Escobar-Camacho et al. 2024 — Mercury in fish and aquatic environments of the Piedmont Ecuadorian Amazon
This study measured total mercury (tHg) in muscle tissue of freshwater fish consumed by indigenous communities in two territories of the Piedmont Ecuadorian Amazon (Cofán-Bermejo and Dureno), alongside tHg in water and sediments from the same rivers. The authors applied ICP-MS following acid digestion to quantify tHg concentrations in approximately 120 fish from multiple species; MeHg in fish muscle was estimated through established conversion factors and literature comparisons rather than direct speciation. Results showed fish tHg concentrations exceeded WHO and Codex Alimentarius maximum limits of 500 µg/kg in several predatory species, with notable inter-species variation reflecting biomagnification along the food web. This is the first systematic mercury occurrence survey for these Amazonian indigenous communities, where subsistence fishing constitutes the primary protein source.
Key numbers
- Sample matrix: freshwater fish muscle tissue (multiple species), water, and sediment from rivers in Cofán-Bermejo and Dureno territories, Sucumbíos Province, Ecuador.
- tHg in fish: values reported by species; predatory fish (e.g., catfish, large characids) exceeded the Codex/WHO limit of 500 µg/kg (0.5 mg/kg) ww in a substantial fraction of samples.
- Method: ICP-MS after acid digestion; analytical method consistent with standard trace-metal protocols for biological tissues.
- Water tHg and sediment tHg also quantified but at concentrations typical of background Amazonian conditions (water in the low ng/L range), suggesting biomagnification rather than point-source contamination as the primary driver.
- Species-specific maxima and means are reported in the source tables; exact values should be verified against original tables in the raw markdown.
Methods (brief)
Total mercury by ICP-MS following acid digestion of homogenized muscle tissue. Fish were caught by local fishers using traditional methods (hook and line, nets) in river reaches used for subsistence fishing. Water samples collected in HDPE bottles; sediment composite cores. No HPLC speciation for MeHg was performed; the study reports tHg and infers MeHg from conversion factors. Analytical QC not fully described in the available markdown.
Implications
Certification: Freshwater fish from artisanal and indigenous fisheries in Amazonian regions represent a contamination pathway not covered by most commercial certification programs; relevant context for consumer advisories on wild-caught freshwater fish. Courses: Illustrates the biomagnification pathway and vulnerability of indigenous communities dependent on subsistence fishing; supports course content on trophic transfer of mercury. App: tHg in freshwater fish from Amazonian Ecuador; relevant to ingredient risk profiling for wild-caught river fish from tropical South America. Microbiome: Mercury exposure in high-fish-consumption populations; potential link to heavy-metal-microbiome interactions in communities with chronic low-level exposure.