Overview
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.
Related evidence
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