Vol. 2, No. 4 , 1996, Page 4 
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Vol. 2, No. 4 , 1996, Page 4 |
There's disturbing new evidence that polychlorinated biphenyls (PCBs), banned in the 1970s but still contaminating much of America's water and soil, are adversely affecting the mental health of a new generation of children-and possibly contributing to the nation's increasing rates of crime and delinquency.
Joseph Jacobson and Sandra Jacobson recently studied 212 11-year-old children whose prenatal exposure to PCBs had been determined by measuring PCB levels in umbilical cord serum and maternal serum and milk at the time of delivery. (The children's mothers were selected for the study because they had eaten fish from Lake Michigan, which is heavily contaminated with PCBs.) The researchers found that prenatal exposure to PCBs was associated with lower overall and verbal IQ scores, even after socioeconomic factors were taken into account. The children with the highest exposures were three times as likely as less-exposed children to have low-average IQ scores, and twice as likely to be delayed at least two years in reading comprehension.
"Our IQ results," the researchers say, "indicate deficits in general intellectual ability, short-term and long-term memory, and focused and sustained attention." They note that the 6.2 point IQ deficit seen in children with the highest PCB exposures "is similar to that reported for low-level exposure to lead."
Joseph Jacobson commented to Science News, "I thought that once they reached a structured school environment, whatever minor handicaps [the children with high PCB exposures] had would be overcome. So I was quite surprised to find that, if anything, the effects were stronger and clearer at age 11 than they had been at age 4."
The new findings may suggest a link between PCB exposure and criminality, because even small declines in IQ (and, in particular, verbal IQ) are a strong risk factor for criminal behavior. Other PCB effects detected in the study by Jacobson and Jacobson-including reading disabilities and reduced attention span-also are linked to criminality.
What's particularly disturbing is that the PCB levels of the "high exposure" subjects in the Jacobsons' study were only slightly higher than typical exposure levels. "These were not people who were eating fish every day," Linda Birnbaum of the Environmental Protection Agency commented, saying that "the data suggest there are subtle changes going on in at least a portion of our population."
The Jacobsons are not the only researchers raising concerns about PCBs' effects on mental health. Edward Lonky and colleagues, at the State University of New York at Oswego, found that infants of women who had eaten substantial amounts of fish from PCB-polluted Lake Ontario scored poorly on several neurological tests.
The Jacobsons note that PCBs are an "equal opportunity" brain hazard, pointing out that "unlike exposure to lead or illicit drugs, which occurs predominantly in economically disadvantaged families, prenatal exposure to polychlorinated biphenyls is unrelated to socioeconomic status.
"Although in the United States environmental concentrations of these contaminants have declined in recent years," they say, "the risk of exposure from toxic industrial waste continues because the amount in use in older electrical equipment and in landfills exceeds the total quantity that has escaped into the environment."
"Intellectual impairment in children exposed to polychlorinated biphenyls in utero," Joseph Jacobson and Sandra W. Jacobson, New England Journal of Medicine, Vol. 335, No. 11, September 12, 1996. Address: Joseph L. Jacobson, Department of Psychology, Wayne State University, Detroit, MI 48202.
"Banned pollutant's legacy: lower IQs," J. Raloff, Science News, Vol. 150, No. 11, September 14, 1996.
"Hormone hell," Catherine Dold, Discover, Volume 17, Number 9, September 1996.