In two separate days in August 1945, atomic bombs were dropped on the cities of Hiroshima and Nagasaki in Japan marking the end of World War II.

People who were within 1.5 kilometers (0.93 miles) of the center of the blasts were instantly killed but burns and exposure to radiation resulted in more deaths days after the nuclear weapons were dropped.

Besides killing about 200,000 civilians and military personnel days and weeks after the bombing, the use of atomic weaponry on these two Japanese cities also impacted the health of the people.

Findings of a new study, however, revealed that the long-term health effects of these atomic bombs were not as severe as many have thought.

In a new study published in the journal Genetics on Aug. 1, molecular biologist Bertrand Jordan looked at more than 60 years of medical research that conducted studies on about 177,000 survivors of the atomic bombings in Japan and their children, and 20,000 individuals who were not exposed to the bomb's radiation.

The researcher found that exposure to the bomb's radiation increased the survivors' risk for cancer by about 10 to 44 percent but on average, they lived only a few months shorter than the people who were not exposed to the radiation. The findings likewise showed no radiation-associated mutations in the survivors' children.

Jordan said that while more detailed tests may reveal subtle differences among the children in the future, the research showed that the risk to their health is not as great as previously feared.

"It is generally thought that abnormal births, malformations, and extensive mutations are common among the children of irradiated survivors, when in fact the follow-up of 77,000 such children (excluding children irradiated in utero) fails so far to show evidence of deleterious effects," the researcher wrote in the study.

The researcher said that many scientists thought that the survivors faced debilitating health effects and elevated risk for cancer and that their children had high rates of genetic disease but the research showed a big gap between these beliefs and what was revealed by the study.

He said that the disparity between the perceived long-term health effects of the bombings and actual data could be attributed to the fact that radiation is a new and mysterious agent that poses an unfamiliar danger to humanity.

Despite his findings, Jordan said that the study should not cause complacency about the threats posed by nuclear weapons and accidents.