Heavy Metal(loid) Contamination in a Mining-Impacted Island Province in the Philippines: A Systematic Review

Introduction: Marinduque, Philippines, has faced persistent heavy metal(loid) contamination following catastrophic mining disasters in the 1990s, including the Boac River spill that released over 1.6 million metric tons of mine tailings. Despite nearly three decades of documented environmental impact, no comprehensive synthesis of the existing literature had been conducted.

Methods: This systematic review followed the PRISMA framework, searching the Scopus database using the keywords "Philippines," "Marinduque," and "metal." From 625 initially identified records, 31 studies met the inclusion criteria. Bibliometric analysis was performed using VOSviewer, including co-occurrence and co-authorship analyses to map thematic clusters and research networks.

Results: Heavy metal(loid) concentrations, particularly Cu, Cr, Mn, Pb, and Zn, consistently exceeded regulatory standards across surface water, groundwater, sediments, soil, agricultural crops, and biota. Bibliometric analysis identified six thematic clusters, with dominant research foci on health risk assessment, machine learning-based prediction, and bioremediation. Publication activity peaked in 2021-2022, driven largely by a government-funded health and vulnerability project. Critical gaps remain in sediment monitoring and long-term ecological impact studies.

Conclusions: Mining-related heavy metal(loid) contamination in Marinduque remains an ongoing environmental and public health concern. Key priorities include continuous monitoring, rehabilitation of abandoned mine infrastructure, phytoremediation and bioremediation strategies, and the integration of findings into provincial environmental policy.