Romero-Estévez et al. 2020 — Cadmium, chromium, and lead in Anadara bivalves, Santa Rosa Island, Ecuador

Romero-Estévez and colleagues measured cadmium, chromium, and lead in soft tissues of two mangrove-bivalve species (Anadara tuberculosa and Anadara similis) that the Afro-Ecuadorean community of Santa Rosa Island, in the Cayapas-Mataje Mangrove Reserve (REMACAM, Esmeraldas Province), harvest both for subsistence and for local commerce. Fifty composite bivalve samples (~10 specimens each) were collected from four sites inside the mangrove concession together with sediment (n = 4) and Rhizophora mangle leaves (n = 4) from the same locations. Concentrations were quantified by flame atomic absorption spectrophotometry on a Perkin Elmer AAnalyst 400 after CEM MARS 6 microwave acid digestion, with DORM-4 fish protein as the certified reference material. Results are reported in mg/kg fresh weight for the bivalves and mg/kg (dry-equivalent matrix basis) for sediments and leaves.

For both species and across all body weights, cadmium exposure exceeded the US EPA RfD of 1 µg/kg/day, implying a non-carcinogenic risk for consumers; lead exposure exceeded the FDA interim reference level of 3 µg/day for children in nearly every scenario, implying a high pediatric risk for A. tuberculosa in particular. Chromium exposure stayed well below the US EPA Cr(III) RfD of 1.5 mg/kg/day in every case. Sediment and leaf concentrations did not correlate with bivalve tissue concentrations, suggesting that the metals accumulated in the bivalves come from contributions in the wider mangrove ecosystem rather than from the immediately co-located substrate.

Key numbers

Units: mg/kg fresh weight for bivalve soft tissue; mg/kg for sediments and Rhizophora mangle leaves (the paper reports both matrices as mg/kg without explicit moisture footnotes — treat as the basis the lab digested at).

Bivalve soft tissue — Table 1

Concentration ranges (or single bulked values, marked *) per location, with replicate RSD and accuracy (recovery) from fortification:

* = a single bulked composite at that site (no within-site range). A. similis was not available at E1 or E2.

EU 1881/2006 maximum levels in bivalves used as comparators: Cd 1.0 mg/kg fresh weight; Pb 1.5 mg/kg fresh weight. The EU has not set a Cr ceiling for bivalves, and neither FAO/WHO Codex CXS 193 nor the US EPA have set Cr ceilings for this matrix.

Cell-level highs and lows:

• Cd — highest single value 0.948 mg/kg FW (A. similis, E4 Estero la Caleta); highest A. tuberculosa cell mean 0.560 mg/kg FW (E2 single composite). Every cell remained below the EU 1881/2006 Cd ceiling of 1.0 mg/kg FW.
• Cr — highest 0.730 mg/kg FW (A. similis, E4); highest A. tuberculosa 0.634 mg/kg FW (E3 upper bound). The Cr quantification limit was 15 mg/kg, well above the cell maxima; reported values are extrapolated from fortification recoveries (i.e., approximate values from the working range, not direct quantification).
• Pb — highest 0.923 mg/kg FW (A. tuberculosa, E3 upper bound) and 0.908 mg/kg FW (A. similis, E3); both below the EU 1881/2006 ceiling of 1.5 mg/kg FW. The Pb quantification limit was 15 mg/kg, also well above the cell maxima; values likewise extrapolated from fortification recoveries.

Other bivalve species collected (single composites, not used for the human-health calculations):

• Prototheca asperrima: Cd 0.15, Cr 0.41, Pb 0.49 mg/kg FW.
• Polymesoda inflata: Cd 0.27, Cr 0.74, Pb 0.36 mg/kg FW.

Sediment and mangrove leaves

Mean values across the four locations (no per-location breakdown for the means; RSD 5.53/2.65/2.93 % for Cd/Cr/Pb sediments; recoveries 80.07–104.58 %).

