demand for more recent and comprehensive measurements as the radioactivity made its way east. These measurements were taken by a cooperative group of organizations under the guidance of a marine chemist with the Woods Hole Oceanographic Institution, and revealed that total radiation levels, of which only a fraction bore the fingerprint of Fukushima, were not high enough to pose any direct risk to human life and in fact were far less than Environmental Protection Agency guidelines or several other sources of radiation exposure deemed safe. Integrated Fukushima Ocean Radionuclide Monitoring project (InFORM) also failed to show any significant amount of radiation and as a result its authors received death threats from supporters of a Fukushima-induced "wave of cancer deaths across North America" theory. Event rating The incident was rated 7 on the International Nuclear Event Scale (INES). This scale runs from 0, indicating an abnormal situation with no safety consequences, to 7, indicating an accident causing widespread contamination with serious health and environmental effects. Prior to Fukushima, the Chernobyl disaster was the only level 7 event on record, while the Kyshtym disaster was rated 6 and the Three Mile Island accident and Windscale fire were rated as level 5. A 2012 analysis of the intermediate and long-lived radioactivity released found about 10–20% of that released from the Chernobyl disaster. Approximately 15 PBq of caesium-137 was released, compared with approximately 85 PBq of caesium-137 at Chernobyl, indicating the release of of caesium-137. Unlike Chernobyl, all Japanese reactors were in concrete containment vessels, which limited the release of strontium-90, americium-241, and plutonium, which were among the radioisotopes released by the earlier incident. 500 PBq of iodine-131 was released, compared to approximately 1,760 PBq at Chernobyl. Iodine-131 has a half-life of 8.02 days, decaying into a stable nuclide. After ten half lives (80.2 days), 99.9% has decayed to xenon-131, a stable isotope. Aftermath There were no deaths from radiation exposure in the immediate aftermath of the incident, though there were a number of (around 1600 non-radiation related) deaths during the evacuation of the nearby population. As of September 2018, one cancer fatality was the subject of a financial settlement, to the family of a former nuclear station workman, while approximately 18,500 people died due to the earthquake and tsunami. The maximum predicted eventual cancer mortality and morbidity estimate according to the linear no-threshold theory is 1,500 and 1,800, respectively, but with the strongest