Yap & Al-Mutairi 2022 — Ni in 19 marine fish species, two molluscs, and one cited mussel dataset from Peninsular Malaysia, with EDI/THQ/EWI risk assessment

This MDPI Biology paper measured nickel in three locally caught seafood types from Peninsular Malaysia — 19 commercial marine fish species from Setiu (Terengganu) on the east coast, the mangrove snail Cerithidea obtusa pooled from 17 west-coast mangrove sites, and the cockle Anadara granosa pooled from 12 west-coast intertidal sites — and compared the resulting human-health risk profile (estimated daily intake, target hazard quotient, and estimated weekly intake) to a 40-site green-lipped mussel Perna viridis dataset that the same group had previously published. Nickel was determined by air-acetylene flame atomic absorption spectrometry on nitric-acid digests of dried-and-ground tissue; DOLT-3 (dogfish liver) certified reference material was recovered at 88.8–119%. Wet-weight Ni ranged 0.11–0.90 mg/kg in the fish muscle, 0.40–6.14 mg/kg in the snail total soft tissue, and 0.15–3.23 mg/kg in the cockle total soft tissue, with all three datasets falling well below the only Ni regulatory ceiling the authors could find (the US FDA molluscan-shellfish action level of 80 mg/kg wet weight). Target hazard quotients for nickel were <1.00 for average and high-level consumers across all three newly measured seafood types; only the high-level mussel consumers of the P. viridis dataset from the polluted Kampung Pasir Puteh sites had THQ values >1.00 in the cited comparison data.

Key numbers

All concentrations in mg/kg (Ni). DW = dry weight as analysed; WW = wet weight via the species-specific conversion factor (cockle 0.20; snail 0.24; fish factor varies per species, supplied in Table 1 of the supplementary materials). EDI in µg/kg-bw/day. THQ dimensionless. EWI = MWI (mean weekly intake) in mg/week per consumer for fish (0.70 kg/week average; 1.40 kg/week high-level) and mollusc (0.28 kg/week average; 0.56 kg/week high-level) intake rates. Risk-assessment basis: 62 kg adult Malaysian, oral reference dose (ORD) 20 µg/kg/day (US EPA), PTWI 91 µg/kg-bw/week (recalculated from EFSA TDI 13 µg/kg-bw/day) = 5642 µg/week (Table 1, p. 7 of 20).

The EWI columns above are reported in the paper as µg/week per kg consumption fraction in Table 1; the body-text “mg/week” notation on p. 14 of 20 refers to per-consumer mean weekly intake (MWI) for the average-level (0.70 kg/week fish, 0.28 kg/week mollusc) and high-level (1.40 kg/week fish, 0.56 kg/week mollusc) consumption rates. The reported MWI ranges as percentages of the 5642 µg/week recalculated PTWI are:

• Fish: average-level 1.36–11.2%; high-level 2.73–22.3%.
• Snail C. obtusa: average-level 1.99–30.5%; high-level 3.97–60.9%.
• Cockle A. granosa: average-level 0.74–16.0%; high-level 1.49–32.1%.
• Mussel P. viridis (cited): average-level 1.64–95.8%; high-level 3.28–192% — only this cited mussel dataset exceeds the recalculated PTWI for some high-level consumers.

The amount of each seafood that a 62-kg adult would need to consume per week to reach the 5642 µg/week recalculated PTWI is reported as: 6.27–51.3 kg for Setiu fish, 0.92–14.1 kg for snails, 1.75–37.6 kg for cockles, and 0.29–17.0 kg for mussels (p. 14 of 20).

Highest and lowest Ni species in the fish dataset (p. 9 of 20): Atule maculatus highest (3.84 mg/kg DW) and Megalaspis cordyla lowest (0.48 mg/kg DW). Inter-species ordering by mean Ni was A. maculatus > T. lepturus > A. indica > N. hexodon > A. chacunda > others.

Regulatory comparator (p. 8 of 20): US FDA/CFSAN molluscan-shellfish action level for Ni = 80 mg/kg WW. All measured fish, snail, cockle, and mussel WW values are at least an order of magnitude below this ceiling.

Methods

Sample preparation: fish were weighed and length-measured at landing (10–20 g of dorsal muscle removed per fish); 20 snails (shell length 32.7–49.3 mm) per site and 20 cockles (shell length 23.6–33.9 mm) per site were pooled by total soft tissue. All samples were oven-dried at 60 °C for 72 h to constant weight, then ground with an agate pestle and mortar.

