Risk assessment of dietary lead exposure among First Nations people living on-reserve in Ontario, Canada using a total diet study and a probabilistic approach
Introduction
Lead (Pb) is a well-studied environmental pollutant with both naturally occurring and anthropogenic sources [1]. Historically, Pb was widely used as an additive in common consumer items such as paints and gasoline as well as in plumbing infrastructure, which resulted in elevated exposures in populations globally [1]. In North America, the level of Pb in these items has been reduced or even eliminated since the 1970′s due to stringent regulations [2], [3]. Despite this decline, management of Pb exposures remains a modern health priority in North America as well as other regions around the world [4].
Epidemiological studies over the past 10 years have shown conclusive evidence of adverse human health effects despite declining magnitudes of chronic Pb exposures in populations; this is most prominently observed with neurodevelopmental impairment among children [5], [6], [7], [8], [9]. In adults, the strongest weight of evidence for adverse health effects is supported by the association between chronic low dose Pb exposures and coronary heart disease characterized by increases in systolic blood pressure, and chronic kidney disease characterized by a reduction in the glomerular filtration rate [10], [11], [12], [13].
In North America, diet is the predominant route of Pb exposure, primarily in the inorganic form [1]. In the general Canadian adult population, the average Pb intake from dietary sources was 0.12 μg/kg/d, as reported by the 2007 Canadian Total Diet Study (TDS) [14]. One of the limitations of TDSs is that they are a general screening tool and are unable to reflect the dietary exposures in populations with unique dietary compositions, such as the Aboriginal people living on-reserve. In Canada, approximately 1.4 million people identify as Aboriginal (First Nations, Inuit, Metis), representing approximately 4.3% of the Canadian population based on results from the 2011 National Household Survey [15]. The largest group of Aboriginal peoples in Canada are the First Nations accounting for approximately 60% of the Aboriginal population. There are over 600 First Nation bands and communities representing over 50 Nations [16]. The largest population of First Nations, comprising more than 200,000 people and 21% of the total First Nations population, reside in the province of Ontario, Canada [16]. About 30% of First Nations peoples live on reserves [15]. The diet of First Nations peoples is composed of a mixture of store-bought (or market foods) and traditional foods. Traditional food systems, which vary between Indigenous communities and are uniquely adapted include foods obtained from “the local, natural environment that are culturally acceptable” [17], which makes it distinct from the diet of the general Canadian population. Pb is found in many foods indirectly because of its ubiquitous nature as a pollutant due to its many industrial uses and natural occurrence as a metal. In traditional foods, however, there is also the potential for direct contamination through hunting with lead-containing shots and ammunition [18], [19]. The assessment of dietary exposures of Pb in First Nations peoples to date has focused on specific traditional food items in small population samples [20], [21], [22]. Although traditional foods are largely unregulated from a contaminant perspective compared to store-bought market foods, they are a key component of health and connectedness in Aboriginal populations on the levels of the individual, family, community, culture, and environment [23], [24]. Therefore, the characterization of their contribution to dietary sources of Pb in First Nations populations is necessary for the development of strategic and culturally relevant risk communication. There are few comprehensive Pb exposure assessments among First Nations. Dietary Pb intake is particularly of interest as toxicological reference values for assessing dietary exposures have been revoked by regulatory agencies [25], [26] given the consistent and evolving body of evidence supporting low dose effects. This has culminated in the general scientific consensus that no threshold for Pb toxicity exists [27].
The objectives of this study were to (i) characterize and quantify sources of Pb in the total diet of First Nations adults in Ontario; (ii) assess the health risk to the population using the new non-threshold approach; and (iii) identify the key contributing food items for Pb exposures. A total diet approach using results from 24-h recall data was used to describe the relative contribution of Pb exposure from market food, traditional food and drinking water consumption. A more detailed probabilistic approach using food frequency questionnaire data was used to assess the Pb exposure from the consumption of traditional food.
Section snippets
Ethics
Ethics approvals were obtained from the Research Ethics Board of the University of Ottawa and Health Canada.
First Nations food, nutrition and environment study (FNFNES)
Dietary patterns and contaminant concentrations in traditional foods were obtained through the First Nations Food, Nutrition, and Environment Study (FNFNES) Ontario region results collected in 2011–2012 [28]. The FNFNES was designed to study the diet of First Nations adults across Canada living on-reserve south of the 60th parallel. A total of 18 First Nation communities from the province
Estimate of dietary Pb exposure
Results from the total dietary study show that Ontario First Nation had an average Pb intake of 0.21 μg/kg/day which is higher than the average of the general Canadian population (0.12 μg/kg/d) (Table 1). Traditional food sources represent 72.7% of the average Pb intake for the population, while representing only 1.8% of the average caloric intake (Supplementary Table A2). Based on responses to the 24-h recall, 13% of the population reported consuming traditional foods. Therefore, First Nations
Discussion
Previous studies have observed terrestrial game, waterfowl, and birds hunted with lead-containing ammunition to have elevated Pb concentrations in homogenized tissue samples due to fragmentation of bullets and shots [35], [36], [19], [37]. Concentration of Pb in moose, deer, and goose hunted with non-lead shot and ammunition have been previously documented to have background Pb concentrations below the Codex maximum contaminant level [38], [39], [40]. In water fowl, the background concentration
Conclusion
This study comprehensively quantifies the dietary Pb exposures in First Nations adults living on-reserve in Ontario for the first time in a total diet context as well as more detailed characterization of annual traditional food consumption patterns. Results indicate the variability in Pb concentration in traditional food items to be the most sensitive input and predictor of risk. Given the range of Pb concentrations in traditional foods beyond previously characterized background levels, it is
Acknowledgements
We would like to express our gratitude to all participants for their cooperation and participation in the First Nations Food, Nutrition and Environment Study (FNFNES). We thank all First Nations community members who collected food and water samples, assisted in data collection, coordinated research activities, and arranged meetings and public gathering to share information. FNFNES is funded by Health Canada and the communication of the results to the communities was also funded by the Canadian
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2021, Science of the Total EnvironmentCitation Excerpt :Given its grave and toxic health implications, its extensive exploitation by humans for millennia, and its environmental persistence, lead (Pb) is a significant contributor to morbidity and mortality among human populations (Lanphear et al., 2018; UNICEF and Pure Earth, 2020). Despite many government efforts to drastically reduce Pb exposure, it remains an important health concern worldwide, including in Canada (Juric et al., 2018; Ngueta et al., 2016; Safruk et al., 2017), especially with prevailing Pb pipe and paint infrastructure (Foley et al., 2011; O'Connor et al., 2018; Troesken and Beeson, 2003). The issue of Pb exposure has become an increasingly relevant topic in urban Saskatchewan, given concerns that a portion of residential water pipes rely on old lead-containing infrastructure and recent reports that Pb levels in tap water exceed the recommended limit of 5 μg/L (Health Canada, 2017).