is this study important?
study demonstrates that modest elevations in PCBs experienced in
the womb elevate the risk of certain childhood diseases.
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.
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.
did they do?
et al. have been monitoring a cohort of mothers and children
recruited during pregnancy to their study in the Netherlands in
the early 1990s.
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.
did they find?
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.
adjusting for confounding variables, they note four primary health
(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.
dioxin TEQ was associated with a higher prevalence of coughing,
chest congestion, and phlegm
PCB exposure was associated with less shortness of breath with
PCB body burden was associated with a lower prevalence of allergic
reactions to food, pollen, dust, and/or household pets.
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."
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).
of their findings warrant further comment.
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."
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
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.