Nuclear traces detected in disputed South China Sea waters
Scientists have detected elevated traces of a radioactive isotope in a portion of the South China Sea, adding a new environmental dimension to one of Asia’s most contested maritime regions.
A joint Philippine-Japanese research team found unusually high levels of iodine-129, a by-product of nuclear fission commonly used to track nuclear activity, despite the Philippines having no nuclear power plants or weapons programmes.
An analysis of 119 seawater samples showed iodine-129 concentrations in the West Philippine Sea — part of the South China Sea that sits within the Philippines’ exclusive economic zone — were around 1.5 to 1.7 times higher than in other Philippine waters.
Researchers said the isotope did not originate locally but likely travelled from further north, pointing to the Yellow Sea as the most probable source.
Previous Chinese studies have linked elevated iodine-129 levels in the Yellow Sea to decades-old nuclear weapons tests and nuclear fuel reprocessing in Europe, with radioactive residues accumulating in northeastern China’s soil and river systems.
From there, scientists believe the isotope was carried into the Yellow Sea and transported southwards through ocean currents, including the Yellow Sea Coastal Current and the Chinese Coastal Current.
While further oceanographic modelling is needed to confirm the exact pathway, the findings suggest radioactive materials can travel thousands of kilometres across national boundaries through marine circulation.
The researchers stressed that the current iodine-129 levels pose no known risk to human health or the marine environment, noting the isotope’s extremely low radioactivity at the concentrations detected.
Instead, they said the discovery highlights iodine-129’s value as a scientific tracer.
This study highlights the need for stronger international monitoring of radioactive substances in shared waters, particularly in politically sensitive regions where environmental data can carry wider strategic implications.
The research was conducted by experts from the Philippine Nuclear Research Institute, the University of the Philippines Marine Science Institute and the University of Tokyo, with funding from Philippine government science agencies.
This story is written and edited by the Global South World team, you can contact us here.
