POSTED 11 AUGUST 2005
In 2005, 60 years after the atomic bomb was invented, the specter of ionizing radiation again lurks behind the news:
"Dirty bomb" attack: How deadly would the released radiation be?
Nuclear waste burial ground in Nevada: Can it operate safely?
Nuclear power: Safe response to global warming and energy shortages?
Depleted uranium weapons: Can they cause cancer?
CT scans and mammograms: Useful medical tools that detect disease with X-rays, or a dangerous source of extra radiation exposure?
Photo: Ohio Dept. of Veterans Affairs
The answer to these questions hinges on the health effects of low-level radiation. You would think we'd have a solid answer for that question. Not.
First, some definitions: Ionizing radiation -- alpha and beta particles, and X-rays and gamma rays -- is released by nuclear reactions in bombs, power plants and uranium-bearing rocks (X-rays are also made in medical equipment). Ionizing radiation can turn atoms into charged particles called ions. The electromagnetic radiation made by flashlights, magnets and cell phones cannot do this.
While we know large doses of ionizing radiation can cause disease or kill, the health impact of lower doses is more elusive. You might expect that if a large dose can harm, a smaller dose would be less harmful, but still not safe. Yet all humans are exposed to background radiation (in the United States, the average is 360 millirems per year), from radon, cosmic rays and other sources, and life expectancy continues to rise.
But what happens when we increase the exposure through exposure to medical X-rays, nuclear waste, or depleted uranium weapons? Is there a "safe-enough" level of added radiation, or will any increase above background cause more cancer?
It's been 60 years since the atomic bombings of Hiroshima and Nagasaki. What did they teach us about the health effects of radiation?
Megan Anderson, project assistant; Terry Devitt, editor; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive