The University of the Philippines Marine Science Institute has detected elevated levels of iodine-129, an isotope indicating nuclear activity, in seawater samples from the West Philippine Sea. These levels are higher than in any other part of the country, despite the Philippines lacking active nuclear power plants or weapons programs. The findings stem from analysis of 119 seawater samples across various sites.
Researchers from the Department of Science and Technology-Philippine Nuclear Research Institute, UP MSI’s Geological Oceanography Laboratory, and the University of Tokyo conducted the study. They found iodine-129 levels in the West Philippine Sea to be 1.5 to 1.7 times higher than at other sampling sites, including the Philippine Rise, Sulu Sea, and various parts of the archipelago.
The team traced the likely source to the Yellow Sea, aligning with recent Chinese studies that link iodine-129 there to decades-old nuclear weapons tests and European nuclear fuel reprocessing facilities. These activities released the isotope into soils and rivers in northeastern China.
It may have reached Philippine waters via ocean circulation systems, such as the Yellow Sea Coastal Current and the Chinese Coastal Current, though further oceanographic modeling is required to confirm transport pathways.
Although iodine-129 is radioactive, the researchers emphasized that current levels in the West Philippine Sea pose no threat to human health or the environment. They stressed the importance of enhancing monitoring and regulation of radioactive materials, particularly those crossing national boundaries. The research was funded by the DOST-National Research Council of the Philippines and the DOST-Philippine Council for Agriculture and Resources Research and Development.