of their work: Commoner
et al. have discovered that a relatively small number of
sources contribute a disproportionately large percentage of dioxin
being deposited this Arctic territory. Their results suggests that
a focused effort on these sources could reduce exposures dramatically.
Citing one example (Coral Harbour, Nunavut), they observe that "total
exposure to dioxin could be reduced by 35 percent if only 19 individual
source--most of them in the United States--could be induced to virtually
eliminate their emissions."
Nunavut lies in the far north of Canada. Even though there are no
significant sources of dioxin there nor elsewhere within 500 kilometers
of this arctic territory's boundary, dioxin concentrations in the
breast milk of Inuit mothers living in Nunavut average twice
the levels observed further south in Canada, near the US border.
exemplifies the ubiquitous spread of persistent bioaccumulative
compounds better than this example.
did they do? Commoner et al. set out to identify sources
of dioxin that might be contributing to high contamination levels
in Nunavut. They did so using computer modeling procedures that
Commoner and his lab had developed for other contaminants within
the US, building on an air transport computer simulation model originally
developed by the US National Oceanic and Atmospheric Administration
did they find? They found that most of the sources of dioxin
reaching the territory Nunavut lie in the United States, indeed
approximately 70-80% is US-produced. Another 5-10% comes from Mexico
while 11-25% come from Canada. Contributions at specific places
within Nunavut vary from place to place within the territory.
amounts (less than 1%) originate in Nunavut, itself. Thus "the
exposure of the Nunavut exposure is therefore almost entirely due
to outside sources."
map shows the highest-ranked individual sources of dioxin
that account for 35% of total dioxin deposition in the vicinity
of Arctic Bay, Nunavut. Many other sources contributed smaller
amounts. The map is representative of many such "source-sink"
maps produced in their analysis.
from Commoner et al. 2000.
regions of Nunavut receive more deposition than northern regions
surfaces receive more than adjacent terrestrial sites
relatively small number of sources are responsible for most of
the depositions. For example, at one typical site studied, only
19 sources are responsible for 35 percent of the deposition. Those
19 sources represent 0.04% of the total sources studied.
3 types of sources--municipal waste incinerators, backyard trash
burning and cement kilns burning hazardous waste--account for
two-thirds of the total dioxin emissions, and 6 types account
of the sources are at least 3000 km (1800 mi) from Nunavut.
conclude that "the known occurrence of dioxin in Nunavut--in
the indigenous population, in the regional food chains, and in marine
and terrestrial ecosystems--is due to the deposition of dioxin transported
from distant sources, which are chiefly in the United States, to
a lesser extent in Canada, and marginally in Mexico.
discussing the implications of their work, Commoner et al.
observe that there is no feasible way to protect food chains from
the deposition of airborne dioxin. This means that protecting Inuit
health requires either a reduction in emissions or a change in diet.
Such a change would "clash with the transcendent importance
of the indigenous diet in Inuit culture."