Raju et al. 2021 — Cadmium and lead in freshwater clam and marine mussel, Cagayan Valley, Philippines
This paper measured Pb and Cd concentrations in soft tissues of two bivalve species collected from Cagayan Valley, Philippines: freshwater clam (Corbicula fluminea) and marine mussel (Mytilus edulis), using Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS). Results showed low concentrations for both metals in both species, well below Malaysian food safety guidelines (Pb limit 1.00 g/g; Cd limit 2.00 g/g), and the authors concluded no significant health risk from consumption of bivalves in this region. The study contributes a data point for a Southeast Asian freshwater and marine bivalve pair but carries significant limitations: the number of individual specimens analyzed is not clearly reported, only two metals were measured, and the Philippine regulatory framework is not cited.
Key numbers
- Corbicula fluminea (freshwater clam): Pb 0.006 g/g dry weight; Cd 0.016 g/g dry weight
- Mytilus edulis (marine mussel): Pb 0.011 g/g dry weight; Cd 0.015 g/g dry weight
- Note: values reported in g/g (i.e., mg/kg), wet-weight basis not specified — authors state results are dry weight from their Table 2 header; both values for both species are below <0.1 g/g described as the comparator threshold
Unit clarification: The paper reports results in g/g dry weight. Converting to ppb (µg/kg wet weight) would require a moisture correction factor not provided in the paper. Values as reported are: Pb 6,000 µg/kg d.w. (clam) and 11,000 µg/kg d.w. (mussel); Cd 16,000 µg/kg d.w. (clam) and 15,000 µg/kg d.w. (mussel). These are unusually high for Pb in bivalves in a region declared low-pollution; the comparison to Malaysian limits of 1.00 g/g and 2.00 g/g (also dry weight) places them well below those limits, suggesting the reporting is consistent internally. Caution is warranted in comparing these dry-weight values to wet-weight regulatory limits without applying a moisture factor.
- Malaysian food safety Pb limit: 1.00 g/g; Cd limit: 2.00 g/g (used as comparator, not Philippine national limits)
- LOD/LOQ not stated in the paper
- No Hg, As, Ni, Al, Cr, or Sn measured
Methods (brief)
Freshwater clam and marine mussel collected from Cagayan Valley sites with BFAR Region 02 permit. Shell and byssus removed; soft tissues washed, homogenized, dried. 1 g dried sample in digestion tube; 10 mL 65% HNO3, heated to 130 °C; filtered and diluted to 25 mL in deionized water. Cd and Pb analyzed by GFAAS at DOST Lab Region 02. Sample count per species not explicitly stated; results are single-point values, not means ± SD.
Evidence tier B: published in Scholars Academic Journal of Biosciences (SAJB), an open-access journal with variable peer-review rigor. Limited methodological detail (no CRM validation, no LOD/LOQ, no explicit n per species). Data useful as a regional data point but not for quantitative synthesis without additional validation.
Implications
Certification: This paper does not contribute quantitative evidence usable for HMT&C threshold-setting due to methodological gaps (no CRM, unclear n, dry-weight basis without moisture factor).
Courses: Useful to illustrate biomonitoring approaches in Southeast Asia and the role of bivalves as environmental indicators, with caveats about reporting rigor.
App: Not directly usable as a contamination profile value without wet-weight conversion.