A new study, funded by the National Institute of Environmental Health Sciences (NIEHS), a component of the National Institutes of Health, the U.S. Environmental Protection Agency and several private foundations, is reporting that a mother’s exposure to urban air pollutants can adversely affect a child’s intelligence quotient (IQ). Certain types of chemicals are released into the air from the burning of coal, diesel, oil and gas, or other organic substances such as tobacco -- this is made worse in urban areas by motor vehicles are a major source of the problem pollutants.
Researchers found that children exposed to high levels of these pollutants in New York City had full scale and verbal IQ scores that were 4.31 and 4.67 points lower than those of less-exposed children. A difference of four points, which was the average seen in this study, could be educationally meaningful in terms of school success, as reflected, for example, in standardized testing and other measures of academic performance. However, the researchers point out that the effects may vary among individual children.
“This research clearly shows that environmental PAHs [pollutants] at levels encountered in an urban setting can adversely affect a child’s IQ,” said Linda Birnbaum, Ph.D., director of NIEHS. “This is the first study to report an association between PAH exposure and IQ, and it should serve as a warning bell to us all. We need to do more to prevent environmental exposures from harming our children.”
This was a major study, conducted by scientists from the Columbia University Center for Children's Environmental Health. The children were followed from utero to 5 years of age. The mothers wore personal air monitors during pregnancy to measure exposure to pollutants and they responded to questionnaires.
249 children were given an intelligence test at age 5 years. The test is regarded as a well validated, reliable and sensitive instrument for assessing intelligence. The researchers developed models to calculate the associations between prenatal pollutant exposure and IQ. They accounted for other factors such as second-hand smoke exposure, lead, mother’s education and the quality of the home caretaking environment. Study participants exposed to air pollution levels below the average were designated as having low exposure, while those exposed to pollution levels above the median were identified as high exposure.
“The decrease in full-scale IQ score among the more exposed children is similar to that seen with low-level lead exposure,” said lead author Frederica P. Perera, PhD.