Tourists visiting popular surf beaches in Western Australia have been warned of a significant "radiation risk" after a study revealed that nuclear fallout still lingers from the 1950s.

The Montebello Islands, or "The Montes", are located just 80km off the coast of Western Australia. Today the scenic, white sand beaches are part of a conservation area but, seventy years ago, they were the site of three British nuclear bomb tests.

Operation Hurricane and Mosaic parts 1 and 2 have left a lasting legacy on the history of the islands. Yet, the invisible after effects have been made clear by a four-year study from Edith Cowan University.

More than half a century later the marine scientists say they have discovered "there remains a radiation risk to marine life and tourists."

In a press release by the university, hundreds of sediment and beach samples were shown to still be highly radioactive.

"We have detected 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," says PhD student Madison Hoffman.

As a marine reserve, the islands are dedicated to the preservation of 150 varieties of protected coral and over 450 species of fish and other delicate forms of sea life. Hoffman says the scientists will go on to see how the nuclear material might be affecting these animals.

PHD student Madison Hoffman and her team have tested more than 100 samples of marine sediment and marine life. Photo / Kathryn McMahon, ECU

On a more pressing matter, the study wants to bring the risks to the attention of tourists.

Due to the high radiation levels, visitors are currently encouraged to keep their trips to under an hour a day. On neighbouring islands there are camping sites and the waters are frequently visited by snorkellers and surfers.

Boat operators run tours out of nearby Karratha and Onslow for fishing and surf charters.

One of the most popular sites is a concrete bollard marking where the first Hydrogen bombs were detonated on June 1956. Part landmark, part warning, on it is inscribed the dates of the test and "WARNING: HAZARDOUS RADIATION LEVELS".

The 1956 Bomb marker has become a top attraction for charter company Monte Bello Safaris. Photo / Montebello Safaris, Instagram

It has become a popular photo op for visitors, many of whom 'plank' or sit legs either side of the radioactive bollard. Possibly not a great idea, given the latest radiation findings.

The field research will continue on into 2024.