Environmental Engineering Reference
In-Depth Information
offal from several seal species (Greenland seal, bearded seal,
ringed seal), baleen and toothed whale species, walrus and
bear, various birds, and a number of saltwater and freshwater
fi sh (fresh or dried). In the summertime, leaves, roots, and
fl owers become increasingly featured in local diets (Deutch
et al., 2007). More than 250 different species of wildlife,
plants, and animals have been identifi ed as forming the rich
framework of the traditional food systems of Arctic peoples
(van Oostdam et al., 2005). Some studies show that tradi-
tional (country) food use as a percent of total dietary energy
varies from a low of 6% in communities close to urban cen-
ters, to over 40% in more remote areas (van Oostdam et al.,
2005). Chemical analyses of these traditional food items of
animal and plant origins now show elevated levels of mer-
cury, along with other toxic metals, and persistent organic
pollutants (Chan and Receveur, 2000; van Oostdam et al.,
2005; Deutch et al., 2007). There is strong evidence to sug-
gest a health inequity that is lined to contamination of tradi-
tional components of diets with dangerous levels of mercury.
A survey of 79 species of marine mammals, terrestrial
mammals, birds, fi sh, and plants in northern Canada found
that the high levels of mercury contamination in many
parts of northern Canada exceeded the guideline level
of 0.5 µg/g total mercury because of the enhanced meth-
ylation of mercury in local aquatic ecosystems (Chan and
Receveur, 2000). About 32% of mammal meat samples and
64% of terrestrial mammal samples tested exceeded 0.5 µg/g.
Assessment of exposure to mercury in one Inuit community
on Baffi n Island, 16 Dene/Métis communities in Denendeh,
Northwest Territories (NWT), 10 Yukon First Nations com-
munities, and one Mohawk community in Quebec showed
that over 50% of residents had dietary exposure levels that
exceeded the provisional tolerable daily intake (PTDI) in the
Inuit community, with the intake levels for high-end con-
sumers (i.e., 95th percentile) being six times higher than the
PTDI (Chan and Receveur, 2000). The increase in exposure
with age was associated with the corresponding age-related
increased intake of country food (van Oostdam et al., 2005).
The point to be emphasized is that the exposures for a large
percentage of the native populations exceed the tolerable
daily intake value (van Oostdam et al., 2005).
The association of the intake of traditional food items, as
determined by dietary surveys, with blood mercury levels
has been demonstrated in a number of epidemiologic studies
in the Arctic (see Hansen et al., 1990). The awareness of the
potential for high exposure to mercury and risk to human
health in the early 1970s has led to extensive programs
aimed at assessing mercury levels in indigenous people in
many areas of the Arctic. As Bjerregaard (1995) noted, the
“Inuit have been studied intensively, possibly more so than
any other ethnic group. In Greenland, the saying goes that
one scientifi c topic has been written for each indigenous
Greenlander. In Canada, the average Inuit family is said to
consist of a mother, a father, two children and an anthro-
pologist.” These studies have produced a rich database that
documents the fact that the indigenous populations of the
Arctic region are being disproportionately exposed to mer-
cury as compared with other populations in their countries.
From 1971 to December 1992, the screening program in
Canada conducted 71,842 tests in 514 native communities
across the country. Out of the 38,571 individuals tested, 1.4%
had blood or blood-equivalent mercury levels in the 100-199
µg/L range and 0.2% had levels
200 µg/L (Wheatley and
Paradis, 1995). The high-enders were fi sh eaters except in
the NWT, where exposure was largely through consumption
of sea mammals. Of the 99 individuals with mercury levels
100 µg/L, 27% were found to have some abnormalities not
attributable to methylmercury, 11% had neurologic fi ndings
possibly attributable to methylmercury, and 62% had no sig-
nifi cant abnormalities (Wheatley and Wheatley, 2000).
Considerably more data (Table 15.1) have become avail-
able since the report by Wheatley and Wheatley (2000).
Walker et al. (2006) and van Oostdam (2005) report that
among the mothers from NWT/Nunavut and Nunavik, only
Inuit exceeded the Canadian total mercury level of concern
of 20 µg/L and, more importantly, almost no Caucasian or
Dene/Métis mothers exceeded the lower guideline of 5.8
µg/L for methylmercury, the benchmark no-effect level (van
Oostdam et al., 2005). The differences among ethnic groups
were attributed to divergence in dietary habits. Among the
fi ve Inuit regions studied by Walker et al. (2006), the percent-
age that exceeded the Canadian guideline level of concern
of 20 µg/L for organic mercury were highest in Nunavik
(16%) and Baffi n (10%). The percentage that exceeded the
5.8 µg/L blood guideline for methylmercury among Canadian
Inuit women ranged from 16% in Inuvik to 79% in Nunavik
and 68% in Baffi n (van Oostdam et al., 2000).
Other studies in northern Canada consistently show
elevated levels of mercury in maternal and cord blood (see
Table 15.1). In Nunavik (northern Quebec), for instance, the
reported mean concentrations of mercury in maternal and
cord blood were 10.4 and 18.5 µg/L, respectively, in a pro-
spective longitudinal study of the effects of methylmercury
and PCB exposure on infant development (Muckle et al.,
2001b). Similar patterns of exceedances are evident in other
circumpolar countries. In two communities of Alaska, mater-
nal blood mercury concentration above the 5.8 µg/L thresh-
old varied from 0% for women in Barrow, where the primary
seafood for residents was terrestrial mammals and bowhead
whales (plankton feeders), to 48% for women in Bethel, where
residents consumed freshwater fi sh and some marine mam-
mals (AMAP, 2003).
In northern Greenland, where the highest mercury
exposure in Greenlanders is documented, more than 80%
of the population exceed the benchmark level of concern
of 5.8 µg/L and 16% exceed the World Health Organization
minimum toxic blood concentration in nonpregnant adults
of 20 µg/L mercury in blood (Hylander and Goodsite,
2006). In the Nuuk Region of Greenland, it was reported
that 3% of mothers had blood mercury concentrations that
exceeded 20 µg/L, while 27% had levels that exceeded the
5.8 µg/L threshold for methylmercury. In two other regions