• Sediment means (mg/kg): Cd 2.14; Cr 29.99; Pb 12.37. Location E3 returned the highest sediment values. Pb was below the quantification limit in three of the four sediment samples; all four leaf samples were below the quantification limit for Cr and Pb, so those concentrations are estimates extrapolated from fortification recoveries.
• Rhizophora mangle leaves (mg/kg, three location-specific means reported in the text): Cd 2.21 / 2.23 / 4.38; Cr 4.22; Pb 3.29 / 3.35. RSDs 5.88/5.83/5.00 % for Cd/Cr/Pb, recoveries 80.89–106.10 %. The text states sediment and leaf concentrations were highest at locations E1, E2, and E3 for Pb, Cr, and Cd respectively, and that neither matrix correlated with bivalve tissue concentrations (Pearson r 0.0731–0.0778 across the three metals in A. tuberculosa; in A. similis r 0.3356 / 0.8393 / 0.0105 for Cd/Cr/Pb).

Regulatory comparators discussed by the authors:

• Ecuadorian Ministerial Agreement N° 005 (2005) regulates A. tuberculosa / A. similis extraction by minimum shell length (4.5 cm) but does not set any contaminant thresholds.
• Ecuadorian Ministerial Agreement N° 097 sets soil/sediment limits of 0.5 mg/kg Cd, 54 mg/kg Cr, 19 mg/kg Pb. Sediment Cd in this study (mean 2.14) is roughly 4× the Ecuadorian sediment limit and ~3× the Canadian CCME interim soil guideline (0.7 mg/kg Cd); Cr and Pb sediment means are below both Ecuadorian and Canadian sediment guidelines.

Human health risk assessment — Tables 2 & 3

The authors compute exposure (Ex, mg/kg/day), non-carcinogenic risk Rx (Ex / RfD; Rx > 1 indicates concern), allowable daily consumption rate CR_lim (g/day), and Pb individual carcinogenic risk (Ex × Pb cancer-slope 0.0085 mg/kg/day from US EPA 2018). Two general-portion scenarios: 200 g for children (BW 14.5 kg) and 400 g for adults (BW 70 kg), under mean, minimum, and maximum metal-concentration sub-scenarios.

US EPA / FDA reference values used:

• Cd oral RfD 0.001 mg/kg/day (US EPA IRIS).
• Cr(III) oral RfD 1.5 mg/kg/day (US EPA IRIS).
• Pb interim reference level 0.003 mg/day for children and 0.0125 mg/day for adults (FDA 2019). No Pb RfD; Pb cancer slope 0.0085 mg/kg/day (US EPA 2018).

For A. tuberculosa (Table 2, mg/kg/day exposure and unitless Rx unless noted):

• Cd Rx — children: mean 4.75, min 2.91, max 7.72 (all > 1); adults: mean 1.97, min 1.21, max 3.20 (all > 1). CR_lim (Cd) children 25.9–68.7 g/day, adults 125.0–331.4 g/day depending on scenario.
• Cr Rx — every cell ≤ 0.01 (no risk in any scenario). CR_lim (Cr) reaches 2,789,062 g/day in the minimum-concentration child scenario.
• Pb Rx — children: mean 2.06, min 0.31, max 4.24; adults: mean 0.20, min 0.03, max 0.42. CR_lim (Pb) children 47.1–647.3 g/day. Pb individual carcinogenic risk: 7.88 × 10⁻⁶ (min) to 1.08 × 10⁻⁴ (max) for children; 2.17 × 10⁻⁵ (mean) for adults — the child maximum scenario sits at the intolerable boundary (> 10⁻⁴), the rest fall in the “acceptable range” 10⁻⁶ to 10⁻⁴ defined by US EPA 2001.

For A. similis (Table 3, same units and structure):

• Cd Rx — children: mean 6.35, min 3.35, max 13.07; adults: mean 2.63, min 1.39, max 5.41 (all > 1, every scenario, both age groups). CR_lim (Cd) children 15.3–59.6 g/day, adults 73.9–287.9 g/day.
• Cr Rx — every cell ≤ 0.01 (no risk in any scenario).
• Pb Rx — children: mean 2.22, min 0.75, max 4.17; adults: mean 0.22, min 0.08, max 0.42. Pb individual carcinogenic risk 1.92 × 10⁻⁶ to 1.06 × 10⁻⁴ (children); 2.34 × 10⁻⁵ (mean adult).

