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Exposure to Pesticides in Utero May Lead to Smaller Head Size in Infants
Study in Environmental Health Perspectives Finds Impact Only in Certain Women

[RESEARCH TRIANGLE PARK, NC] When certain women were exposed to a common pesticide while pregnant, their babies were born with smaller heads, according to a study published in the March issue of the peer-reviewed journal Environmental Health Perspectives (EHP). Smaller head size is predictive of lower IQ and cognitive abilities and may be associated with attention deficit/hyperactivity disorder.

On the other hand, pesticide use was not associated with abnormal fetal growth or gestational age in the larger group of newborns studied. Decreased head size was found more often only in those women with lower activity of a particular enzyme known as paraoxonase-1, or PON1.

As part of an ongoing study, researchers evaluated the effects of pesticide exposure during pregnancy on 404 births that took place between May 1998 and May 2002 at Mount Sinai Hospital in New York City. Exposure to the pesticide chlorpyrifos was assessed by a prenatal questionnaire administered to the mothers early in their third trimester, and by analysis of pesticide levels in the mother's urine. There was no correlation between birth weight, length, head circumference, or gestational age and either self-reported or measured pesticide exposure. However, when the level of maternal PON1 activity was taken into account, detectable maternal pesticide exposure, coupled with low maternal PON1 activity, was associated with a small but significant reduction in head circumference among the women's newborns.

The study authors explain the potential association between PON1 and a negative reaction to the common household pesticide, saying that an adverse effect on head circumference is biologically plausible because chlorpyrifos is a potential neurotoxicant that can be detoxified by PON1 before it can inactivate acetylcholinesterase in the peripheral and central nervous system.

Scientists from Environmental Health Perspectives offered suggestions for pregnant women. "Overall, the only correlation between pesticide exposure and fetal growth in this study sample was in women with low levels of PON1 activity," said Dr. Jim Burkhart, science editor for EHP. "However, since women can't easily find out their levels of PON1 activity, it makes sense that pregnant women should limit their pesticide exposure. They should use the smallest amount possible, have others place it, and just do what they can to minimize contact."

The lead author of the study was Gertrud S. Berkowitz of the Mount Sinai School of Medicine. Other authors were James G. Wetmur, Elena Birman-Deych, Josephine Obel, Robert H. Lapinski, James H. Godbold, Ian R. Holzman, and Mary S. Wolff.

EHP is the journal of the National Institute of Environmental Health Sciences, part of the U.S. Department of Health and Human Services. More information, including the full report, is available online at http://www.ehponline.org/.

Editor's note: Working media can register to receive press releases via e-mail by visiting www.ehponline.org/press, calling 919-653-2582, or e-mailing media@ehp.niehs.nih.gov.