Some islands in the Pacific Ocean used by U.S. military for atomic testing are still too radioactive for humans to live there safely.
According to Popular Science, a new study published in the Proceedings of the National Academy of Science (PNAS) found that Bikini Atoll and the Enewetak Islands still feature background levels of gamma radiation far higher than scientists predicted when they conducted nuclear weapons tests between 1946 and 1958.
The military tested 67 weapons on the island chain after evacuating the islands’ 200 or so inhabitants. The relocation of those indigenous people, however, was never intended to be permanent. Scientists of the atomic era predicted that levels of background radiation would eventually fall to a level that would be safe for humans to resettle there.
Study participant Autumn Bordner from Columbia University’s Center for Nuclear Studies and a team of researchers traveled to three of the islands and measured current radiation levels. Previous estimations of the amount of gamma radiation still lingering on the islands were based on measurements taken decades ago, the study said.
Bordner and the group conducted the only recent study to “report on timely measurements on three different atolls, and also provide detailed fits and simulated maps across several islands, including the islands of Bikini and Rongelap.”
In August of 2015, the team covered more than 1,000 miles over the course of two weeks. They took radiation readings and compared them to control group readings taken at Majuro Atoll in the southern Marshall Islands and readings taken from Central Park in New York City.
Popular Science said, “Central Park and the Majuro Atoll experience 13 and 9 millirems of radiation per year, respectively. Enewetak had the lowest radiation levels, at 7.6 mrem/y, which makes sense, since the island has had extensive cleanup efforts. Rongelap has higher levels at 19.8 mrem/y, and Bikini Atoll has the most radiation of the islands studied, with a mean of 184 mrem/y.”
The authors noted that these measurements are largely unchanged since those taken in the mid-1990s, in spite of two decades’ time to allow radiation levels to decay and fall.