From 1966 to 1974, France blew up 41 nuclear weapons in above-ground tests in French Polynesia, the collection of 118 islands and atolls that is part of France. The French government has long contended that the testing was done safely. But a new analysis of hundreds of documents declassified in 2013 suggests the tests exposed 90% of the 125,000 people living in French Polynesia to radioactive fallout—roughly 10

The findings come from a 2-year collaboration, dubbed the Moruroa Files, between Disclose, a French nonprofit that supports investigative journalism; Interprt, a collective of researchers, architects, and spatial designers affiliated with the Norwegian University of Science and Technology who focus on environmental issues; and the Science & Global Security program at Princeton. The findings were presented on 9 March on the project’s website, in a book, and in a technical paper posted to the arXiv preprint server.

Declassified documents suggest actual exposures were between two and 20 times higher than France’s Atomic Energy Commission (CEA) estimates… Reasons for the discrepancies vary from test to test, he says. For example, CEA acknowledged that the first test, dubbed Aldébaran, exposed residents of the Gambier Islands to relatively high levels of fallout. But actual exposures were likely higher still… Although CEA noted that contaminated rainwater fell on the island, he says, it failed to consider that many residents likely drank the contaminated water, collected in household cisterns, for days.

Most important, the documents suggest a single test in 1974, called Centaure, exposed the entire population of Tahiti—87,500 people at the time—to fallout. French authorities set off a relatively tiny atom bomb with an explosive yield equal to 4 kilotons of TNT, and weather forecasts predicted that winds should carry fallout to the north. Instead, the wind blew to the west, carrying the plume directly over Tahiti. A new simulation based on data in the documents shows how the plume of radiation wafted over the island. CEA estimated that people on the island received a dose of about 0.6 mSv.  However, Phillipe and colleagues argue that CEA underestimated the total amount of radiation that accumulated on the ground over several days, didn’t account for radiation lingering in vegetables consumed later…

The new analysis moves the vast majority of French Polynesians past the exposure threshold to qualify for compensation. Philippe and Schoenberger would like to see France do away with the exposure standard and compensate anyone who lived through the tests and developed a qualifying cancer. “Our hope is to demonstrate that this kind of threshold can be prejudicial to claimants just because of the difficulties of proving exposure,” Schoenberger says.

Philippe estimates that, assuming a cancer rate of 0.2% per year, roughly 10,000 cancer patients or their families would qualify retroactively and that compensating them would cost about €700 million. Future cancers would cost about €24 million per year, he estimates. However, Hughes says it remains to be seen whether the French government will even acknowledge the analysis. “My fear is that they will simply ignore it,” Hughes says.

The declassified documents also show the French government routinely failed to warn Polynesians about the radiation risks, Philippe says. In the Centaure test, authorities could have warned Tahitians about the approaching fallout 2 days in advance, but did not. Ironically, Philippe notes, the United States, the Soviet Union, and other countries were monitoring the tests remotely. “Everybody knew what was going on,” he says, “except the Polynesians.”

Excerpt from Adrian Cho, France grossly underestimated radioactive fallout from atom bomb tests, study finds, Science, Mar. 11, 2021