ECU study finds radiation risk at WA’s Montebello Islands nuclear test site 70 years on

More than half a century since Britain conducted the first nuclear tests in Australia — in WA’s north — marine scientists have made the concerning discovery a radiation risk remains for marine life and tourists.

The Montebello Islands, an archipelago of about 174 small islands located 120km off the WA coast near Barrow Island, were used by the British in 1952 to conduct its first-ever atomic weapon test on Trimouille Island as part of Operation Hurricane.

Subsequent British tests were conducted at sites on mainland Australia, before two more on Montebello’s Trimouille and Alpha Islands in 1956, the second one which — codenamed Mosaic G2 — was the largest nuclear explosion in Australia, with an official yield of 60 kilotonnes.

Mosaic G2 was later described as an “exceptionally dirty explosion”, whose radioactive fallout contaminated large areas of mainland Australia as far away as the Queensland towns of Mount Isa, Julia Creek, Longreach and Rockhampton.

The British-led nuclear tests were carried out in co-operation with Australia amid concerns about communist expansion, particularly in parts of Asia.

Then Prime Minister Robert Menzies said he felt Australia needed to cultivate its ties with “great and powerful friends” such as Britain, and agreed to the tests in the interests of national security.

Seventy years on from the blasts, scientists led by Edith Cowan University’s Madison Hoffman have warned tourists and ecologists the area remains a radiation risk.

Future of Montebello marine life unclear

The Montebello Islands are ranked among the world’s most biodiverse marine environments, with more than 150 varieties of coral, 450 species of fish, 630 types of molluscs and 170 species of sea stars and urchins.

Ms Hoffman and her team collected and tested more than 100 samples of marine sediment and marine life from the archipelago’s underwater ecosystem to compile the preliminary findings of the four-year research project.

“It is really important we try to understand exactly what type of radionuclides and what levels of radiation remain in the marine ecosystem at the Montebello Islands,” she said.

“We’re focusing now on mapping out areas where higher levels of radionuclides are found in marine sediment all around the Marine Park.

“The next step will be to test the different organisms that we collected, from aquatic plants and sea cucumbers right through to coral trout.”

Analysis of the samples collected revealed levels of radionuclides from the nuclear tests above what would be considered a background reading, or “levels that you might get from the sand at your local beach”.

Despite the findings, the significance of the threat to marine life at Montebello Islands remains unclear.

“The final phase of the project will be to use these readings and some sophisticated models to see if there is any impact on the marine creatures that live, breathe and reproduce in the sediment,” Ms Hoffman said.

The Australian Institute of Marine Science’s expert in contaminant risks to marine ecosystems Dr Darren Koppel weighed in on the findings, saying while the study detected radioactivity around the Montebello Islands the levels were still considered “low”.

This, he said, meant acute toxicity — obvious toxicity to plants, animals, and humans from short-term exposures — was very unlikely. However, any longer-term effects were less clear and more.

“A recent study by Australian Nuclear Science and Technology Organisation and WA Department of Biodiversity Conservation and Attractions found the radiation doses adult sea turtles receive around the Montebello Islands are more than a hundred times lower than the lowest radiation levels that are known to cause radiation effects,” Dr Koppel said.

“It is possible that exposure to low levels of radiation over long periods of time can cause chronic toxicity to plants and organisms.

“We do not have much data on the chronic effects of radiation to marine organisms, so this type of research is critical to fill those data gaps. The most likely effect is that sensitive organisms and plants will have stopped living or growing in the areas with higher radioactivity leaving only the more tolerant species.”

Tourists warned to limit exposure

The Montebello Islands Marine Park has more than 250 low-lying limestone islands and islets, covering almost 60,000ha of ocean.

The only way for tourists to access the archipelago is by boat, with fishing charters operating out of Karratha and Onslow.

Each year the Islands are frequented by fishers, divers and snorkellers attracted to its coral reefs, vibrant tropical fish and rich maritime history.

Camping is permitted in some areas on Primrose, Bluebell, Hermite, Crocus and Renewal Islands all-year round and between April and September on Northwest Island.

While Ms Hoffman cannot quantify the threat the radiation poses to humans, the research project is expected to continue into 2024 and she hopes it will be something she can determine soon.

However, the results of ECU’s study have prompted fresh warnings for tourists, with visitors urged to keep their trips to an hour a day.

Dr Koppel said visitors to the area should only stay the recommended time and avoid disturbing soils and sediments or relics as they may contain small radioactive particles.

Chief radiation health scientist at the Australian Radiation Protection and Nuclear Safety Agency Dr Rick Tinker said despite the elevated radiation levels, the health risk to visitors was low.

“Montebello Islands are not inhabited by people. Therefore, the health risk is low,” he said.

“There are no changes to existing arrangements for tourists. Tourists should continue to follow local instructions which restrict access within the protected marine park.

“The area is classed as an ‘Existing Exposure Situation’ — this is where radiation levels in the environment are higher than background, but are not considered to be excessively dangerous.”

Dr Tinker said any attempts to remove the radiation that remained in the area were not justified and could actually devastate local ecosystems.

“The levels in the environment at Montebello are not near those required to present as acute radiation syndrome,” he said.

“They are at least 1000 times lower than these levels. Therefore, no extra precautions in addition to those already in place are required.

“ARPANSA continues to fund and support the work that ECU is undertaking to assess impacts of radiation at Montebello Islands as part of our purpose to protect people and the environment from the harmful effects of radiation.”