Effects of residual radiation secretly studied by US military

August 9, 2015

U.S. military secretly studied residual radiation in Hiroshima and Nagasaki even after denying risks

http://mainichi.jp/english/english/newsselect/news/20150809p2a00m0na014000c.html

Invested in building its nuclear prowess during the Cold War, the U.S. military secretly continued to study the effects of residual radiation from the atomic bombs in Hiroshima and Nagasaki even after it denied any risks from residual radiation shortly after the end of World War II, the Mainichi Shimbun has learned.

The U.S. government issued an official statement in September 1945 saying that any residual radiation from the two atomic bombs that were dropped on Japan had no effects on the human body. It had emerged, however, that scientists from both Japan and the U.S. had surveyed residual radiation in Hiroshima and Nagasaki multiple times until 1948.

Internal U.S. military documents obtained by the Mainichi now show that the military had secretly studied residual radiation levels in Hiroshima and Nagasaki in March 1950, four-and-a-half years after the atomic bombs were dropped, with researchers reporting to officials in the U.S. that their findings proved that radioactive residue remained for a long time. The survey was led by the Armed Forces Special Weapons Project (AFSWP), which was established in 1947 to promote the U.S. military's nuclear strategy.

The approximately 100 pages of documents were found in the National Academy of Sciences archives, and include letters exchanged between senior officials of the Atomic Bomb Casualty Commission (ABCC), which was based in Hiroshima and Nagasaki, and scientists in the U.S., as well as the minutes from meetings. They noted that the radioactive materials that were found had relatively low levels of radiation, but that the study's results should be classified. According to researchers, many AFSWP documents relating to nuclear policy have not been declassified.

In March 1950, two American scientists and an ABCC doctor gathered samples from 11 sites in the Koi district of Hiroshima and the Nishiyama district of Nagasaki, where radioactive "black rain" fell after the bombings, according to the documents. Using film and instruments that detect radioactivity, the researchers found that radiation at 10 of the 11 sites clearly exceeded those of environmental radiation levels.

The scientists reported that some of the samples were taken from soil on farms where vegetables were being grown, prompting senior ABCC officials to consider studying whether radioactive materials could be absorbed by the human body through breathing and food. The samples collected by the researchers were sent to the U.S.

"The U.S. military's denial of the effects of residual radiation at such an early point in time was a political move to stop the U.S. from being held responsible for the various effects of the atomic bombings," says Hiromi Hasai, a nuclear physicist and professor emeritus at Hiroshima University. "In the 1950s, meanwhile, the ABCC was considering conducting a long-term study on the effects of residual radiation, so they were probably concerned about it."

On March 29, 1950, in a letter to scientists at the National Academy of Sciences-National Research Council -- which had established the ABCC in 1947 -- then ABCC director Carl Tessmer wrote that while some may say that the radiation levels that had been detected were low and did not have any effects, it was not advisable to neglect the issue for the next 10 years. He stressed that the effects of low-level residual radiation was unknown territory, and needed to be uncovered.

The ABCC's studies on the effects of radiation involved comparing the rate at which cancer and birth defects were found in groups of people who were exposed to the atomic bomb and those who were not. The data would then be used to estimate the risks people faced by radiation exposure doses. Tessmer explained concern that if there were those who were not in Hiroshima or Nagasaki at the time of the atomic bombings but lived there afterward and suffered internal radiation exposure, the study would fail to provide an accurate assessment of the risks.

Scientists in the U.S. advising the ABCC instructed the researchers to determine if local residents had absorbed radioactive materials through water, food, or breathing. They recommended testing the local drinking water and the lung cells of dead people who had lived in one of the two cities but were not exposed to the actual bombs for radioactive material. They also suggested the possibility of testing the bones of those who were exposed to the bombs and were buried in communal graves.