Exposure to weed killer associated with lower birth weight.

Mar 10, 2010

Barr, DB, CV Ananth, X Yan, S Lashley, JC Smulian, TA Ledoux, P Hore and MG Robson. 2010. Pesticide concentrations in maternal and umbilical cord sera and their relation to birth outcomes in a population of pregnant women and newborns in New Jersey. Science of the Total Environment doi:10.1016/j.scitotenv.2009.10.007.

Synopsis by Kim Harley, Ph.D.

Women exposed to higher levels of the herbicide, metolachlor, give birth to smaller babies than women with low exposure, report the study's authors.

Prebirth exposure to an herbicide may affect a baby's birth weight, suggest findings from a recent study. Babies born to women with higher levels of the herbicide metolachlor in their babies' umbilical cord blood weighed less than babies born to women with lower measured levels of the pesticide.

This is the first study to find that levels of this weed killer are associated with fetal growth in humans.

Metolachlor is a weed killer that is applied to soil to prevent the growth of weeds. It is widely used in agriculture and along roadsides. Metolachlor is frequently found in ground water due to agricultural runoff.

Researchers enrolled 150 women giving birth in a New Jersey hospital. Levels of eight pesticides were measured in mothers’ blood and in the umbilical cord blood. Infant birth weight, length and head circumference were also measured.

Only metolachlor was associated with decreased birth weight. Interestingly, organophosphate pesticides, which are acutely toxic pesticides and have been subject to much public scrutiny, were not associated with birth outcome. Although one study reported that organophosphate pesticides were associated with decreased birth weight, this is the third study that has failed to replicate this finding.