Professor James Leckie

The Stanford Challenge

It may seem obvious that pregnant women and children are the most vulnerable to the health effects of toxins. But until recently, exposure to toxic substances such as pesticides was chiefly studied in only one subject group: adult males. Professor James O. Leckie set out to change that.

An environmental chemistry scholar who has focused on contaminants in groundwater, Leckie—a faculty member since 1970 and the C.L. Peck, Class of 1906, Professor of Environmental Engineering and Applied Earth Sciences,— became interested, through conversations with colleagues in pediatrics, in children's exposure to chemicals. Leckie and his colleagues talked about pesticide exposure among the children of California's farm laborers, and they wondered how much work had been done to understand it. Leckie reviewed the literature in the field and quickly realized that the study of children's exposure to toxins, especially through the skin, was very poorly developed. He also found that most studies had been conducted by public health specialists rather than engineers or chemists. Leckie decided it was time to apply engineering methods and math-based modeling to the field.

He began in 1994 with a small seed grant from the dean of research. Leckie's goal was to develop a mathematical tool that could be used to understand how children are exposed to chemicals. Eventually, this tool could run scenarios simulating the value of various kinds of interventions and could thus help policymakers create strategies to limit the risks to children.

But before he could make an accurate model, Leckie would need to incorporate data on how children interact with objects in the world around them. That was when he discovered that a huge stumbling block stood in his way. Child behavior scholars told Leckie that there was no source for the detailed information he needed about children's activity patterns—what they put in their mouths, what they touch, what they swallow, and how often they do so. "The data at the level we needed didn't exist," he says.

Leckie realized he'd have to gather much of the information himself. He was embarking on a project that would take him into the fields of child behavior and physiology as well as exposure modeling. His research got an unexpected boost in 1996, when the Environmental Protection Agency (EPA)—whose standard population for testing health effects of pesticides had been adult males—was required by the new Food Quality Protection Act to evaluate the effects of pesticides on children. From home insecticides to agricultural pesticides, a wide range of chemicals needed new study. The EPA awarded Leckie a $541,000 grant, and chemical companies added more funding. After completing a preliminary study, Leckie began a collaboration with public health scholars at the University of California, Berkeley, who had experience working with human subjects and taking samples of environmental toxins. The team gained National Institutes of Health and EPA funding to expand their work to 100 children.

For the project, families in California's Salinas Valley were recruited to participate in the four- to eight- hour-long sessions of "children doing whatever kids do," Leckie says. With undergraduate and master's students' help, Leckie videotaped the children in their normal settings—indoors, outdoors, in cars—and then transcribed the tapes' data on each body part's actions every second, inputting it into a software matrix. At the same time, his public health colleagues took environmental samples—from dust, air, and surfaces in children's homes— and collected "wipes" of children's hands. Leckie is combining the data from the videos with the samples and hand wipes gathered on-site to ensure the accuracy of the mathematical models he has developed to estimate chemical exposure.

Through these efforts, Leckie has gathered "a unique data set that only exists here," the basis for his model of children's exposure to toxins such as the banned pesticide DDT and organophosphates contained in flea bombs. The verdict is not in yet on the results, but ultimately, he hopes his work will help policymakers find ways to change chemicals' uses, reducing the risk of exposure to specific toxins.

Leckie says his research would never have taken place without the support of his first small grant—one similar to those now awarded by the Environmental Ventures Projects—and without Stanford's emphasis on multidisciplinary approaches. "The problems we face are so complex that no one team can solve them—you need multiple perspectives," he says. "Here at Stanford, early on, it was recognized that promoting collaborative work was important to our success in the field."