Children are active, curious, and unpredictable, which made it difficult for scientists to accurately assess their exposure to agricultural pesticides until a University of Washington research team developed a tracking system built right into the children's clothes.

They developed wearable global positioning system (GPS) sensors that allow researchers to track the time children spend in pesticide-affected areas, particularly when aerial spraying takes place near their homes and playgrounds.

In farming communities, homes and playgrounds are often located near where crops are sprayed. Some crops, such as potatoes, are sprayed with crop-dusting aircraft, which lay down an aerial cloud that can drift, even on a calm day. Washington ranks second to Idaho in US potato production, making this an important exposure. Exposures to children are of concern because of the ways pesticides are believed to affect their growing bodies.

One problem with estimating children’s pesticide exposures has been the difficulty in tracking the time they spend in pesticide-affected areas. Wearable GPS sensors may provide a practical research tool for time-location analysis.

TIME-LOCATION ANALYSIS

The time-location analysis project began in 1999 when graduate student Kai Elgethun came to work with Professors Rich Fenske and Mike Yost in the Pacific Northwest Agricultural Safety and Health Center. Part of his funding came from the Center for Children’s Environmental Health Risks Research, which investigates the risks to children from exposure to agricultural pesticides. Elgethun had worked with Allan Felsot, an environmental toxicologist with Washington State University’s Tri-Cities campus in Richland, who has become a project collaborator.

In this photo, a girl leaves her house (far right), and walks ot the playground (left) where she plays. The long white building is a potato storage shed. Courtesy of Kai Elgethun

Elgethun brought with him a fascination for maps and spatial relationships. “Maps provide a tangible way for a lay person to understand what’s going on,” he said, making them an important tool in risk communication. His arrival coincided with improvements in GPS technology that allowed more precise monitoring of location. Children could now be tracked to within three meters, which can show whether they are indoors or out, or in the yard or playground. Velocity can also be calculated from GPS, showing whether a child is on foot, riding a bike, or traveling in a car. Differences in velocity on foot could indicate differences in breathing rate, adding another layer of exposure data.

GPS AND GIS

The global positioning system can track a child’s movements, which can be overlaid on a Geographic Information System (GIS) map. Concentrations of pollutants can also be overlaid, and can be synchronized with the time a child was in the area. Local weather conditions can be factored in to predict the fate and transport of the pollutant.

In theory, all of this should work well together. In reality, it wasn’t easy to design a wearable GPS transmitter that would be acceptable to finicky kids. Researchers became clothing designers, sewing radio transmitters into vests and overalls. The fashions were first tested with children of faculty and staff. Bib overalls were “a big failure,” Elgethun recalls. Boys liked the vests better, but girls would wear them only if they could decorate them with stickers of butterflies and stars.

Then the researchers faced technical challenges in positioning the antennae correctly across a child’s shoulders and finding vests that were breathable enough to wear in summer in Eastern Washington.

FINDINGS

Once those hurdles were overcome, the vests provided useful information. More than 50 children were tested. They spent time at the neighborhood playground, which prompted researchers to test for pesticide on the playground equipment (they found some residues). They didn’t find pesticides in the houses, meaning that it was safe to keep kids indoors during spraying.

One surprise was how many times during the day kids go in and out of the house. “Only GPS could capture that,” Elgethun said, because questionnaires just can’t capture the “erratic, unpredictable behavior” of children.

Researchers found that pesticide drift was minimal immediately after spraying. A surprising finding was volatilization from the midday sun. This was the first time this phenomenon had been evaluated in a human exposure study.

The types of pesticides used on potatoes break down quickly in the environment, so exposures are of concern only for a few days. The farmers had applied the pesticides correctly, Elgethun said, and by following simple recommendations, parents can protect their children from exposure.

RECOMMENDATIONS

• Keep children inside during aerial spraying
• Keep the windows shut (air conditioning is effective)
• Turn the air conditioner to “recirculate” mode
• Bring the kids inside if the weather warms up later in the day after spraying

FOR FURTHER READING

Elgethun K, Fenske RA, Yost MG, Palcisko GJ. “Time-location analysis for exposure assessment studies of children using a novel global positioning system instrument,” Environmental Health Perspectives 111(1):115, January 2003.

Kai Elgethun shows a child the GPS readings from his vest. Kathy Sauber

Washington is the nation's second largest potato growing state. USDA ARS