The authors conclude that Cd is the dominant risk metal: even at minimum tissue concentrations, both species exceed the Cd RfD for both children and adults. Pb is a child-specific risk that becomes a serious concern at maximum concentrations. Cr at the measured concentrations does not pose a risk under either US EPA Cr(III) RfD or the EU bivalve comparator.

Methods (brief)

Sampling sites: four locations across the Santa Rosa community within the REMACAM concession (Esmeraldas Province, northwestern Ecuador). Local community members harvested bivalves by hand for 1 h per session using their normal harvesting technique, without size pre-selection. Fifty composite samples (~10 specimens each) were formed across the four sites and two species. Four sediment subsurface samples (~30 cm depth) were extracted with a stainless steel scoop per US EPA SESDPROC-200-R3 procedure, and four Rhizophora mangle leaf samples were collected per location.

Samples were stored in self-sealing plastic bags, refrigerated, and transferred to the Environmental Management Laboratory of Pontificia Universidad Católica del Ecuador, Esmeraldas (PUCE-Esmeraldas) for classification by species/length/width into 18 subgroups. Soft tissues were dissected, washed with high-quality reagent water (18.2 MΩ·cm at 25 °C), oven-dried at 60 °C to constant weight after 72 h (water content also measured at 105 °C), and milled. About 0.5 g of milled tissue was digested in 7 mL of 65% HNO₃ (Fisher Chemical) in Teflon vials in a CEM MARS 6 microwave digester per method IPN AC-06-00 (CIIEMAD-IPN 2011), then filtered and brought to 25 cm³ final volume. Metals were quantified by flame atomic absorption spectrophotometry on a Perkin Elmer AAnalyst 400. Calibration covered 0.01–1.00 mg/L for Cd and 0.3–5.0 mg/L for Cr and Pb. Triplicate analyses, fortifications, and certified reference material DORM-4 (National Research Council Canada fish protein) provided quality control. Sediments were processed per US EPA Method 3051A and leaves per the in-house natural-flour method validated for plant tissues (Romero-Estévez et al. 2019). Both environmental matrices were analyzed on the same FAAS instrument.

Detection limits (analytical): Cd 0.15 mg/kg, Cr 0.55 mg/kg, Pb 0.45 mg/L (the paper states mg/L for the Pb detection limit; both Cr and Pb LOQs are 15.0 mg/kg). Quantification limits: Cd 0.5 mg/kg, Cr 15.0 mg/kg, Pb 15.0 mg/kg. AOAC 2002 quality criteria: RSD acceptance limit 11 %, accuracy acceptance limits 80–115 %. The certified reference material recoveries reported were 84.91 % (Cd), 86.19 % (Cr), and 91.59 % (Pb).

Risk-assessment formulas: Ex = (C × CR)/BW (US EPA 2000), Rx = Ex/RfD (US EPA 1986), CR_lim = (RfD × BW)/Cx × 1000 (US EPA 2000), individual carcinogenic risk = Ex × cancer potency (US EPA 2001). Statistical analysis: arithmetic means, SDs, recoveries; Pearson correlations between bivalve / sediment / leaf concentrations at α = 0.05.

Limitations:

• Cr and Pb concentrations in bivalves (and Pb in three of four sediments, plus Cr and Pb in all four leaves) fell below the analytical quantification limit (15 mg/kg). Reported values for these analytes are extrapolated from fortification recoveries within the calibrated working range rather than directly quantified. The authors acknowledge this explicitly. Treat the reported Cr and Pb tissue values as estimates with wider uncertainty than the Cd values.
• Several sites (E1, E2) yielded a single bulked composite for A. tuberculosa (n = 1 per cell), so the per-site “concentration” carries no within-site variance.
• A. similis was unavailable at sites E1 and E2; the species comparison rests on two of the four sites only.
• The bivalves were composited (~10 specimens each); individual-bivalve variance is not measurable from this design.
• Risk math uses generic 200 g (children) and 400 g (adult) portion sizes drawn from a survey-based recipe (ceviche, 3–5 portions/week). Individual exposure under different consumption patterns will scale linearly with intake.
• The Pb cancer-slope factor (US EPA 2018) is itself contested by other regulatory bodies; treat individual carcinogenic-risk numbers as US EPA-framework outputs rather than universal estimates.

