Scientists in Australia have discovered plutonium levels up to 4,500 times higher than normal in marine sediment samples collected from the Montebello Islands off Western Australia – the site where the British government conducted three nuclear tests between 1952 and 1956.

The research, published in Marine Pollution Bulletin, was based on 66 samples taken by a dive team in 2020 and highlighted the site as one of the most contaminated by man-made radioactive material in the southern hemisphere.

The lead researcher, PhD student Madison Williams-Hoffman from Edith Cowan University, said the plutonium came from the “nuclear rain” of the explosions and settled to the seabed and the environment. The element, which remains active for thousands of years, is particularly dangerous when inhaled or ingested, although it does not penetrate the skin.

The tests were carried out on a ship and towers near Trimouille and Alpha islands, which are now part of a protected marine park known for its biodiversity and the endangered species it is home to.

Despite the absence of immediate risk to human health, as found in previous fish research, scientists point to the need for mapping pollution hotspots, monitoring bioaccumulation and assessing ecosystem impacts.

Australia’s Nuclear Safety Administration (ARPANSA) supported the research, stressing that it provides valuable data on the long-term impact of nuclear explosions on the environment.

Visitors to the park are warned not to stay on the islands for more than an hour a day and not to touch the ground. According to Tim Hunt, the site manager from the Western Australian Parks and Wildlife Directorate, the current restrictions are considered adequate but will be reviewed if required.

Researcher Williams-Hoffman concluded: “This is the first step. Now that we have the picture of the pollution, the next step is to study how and if the marine ecosystems that live there are affected.”