Fuentes-Lopez et al. 2025 — Total mercury in carnivorous freshwater fish, La Mojana, Colombia
This study quantifies total mercury (tHg) concentrations in muscle tissue of 326 carnivorous freshwater fish from the San Jorge River in La Mojana, Sucre, Colombia — a region heavily impacted by gold mining and agricultural pesticide use — and links tHg accumulation to nematode parasite burden and liver pathology. Across all nine species and both seasons, mean tHg was 0.31 ± 0.01 µg/g wet weight, with individual species exceeding regulatory thresholds during certain seasons and consumer risk assessments indicating hazard quotient (HQ) values above 1 for frequent consumers, particularly pregnant women, nursing mothers, and young children. The study provides species-level tHg distributions and safe weekly consumption limit estimates for a fish-dependent community in northwestern Colombia.
Key numbers
Analytical method: direct mercury analyzer (DMA-80 TriCell Milestone), USEPA 7473; LOD 0.003 µg/g. Certified reference material: ERM-BB422 (fish muscle, reference 0.601 µg/g). CRM DORM-3 recovery: 99.8% (n=5). All values total Hg (tHg) in µg/g wet weight (ww). MeHg fraction assumed at 90% of tHg for risk calculations per USEPA 1999.
Overall (n=326 fish, all species combined): mean tHg 0.31 ± 0.01 µg/g ww.
Peak species-season concentrations:
- Sternopygus macrurus (rainy season): mean tHg 0.46 ± 0.08 µg/g ww — highest in rainy season
- Cynopotamus magdalenae (dry season): mean tHg 0.54 ± 0.03 µg/g ww — highest in dry season
Species sampled (n per species per season):
- Hoplias malabaricus (Moncholo): rainy n=17, dry n=17; trophic level 4.5 — apex carnivore
- Plagioscion surinamensis (Pacora): rainy n=23, dry n=38; trophic level 4.5
- Pseudoplatystoma magdaleniatum (Bagre rayado): rainy n=5, dry n=16; trophic level 4.3
- Sorubim cuspicaudus (Bagre blanquillo): rainy n=10, dry n=19; trophic level 4.3
- Cynopotamus magdalenae (Chango): rainy n=34, dry n=29; trophic level 4.2
- Polydactylus virginicus (Barbul): rainy n=12, dry n=21; trophic level 3.7
- Trachelyopterus insignis (Cachegua): rainy n=3; trophic level 3.5
- Caquetaia kraussii (Mojarra amarilla): trophic level 3.2 (estimated)
- Sternopygus macrurus (rainy n not specified individually in abstract)
Nematode co-findings: overall nematode prevalence 46% (Contracaecum sp.); positive Spearman correlation between tHg and parasite abundance across species; all 326 fish exhibited hepatic histopathological alterations.
Risk assessment:
- Hazard quotient (HQ) >1 for frequent consumers (standard portion 230 g, 70 kg adult), indicating potential non-cancerous systemic effects
- Elevated risk identified specifically for pregnant/lactating women (portion 113 g, 75 kg) and children aged 3, 4, 5 years (portions 31.2, 42.5, 48.2 g; body weights 13.4, 15.7, 21.1 kg)
- Maximum allowable weekly consumption limits calculated per species using CRmw = 49/(C × MS)
Comparison reference: US FDA/EPA advisory limit for total Hg in commercial fish is 0.46 µg/g ww for most species and 1.0 µg/g ww action level; the EU limit for most commercial fish is 0.5 µg/g ww (Regulation EC 1881/2006). Several species-season combinations approach or exceed these thresholds.
Methods (brief)
tHg measured directly by DMA-80 TriCell Milestone (combustion-based direct mercury analysis), USEPA method 7473; no acid digestion required; samples analyzed in duplicate with <10% RSD; LOD 0.003 µg/g. All values are total Hg; MeHg was not independently speciated — the study uses the standard assumption that 90% of tHg in fish muscle is MeHg for risk calculations. Study design: cross-sectional collection during both rainy (September to November 2022, May to November 2023 implied) and dry (December to March 2022-2023) seasons; 326 specimens, 9 carnivorous freshwater species, San Jorge River (La Mojana), Sucre department, northwest Colombia. Trophic level data from FishBase.
Implications
Certification: This paper applies to freshwater fish product categories rather than seafood in the primary HMT&C product universe (infant formula, baby food, protein powder). However, it is directly relevant if HMT&C ever extends to freshwater fish ingredients or if future products incorporate Colombian freshwater fish. The study also illustrates the standard 90% MeHg:tHg assumption used in fish risk assessment, which is a methodological anchor for wiki pages on mercury speciation in fish.
Courses: Good case study illustrating how gold mining contamination propagates through freshwater food webs, how trophic level correlates with tHg accumulation, and how hazard quotient calculations generate species-specific safe consumption limits for vulnerable populations.
App: tHg concentrations for these nine South American freshwater fish species are relevant for any Colombian regional exposure estimates. Note geographic specificity — La Mojana is a mining-impacted environment and values may be elevated relative to unimpacted freshwater systems.
Microbiome: Not applicable from this study.