As part of an ongoing monitoring program, the Japanese government is measuring the radiation exposure of people near the Fukushima plant. The nuclear emergency may be largely contained, but not all of the news is good.
Fukushima made headlines the world over when a tsunami and earthquake caused several uncontrolled explosions in the coastal nuclear energy plant. With residents nervous, but hesitant to move out, monitoring the ongoing exposure of the populace has been critical. Recent measurements on dosimeters and urine tests have indicated that it may be time for certain residents to make some difficult decisions about leaving the area.
Fifteen residents near Fukushima have had urine tests that have revealed traces of radioactive Iodine-131. This isotope of Iodine has a half-life of 8 days, so it does not pose a long-term threat as long as it is not ingested. Inside the body, the isotope accumulates in the thyroid. After Chernobyl, many nearby victims developed thyroid cancer as a result of drinking contaminated milk. Just after the emergency at Fukushima, the Japanese government distributed iodine tablets. The tablets were of a non-radiactive isotope of iodine that was meant to saturate the thyroid and prevent any more uptake of radiactive elements. It seems that, at least in a few cases, the radioactive isotopes were not entirely blocked.
This results of these tests are unwelcome, but not worthy of panic. Even those who did have radioactive isotopes present in their urine only approached the maximum annual safe dose of 20 milliseverts of radiation exposure. But there are still other concerns. More radioactive isotopic elements, such as Ceasium, were present in the ground around the nuclear plant. While Iodine-131 has a half-life of eight days, these isotopes have a half life of between two and thirty years. Although the two months of testing only showed that the present isotopes would have given residents doses of nearly 15 milliseverts in the last two months - still under the annual safe dose - the continuing presence of these isotopes will result in raised radiation exposure for people in the area. The government is giving pregnant women and children personal dosimeters to help them constantly monitor their exposure. Those residents who want to stay will have to be careful about local produce and water.
Via New Scientist.