Why is this study important?

This study demonstrates that modest elevations in PCBs experienced in the womb elevate the risk of certain childhood diseases.

It is an important demonstration of the interaction between contamination and infectious disease agents. The contaminants undermine immune system function and thus decrease resistance to pathogens.

Results of this nature are accumulating from a variety of sources. They have important implications for the real costs of exposure to contamination, because they suggest that contamination's true costs are likely to be underestimated when illnesses and mortality are attributed to the infectious agent when the disease would have been resisted had it not been for immune system impairment.

What did they do?

Weisglas-Kuperus et al. have been monitoring a cohort of mothers and children recruited during pregnancy to their study in the Netherlands in the early 1990s.

Births were normal without congenital defects, diseases or perinatal complications. Roughly half of the infants were breast-fed, the other half bottle fed. The researchers measured PCB and dioxin contamination in maternal and cord blood and in the breast milk of mothers breastfeeding their infants. They followed examined the health status of the infants during early childhood. And at the age of 42 months they measured current PCBs in the children's blood.

What did they find?

In an earlier report on this cohort, Weisglas-Kuperus described changes in immune system parameters related to contamination levels which at that time had no clear health effect. In the current study, with the same infants at an older age (3 1/2 yrs), they again found changes in immune system parameters related to PCB contamination levels. And in contrast to the previous study, they also found significant effects on health.

After adjusting for confounding variables, they note four primary health effects:

• current (i.e., measured at age 42 months) PCB body burden was associated with a higher prevalence of recurrent middle-ear infections and of chicken pox and a lower prevalence of allergic reactions.
• higher dioxin TEQ was associated with a higher prevalence of coughing, chest congestion, and phlegm
• prenatal PCB exposure was associated with less shortness of breath with wheeze
• current PCB body burden was associated with a lower prevalence of allergic reactions to food, pollen, dust, and/or household pets.

They then concluded that "in Dutch preschool children the effects of perinatal background exposure to PCBs and dioxins persist into childhood and might be associated with a greater susceptibility to infectious diseases."

Their observations are broadly consistent with several other studies of children exposed in utero to PCBs, including patterns reported for exposed children in Taiwan (1,2) and in the Canadian arctic (3).

Two of their findings warrant further comment.

First, they observed that "the negative effect of a higher postnatal PCB exposure was counteracted by the positive effect of a longer duration of breast-feeding in infancy."

This is important. Current information on the impacts of contamination in breast milk indicate that the benefits of breast feeding outweigh the risks of these background levels of PCB contaminantion within breast milk. Mothers should not stop breast feeding because of background PCB levels. The fact that there are health consequences of PCB contamination instead means, according to Weisglas-Kuperus et al., that "perinatal exposure to PCBs, dioxins, and related compounds should therefore be lowered by reducing the intake through the food chain at all ages, rather than by discouraging breast-feeding."

Their observation that decreased allergies and wheezing were associated with PCB exposures is intriguing. The interpretation they offer is hypothetical, that the increased number of infections acquired in early childhood because of decreased resistance to disease agents may paradoxically then lead to a lower prevalence of allergic diseases. This hypothesis has been advanced to explain dramatic increases in the industrialized world in childhood asthma: no comparable increase is seen in the developing world. Some authors have proposed that better child care related to childhood diseases inadvertently increases susceptibility to asthma. While this may appear plausible in broad comparisons of the developed to the developing world, within the developed world, specifically in the US, it is the children with the worst health care--specifically inner city minorities--that have the highest asthma rates.

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