POSTED 11 AUGUST 2005
Radiation returns
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?
The Department of Energy must jump enormous technical hurdles before opening this repository for nuclear waste in Nevada. Are the radiation exposure standards strict enough? Too strict? It all depends on the real health hazard of low-level radiation. Photo: NRC
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?
CT scans are a valuable medical tool, but they
increase our exposure to ionizing radiation. 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?
August 8, 1945: Smoke rises 60,000 feet above the Japanese
port of Nagasaki, after the second atomic bomb ended World War II. Long-term
studies of atomic-bomb survivors at Hiroshima and Nagasaki are key evidence on
the health impact of low-level radiation. Photo: NARA
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