Digestion: 0.50 g of homogenized dry sample + 5.0 mL concentrated HNO3 (AnalaR grade, BDH 69%) in a hot-block digester at 40 °C for 1 h followed by 140 °C for 3 h. Digests were diluted with double-distilled water and filtered through Whatman No. 1 into acid-washed pillboxes.

Instrument: air-acetylene Flame Atomic Absorption Spectrometer (FAAS), Thermo Fisher Scientific ICE 3000 series AA (USA), Ni detection limit 0.010 mg/L.

QA-QC: certified reference material DOLT-3 (dogfish liver, National Research Council Canada) recovered 88.8–119%; all glassware was soaked overnight in 10% nitric acid before use; procedure blanks and sample triplicates were run for quality control.

Wet-weight conversion: species-specific DW→WW conversion factors were applied — 0.24 for C. obtusa and 0.20 for A. granosa — with the fish conversion factor reported per-species in Table 1 of the supplementary materials.

Health-risk assessment math:

• EDI = (Mc × CR)/bw, where Mc = metal concentration on WW basis (mg/kg), CR = consumption rate (g/person/day), bw = 62 kg adult Malaysian. CR values: fish 100 g/day (average), 200 g/day (high); mollusc 40 g/day (average), 80 g/day (high).
• THQ = EDI/ORD; ORD for Ni = 20 µg/kg-bw/day (US EPA regional screening level).
• EWI = EDI × 7 days.
• Recalculated PTWI for Ni: the paper notes EFSA has not established a PTWI for Ni; the authors derive PTWI = 91 µg/kg-bw/week from the EFSA TDI of 13 µg/kg-bw/day (13 × 7 = 91), giving 5642 µg/week for a 62-kg adult.
• Comparison against the FDA/CFSAN molluscan-shellfish action level of 80 mg/kg WW.

Speciation

No speciation. The paper reports total nickel only. The introduction notes that the +2 oxidation state (Ni²⁺) is the most common species in environmental and biological systems but does not separate oxidation states analytically.

Quality control

• CRM DOLT-3 recovery 88.8–119% — at the upper edge of typical acceptance bounds (75–125% is the common rule of thumb); not flagged as out-of-range but worth noting that the upper-end recoveries imply some matrix-driven enhancement.
• FAAS detection limit Ni 0.010 mg/L; per-sample LOD on WW basis is not stated as a single number because of the per-species conversion factors.
• Sample triplicates and procedure blanks run; no per-sample RSD reported in the paper text or in the Table 1 summary.

Implications

The paper records that for the three newly measured Peninsular Malaysian seafood types, Ni concentrations on a wet-weight basis are at least an order of magnitude below the only seafood-specific Ni regulatory ceiling the authors could identify (US FDA molluscan-shellfish action level of 80 mg/kg WW), and that the corresponding target hazard quotients are below 1.00 for both average and high-level consumers — i.e., no non-carcinogenic risk from Ni at the modelled Malaysian consumption rates. The only exceedance the paper documents is in the cited Perna viridis mussel dataset from polluted Kampung Pasir Puteh sites for high-level consumers (THQ up to 1.25); that exceedance is not from the newly measured data in this study but from a prior 40-site survey by the same group.

The per-species and per-site detail in the supplementary tables (Tables S4–S7, referenced but not present in the truncated PDF read here) is what makes the fish data potentially useful for any future per-species pooled-percentile work on marine non-predatory finfish; the supplementary materials should be retrieved separately if that synthesis is undertaken. The single-estuary fish design (Setiu, 19 species, August 2016 – February 2017, three replicates per species) is a constraint on inferring Peninsular Malaysian fish-as-marketed Ni; the snail and cockle datasets are more spatially distributed but pool across 3–4 sampling years.

This paper is also useful as a worked example of the EFSA-TDI-to-PTWI recalculation move (multiplying the daily TDI of 13 µg/kg-bw by 7 to get a weekly comparator of 91 µg/kg-bw/week) that other Ni-in-seafood risk assessments in the corpus apply differently; documenting this paper’s choice supports the regulatory-page work on regulations/efsa-nickel-tdi.

