Coverage in Science Magazine on Dutch research examining immune system effects of PCBs in breast milk.

Science
21 April 2000, p424-425
Society of Toxicology Meeting.
Hazards of Particles, PCBs Focus of Philadelphia Meeting
Jocelyn Kaiser

Low-Level PCB Dangers
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.

The 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."

Previous 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.

To 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 with PCBs.

When 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.

That 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.

The 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 dioxins.

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