Indigenous Arctic Canadians have a higher prevalence of gastric neoplasms relative to North Americans of European ancestry. We investigated the hypothesis that low-dose methylmercury exposure from eating fish/whale increases the risk of gastric cancer in Arctic communities. We used intermediate endpoints from an established model of gastric carcinogenesis: intestinal metaplasia, atrophy, and severe chronic gastritis. During 2008-2012, we obtained gastric biopsies from participants of community-driven projects in 3 communities. In 2016, we collected hair samples to measure methylmercury levels and interviewed them about diet. In cross-sectional analysis, logistic regression estimated odds ratios for the estimated effect of hair-methylmercury concentration on the prevalence of each pathology outcome stratified by selenium intake. Among 80 participants, prevalence of intestinal metaplasia, atrophy and severe chronic gastritis was 17, 29 and 38%, respectively. Adjusted Odds of severe chronic gastritis and atrophy were highest at hair-methylmercury concentrations ≥1μg/g when estimated selenium intake was 0, and approached 0 for all methylmercury levels as estimated selenium intake increased. Gastric pathology increased with methylmercury exposure when selenium intake was low. Though limited by small numbers, these findings suggest selenium ingested by eating fish/whale may counter harmful effects of methylmercury exposure in Arctic populations.
Keywords: Severe Gastritis; circumpolar Health; gastric Atrophy; gastric Cancer; indigenous Health; intestinal Metaplasia; methylmercury.