Land slated for development on Treasure Island contains elevated concentrations of cesium-137, a byproduct of nuclear fission associated with an increased risk of cancer, according to an independent analysis commissioned by the Center for Investigative Reporting.
The findings, discovered through soil samples gathered by reporters and tested by two independent certified laboratories, appear to undermine past statements by the Navy about the land’s historic uses and the present condition of the island.
Results show cesium-137 levels up to three times that previously acknowledged by the Navy and at least 60 percent higher than the Navy’s own thresholds for environmental safety.
The tests raise questions that “should be fully vetted by the Navy,” said Gary Butner, former chief of the radiologic health branch at the California Department of Public Health and a state watchdog for the Treasure Island cleanup until he retired in 2011.
[…]
Reluctant to test
Butner and other state radiation specialists have for years complained that the Navy has been reluctant to test for fission byproducts such as cesium-137 – despite a Cold War history suggesting the possibility of such contamination.
Instead, the Navy has focused on radium-226, used for glow-in-the-dark ship deck markers and gauges commonly discarded at military bases during the mid-20th century.
The distinction is significant: If Treasure Island were contaminated only with radium, that would be consistent with the former base’s public face as a way station and barracks for sailors on their way to the Pacific.
Potential contamination by fission byproducts such as cesium-137, however, points to possible aftereffects of Treasure Island’s more guarded history: host to radioactive ships from Bikini Atoll atomic tests and an education center training personnel for nuclear war.
The Navy repeatedly has rebuffed health officials’ demands that Treasure Island be thoroughly vetted for radioactive contamination – a multimillion-dollar job – before it is made available for a planned high-rise development.
[…]
Soil tests by Eberline Services showed cesium-137 contamination of 0.180 picocuries per gram. Tests of the same samples by New World Environmental, a former Treasure Island cleanup subcontractor, showed higher levels: up to 0.315 picocuries per gram. A picocurie, or one-trillionth of a curie, is a standard measure of the intensity of radioactivity in a sample of material.
Last April, the Navy reported that it had conducted 200 soil tests and that the greatest concentration of cesium-137 it had found on Treasure Island was 0.104 picocuries per gram.
Both of the lab results commissioned by the Center for Investigative Reporting also exceeded the Navy’s threshold for releasing land for development at Treasure Island: 0.113 picocuries per gram.
Continue reading at Treasure Island soil tests raise concerns
*Note: Curie is a non-SI (International System of Units) unit of radioactivity. To convert 1 curie to SI unit of radioactivity, it is 37 gigabecquerel, thus 1 picocurie is equivalent to 0.037 Bq. Numbers appeared in the above citation in SI unit equivalent are as follows: 0.180 picocuries/g = 6.66 Bq/Kg, 0.315 picocuries/g = 11.655 Bq/Kg, 0.104 picocuries/g = 3.848 Bq/Kg.
By converting the numbers to Bq/Kg, I confess that I am appalled to realize how I myself become used to talk about contamination levels of several tens, hundreds, even thousands after Fukushima tragedy. This news makes us realize the way it should be, namely, a contamination of a few Bq/Kg level is hazardous enough which we should be concerned about.
サンフランシスコ、ベイブリッジ中間点にあるトレジャー・アイランドというかつて海軍基地だった人工島において、高層住宅開発の土壌検査をしたところ放射能汚染が確認され問題になっているというニュースです。この問題となっている汚染のレベルをBq/Kgに換算したところ、福島原発事故以降いかに自分自身が数十、数百、あるいは数千といった汚染の話に「慣れて」しまっているかを思い知らされ愕然としています。本来はこうあるべきだったということ、つまり数ベクレル／Kgという数字はすでに十分その危険性を警戒するべき汚染であるということに改めて気付かせてくれるニュースです。