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New standards for radiation-linked cancer

September 29, 2012


More standards for recognizing nuke workers' cancers released



The Ministry of Health, Labor and Welfare (MHLW) on Sept. 28 released standards on compensation for nuclear workers afflicted with stomach, esophagus, and colon cancer caused by radiation exposure.

To qualify, workers must have been exposed to at least 100 millisieverts of radiation in total, with five years having passed since they began engaging in nuclear work -- conditions that would indicate a strong relationship between nuclear work and the three types of cancer. Different standards exist for other cancers such as leukemia.

According to Tokyo Electric Power Co., as of the end of August, 167 workers involved with recovery work at the Fukushima No. 1 Nuclear Power Plant had been exposed to over 100 millisieverts of radiation.

In December 2009 and February 2011, before the Fukushima disaster, there were two applications from nuclear plant workers seeking recognition of stomach, esophagus, and colon cancer as work-related illnesses. Based on past records, a MHLW panel investigated the issue and put together a report stating that recognition of raised risk for these three types of cancer started within the range of 100 and 200 millisieverts, with the minimum latent period of related cancers ranging between roughly five and 10 years. The newly announced standards are based on this report.

The MHLW has not disclosed whether it approved the two compensation applications.

Since 1976, 11 nuclear plant workers have been recognized as being victims of work-related radiation illnesses. Six had leukemia, two had multiple myeloma, and three had malignant lymphomas -- illnesses with separate recognition standards. For leukemia workers must have been exposed to at least 5 millisieverts for radiation for a year. The corresponding levels for multiple myeloma and malignant lymphomas are 50 millisieverts and 25 millisieverts, respectively.

Based on observational studies of survivors of the Hiroshima and Nagasaki bomb blasts, the International Commission on Radiological Protection (ICRP) says that the risk of developing cancers, excluding blood cancers like leukemia, increases linearly upward from a combined dosage of 100 millisieverts. They say the risk of dying from cancer at 100 millisieverts is 0.5 percent higher than normal. The effects of less than 100 millisieverts are unknown, but the ICRP recommends keeping radiation exposure as low as possible.

Furthermore, heavy radiation exposure over a short time leads to symptoms like losing hair and bleeding, and can cause death as well. Two plant workers died after being exposed to 6 to 20 sieverts at the nuclear accident in Tokai, Ibaraki Prefecture in 1999.


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