Researchers appeal for in-depth analysis of RERF data on “black rain”

by Michiko Tanaka, Staff Writer

On February 17, the Radiation Effects Research Foundation (RERF), located in Minami Ward, Hiroshima, took part in a public symposium in the east wing of Hiroshima Peace Memorial Museum and engaged in discussion with researchers who are concerned about the potential adverse effects of the A-bomb’s “black rain” on human health. Earlier, it had been revealed that RERF has held data on approximately 13,000 people thought to be exposed to the black rain in the aftermath of the atomic bombings. One after another, the researchers at the symposium requested that more detailed analysis be done on this data.

The symposium was organized by the Hiroshima branch of the Japan Congress of Journalists. Toshiteru Okubo, the chair of RERF, and Kotaro Ozasa, the chief of RERF’s Epidemiology Department, took the podium and reported anew on their analysis of the data, saying that they found no indication of an increase in the risk of cancer among those exposed to the black rain.

In response, Megu Otaki, a professor at Hiroshima University’s Research Institute of Radiation Biology and Medicine (RIRBM), pointed out that those exposed to the black rain in Nagasaki had a 30 percent greater risk of dying of solid cancers, and said the results of the data analysis did not correspond to this fact. He said that a reason for the discrepancy must exist, then appealed for an in-depth analysis of the data.

Koya Honda, the president of the Nagasaki Doctor and Dentist Association, who had identified the existence of the data, mentioned a case in which severe hair loss, believed to be an acute symptom of exposure to the A-bomb’s radiation, was confirmed at a location more than two kilometers from the hypocenter. He stated that this symptom could not be explained by exposure to the initial radiation and stressed the need to shed light on the effects of indirect exposure to radiation, including the black rain.

Dr. Okubo, though, indicated that he was unwilling to pursue further research focused on the data, saying, “We would like to do what we can. But this is not a research program designed to examine the impact of the black rain.”

A series of requests were made from the floor, calling on RERF to better serve the community of A-bomb survivors. Dr. Okubo replied, “I understand how you feel. But research cannot be trusted unless it’s conducted in a neutral setting.”


RERF’s data on the “black rain”
The data held by RERF consists of portions of the responses obtained during interviews with about 120,000 people of Hiroshima and Nagasaki from the 1950s to the early 1960s. Roughly 13,000 people answered “yes” to the question about whether they were exposed to the rain that fell in the aftermath of the atomic bombings, and most of these were from Hiroshima. They were also asked about the location of their exposure to the rain; if they suffered from any of 14 kinds of acute symptoms, including hair loss and fever; the severity of their symptoms; and when they developed these symptoms. The presence of the data was disclosed in November 2011. In December 2012, RERF announced the results of its analysis, saying that there was no increased risk of developing cancer among those exposed to the black rain.

(Originally published on February 18, 2013)