Implications for wiki use

This page contributes a small-n (n = 50 composites, ~6 cells × 2 species) tropical-mangrove dataset for Anadara bivalve occurrence and human-exposure risk on the Pacific coast of Ecuador. The Cd values across both species are within the EU 1881/2006 bivalve maximum (1.0 mg/kg FW) but uniformly exceed the US EPA Cd oral RfD when scaled by the locally-typical 200 g child / 400 g adult portion, which is the analytically informative finding rather than a regulatory exceedance. Pb values stay below the EU 1881/2006 bivalve ceiling (1.5 mg/kg FW) but exceed the FDA interim reference level for children in the mean and maximum concentration scenarios.

For routing purposes, the source belongs to bivalve-molluscs, shellfish, and seafood ingredient pages and to the shellfish and seafood product pages. It is also Cd-exposure context (the dominant analyte by risk margin), Pb-pediatric-exposure context, and a relatively rare instance of Cr in bivalve mollusc tissue with sediment and mangrove-leaf comparator matrices. Pooling into shellfish wet-weight occurrence distributions is appropriate for Cd; for Pb and Cr it would be appropriate only with the caveat that the tissue values were extrapolated rather than directly quantified.

Wiki pages this source may touch

• bivalve-molluscs
• shellfish
• molluscs
• seafood
• shellfish
• seafood
• cadmium
• chromium
• lead
• eu-1881-2006-contaminants-superseded
• epa-iris-cadmium-rfd
• epa-iris-lead-rfd

Sources

• Romero-Estévez D, Yánez-Jácome GS, Dazzini Langdon M, Simbaña-Farinango K, Rebolledo Monsalve E, Durán Cobo G, Navarrete H. 2020. “An overview of cadmium, chromium, and lead content in bivalves consumed by the community of Santa Rosa Island (Ecuador) and its health risk assessment.” Frontiers in Environmental Science 8:134. DOI: 10.3389/fenvs.2020.00134.
• Manual-fetch PDF: raw/manual-fetch/Kimi_Agent_Download Corruption Issue/seafood_papers/04_Shellfish/An Overview of Cadmium, Chromium, and Lead Content in Bivalves Consumed by the Community of Santa Ro.pdf (SHA-256 5404a94bfb82b4cf2ff9581f78d3a4bc984e778061f46a0a82dc4e7469ef76f4).

Verification notes

• 2026-06-03 Claude fresh ingest from manual-fetch/Kimi_Agent_Download Corruption Issue/seafood_papers/04_Shellfish. Numbers cross-checked against the Abstract, Tables 1–3, and the Results/Discussion sections of the published PDF.
• Brand firewall (Part 12): the source names no commercial brands. The Afro-Ecuadorean fishing community of Santa Rosa Island is the harvesting population, not a brand; the four sampling sites (E1–E4) are named per the paper’s geography.
• Analyte speciation: Cr was measured as total Cr by flame AAS (no Cr-VI speciation); the page therefore uses metals: [Cr] not [Cr-VI]. The authors compare to US EPA Cr(III) RfD because Cr(III) is the species relevant for dietary exposure, but the measurement itself is total Cr.
• Pb and Cr tissue concentrations are below the analytical quantification limit of 15 mg/kg; reported values are extrapolated from fortification recoveries (authors’ explicit acknowledgment). This is flagged in the Key numbers section and in Limitations rather than presented as direct quantification.
• The 1881/2006 cross-link is to the superseded EU contaminants framework because that is the version the paper itself cites (the paper is from 2020; EU 2023/915 came after publication).
• Sediment and Rhizophora mangle leaves are environmental matrices, not food. They are included in Key numbers because they are part of the paper’s Cd / Cr / Pb story and inform the discussion of bioaccumulation pathways, but they do not route to product or ingredient pages.
• Bivalve species Prototheca asperrima and Polymesoda inflata are mentioned in the Results as single-composite passing samples; they are not assessed for human-health risk and the page records them as a single bullet under “Other bivalve species” rather than treating them as quantitative occurrence data.

Page history

The five most recent substantive edits to this page. 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.