Kids Brains on Pesticides?

Pesticide chlorpyrifos CPF linked to brain differences and lower IQs in children

(RxWiki News) Knowing what pesticides are used around you or on the food you eat may not always be possible. But knowing the effect they can have on unborn children may help you decide how to shop.

Chlorpyrifos (CPF) is a widely used pesticide that has been used in agriculture since 1965.

Although use of it in residential areas was phased out by the U.S. Environmental Protection Agency in 2001, it was commonly heavily used in cities and continues to be used today away from urban areas.

"Avoid pesticide exposure and consider organic food while pregnant."

Virginia Rauh, ScD, an epidemiologist at the Heilbrunn Center for Population and Family Health and the Columbia Center for Children's Environmental Health, led a study to look at the specific physical ways children's brains are affected by exposure to the pesticide CPF.

CPF has been found in amniotic fluid and can cross the placenta to the baby. Past studies have already shown links between CPF exposure and lower birth weight, smaller head size, attention problems, developmental differences in children and abnormal reflexes in newborns.

Another three studies found an association between CPF exposure and lower IQs in children. However, these studies have not shown whether CPF exposure actually has an association with physical differences in the brain.

The researchers looked at MRI images of 40 children, ranging in age from 5 to 11, who were part of a larger study group where their exposure to CPF and other pollution was already documented.

Twenty of the children were born to mothers to had high exposures to CPF while they were pregnant (more than 4.39 pg/g), as determined by an analysis of the umbilical cord blood. The other 20 children had low exposure to CPF.

All the children had been exposed prenatally to tobacco smoke in the general environment and to low amounts of polycyclic aromatic hydrocarbons (PAHs), a common pollutant found in soil or in particles in the air that comes from burning oil, coal, wood and other carbon-containing substances.

The researchers also ensured that other characteristics of the children in the two groups were equivalent.

An analysis of the MRI images revealed that children who had high exposure to CPF tended to have certain parts of their brains more enlarged than the children who had low exposure to CPF. They also showed other structural changes in their brains that differed from the structure of brains that have developed normally.

The brain size overall of the children was not different across the two groups, but there was significant enlargement in nine specific regions of the brain.

The researchers also found that the amount of enlargement in the surface of one region corresponded to the amount of exposure that the child had of CPF. The higher the exposure, the more enlargement there was.

Brains of males and females have differences in certain regions, but the researchers found that these differences were disrupted in the brains of children with high exposure to CPF.

For example, females have slightly larger areas in the right parietal lobe of the brain than males have, but this was not observed at the appropriate size difference in the children with high exposure.

In addition, another area where males have a larger part than females was reversed in the brains of high-exposure children.

These abnormalities of the normal sex differences seen in male versus female brains were not seen in the children with low exposure to CPF.

The researchers also gave the children IQ tests and found an inverse relationship to their exposure to CPF. This means that a higher exposure was linked to a lower IQ score.

Rauh's team concluded that observable structural changes in the brain were associated with children's exposure to CPF.

"This study reports significant associations of prenatal exposure to a widely used environmental neurotoxicant, at standard use levels, with structural changes in the developing human brain," they wrote.

They noted that the study was limited in the sense that it could not necessarily take into account all the possible environmental variables that could have played a part in these brain differences, as well as the role genetics could have played.

Nevertheless, they said their findings have public health implications for the children who have been exposed to CPF.

The associations between "prenatal exposure, brain structure and neurocognitive alterations" when children are aged 5 to 11 "suggest that the neurotoxic effects of CPF are long term, at least extending into the early school years," they write.

It also appears the effects are not reversible. They point out that the continued use of CPF puts people in non-urban communities at risk and likely provides lower levels of exposure to people who consume agricultural products that have CPF residue on them.

The study was published online April 30 in the Proceedings of the National Academy of Sciences journal.

The research was funded by the National Institute of Environmental Health Sciences Grants, the U.S. Environmental Protection Agency Grants, the National Institute of Mental Health Grants and the John and Wendy Neu Family Foundation.

One of the authors reported providing expert testimony about the health effects of chlorpyrifos on behalf of government entities, corporations and/or individuals.

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Review Date: 
April 25, 2012