Overview
This study measures total mercury (tHg) in two commonly consumed piscivorous fish species (tucunaré, Cichla spp., and pescada, Plagioscion squamosissimus) in the Tapajós River basin of the Brazilian Amazon, a region with active artisanal gold mining since 1970, and compares these values to tHg in hair samples from 110 pregnant women who had just given birth in Itaituba. Fish tHg concentrations exceeded the FDA/EPA safety limit of 0.5 mg/kg for P. squamosissimus in both seasons and for Cichla spp. in the dry season; 48% of pregnant women had hair tHg above the US EPA reference dose of 1.0 mg/kg, signalling substantial fetal MeHg exposure risk.
Key numbers
- Fish tHg (dry season):
- Cichla spp.: 0.62 ± 0.07 mg/kg (= 620 ± 70 ppb) wet weight; exceeds FDA/EPA limit of 0.5 mg/kg
- Plagioscion squamosissimus: 0.73 ± 0.08 mg/kg (= 730 ± 80 ppb); exceeds FDA/EPA limit
- Fish tHg (rainy season):
- Cichla spp.: 0.39 ± 0.04 mg/kg (390 ± 40 ppb); below FDA/EPA limit (0.5 mg/kg)
- P. squamosissimus: 0.84 ± 0.08 mg/kg (840 ± 80 ppb); exceeds FDA/EPA limit
- Human hair tHg: mean 1.6 ± 0.2 mg/kg across 110 pregnant women
- 48% of participants above US EPA hair reference dose of 1.0 mg/kg
- US EPA hair RfD of 1.0 mg/kg corresponds to PTWI of 0.7 µg/kg body weight for MeHg from maternal diet
- Fish consumption: 67% of participants reported eating P. squamosissimus; 44% ate Cichla spp.
- n_fish = 120 samples (30 per species per season); n_women = 110
- Seasonal variation: P. squamosissimus tHg higher in rainy season (0.84) vs dry (0.73); Cichla spp. tHg higher in dry season (0.62) vs rainy (0.39)
- Analytical method: DMA-80 direct mercury analyser; certified reference materials NIES 13 (hair) and BCR-463 (tuna); recoveries 94% and 97%
- Note: the paper reports total mercury (tHg); >95% of tHg in piscivorous fish from this region is MeHg (per cited literature), so tHg serves as a proxy for MeHg in this context, but values are reported as tHg in the source
Methods (brief)
Direct mercury analysis (DMA-80, Milestone) without pretreatment; thermal decomposition, catalytic conversion, amalgamation, spectrophotometry at 253.55 nm. LOD 0.0015 ng. Samples purchased monthly from same artisanal fishermen, July 2018 to June 2019, covering dry (July-December) and rainy (January-June) seasons. Hair collected from participants at childbirth; 4 cm from root, representing approximately 4 months of mercury exposure during late pregnancy.
Implications
Certification: Supports HMT&C flagging of high-trophic piscivorous fish from artisanal-mining river basins as highest-risk for tHg/MeHg. FDA/EPA safety limit of 0.5 mg/kg tHg in fish for pregnant women is the operative US threshold; both species tested exceed it in at least one season. Courses: Exemplary case study for fish tHg/MeHg pathway to pregnant women; illustrates why trophic level, region (artisanal gold mining), and season all affect fish mercury concentrations. App: If an app ingredient list includes fish species sourced from Amazon basin or other artisanal-mining regions, tHg risk should be elevated even for species that appear low-risk in US commercial data. Microbiome: Not addressed.
Wiki pages updated on ingest
Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Change | Description |
|---|---|---|---|
| e317189 | 2026-08-11 | correction | 6 sections added; narrative text revised |