Vol. 4, No. 3, 1998 Page 1&4


Learning disabilities, while common in the general population, are almost epidemic among delinquents and criminals. Up to three-fourths of delinquents have learning disabilities, and up to a third of teenagers with learning disabilities will be arrested within five years after leaving school.

That's why new research by Elizabeth Guillette and colleagues is intriguing researchers interested in the roots of criminality. Guillette et al., studying Yaqui Indians in Northern Mexico, report a stunning link between pesticide exposure (at levels possibly comparable to agricultural areas in the U.S.) and motor and mental problems similar to those seen in children with learning disabilities.

The researchers studied Yaqui four- and five-year-olds living in two different regions: lowland agricultural areas, in which fields are sprayed up to 45 times per crop and two crops are grown per year; and foothills, where virtually no pesticides are used. The Yaquis were selected, the researchers say, to eliminate many possible confounding factors. The two groups of study subjects are genetically and culturally similar, and have similar diets and standards of living.

The researchers evaluated 33 children from high-pesticide agricultural areas, and 17 control subjects from the foothills. They report that "the exposed children demonstrated decreases in stamina, gross and fine eye-hand coordination, 30-minute memory, and the ability to draw a person." Differences in drawing ability were particularly startling: four-year-olds from the foothills, for instance, were able to draw stick figures with correct features, while pesticide-exposed four-year-olds drew meaningless scribbles. This suggests, the researchers say, "a breakdown between visual sensory input and neuromuscular output, as found with brain dysfunction."

Similarly, Guillette et al. say, the pesticide-exposed children's poor hand-eye coordination could indicate brain dysfunction. In addition, the researchers say, "The inability to remember a meaningful statement after 30 minutes has implications for school performance and performance in social activity."

Although the researchers did not specifically study behavior, they note that foothills children often played in groups, participating in games, pretend parties for dolls, and similar activities. The valley children, on the other hand, "appeared less creative in their play; they roamed the area aimlessly or swam in irrigation canals with minimal group interaction."

Equally striking was the difference in aggressive behavior: the valley children hit their siblings, and became aggressive when corrected by their parents. "These aggressive behaviors," Guillette et al. say, "were not noted in the foothills." In a personal communication, Guillette noted, "Overall, disruptive behavior was the norm with exposed children."

Neurotoxicologist David Carpenter, commenting on the study in a Science News article, said, "I know of no other study that has looked at neurobehavioral impacts-cognition, memory, motor ability-in children exposed to pesticides." He notes that the study's implications are "horrendous," because the level of impairment shown in the pesticide-exposed children "is incredible-and may prove irreversible."


"An anthropological approach to the evaluation of preschool children exposed to pesticides in Mexico," Elizabeth A. Guillette, Maria Mercedes Meza, Maria Guadalupe Aquilar, Alma Delia Soto, and Idalia Enedina Garcia, Environmental Health Perspectives, Vol. 106, No. 6, June 1998, pp. 347-353. Address: E. A. Guillette, 32 SW 43rd Terrace, Gainesville, FL 32607.


"Picturing pesticides' impacts on kids," J. Raloff, Science News, Vol. 153, June 6, 1998.

Related Articles: [1998, Vol. 4] [2000, Vol. 6] [2005, Vol. 11]

Return to:
[Author Directory] [Front Page] [Issue Index] [Subject Index] [Title Index]