Just last week, the US Centers for Disease Control and Prevention reported that roughly 90 percent of Americans carry pesticides in their bodies, the health risks of which are largely unknown.

In this latest study, both students and school employees were affected, and school pesticide use wasn't always to blame. In about 30 percent of the cases, pesticide drift from adjacent farmland was the source of the exposure.

'These Episodes Are Preventable'

"We looked at surveillance data from three surveillance systems for pesticide poisoning cases from pesticide exposure at school or from drift from neighboring farms, and found approximately 2,500 cases," said study co-author Dr. Geoffrey Calvert, a medical officer with the National Institute for Occupational Safety and Health in Cincinnati.

"Fortunately, most were low severity, such as skin rashes or eye irritation, but we don't want to see any illnesses occurring," he added. Plus, the authors noted that the actual incidence of pesticide-related illnesses may be even higher because some of the symptoms mimic other illnesses and may not be properly diagnosed.

Calvert and his colleagues advised schools to use integrated pest management techniques and try to reduce or eliminate pesticide drift from nearby farms, to reduce the amount of pesticide-related illnesses.

"Far too many cases of acute pesticide poisoning occur among schoolchildren each year. These episodes are preventable," said Dr. Philip Landrigan, director of the Center for Children's Health and the Environment, and the department of Community and Preventive Medicine at Mt. Sinai School of Medicine in New York City.

"Children are more susceptible to pesticide exposure because they breathe more air pound for pound than adults, they play on the floor, and they live about two feet off the floor, where pesticides linger, rather than five to six feet off the floor like adults," Landrigan added.

Pesticide Use at Schools

To gather the data for this study, the researchers used three national pesticide surveillance systems: the National Institute for Occupational Safety and Health's Sentinel Event Notification System for Occupational Risks (SENSOR), the California Department of Pesticide Regulation (CDPR) and the Toxic Exposure Surveillance System (TESS).

From 1998 to 2002, the researchers found 7.4 per million children and 27.3 per million full-time school employees had acute pesticide-related illnesses.

Most -- 89 percent -- of the 2,593 acute pesticide-related illnesses from school exposure were of low severity. That means, according to Calvert, that no medical intervention was necessary, and the illness, usually a skin rash or eye irritation, resolved on its own within a few hours.

Insecticides caused 35 percent of the illnesses, while disinfectants caused 32 percent. Calvert said that disinfectants were included if they contained antimicrobial properties. Thirteen percent of the illnesses were associated with repellants, and 11 percent with herbicides. The remaining 9 percent were attributed to other causes, such as rodenticides or fungicides.

Sixty-nine percent of the illnesses resulted from pesticide use at schools, while 31 percent was attributed to drift from nearby farmland.

Toxic Chemicals Should Be Last Resort

The authors recommended that schools adopt integrated pest-management techniques and create buffer zones between schools and farms, as well as take other measures to prevent drift.

"Pests can be effectively and economically controlled using integrated pest management," said Landrigan. "Schools need to operate on the premise that toxic chemicals are the last resort rather than the first resort. Don't reflexively reach for chemicals."

Calvert said that integrated pest management means that rather than routinely spraying for pests, schools should first attempt to prevent pest problems from occurring. That means keeping the kitchens clean and food in airtight containers, and sealing up any cracks and crevices where pests can enter the building.

"Only after you've taken those measures do you then treat for specific pests, but only using pesticides with the lowest toxicity, and only by someone well-trained in using pesticides," Calvert said.

Buffer Zones

To reduce the problem of drift requires cooperation and, ideally, pesticides should be sprayed on neighboring farms when children and employees aren't present at the school. Again, the pesticides should only be applied by well-trained personnel, Calvert said. Buffer zones between the school and the farm would also help.

"These episodes are occurring far too often, and that's really not acceptable. These episodes are preventable, and parents, educators, school boards and community officials need to take aggressive steps to reduce pesticide exposure," Landrigan said.

More information: The Environmental Protection Agency has more information about integrated pest management in schools.