Evidence of causal connection between radiation exposure and cataracts is found in A-bomb survivors

by Michiko Tanaka, Staff Writer

The Radiation Effects Research Foundation (RERF), located in Minami Ward, Hiroshima, has arrived at a new finding based on research involving the health examinations of A-bomb survivors. RERF found that the risk of developing severe cataracts rose when the crystalline lenses of A-bomb survivors were exposed to A-bomb radiation of more than 500 millisieverts. The new finding has led to a revision in the standard set by the International Commission on Radiological Protection (ICRP), as no detailed data had been available on the threshold of radiation exposure which could result in severe cataracts and failing vision.

RERF looked at 6,066 A-bomb survivors who received medical examinations once every two years from 1986. Of this total, RERF researchers analyzed the cases of 1,028 people who had undergone cataract surgery by 2005 after obtaining such information as their symptoms and their level of radiation exposure and age at the time of the bombing.

As a result of a comparative study of A-bomb survivors who suffered seemingly little effect from their radiation exposure and those exposed to radiation of 500 millisieverts or more, a clear casual relationship between radiation and the onset of the disease was confirmed in the latter group. As an example, for people who were exposed to one sievert (1000 millisieverts), RERF estimates that another 100 of every 1000 will develop severe cataracts within 30 years.

Previously, based on this research’s interim findings, ICRP lowered the maximum permissible amount of radiation exposure to crystalline lenses in cases of acute exposure from 5 sieverts to 500 millisieverts, one tenth of the previous standard, in April 2011.

RERF released its findings in the August issue of a U.S. journal. Kenji Kamiya, the director of Hiroshima University’s Research Institute for Radiation Biology and Medicine, who specializes in medical care for radiation damage, praised the research, saying, “It’s the first time that detailed data has been obtained regarding the effects of radiation exposure in cases of severe cataracts. From the viewpoint of radiological protection, these are significant findings.”

(Originally published on October 2, 2012)