Prenatal exposure to PAH's associated with lower IQ in young children who were exposed in utero

Prenatal exposure to PAH's associated with lower IQ in young children who were exposed in utero

Researchers recruited pregnant mothers between 1998 and 2003; the mothers were monitored for their exposure to polycyclic Aromatic Hydrocarbons (PAH's) throughout their pregnancy.  PAH's are one of the byproducts of incomplete combustion of fossil fuels, tobacco, and other organic matter, and have been associated with cancer and other health and environmental problems.  [A synopsis of the human health effects can be found at http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~zyPGLL:1:human; a summary of animal toxicity studies can be found at http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~zyPGLL:1:animal.  A summary of environmental fate and exposure can be found at http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~zyPGLL:1:enex.]
 
The researchers gave 249 English-speaking children IQ tests at 5 years of age.  The children's PAH exposures ranged from 0.49 nanograms per cubic meter (ng/m3) to 34.48 ng/m3.  140 of the 249 children were classified as having a "high" PAH exposure.  Children exposed to greater than the median 2.26 ng/m3 had an IQ score that was 4.31 points lower on average than those with less exposure.  Verbal IQ scores were 4.67 points lower.  Scores were controlled for maternal intelligence, home environment quality, tobacco smoke exposure, and other factors.  The researchers noted that the IQ decrease was equivalent to a lifetime blood lead concentration between 5 micrograms and 9.9 micrograms per deciliter.  The researchers also noted that PAH exposure can cause complications with the immune system, metabolism, and neurological functions throughout life.