Volumes 527–528, 15 September 2015, Pages 150–158
Assessing determinants of maternal blood concentrations for persistent organic pollutants and metals in the eastern and western Canadian Arctic
- Under a Creative Commons license
Open Access
Highlights
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- In 2005–07, younger age was related to lower levels of chemicals in northern Canada.
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- Eastern Inuit who consumed marine mammals showed elevated levels for POPs and Hg.
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- Non-diet effects may contribute to chemical concentrations in Arctic aboriginal groups.
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- Positive associations between smoking and contaminant levels require more study.
Abstract
Aboriginal
peoples in the Canadian Arctic are exposed to persistent organic
pollutants (POPs) and metals mainly through their consumption of a
traditional diet of wildlife items. Recent studies indicate that many
human chemical levels have decreased in the north, likely due to a
combination of reduced global chemical emissions, dietary shifts, and
risk mitigation efforts by local health authorities. Body burdens for
chemicals in mothers can be further offset by breastfeeding, parity, and
other maternal characteristics.
We have assessed the
impact of several dietary and maternal covariates following a decade of
awareness of the contaminant issue in northern Canada, by performing
multiple stepwise linear regression analyses from blood concentrations
and demographic variables for 176 mothers recruited from Nunavut and the
Northwest Territories during the period 2005–2007. A significant
aboriginal group effect was observed for the modeled chemicals, except
for lead and cadmium, after adjusting for covariates. Further, blood
concentrations for POPs and metals were significantly associated with at
least one covariate of older age, fewer months spent breastfeeding,
more frequent eating of traditional foods, or smoking during pregnancy.
Cadmium had the highest explained variance (72.5%) from just two
significant covariates (current smoking status and parity).
Although
Inuit participants from the Northwest Territories consumed more
traditional foods in general, Inuit participants from coastal
communities in Nunavut continued to demonstrate higher adjusted blood
concentrations for POPs and metals examined here. While this is due in
part to a higher prevalence of marine mammals in the eastern Arctic
diet, it is possible that other aboriginal group effects unrelated to
diet may also contribute to elevated chemical body burdens in Canadian
Arctic populations.
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Keywords
- Arctic;
- Inuit;
- Persistent organic pollutants;
- Mercury;
- Pregnant
1. Introduction
The
presence of persistent organic pollutants (POPs) and metals in the
blood and other tissues of people from the Canadian Arctic and other
circumpolar nations is well documented. Although there are natural and
point sources of these chemicals (Kirk et al., 2012), global pollution and long-range atmospheric transportation are the main sources in the Arctic (Macdonald et al., 2000).
Because of their physical–chemical properties, these chemicals can
biomagnify through the marine food web system and can reach high
concentrations in predatory species such as marine mammals (Borgå et al., 2004 and Braune et al., 2005).
Aboriginal populations in northern Canada are thus at higher risk of
exposure to POPs and metals because of their traditional diet (Van Oostdam et al., 2005 and Donaldson et al., 2010). This is especially true for Inuit populations who rely more extensively on marine mammals, such as seal and whale (Kuhnlein et al., 2000 and Potyrala et al., 2008).
Consequently, coastal Inuit populations from Nunavut and Nunavik (in
northern Québec) have shown higher concentrations of POPs and mercury in
their blood than their non-coastal counterparts from the Northwest
Territories who are more likely to consume inland items such as fish and
caribou (Muckle et al., 2001, Butler Walker et al., 2003, Butler Walker et al., 2006, Dewailly et al., 2007, Donaldson et al., 2010 and Curren et al., 2014).
Increased
exposure to metals and POPs has been linked to a wide array of
potentially adverse health outcomes, particularly for the developing
fetus along with subtle health effects that persist into childhood (Dewailly et al., 2000, Dewailly and Weihe, 2003, Dallaire et al., 2006, Gilman et al., 2009, Boucher et al., 2010, Boucher et al., 2012a, Boucher et al., 2012b and Ethier et al., 2012).
Accordingly, human biomonitoring studies conducted in the Canadian
Arctic across 1992–2007 have frequently examined expectant women to
elucidate risk for the child (Donaldson et al., 2010).
During a similar period, northern studies have extended tissue
collection to both men and women, such as through the International
Polar Year Inuit Health Survey in 2007–2008 (Saudny et al., 2012 and Laird et al., 2013),
to better understand exposures within the entire adult populations and
also across generations of aboriginal peoples whose modern dietary
preferences may be shifting away from certain traditional foods. Dietary
choice in the Arctic, and thus extent of exposure to certain foodborne
chemicals, is a complex contemporary issue because the substantial
cultural and nutritional benefits of traditional foods (Donaldson et al., 2010 and Egeland et al., 2011)
may be offset by concern for contaminants in some populations.
Moreover, dietary shifts to certain market foods may result in higher
exposures to other environmental contaminants (Binnington et al., 2014).
Maternal
studies conducted in the mid to late 1990s under the auspices of the
Northern Contaminants Program (NCP) established a baseline of exposure
for people from the Canadian Arctic. Blood collected in the subsequent
decade during follow-up studies indicated that concentrations of many
organochlorine pesticides and polychlorinated biphenyls (PCBs) declined
in aboriginal women from Nunavut, the Northwest Territories, and
Nunavik, oftentimes by 50–75% across studies (Donaldson et al., 2010).
These observations suggest positive outcomes for POP regulations (such
as the Stockholm Convention on Persistent Organic Pollutants) that have
been enacted to protect environmental and human health. However, the
trend for mercury is less clear. Both increasing and decreasing trends
have been observed in Arctic biota (Braune et al., 2005 and Rigét et al., 2011). Human blood levels in the Canadian Arctic appear to show a general decline (Donaldson et al., 2010),
which may reflect the compliance to health messaging concerning lower
mercury intake or simply a result of dietary change of consuming less
country foods. Body burden of cadmium has consistently been very high in
NCP studies because of the high rate of smoking among aboriginal adults
(Donaldson et al., 2010).
The
purpose of this study is to investigate the relationship between body
burdens of POPs and metals with lifestyle and dietary factors in
pregnant women from the Inuvik Region of the Northwest Territories and
the Baffin Region of Nunavut who participated in follow-up studies
conducted in 2005–2007. To our knowledge, these studies provide the most
current information of maternal levels of chemicals for aboriginal
populations in these regions. This analysis examines aboriginal group
and geographic differences (after adjusting for covariates) to obtain
insight on the impact of diet and other behavioral choices for mothers
(and, by extension, their unborn children) during this period. Further
declines in human levels of POPs and metals in northern Canada are
anticipated. The outcome of this analysis will inform study design for
the next generation of human biomonitoring activities in the Canadian
Arctic, along with public intervention and educational initiatives by
local health authorities concerning dietary exposures to chemicals.
