This study examined the effects of prenatal exposure of poly aromatic hyrodcarbons (PAH) on cognitive and motor development at 12, 24 and 36 months of age. Through the course of the study 536 mother-infant pairs participated. Mothers wore personal air monitoring packs during the third trimester of pregnancy. Infants were tested using the Bayley Scales of Infant Development-Revised (BSID-II) to assess cognitive and pyschomotor development. This test is shown to be accurate of such effects in toxic exposures, such as lead.
Following air monitoring mother-infant pairs were divided into high and low exposure groups. Testing showed little effect of PAH exposure on psychomotor development but significant effects on cognitive and behavioral abilities. Although the mean difference between high and low exposed on cognitive functioning was approximately five points, the odds ratio of having an effect in the high exposure group was almost three times that in the low exposure group. Because many of these children from lower socioeconomic groups did not have optimum cognitive functioning to begin with, such decrement can be quite signiricant for school functioning, social abilities and general success in society.
The mechnism of action for this effect is not known but there are a number of possible reasons for this outcome. First, there may be some endocrine effect of PAHs which can affect development. Endocrine developmental effects has been shown before with numerous other chemicals. Second, there may be some gene-PAH interaction which alters development. And third, there may be some effect on placental transfer of critical oxygen to the developing fetus.