HIROSHIMA (Kyodo) — A study by Hiroshima University researchers has shown men who entered Hiroshima just after the 1945 atomic bombing on the same day faced greater chances of death from cancer than those who came to the city three days after the blast.

The findings suggest that human health may be impaired by residual radiation from radioactive materials produced by a nuclear detonation and challenge the view by a government-funded institute that such radiation caused no major difference in cancer risk among people who were at the city right after the bombing.

The team at the university’s Research Institute for Radiation Biology and Medicine will present the results of their statistical analysis Sunday at a meeting of the Japan Radiation Research Society to be held in Aomori City.

Keiko Otani, an assistant professor involved in the study, which focused on men aged between 30 and 49, said men in that age bracket were likely to have been asked to look for family members or carry their bodies near ground zero.

“We can assume they may have been most affected by residual radiation by inhaling dust containing radioactive materials,” she said

The study tracked 28,638 men registered in a database between 1970 and 2011. They were among the people who entered a 2-kilometer radius of the epicenter within two weeks of the bombing.

The team analyzed data on 4,610 men who died from solid cancerous tumors by their ages and the date they entered the area. Leukemia deaths were excluded.

The team compared those who entered the area on the day of the bombing on Aug. 6 with those who did so on Aug. 9 when the effects of residual radiation were thought to have almost faded.

The survival rate of those men aged between 30 and 49 who entered the area on Aug. 6 was lower than those who went there three days later, the study found.

More specifically, the risk of dying from cancer at age 75 was 18 percent higher among those who were aged 30 at the time and 40 percent higher among those who were aged 40, it said.

In December last year, the Hiroshima-based Radiation Effects Research Foundation, funded by the Japanese and U.S. governments, said exposed doses from residual radiation made no major impact on risk calculation, saying they fall within the error margin in estimating initial radiation doses.

Kyodo News, October 18, 2013