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The Threat of Radiation

After the March 2011 Tohoku earthquake and tsunami that struck Japan and caused the Fukushima Daiichi nuclear power plant incident, many professionals in the media and sciences predicted the worst outcomes for the land, sea and people of the region. Now, due to recent studies conducted by a team of international professionals on Fukushima radioactivity levels, the outcomes may not be as bad as once predicted.

Eight months after the 9.0 earthquake that caused one of Japan’s most alarming nuclear scares, two studies published in the latest Proceedings of The National Academy of Sciences, show maps of “hotspots” where radioactive levels are highest as well as those areas in which they are the safest. These studies will help the government of Japan choose which regions to officially abandon, which to return to farming or which to remove the affected top-soil first before rebuilding. The studies will also help researchers understand more about how radioactivity is spread via rain and transferred by mountains by the patterns shown in the maps.

The studies are in stark contrast to the original speculation that the area surrounding the Fukushima Daiichi nuclear power plant will be uninhabitable due to the high levels or radiation.

One of the studies, which focuses on the levels of different radioactive isotopes, looks at the levels of different isotopes present in the region their respective half-lives , and their spread among the region due to rain, wind and mountains. These studies took note of the dangerous and long-living Cesium-137 in particular, which has a half-life of 30.1 years, as well as the much less damaging Iodine-131, which has a half-life of simply 8 days.

Wind spreads the substances to other areas, and rain-washes it into the ground, where it ends up contaminating the soil, and mountains block the spread’s path to other regions. Due to the mountain block, the study found that the spread of these isotopes were blocked by mountain regions in the main island of Honshu and thus protected the western and northwestern region of Japan.

The case with the eastern spread of the radiation is a different story, with levels of Cesium-137 exceeding 2,500 becquerels per kilogram in the area surrounding the epicenter of the disaster, leaving food production severely impaired. This is particularly alarming because Cesium-137 is known to integrate into muscle tissue, and as such, poses a serious threat to living organisms. However, nearby prefectures such as Iwate, Miyagi, Yamagata, Niigata, Tochigi, Ibaraki and Chiba only read 250 becquerels per kilogram, leaving them partially impacted and with possibilities of repopulation and re-farming in the near future.

The second study focused on gamma radiation levels emitted by the soil contaminated with Cesium-137 and other isotopes. Then they compared them to weather patterns and found out that two major downpours washed most of the radiation into the soil. These happened on March 15-16 in Fukushima, the most affected regions, and on March 21-23 in surrounding prefectures in Tochigi, Ibaraki, Saitama and Chiba.

The radiation levels were found to not be as high as originally predicted but still remain formidable. North of the Fukushima power plant incident, levels of Cesium-137 radiation were measured as 200 times greater than normal while areas east of the Fukushima power plant incident and neighboring prefectures were only 10 times above normal radiation levels at 0.5 microsieverts per hour.

The third study measured the level of radiation in people by surveying more than 5,000 people over a three-month period after the disaster. The results showed levels of radiation in people being lower than predicted with only 10 people with high doses of radiation present.

These results suggest that current radiation levels in certain areas in Japan are not as severe as originally thought. Thanks to the proper precautions being enacted directly after the incident, the Japanese people are not at as high a risk for diseases related to extensive radiation exposure, including cancer.