Persistent Organic Pollutants and Heavy Metals (Including Mercury) - The Changing Arctic Environment: The Arctic Messenger - page 146

concern was not related to acute toxicity. For most POPs, this was not high at concentra-
tions found in the environment. Instead, the concern was with exposure to comparatively
low doses received either over a lifetime or at a particularly vulnerable period in the an-
imal's life (usually at the embryonic stage or very soon after birth). There was a common
family of health outcomes from laboratory studies of certain POPs (at that time, mainly
PCBs, dioxins and DDT) and of effects in wildlife populations exposed to high levels of
the same substances. What is more, the report showed that because of biomagnification,
it is possible in the special circumstances of Arctic ecosystems for POPs to reach concen-
trations in the fatty and oily tissues of top predators that are in the same general range as
those that produced effects in the laboratory studies. Humans whose diet is at the end of a
long food chain (this usually means an aquatic one) are the top predators of that food chain.
Figure 8.3 provides a glimpse of the potential significance of biomagnification of POPs to
people in the Arctic whose traditional diet includes a large proportion of top marine pred-
ators. The graph (from the AMAP 2009 Assessment of Human Health in the Arctic ) shows
the percentage of mothers and women of childbearing age in Canada and Greenland that
exceed guideline limits for PCB (measured as Aroclor 1 ) in blood. The guidelines are those
used in Canada to indicate a “level of concern” (>5 μ g/l) and a “level of action” (>100 μ g/l)
(Health Canada, 1986). Notice that in some locations where data are available, in the 1990s
and since 2000, levels of PCBs appear to have declined (such as Baffin Island and Inuvik).
This is probably due to a combination of dietary change and a decline in environmental
levels in response to recent regulatory controls on these substances.