Effects of prenatal exposure to pesticides

Mar 9 2006

Children in Ecuador whose mothers were exposed to pesticides while pregnant had increased blood pressure and diminished ability to copy geometric figures as compared to a control group, according to an epidemiological study in the March issue of Pediatrics.

The results appear to be independent of current exposure to the chemicals. The mothers themselves were reported to be healthy.

A team of researchers led by Philippe Grandjean, adjunct professor in the Department of Environmental Health at HSPH, analyzed data on 72 children aged seven or eight years old in the rural Tabacundo-Cayambe area in Northern Ecuador. The children were examined by a physician and were given a battery of standardized tests for neurobehavioral functions. Thirty-seven of the children had mothers whose self-described occupational histories indicated that the women had been exposed to pesticides during pregnancy, typically by working in greenhouses. Dose-response relationships and the exact timing of the exposures' impact were not established due to the nature of the study design.

In the exposed children, the average systolic blood pressure was higher than in those who were unexposed (104.0 mm Hg versus 99.4 mm Hg). An increase in diastolic pressure was not statistically significant. Hypertension among children and adolescents is defined based on a range of blood pressures in healthy children, and children above the 95th percentile are considered hypertensive. In the Pediatrics study, nine children exceeded the approximate 95th percentile of 113 mm Hg. Seven of those children had prenatal pesticide exposure.

Prenatal pesticide exposure was also associated with a decreased ability to copy figures presented to the children as part of a standardized Stanford-Binet test. Adjusted regression analysis indicated that the exposed children experienced a developmental delay on this aptitude of four years. The authors noted that the confidence interval, or range of value, for this coefficient was relatively wide but was a statistically significant finding in a study of limited size, suggesting that the effect could be substantial.

In the part of Ecuador in which the children live, malnourishment is frequent. The authors used delayed growth, or stunting, to explore the role of nutrients in the study's results. Stunting is viewed as an indicator of malnutrition and is defined according to a height-for-age scale. Stunting was associated with decreased copying ability in both exposed and non-exposed children. The researchers found that stunting had no clear effect on blood pressure. They therefore concluded that prenatal pesticide exposure may add to the already deleterious effects of malnutrition.

Current pesticide exposure was measured by excretion of pesticide metabolites in urine and was associated with increased reaction time, one of the standardized tests given for neurobehavioral function, indicating that current and prenatal exposures result in different outcomes. Effects caused by exposure in utero may last into childhood.

"These results suggest that more attention should be paid to protecting the developing brain and that we should seriously consider adopting and enforcing a greater margin of safety in protecting both fetuses and children from potential toxic exposures," said Grandjean.