PCBs May Stunt Baby's Growth
Exposure to toxins affects mental, motor development, German study suggests
THURSDAY, Nov. 8, 2001 (HealthDayNews) -- Babies exposed before and possibly after birth to a group of banned but lingering chemicals show signs of mental and motor impairment as they grow, a new study says.
German scientists say exposure to polychlorinated biphenyls (PCBs) in the womb and through nursing is almost as stunting to child development as living in a home where parental love and attention and other important stimulation is lacking. Their findings appear in the Nov. 10 issue of The Lancet.
The U.S. Environmental Protection Agency banned PCBs in 1976 because of their propensity to cause cancer in animals. But the long-lived chemicals, which include dioxins, still can be found in the environment, particularly in fish.
Earlier research has shown that women who eat PCB-tainted fish regularly for several years before pregnancy tend to deliver lighter babies who are prone to memory trouble and have lower intelligence quotients.
"Studies have found an association between PCB exposure before birth and neurodevelopment, but results have been inconsistent. The big mystery is why it shows up to be especially strong in some populations and not others," says Dr. Matthew Longnecker, a PCB expert at the National Institute for Environmental Health Sciences, in Research Triangle Park, N.C.
In the Faroe Islands, off Iceland and Scotland, for instance, residents are exposed to extremely high doses of PCBs from eating whale blubber. Yet babies there don't appear to suffer any adverse effects from the chemicals, Longnecker says.
In the new study, Gerhard Winneke, of Heinrich-Heine University in Düsseldorf, and his colleagues looked for effects of PCB exposure in 171 pairs of mothers and infants, all of whom appeared healthy.
The researchers checked for PCBs in both umbilical cord blood and breast milk to gauge exposure before and after birth. And they took blood from the children when they were 3½ years old. They also evaluated the babies' home lives when they were 18 months old, assessing factors known to affect development, including the availability of age-appropriate toys, a mother's ease with her baby and her signs of aggression toward the child, and whether the child had its own play space.
Winneke's group charted the children's mental and motor development at 7, 18, 30 and 42 months, using two standardized tests: the Bayley Scales of Infant Development, used through the 30-month evaluation, and the Kaufman Assessment Battery for Children, used for the 42-month exam.
Between 7 months and 30 months of age, babies in the top 5 percent of PCB exposure in breast milk scored about eight points lower on the Bayley mental test and about nine points less on the exam's motor section than those in the lowest 5 percent of exposure. Babies who consumed more of the chemicals through nursing also tended to have lower scores in month 42 of the study.
Babies whose home stimulation scores were the lowest also tested worse on the motor and mental exams, and by an amount roughly equal to that linked to high PCB exposure, suggesting that the chemical and an under-stimulating environment are similarly harmful to childhood development, the study says.
Even babies who had the most stimulating home life could suffer if exposed to high levels of PCBs, Winneke says. "We found that the negative PCB effect is seen across the whole range of home values," he says.
Germany banned PCBs a few years after the United States, so exposures to women and infants there are likely to be somewhat greater than for people in the United States, Winneke says. He says his study didn't look at babies born after 1995, and environmental levels of the chemicals have dwindled in the six years since.
Still, Longnecker, who is collaborating with Winneke on other research, says scientists shouldn't ignore the latest findings because at least one study has shown that even relatively low PCB exposure levels might be harmful to infants.
In an editorial accompanying the journal article, Joseph and Sandra Jacobson, Wayne State University researchers who've studied the effects of PCBs on childhood development, say the German work is consistent with animal studies. However, they say the study wasn't able to conclusively prove that exposure through breast-feeding reduced a child's scores on mental and motor tests.
Rather, they say the effect may really be the result of exposure to chemicals in the womb.
It's also possible that the German results are the result of statistical massaging. One epidemiologist familiar with the work says the analysis the researchers used favors positive findings. A different method of looking at the numbers would have found a much smaller effect, if any at all, the researcher says.
What To Do
Food safety officials warn pregnant women to avoid fish known to be contaminated with PCBs. For information on whether locally caught fish could be tainted with the chemicals, call your state or local department of fish and game.
To find out more about PCBs, visit the Environmental Protection Agency online.
For more on PCBs and pregnancy, try this King County, Washington, Web site.