Don't worry too much about the hint of radiation reaching U.S.
shores from the damaged nuclear reactors in Japan, experts say.
So far, it's much less than we'd get from a chest X-ray.
But consider this: Every day, all day long, we're bathed in low
levels of radiation ---- cosmic rays from outer space, radon in our
houses, uranium deposits in the soil, radio signals from every AM
and FM station in range, airport full-body scanners, dental X-rays,
cellphones, even tiny hints lingering from the A-bomb tests of the
1940s and '50s.
And remember that radiation is cumulative. Most scientists agree
there's no such thing as a harmless dose.
Now relax. It's less scary than it sounds.
"It's absolutely true there's no safe dose. But we're likely to
be OK if we remain vigilant," says Dr. Nagy Elsayyad, a radiation
oncology expert at the University of Miami Sylvester Comprehensive
Not all radiation is equal. What comes from medical X-rays,
airport scanners, leaking nuclear plants and similar sources is
ionizing radiation ---- the dangerous kind, capable of causing
cancer, increasingly so as time and dosage increase. But much of
the radiation around us, from radio waves to cellphone signals to
leaky microwave ovens, is the non-ionizing type never proven to
cause illness, say scientists ---- well, most scientists.
World War II newsreel footage from Hiroshima and Nagasaki shows
the doomsday effects of nuclear bombs exploding over cities,
killing hundreds of thousands from the immediate blast and tens of
thousands more later on, from high-dose radiation poisoning. And
the current nuclear crisis in Japan has prompted new fears of
But lower, everyday levels we experience routinely are less easy
to grasp. For example, the Federal Aviation Administration
estimates an airline pilot spending a 25-year career flying at
30,000 feet between Chicago and New York will experience enough
extra cosmic radiation through the thinner atmosphere to increase
his or her cancer risk by about 0.3 percent.
Another natural source, radon, is an invisible, odorless,
radioactive gas emitted from soil.
In all, natural sources expose the average earthling to about
6.2 millisieverts (mSv) of radiation annually. The millisievert is
the common unit for measuring radiation exposure; one millisievert
equals about 10 chest X-rays. There are other ways of measuring
radiation, but the millisievert is the most widely used.
The trick is to limit our exposure to ionizing radiation above
that universal 6.2 mSv, Elsayyad says. The National Council on
Radiation Protection recommends we get no more than one additional
unit per year.
To put it in perspective, measuring in millisieverts, a chest
X-ray adds 0.1, a mammogram adds 0.7, a high-altitude,
cross-country airplane flight adds 0.05 and a medical CAT scan adds
10. The new full-body scanners at airports may be intrusive, but
their radiation level is low ---- far less than 0.1 mSv, according
to the American Cancer Society.
Although scientists differ on the effects of low-level exposure
to ionizing radiation, most believe no dose is safe.
"There is no safe level of exposure, whether from food, water or
other sources. Period," said Jeffrey Patterson, immediate past
president of Physicians for Social Responsibility, in a statement
calling for a nationwide moratorium on new nuclear reactors in the
United States following the incidents in Japan.
A few differ: "There is no way to determine precisely the risks
of low-level radiation," writes Kenneth Strubler, director of
medical physics at the Greater Baltimore Medical Center, in the
online journal radiologynursing.org. "To date, no proven body of
evidence has established an increase in human disease as a
consequence of radiation rates comparable to those of Earth's
natural background ---- or even 10 times higher."