Public fears rose after high levels of radiation were detected near the Fukushima No. 1 nuclear power plant and many residents were exposed to radioactive substances.
Public fears rose after high levels of radiation were detected near the Fukushima No. 1 nuclear power plant and many residents were exposed to radioactive substances.
But while higher than normal levels of radiation have been recorded in various parts of Japan, experts and government officials said the figures do not represent levels that could immediately affect human health.
Throughout their daily lives, humans are exposed to radiation from outer space and the land. Over the course of a year, an individual is exposed to 2,400 microsieverts (one millisievert is the equivalent of 1,000 microsieverts).
Although anyone exposed to a high level of radiation at one time will be seriously affected, an individual is exposed to 50 microsieverts when taking a chest X-ray exam, 200 microsieverts when taking a round-trip flight between Tokyo and New York and 6,900 microsieverts for a chest CT scan.
Prefectures in eastern Japan announced radiation levels in the air detected on Tuesday. (One microgray per hour was converted as 1 microsievert per hour).
The highest radiation level recorded was 23.18 microsieverts in Fukushima Prefecture. Ibaraki Prefecture had a recording of 5.575 microsieverts, while Tokyo had a reading of 0.809 microsieverts.
Tokyo's figure was much greater than the 0.035 microsieverts that is considered normal.
During the 1999 criticality accident in Tokai, Ibaraki Prefecture, at a nuclear fuel reprocessing facility operated by JCO Co., neutron rays were leaked, and about 660 residents who lived nearby were exposed to radiation.
However, in 2000, when experts considered the health effects, they concluded that the radiation levels were not at a level that could clearly affect health.
Hisanao Okura, the former head of the Ibaraki Prefectural Central Hospital, who was in charge of the residents exposed at that time, said of the latest incident, "From the media reports, the radiation levels in the present case (for residents) are not at a level that would affect human health."
Radiation exposure can occur externally and internally.
Kazuo Neriishi, an adviser to the Radiation Effects Research Foundation, said everyone experiencing external exposure should be examined and radiation levels measured. If any radiation materials are found on an individual's skin, it should be washed away using a towel, water and soap. Washing the skin well with water and soap will remove the radiation from the skin surface.
Even if internal exposure to radiation occurs, if the amount is small, it will eventually be discharged from the body.
According to Yasushi Asari, a professor of emergency medicine at Hirosaki University, if the radioactive material is iodine, thyroid gland cancer can be prevented by drinking non-radiated iodine beforehand.