results showed that children in the study school located near a CAFO were more likely to have a parent who smoked, which is a risk factor for asthma, the significance of parental smoking diminished when analyzed with other variables such as pet ownership, age and residence in a rural area or on a farm.
Kline stressed caution in considering the study results showing the difference in asthma diagnoses between the two schools. "Since different physicians were diagnosing asthma among the two groups, it's possible that one group may have been more or less likely to receive an asthma diagnosis for similar symptoms," he said.
What the study suggests, he added, is more research on the health effects of CAFOs.
"This is such a trigger issue in Iowa and other agricultural states, so we need to look at these results with caution," Kline said. "More study is needed on the effect of these environments on the community, not just on workers at these facilities or people who are more directly exposed."