21 April 2000, p424-425
Society of Toxicology Meeting.
Hazards of Particles, PCBs Focus of Philadelphia Meeting
Without question, PCBs are nasty chemicals. These polychlorinated
biphenyls, as they are properly known, accumulate in the food chain
and cause a variety of ill effects in lab animals, from liver damage
to cancer. For that reason, most developed countries banned the
use of PCBs and many similar chemicals decades ago. Despite that,
PCBs can still be found, often in minute levels, in the body fat
of all people examined. New evidence presented at the meeting now
suggests that even these low levels of PCBs may affect development
in young children.
work comes from Nynke Weisglas-Kuperus, a developmental pediatrician
at Sophia Children's Hospital in Rotterdam, the Netherlands, and
her colleagues. They found that PCBs and related chemicals called
dioxins, passed by Dutch mothers to their babies during pregnancy
and in breast milk, appeared to weaken the infants' immune systems.
This in turn contributed to more infections in the first 3 1/2 years
of life, Weisglas-Kuperus reported. "These are really subtle
effects," says dioxin toxicologist Linda Birnbaum of the U.S.
Environmental Protection Agency.. But, she adds, if they translate
into lots more childhood infections over a population, "that
has an impact."
work in both animals and humans had suggested that PCBs and dioxins,
which are still produced as byproducts of incineration and industrial
bleaching, suppress the immune system. For example, they've been
blamed for spurring a 1988 virus outbreak that killed 20,000 European
harbor seals feeding on PCB-tainted fish. And in Taiwan, a group
of infants born to mothers who had accidentally consumed high doses
of PCBs in 1979 had an elevated rate of infections.
find whether health effects might also arise from the lower exposures
more typically seen in developed countries, in 1990 Weisglas-Kuperus
and colleagues began a long-term study of 207 mothers and infants
living outside Rotterdam. Roughly half the mothers nursed their
babies and the others fed them formula, which was not contaminated
the infants were 18 months old, the researchers detected slight
changes in the immune cells of some of them, particularly those
who had been breast-fed, suggesting that their immune systems had
been influenced by PCB exposure and might be less able to fight
infections. These changes correlated with PCB and dioxin levels
in blood from the babies' umbilical cords and in the mothers' blood
and breast milk. At that time, however, those with greater immune
changes didn't get sick more often than the other babies.
changed when the researchers reexamined the children at age 3 1/2,
when a typical child has had many infections. As before, they found
that the toddlers whose mothers had more PCBs in their blood had
higher levels of certain T cells. The researchers then looked at
the current level of PCBs in the children's blood and their history
of infections. After adjusting for confounding factors such as parental
smoking, which tends to increase infection rates in children, and
breast feeding, which, while exposing the babies to PCBs, is also
well known to boost immunity, they found that children with high
PCB exposures at age 3 1/2 were eight times more likely to have
had chickenpox, and three times more likely to have had at least
six ear infections than those with lower exposure.
Weisglas-Kuperus team continues to monitor the children for neurological
and other effects. But she says the immune suppression alone underscores
the importance of strict regulations on the release of PCBs and