Pesticide exposure before birth consistently linked to lower IQ

Kathleen Blanchard's picture
Pesticides, Organophosphates
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Organophosphates (OP’s) are linked to lower IQ in children, in findings that investigators say are “substantial” and “significant”. Three new papers document the effect of neurotoxic pesticides on a child’s IQ that happens from a mother’s exposure during pregnancy.

Pesticide link to child's lower IQ population wide

One of the reasons the finding is significant is because the lower IQ scores in children, linked to pesticides, involved population wide studies. Research was conducted in New York and California, in urban and agricultural settings.

Brenda Eskenazi, UC Berkeley professor of epidemiology and of maternal and child health explains, "These associations are substantial, especially when viewing this at a population-wide level.”

The studies, published in Environmental Health Perspectives, showed a 5.5 drop in IQ in children of women exposed to pesticides during pregnancy, for every tenfold increase in organophosphate exposure that the scientists checked in maternal urine and in umbilical cord blood.

Eskenazi notes, "That difference could mean, on average, more kids being shifted into the lower end of the spectrum of learning, and more kids needing special services in school."

Researchers at University of California, Berkeley, Mt. Sinai and at Columbia University sampled pesticide metabolites in the urine of mothers. Scientists at Columbia looked at levels of a specific pesticide called chlorpyrifos in umbilical cord blood.

The Mt. Sinai study found early signs of lower cognitive functioning from pesticide exposure, beginning at age 12 months.

Chlorpyrifos is used on crops, to kill lice, cockroaches, grubs, beetles, flies and fire ants to name a few of the applications. At one time, it was used to control mosquito populations. It is also used on farm animals. The pesticide is also used on lawns and ornamental plants. Use of the pesticide is now banned in the US for home use, because of the danger to children. Studies show humans exposed to chlorpyrifos develop autoimmune antibodies.

Adverse health effects of pesticides found in multiple studies

Women who are pregnant during spring and summer months have been found to bear children with more birth defects, compared to other months. Researchers speculate the cause is pesticides responsible for higher rates of birth defects.

Paul Winchester, M.D., Indiana University School of Medicine professor of clinical pediatrics explains, "Elevated concentrations of pesticides and other agrochemicals in surface water during April through July coincided with significantly higher risk of birth defects in live births conceived by women whose last menstrual period began in the same months.” The finding was published in the April 2009 medical journal “Acta Pædiatric”.

Researchers from the American Society of Hematology found a link between a rare blood disorder known as MGUS (monoclonal gammopathy of undetermined significance), which precedes multiple myeloma, in a study published June 2009. The disorder occurs in higher number in farmers.

Lead author Ola Landgren, MD, PhD, of the National Cancer Institute (NCI) said the findings were important for agricultural employees and suggested more research.

UC Berkeley links lower IQ from prenatal pesticide exposure by age 7

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The California study followed 329 children who were part of the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study that began enrolling women in 1999. The children were followed from birth.

The women and children were monitored at a CHAMACOS clinic regularly. Mothers provided two urine samples during pregnancy to test for levels of dialkyl phosphate (DAP) that is a metabolite of 75 percent of insecticides.

Urine samples were taken from the children between ages 6 months and 5 years at regular intervals and their IQ was assessed at age 7. A standard test was use to assess the children’s verbal comprehension, perceptual reasoning, memory and processing speed.

The researchers were able to correlate pre-natal exposure to pesticides to lower IQ, but not to exposure after birth. The researchers say they cannot track the lower IQ scores in children at age 7 to any specific pesticide, but note checking metabolites in urine “is one of the strongest methods available to study how environmental factors affect children's health."

Lead author Maryse Bouchard, who was involved at the study as a UC Berkeley post-doctoral researcher said, "It is very unusual to see this much consistency across populations in studies, so that speaks to the significance of the findings.

Bouchard notes children whose mothers were exposed to the pesticides during pregnancy are now in school, allowing researches to get a good idea of how well they are functioning cognitively.

Consumer advice and action

Asa Bradman, associate director of the Center for Environmental Research in Children's Health (CERCH) at UC Berkeley, says many people are exposed to pesticides in the home, schools and around buildings that is compounded if used in the home.

The recommendation for the public is to reduce the amount of pesticides used in the home and in gardens, and instead use bait stations and avoid sprays. The authors note most home and garden pests can be controlled without pesticides.

They also warn that florists, gardeners, pesticide manufacturing workers and farmers are at higher risk from organophosphate harm, though their use has been steadily declining in the United States.

Before eating fruits and vegetables, take time to use a soft brush to remove pesticide residue, and consider buying organic. The authors also express fears that the findings will lead to avoidance of fruits and vegetables that most Americans consume less than is recommended.

The newest study shows prenatal exposure to pesticides, known as organophosphates, is associated with lower IQ scores in children determined in tests taken at age 7. An accompanying study finds cognitive deficits in children whose mothers were exposed to organophosphates starting at age 12 months, and continuing into childhood. The finding follows a study from the same population that showed pesticide exposure before birth is associated with attention disorders by age 5.

Environmental Heath Perspectives

Image credit: Wikimedia Commons
Author: U.S. Navy photo by Photographer’s Mate 2nd Class Michael D. Heckman

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