Prenatal PAHs linked to lower cognition at age five.

Jun 14, 2010

Edwards, SC, W Jedrychowski, M Butscher, D Camann, A Kieltyka, E Mroz, E Flak, Z Li, S Wang, V Rauh and F Perera. Prenatal exposure to airborne polycyclic aromatic hydrocarbons and children’s intelligence at age 5 in a prospective cohort study in Poland. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.0901070.

Synopsis by Patrick H. Ryan

A child's cognitive development may be affected by exposure while in the womb to high levels of air pollutants.

Intellectual delays in kindergarten-aged kids may result from prebirth exposures to common air pollutants called polycyclic aromatic hydrocarbons (PAHs), according to a study of Polish children. The researchers report that 5-year-old children whose mothers had higher exposures to PAHs when they were pregnant performed worse on tests that measured cognitive abilities, lowering their IQ by more than three points.

The results suggest that prenatal exposure to the ubiquitous air pollutants has a detrimental – and potentially long-term – impact on the neurodevelopment of children. This study is only the second to compare childhood cognition with prenatal exposure to certain PAHs. A parallel study of mother/child pairs in New York City found similar results.

PAHs are released into the air from gasoline and diesel vehicles, coal burning, home heating, cooking and tobacco smoke. Benzo-a-pyrene is one type of PAH. Animal and human studies indicate that the chemicals can affect neurodevelopment, intelligence and physical growth. They are also known to cause cancer.

The fetus and young child are more susceptible to the harmful effects of these and other environmental toxicants – such as lead – because the central nervous system and brain are rapidly growing and developing during this time.

Preganant, nonsmoking women living in Poland participated in the study. The women wore air sampling backpacks for two days during the second or third trimester of pregnancy. The air samples were analyzed for eight types of PAHs to assess personal exposure to PAHs. Blood samples from the mother and umbilical chord were taken at birth, and the women filled out questionairres about their health, home/work environments and personal information. The 214 children in the study were tested at age five for nonverbal reasoning and intelligence using standarized tests that rely on pictures and patterns.

The average exposure levels of the Polish women to PAHs was 39.5 nanograms per cubic meter (ng/m3). The exposures are almost 10 times as high as the average of 3.48 ng/m3 measured in the women participating in the parallel New York City study.

Children prenatally exposed to the higher levels of PAHs measured had significantly reduced intelligence test scores after accounting for prenatal exposure to tobacco smoke, the gender of the child, and maternal education.

The scores indicate a drop in intellegence quotients of more than three points for those most exposed. Even slight changes in IQ can affect school performance, life-long learning and societal functioning.