It's well known that serious air pollution can cause of all kinds of nasty health problems - headaches, nausea, allergic reactions, chronic respiratory disease, lung cancer and heart disease counted among them. But according to new statistical correlation, it can also make unborn children stupid at small levels. 

An analysis by the Columbia Center for Children's Environmental Health (CCCEH) carried out in Krakow, Poland correlated prenatal exposure to pollutants and children's cognitive development by age 5. Writing in Environmental Health Perspectives, they claim that children exposed to high levels of polycyclic aromatic hydrocarbons (PAHs) in Krakow had a significant reduction in scores on a standardized test of reasoning ability and intelligence at age 5.

PAHs are released into the air from the burning of fossil fuels for transportation, heating, energy production, and from other combustion sources.

"The effect on intelligence was comparable to that seen in NYC children exposed prenatally to the same air pollutants," noted Frederica Perera, professor of Environmental Health Sciences and director of the CCCEH at the Mailman School of Public Health, and senior author. "This finding is of concern because IQ is an important predictor of future academic performance, and PAHs are widespread in urban environments and throughout the world."

The study included a cohort of 214 children who were born to healthy, non-smoking Caucasian women in Krakow, Poland between 2001 and 2006. During pregnancy, the mothers completed a questionnaire, wore small backpack personal air monitors to estimate their babies' PAH exposure, and provided a blood sample and/or a cord blood sample at the time of delivery. The children were followed through the age of 5 when they were tested using the Raven Coloured Progressive Matrices (RCPM) Test of reasoning ability and intelligence. 

Researchers say they accounted for other factors such as second-hand smoke exposure, lead and mother's education. Study participants exposed to air pollution levels below the median (17.96 nanograms per cubic meter) were designated as having "low exposure," while those exposed to pollution levels above the median were identified as "high exposure."

"Air pollution knows no boundaries," said Linda Birnbaum, director of the National Institute of Environmental Health Sciences epidemiology group, which publishes Environmental Health Perspectives. "Researchers around the globe are finding that air pollution is harmful to children's development." 

Citation: Edwards et al., 'Prenatal Exposure to Airborne Polycyclic Aromatic Hydrocarbons and Children’s Intelligence at Age 5 in a Prospective Cohort Study in Poland', Environmental Health Prospectives, ' April 2010; doi:10.1289/ehp.0901070