A reflection on Fukushima nuclear disaster: view of Taiwan doctor.

On 11 March 2011, the Fukushima nuclear disaster shocked the world. A 9.0 magnitude earthquake induced a tsunami, which then shut down the power supply of cooling system of the nuclear plant. The nuclear reactor exploded due to overheat and hydrogen accumulation. Radioactive materials were released and plutonium was detected positive in the soil of the power plant. It is the most severe nuclear accident after the Chernobyl event. According to the nuclear safety agency of Japanese government, Fukushima Daiichi nuclear disaster was a level-7 event, the same as Chernobyl disaster. Taiwan, although 2000 kilometers away from Japan, is still under the threat of radiation exposure. Being doctors, it is our responsibility to understand the management of radiation exposure and to educate people. The radiation effect on human varies with the exposure dosage. When the exposure dosage is less than 500 mSv (millisievert), there are no symptoms, but white blood cell count decreases. Symptoms of fatigue, vomiting, poor appetite, transient hair loss, and decreased red blood cell are developed when human is exposed to 1000e2000 mSv dosage. Between 2000e4000 mSv dosage, exposure induces bone marrow damage, and granulocytopenia or aplastic anemia may occur. Exposure doses higher than 4000 mSv cause human death directly. Among the main products of nuclear fission, the radioactive iodine isotopes including I and I are the targets of stable iodine protection. The protection are against two kinds of radiation effect: deterministic effect and stochastic effect. Deterministic effects are caused by high level of radiation exposure, and people in the vicinity of nuclear accident are at the greatest risk. These iodine isotopes will be concentrated in the thyroid gland if contaminated foods are ingested or radioactive materials in the air are inhaled, causing hypothyroidism and acute thyroiditis. Stochastic effect, also named the chronic health effect, can affect people as far as 500 kilometers away. It is not closely dose-dependent, but possibility of thyroid cancer and autoimmune thyroiditis increases with increasing radiation exposure. People at high risk of radioactive iodine exposure should take stable iodine before exposure or as early as possible. The mechanism is the Wolff-Chaikoff effect, to inhibit the thyroid gland for uptake of radioactive iodine. When large amount of iodine is given, iodopeptides are formed, which would