Hundreds of nuclear tests were conducted in the Pacific Islands by the US, France and Britain between 1946 and 1996.

In the central Pacific the US conducted more than 100 tests, 67 of them at Bikini and Enewetak atolls in the Marshall Islands, a group of atolls about halfway between Australian and Hawaii and home to 55,000 people. Bikini, Enewetak and the nearby Rongelap atolls had to be evacuated due to the massive fallout from the tests and the Bikini and Rongolap islanders are yet to permanently return home.

France started its Pacific testing program in 1966, holding 193 tests at Mururoa and nearby Fangataufa atolls in French Polynesia. The first 41 were atmospheric but testing was moved underground in 1975 in the face of loud protests from throughout the region. A total of 152 underground tests were held before testing stopped altogether in 1996.

The biggest problems so far have arisen in the Marshall Islands where the atmospheric nuclear tests by the US were "dirtier and much bigger" than the French tests, according to journalist and author David Robie, who has written extensively about the legacy of nuclear testing in the Pacific.

The Marshall Islands Nuclear Claims Tribunal, set up with the agreement of the US to hear claims relating to the testing, says the Marshall Islands tests comprised only 14 percent of all US nuclear tests but accounted for 80 percent of the nuclear yield or fallout of all US atmospheric tests.

In 1954, the infamous Bravo test -- a bomb 1,000 times more powerful than the one which devastated Hiroshima at the end of World War II -- caused massive contamination. Test scientists underestimated its size and a change in wind direction caused fallout to quickly reach the inhabited Rongelap and Utrik atolls as well as a nearby Japanese fishing boat.

Fine, white radioactive ash fell on unprotected residents of Rongelap, around 160 km (100 miles) from the test site at Bikini.

The islanders rapidly developed symptoms of radiation sickness including nausea, vomiting and burning of the skin, eyes and mouth. They were evacuated two days after the test but returned in 1957.

They left again in 1985 due to continuing fears about the effects of the nuclear contamination and continuing health problems, including a high incidence of thyroid cancers and birth defects.

Robie was on board the Rainbow Warrior in 1985 when it evacuated over 300 people and their belongings from Rongelap atoll to Mejato Island 180 kilometres (about 112 miles) away.

-- More than 500 cancers caused says US institute --

The legacy continues and hearings started in the US Congress in May over Marshall Islands claims for more than three billion dollars in compensation for the continuing effects of nuclear testing.

The US government provided 270 million dollars compensation to the claims tribunal in an agreement that expired in 2001, but islanders say that level is woefully inadequate based on recent US government studies.

The tribunal has also awarded payments for health problems and damage to land but has long since run out of money to pay awards totalling well over one billion dollars.

The US government maintains only four atolls -- Bikini, Enewetak, Rongelap and Utrik -- were affected by radiation but Marshall Islands leaders say many other inhabited islands have also suffered.

"We're finding people on remote islands with high percentages of cancers," Foreign Minister Gerald Zackios said before the US Congress hearing started.

A US National Cancer Institute report issued late last year concludes that US nuclear tests in the Marshall Islands could be expected to directly cause about 530 cancers, more than half of which have yet to appear. This was to be raised as a key piece of evidence by Marshall Island representatives at the hearings.

Rayon William, a Rongelap Islander, said she returned home with other islanders when US authorities said it was safe in 1957. But she said the food she ate then was contaminated with radioactivity from the test three years earlier.

"I've experienced many illnesses as a result of living in a contaminated island," she said.

It was not until after Greenpeace evacuated the Rongelap residents in 1985 that the US Congress funded scientific studies which confirmed islanders' fears that their home atoll was still contaminated.

Subsequently Congress funded a 45 million dollar trust fund that is now paying for a clean up and resettlement program.

Bikini and Rongelap are still to see the permanent return of their islanders but ironically divers have returned to both for the pristine sea life, which has flourished in the absence of humans.

The impact of the French testing in French Polynesia has been difficult to ascertain with little information released by the French authorities.

The test sites at Mururoa and Fangataufa were 100 kilometres (62 miles) from the nearest inhabited atoll of Tureia and 1,200 kilometres (750 miles) from French Polynesia's capital in Tahiti.

Inhabitants of the Gambier islands in the southeast corner of French Polynesia called in May for access to defence ministry files on the impact on their health of 30 years of French nuclear tests on Pacific atolls.

Roland Oldham is president of the "Mururoa e Tatou" (Mururoa and Us) association of some 5,000 Polynesians who worked on the two nuclear sites in Polynesia between 1966 and 1996. He says reports stamped "Secret" from 1966 mentioned considerable radioactive fallout on the inhabited islands and atolls close to Mururoa, in particular on the island of Mangareva in the Gambier archipelago.

The French defence ministry in May described as "baseless" allegations by two French dailies that the army knowingly exposed the people of French Polynesia to heightened risks during nuclear tests.

"The conditions under which the people of French Polynesia were protected at the time of the atmospheric nuclear tests were strictly the same as those applied to military personnel conducting the tests," defence ministry spokesman Jean-Francois Bureau said.

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