Silent Burden of Mercury: Environmental Exposure and Determinants Among Indigenous Communities in the Colombian Amazon

Mercury contamination remains one of the most persistent environmental and public health challenges in the Amazon, where fish consumption represents the primary pathway of exposure to methylmercury. This study assessed the prevalence and determinants of mercury exposure among indigenous communities of Taraira, Vaupés, in the Colombian Amazon. A cross-sectional survey was conducted in 2017 across eleven communities affiliated with the Association of Indigenous Captains of Taraira (ACITAVA). Sociodemographic, occupational, and dietary data were collected through structured interviews, and total mercury concentrations were determined in blood, urine, and hair samples using thermal decomposition–amalgamation atomic absorption spectrophotometry (EPA 7473). Among 238 participants (56.3% male; mean age 36.9 years), mean mercury concentrations were 80.4 µg/L in blood, 15.1 µg/L in urine, and 19.8 µg/g in hair, with 100% of blood and hair samples exceeding international reference limits. Higher mercury levels were significantly associated with fish consumption from the Apaporis River, residence in multiple locations within the municipality, and secondary education level (p < 0.05). In multivariate analysis, blood mercury was the strongest predictor of hair mercury (β = 0.707, p < 0.001), and the model explained 64.5% of the variance. These findings reveal chronic environmental mercury exposure among indigenous populations not directly involved in mining activities, emphasizing the transboundary nature of contamination in Amazonian watersheds. Strengthening biomonitoring programs and promoting safer dietary practices are essential to protect the health and cultural integrity of these vulnerable communities.