Re-evaluation of blood mercury, lead and cadmium concentrations in the Inuit population of Nunavik (Québec): a cross-sectional study

Abstract

BackgroundArctic populations are exposed to mercury, lead and cadmium through their traditional diet. Studies have however shown that cadmium exposure is most often attributable to tobacco smoking. The aim of this study is to examine the trends in mercury, lead and cadmium exposure between 1992 and 2004 in the Inuit population of Nunavik (Northern Québec, Canada) using the data obtained from two broad scale health surveys, and to identify sources of exposure in 2004.MethodsIn 2004, 917 adults aged between 18 and 74 were recruited in the 14 communities of Nunavik to participate to a broad scale health survey. Blood samples were collected and analysed for metals by inductively coupled plasma mass spectrometry, and dietary and life-style characteristics were documented by questionnaires. Results were compared with data obtained in 1992, where 492 people were recruited for a similar survey in the same population.ResultsMean blood concentration of mercury was 51.2 nmol/L, which represent a 32% decrease (p < 0.001) between 1992 and 2004. Mercury blood concentrations were mainly explained by age (partial r2 = 0.20; p < 0.0001), and the most important source of exposure to mercury was marine mammal meat consumption (partial r2 = 0.04; p < 0.0001). In 2004, mean blood concentration of lead was 0.19 μmol/L and showed a 55% decrease since 1992. No strong associations were observed with any dietary source, and lead concentrations were mainly explained by age (partial r2 = 0.20.; p < 0.001). Blood cadmium concentrations showed a 22% decrease (p < 0.001) between 1992 and 2004. Once stratified according to tobacco use, means varied between 5.3 nmol/L in never-smokers and 40.4 nmol/L in smokers. Blood cadmium concentrations were mainly associated with tobacco smoking (partial r2 = 0.56; p < 0.0001), while consumption of caribou liver and kidney remain a minor source of cadmium exposure among never-smokers.ConclusionImportant decreases in mercury, lead and cadmium exposure were observed. Mercury decrease could be explained by dietary changes and the ban of lead cartridges use likely contributed to the decrease in lead exposure. Blood cadmium concentrations remain high and, underscoring the need for intensive tobacco smoking prevention campaigns in the Nunavik population.

Prevalence of unexplained anaemia in Inuit men and Inuit post-menopausal women in Northern Labrador: International Polar Year Inuit Health Survey

“…The primary source of lead for Inuit is thought to be through bird and game tissues contaminated with lead shot, 19,20 though age may be the most important predictor. 21 In general, blood lead levels have declined among Inuit over time in accordance with national regulations, yet concentrations are still higher for Inuit than among general population comparison groups. 21 Although there are toxic effects of lead on several enzymes involved in heme synthesis at concentrations as low as 50-100 μg/L, 22 overt anaemia occurs only with acute toxicity (≥600 μg/L).…”

“…21 In general, blood lead levels have declined among Inuit over time in accordance with national regulations, yet concentrations are still higher for Inuit than among general population comparison groups. 21 Although there are toxic effects of lead on several enzymes involved in heme synthesis at concentrations as low as 50-100 μg/L, 22 overt anaemia occurs only with acute toxicity (≥600 μg/L). Therefore, given the moderate blood concentrations in this population, lead is not likely an important cause of anaemia.…”

Prevalence of anemia among Inuit women in Nunavik, Canada

“…Also, mercury and lead levels were positively correlated with SF and negatively with TIBC, indicating that a better iron status was found among women with higher blood metal levels. The relationships between blood lead and mercury and sociodemographic and dietary data have already been studied in this population (22). In the 2004 Nunavik Health Survey, mercury and lead concentrations in adults were mainly explained by age.…”

“…Detection limits were 0.001 µmol/L for lead and 0.5 nmol/L for total mercury. Accuracy and precision were measured using reference materials from external quality assessment schemes of the Centre de Toxicologie (INSPQ, Quebec) (22).…”

“…In the 2004 Nunavik Health Survey, mercury and lead concentrations in adults were mainly explained by age. The most important source of exposure to mercury was marine mammal meat consumption, whereas blood lead Anemia in Inuit women, Nunavik concentrations increased slightly with higher annual wildfowl consumption (22). These food sources of heavy metals are also major sources of iron in the diet of Nunavik women (42), which could explain the positive association observed between blood levels of heavy metals and iron status.…”