Quantification of Cadmium and Lead in Oysters (Magallana bilineata, Roding 1798) from Coastal Barangays of Panabo City, Davao del Norte, Philippines: A Baseline Study for Policy Development

Abstract

Heavy metal contamination in marine environments poses significant risks to both ecosystems and human health, particularly affecting filter-feeding organisms like oysters that bioaccumulate toxic substances. In the Philippines, Magallana bilineata is a commercially important oyster species, making it essential to monitor contaminants such as cadmium (Cd) and lead (Pb) for food safety. While studies have explored heavy metal contamination in other bivalves in the Davao region, there is limited data on oysters specifically from the coastal barangays of Panabo City. This study aimed to quantify Cd and Pb concentrations in oysters collected in April 2025 from three coastal barangays: San Vicente, San Pedro, and JP Laurel. Using a descriptive, cross-sectional design, samples were analyzed through Dry Ashing-Atomic Absorption Spectrometry (AAS), and the Kruskal-Wallis ANOVA was applied to assess spatial differences in metal levels. Results showed that Cd concentrations in all sites were within the 1.0 ppm limit set by Fisheries Administrative Order No. 211 (2001), with statistically significant differences between barangays (p = 0.034). However, Pb concentrations in oysters from JP Laurel exceeded the safety threshold of 0.5 ppm, reaching up to 1.5 ppm, although differences across sites were not statistically significant (p = 0.116). The elevated Pb levels in JP Laurel suggest localized contamination, possibly from industrial or agricultural runoff near the Lasang River. This study emphasizes the need for routine monitoring, stricter pollution control policies, shellfish sanitation certification, and increased public awareness to ensure sustainable aquaculture and seafood safety in the region.