Radiation Risks Diminish With Distance

June 4, 2002 -- Amid fears of a nuclear conflict between India and Pakistan, experts estimate hundreds of thousands of people would be killed instantly in a nuclear attack on a city in either country, but it may be the spread of radiation that poses the biggest danger.

While there isn't enough known about the size and strength of the present nuclear arsenal maintained by India or Pakistan to make accurate estimates, studies of the attacks on Hiroshima and Nagasaki in Japan during the World War II and the meltdown of Chernobyl's reactor in the 1980s have provided researchers with information suggesting what may happen to victims and how far the radiation will reach.

Distance is a crucial factor, and for those living as far away as the United States negative health effects of fallout from these past events have not been noted.

"We didn't see any remote effects on populations from the Hiroshima or Nagasaki detonations [and while] the Chernobyl incident reached through much of Europe, there aren't any recorded consequences in terms of health effects that are outside of the immediate areas," says Dr. A. Bertrand Brill, research professor of radiology and radiological sciences and research professor of physics at Vanderbilt University School of Medicine in Nashville, Tenn.

"If there are substantial amounts of radioactive material that are injected into the atmosphere, we likely will be able to measure that in the United States," says Kenneth Mossman, professor of health physics and director in the Office of Radiation Safety at Arizona State University in Tempe. "Will it have a significant health impact in the United States? Not likely. However, individuals who live in the region where the detonations could occur will have substantial health impacts."

Risk Spreads Out From Ground Zero

How far the effects of a nuclear detonation will reach depends upon many factors, such as the weather and whether the bomb was detonated above the ground or at ground level. A bomb that explodes at ground level creates much more fallout, which can carry radiation up to several hundred miles.

Ramana V. Mani, a physicist at Princeton University in New Jersey, estimates that an attack on Bombay, India, would kill 150,000 to 850,000 people, depending on how the bomb was detonated. These deaths would be the immediate result of the bomb's blast. But for those who survived the blast, some would succumb within a few days or weeks from the exposure to the lethal doses of radiation.

"There is a syndrome called acute radiation sickness," says Scott Davis, professor of epidemiology at Fred Hutchinson Cancer Center and chairman of the department of epidemiology at the University of Washington in Seattle. "It is basically a breakdown of multiple body systems at once. The [radiation] doses are so high that multiple kinds of cells throughout the body are killed and it results in system failure."

Following these acute exposure deaths, the long-term effects of radiation in the form of cancers will span decades. According to Davis, after the bombings in Japan, the first wave of cancer to appear was leukemia within five to 10 years — followed by increases of solid-tumor cancers such as those of the breast and thyroid. And research has indicated that some may be more susceptible to developing these cancers than others.

"It's pretty clear that when you are exposed at younger ages, the risk of developing thyroid cancer is considerably greater than if you are exposed as an adolescent or an adult," says Davis. "Breast cancer shows a similar effect and exposure around the time of puberty carries with it a higher risk for the same dose than if you were exposed at other ages."

A U.S. intelligence report estimated that a full-scale nuclear exchange between India and Pakistan would result in the deaths of up to 12 million people directly related to the blast and the lethal doses of radiation that follow.

"What we are looking at is a spectrum of possible effects," says Mossman. "The farther away you live [from the epicenter of a bomb], the higher the probability that you will not be harmed in an acute sense, but you may be at a higher risk for cancer that will be evident decades later."

Experts fear any move toward the use of nuclear weapons could only lead to a worsening scenario.

"The whole idea that the genie is getting out of the bottle in terms of modern warfare would be terrible," says Brill.