MANILA (January 18) — Tiny traces of a radioactive substance linked to past nuclear activity have been detected in the West Philippine Sea, prompting scientists to call for closer monitoring — even as they stress there is no risk to public health or the marine environment.
Marine scientists from the University of the Philippines Marine Science Institute (UP MSI) found elevated levels of iodine-129 in seawater samples from the WPS, higher than anywhere else tested in Philippine waters. Iodine-129 is a long-lived radioactive isotope often used by scientists as a tracer to detect nuclear-related pollution.
Importantly, the Philippines has no nuclear power plants and no nuclear weapons program, meaning the source of the isotope is not domestic.
What was found — and where it likely came from
The findings came from the analysis of 119 seawater samples collected from the WPS, the Philippine Rise, the Sulu Sea and other marine areas across the country. Results showed iodine-129 levels in the WPS were about 1.5 to 1.7 times higher than those recorded elsewhere.
The study was carried out by researchers from the Department of Science and Technology-Philippine Nuclear Research Institute, UP MSI’s Geological Oceanography Laboratory, and the University of Tokyo.
Based on ocean circulation patterns and isotope signatures, scientists traced the most likely source to the Yellow Sea, where earlier studies have linked iodine-129 to decades-old nuclear weapons tests and nuclear fuel reprocessing facilities in Europe. Over time, the isotope entered rivers and coastal waters in northeastern China and was carried southward by ocean currents.
“These substances can travel vast distances through the ocean,” the researchers said, noting that currents such as the Yellow Sea Coastal Current and the Chinese Coastal Current may have transported the isotope into Philippine waters.
Should coastal communities worry?
Scientists were clear: the detected levels are extremely low and pose no threat to people, fisheries or marine ecosystems.
Iodine-129 is radioactive, but at the concentrations found, it is mainly useful as a scientific marker, helping researchers understand how pollutants move across seas and national boundaries.
“This is not a contamination scare,” the researchers emphasized. “It’s a reminder that what happens elsewhere in the world can eventually reach our waters.”
Why the findings still matter
While there is no immediate danger, scientists said the discovery highlights the importance of long-term monitoring, transparency and regional cooperation — especially as nuclear energy use and waste management continue in other parts of the world.
Radioactive materials, once released, do not respect borders. Strengthening marine monitoring systems, the researchers said, helps ensure early detection, better preparedness and informed decision-making to protect coastal communities.
The study was funded by the DOST–National Research Council of the Philippines and the DOST–Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development.
