On March 11, 2011, Japan was hit by a massive earthquake measuring 9 on the Richter scale, which triggered a tsunami and a nuclear power plant explosion. The nuclear leaks caused by the nuclear power plant explosions have had catastrophic consequences for the atmosphere and marine environment. It has been reported that 33 children have been diagnosed with thyroid cancer in Fukushima Prefecture, up 7 from 26 in November last year. Recently, a study was conducted on how the occurrence of thyroid cancer is related to the amount of radiation. What should be the safe range of radiation exposure in mSv? Why are children more prone to develop the disease? The thyroid gland is the largest endocrine gland in the human body and is located under the thyroid cartilage immediately in front of the third and fourth cartilage rings of the trachea, and consists of two lobes and the isthmus. It is usually located 2-3 cm below the larynx and is shaped like a bow tie. “Thyroxine is a hormone secreted by the thyroid gland, which is a very important factor in maintaining normal growth and development of the human body, and iodine is the raw material necessary for the synthesis of thyroxine.” Xiao Wenhua told reporters that the amount of iodine content has a direct relationship with thyroid disease. At present, there are three means of thyroid disease treatment: surgery, anti-thyroid drug control and isotope treatment. Thyroid cancer is the most common malignant tumor of the thyroid gland, accounting for about 1% of all malignant tumors in the body. Except for medullary carcinoma, the vast majority of thyroid cancers originate from follicular epithelial cells. ”There are many factors that cause cancer, including chemical and physical factors. The most important physical factors are rays, such as gamma rays, X-rays, radon and radium, which can directly damage DNA, and poor repair of damaged nucleic acid will easily produce tumor cells, which, together with the decline of the body’s immune function and further development, may become cancer.” Xiao Wenhua said. When it comes to why nuclear radiation is so closely related to thyroid cancer, Xiao Wenhua believes that because the thyroid gland is naked and easily exposed to radiation is a very important factor. Secondly, thyroid cancer is related to the amount of radiation exposure during childhood; the earlier the age of exposure to radiation, the higher the chance of developing cancer and the earlier the age of disease. The nuclear meltdown in Japan, which exposed children to large amounts of radiation, is a special case. Iodine-131 is the main culprit: “The increased incidence of thyroid malignancies in Fukushima may be due to the large amount of radioactive material iodine-131, which is a radioactive isotope of iodine, that is absorbed by the thyroid gland and causes damage. Currently, there is no threshold for how much radiation exposure will cause cancer, but it is accepted in the medical community that the greater the exposure, the greater the risk of cancer.” Dr. Wensheng Wang, chief physician, said that thyroxine has many important functions such as maintaining growth and development, promoting body metabolism, and thyroxine is synthesized and manufactured by the thyroid gland using iodine, so when radioactive iodine is taken into the thyroid gland as a raw material for manufacturing thyroxine, the radiation produced may cause chromosomal damage to thyroid tissue cells or even cause chromosome breakage. Although the body has a self-repair function for chromosomes, if errors occur in the repair process, normal cells may be transformed into malignant cells, resulting in malignant thyroid tumors. Malignant tumors that are transformed from thyroid epithelial cells are called thyroid cancer, and malignant tumors that are transformed from thyroid lymphoid tissue cells are called thyroid lymphoma. Iodine is an essential trace element, and it is generally believed that iodine deficiency is endemic to goiter. Iodine deficiency leads to a decrease in thyroid hormone synthesis and an increase in thyrotropic hormone (TSH) levels, which stimulates thyroid follicular hyperplasia and goiter. There is no significant change in the incidence of thyroid cancer before and after iodized salt prophylaxis, and the proportion of papillary thyroid cancer increases after the implementation of effective iodized salt prophylaxis. Papillary carcinoma incidence. Irradiation of the thyroid gland of rats with X-rays can induce the development of thyroid cancer in animals, resulting in deformation of the nucleus and a significant decrease in thyroxine synthesis, leading to carcinogenesis; on the other hand, the thyroid gland is destroyed and cannot produce thyroid hormone, resulting in the secretion of a large amount of thyroid stimulating hormone (TSH), which can induce thyroid follicular hyperplasia and play a role in promoting thyroid cell carcinogenesis. Xiao Wenhua introduced that surgery is the main treatment for thyroid cancer, and there are also auxiliary treatments such as nuclear hormone, thyroid hormone and external irradiation. The surgical treatment of thyroid cancer includes surgery on the thyroid gland itself and cervical lymph node dissection. The extent of thyroid removal is still divided, with the smallest range being lobectomy plus isthmus, and the largest to total thyroid removal. ”In fact, the fact that individual cells in the body become tumor cells does not necessarily mean that they will develop into malignant tumors. The ‘surveillance’ function of the body’s immune cells also plays an important role in removing malignant cells, and the high incidence of most tumors in the elderly population is directly related to the decline of immune function in the elderly population.” According to Wang, the reason why children exposed to nuclear leakage are prone to thyroid cancer is not only because children’s cells proliferate vigorously and are more sensitive to radiation, but also because children’s immune system is not well developed and their immune function is not sound enough, for example, “children are more likely to suffer from viral infections”.