As the father of four grown children, Guillette was always concerned about the implications of endocrine disrupters for children. But as a zoologist he just couldn't envision studying actual human effects by himself.
In this case, a suitable collaborator was already close at hand. Guillette's wife, Elizabeth, a medical anthropologist at UF, was able to identify a perfect natural laboratory in and around the Yaqui Valley of northwestern Mexico. There she found two groups of people, located about 50 miles apart, who were demographically near-identical except for their exposure to pesticides.
The Sonoran Mayan people of the valley split philosophically over the use of pesticides and other modern agricultural techniques during the country's Green Revolution of the 1940s and '50s. Residents who remained in the valley embraced pesticides, herbicides, and other agricultural chemicals, while the other group moved to the foothills and stuck to organic farming.
Aside from that one difference, says Elizabeth Guillette, "these groups were the same in every respect—culturally, genetically, and socioeconomically. They had the same diet, the same child-rearing practices, and the same school system."
But when she asked children from the two communities to perform simple play activities, like catching a ball or drawing stick figures, "the kids who had been exposed to pesticides lagged far behind."
Follow-up studies that Elizabeth Guillette published with her husband and several other collaborators in Environmental Health Perspectives in 2006 showed that daughters born to women who were exposed to pesticides had significantly less mammary tissue than their counterparts in the foothills.
Lou Guillette says that private agencies have translated the research results into Spanish and have done extensive outreach in the area to encourage residents to limit their exposure to chemicals.