Verification notes

• PDF source provenance: 20-page PDF (pdfinfo confirms 20 pages) residing in raw/manual-fetch/Kimi_Agent_Download Corruption Issue/seafood_papers/02_Marine_Nonpredatory/. Despite the parent folder being named after the Kimi-agent download corruption batch, this PDF is intact: title, abstract, all results sections, all figures, full discussion, conclusions, and references read cleanly. SHA-256 7ee0a433fbde838914ef8c2f52115fb93f36ec170e3525514fa273828b2a4934. Supplementary materials (Tables S1–S10) are referenced in the body and the Supplementary Materials section but are not bundled into the PDF copy under review; they are available from https://www.mdpi.com/article/10.3390/biology11030376/s1.
• Cite-key construction: yap-almutairi2022-nickel-seafood-malaysia — first author surname hyphenated with second author surname (consistent with the two-author byline) + year + analyte + matrix + jurisdiction. No collision with other Yap papers in the corpus as of 2026-06-03 (ls wiki/sources/ | grep -i yap returned no matches; the cited self-reference Yap et al. 2016 [35] is not yet ingested).
• Brand firewall (Part 12): no brand names, no commercial product identifiers, no retail purchase data. Sampling sites are public fishing landing sites (Kampong Fikri, Kampung Rhu Sepuluh) and named ecological sites (Belanak/Juru for snails, Pantai Jeram for cockles). Documented as geographic provenance, not as brand attribution.
• Wiki/HMTc firewall (Part 2): no HMTc threshold proposals, no comparison to certification values, no consumer translation. The FDA molluscan-shellfish 80 mg/kg WW action level, the EFSA Ni TDI of 13 µg/kg-bw/day, and the authors’ recalculated PTWI of 91 µg/kg-bw/week are recorded as the comparators the paper used, not as wiki-endorsed thresholds.
• Taxonomy choices: metals: [Ni] (only nickel is measured); ingredients: [fish, seafood, molluscs, bivalve-molluscs] (all four are live ingredient pages; cockle and snail do not have dedicated ingredient slugs as of 2026-06-03 and stay as matrices tokens — cockle, mangrove-snail, green-mussel, mollusc-soft-tissue); products: [fish-marine-non-predatory, seafood, shellfish] (all three are live product pages, and the folder name “02_Marine_Nonpredatory” aligns with the marine-non-predatory routing — the fish set is dominantly small pelagic and demersal species like Decapterus, Rastrelliger, Pampus, Megalaspis, Anodontostoma, Johnius, with some predatory species like Scomberomorus commerson and Otolithes ruber mixed in; the snail/cockle/mussel sets route to shellfish and seafood).
• Jurisdiction: MY (Malaysia) — sampling and consumption-rate modelling all anchored on Peninsular Malaysia.
• Evidence tier: B. Peer-reviewed MDPI Biology article with documented FAAS methodology, DOLT-3 CRM recovery (88.8–119%, at the upper edge of acceptable), transparent risk-assessment arithmetic, and reproducible numbers. Not A because: the fish dataset is thin (3 replicates × 19 species at a single estuary, single 2016–2017 collection window); the snail and cockle datasets pool across 3–4 sampling years (2005–2010); the mussel dataset is cited verbatim from Yap et al. 2016 rather than newly measured; per-sample RSD is not reported. Not C because the analytical and risk-assessment methods are documented and the QA-QC is real.
• The fish-species ordering by Ni (A. maculatus > T. lepturus > A. indica > N. hexodon > A. chacunda > others) and the highest/lowest pair (A. maculatus 3.84 mg/kg DW max; M. cordyla 0.48 mg/kg DW min) are extracted from the figure text on p. 9 of 20 rather than from a per-species table in the body of the PDF; Tables S4–S10 would contain the per-species and per-site values.
• The EWI body-text “mg/week” notation on p. 14 of 20 and the Table 1 “EWI” notation in µg/week are reconciled in Key numbers: the Table 1 EWI columns are per-mean values in µg/week (a single mean fish replicate yields 1.24–10.2 µg/week Ni intake at the species mean), and the body-text MWI in mg/week is the per-consumer weekly intake after the 0.70 kg/week or 1.40 kg/week consumption multiplier (e.g., for Atule maculatus at 0.90 mg/kg WW, MWI = 0.90 × 0.70 = 0.63 mg/week ≈ 11.2% of 5642 µg/week PTWI).

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