Radiation Harms Cells Longer
researcher says it could be a protective mechanism
By Janice Billingsley
MONDAY, March 31 (HealthScoutNews) -- In a surprising finding,
scientists have found that cells take a longer time to repair
lower X-ray doses than after higher doses.
Radiation damages all cells, which then must repair themselves
To date, scientists had thought that cell repair takes the
of time no matter how much radiation the cell is exposed to,
but a new
study discovered that cells exposed to lower doses of radiation
amount similar to dental X-rays -- actually take from days
longer to repair than cell damage caused by higher levels
which usually takes only a few hours to one day.
"The difference in repair between low and high doses
of X-rays did
indeed surprise us," says study author Markus Lobrich,
a professor of
radiation biology at the University of Saarland in Homburg,
results appear in the March 31-April 4 Proceedings of the
Academy of Sciences.
The doses given in most diagnostic tests, like dental X-rays,
mammograms, and CT scans, are considered low-dose, while the
given to cancer patients is high-dose, Lobrich says. For example,
dose of radiation, aimed at killing cancer cells, is between
2 and 5 Gy.
(Each Gy is one joule of energy absorbed in a mass of 1 kilogram).
cancer therapy, patients are treated with daily doses of about
2 Gy. In
contrast, a CT scan is only about 0.02 Gy, a mammogram about
0.01 Gy and
a dental exam usually less than 0.01 Gy.
Lobrich says the discrepancy between the rate of cell repair
low- and high-dose radiation could mean an increase in cancer
those who have low-dose radiation, or, conversely, it could
protective mechanism that actually decreases cancer risk.
When cells repair themselves from radiation, they aren't
to their exact, original form, he says. In pasting back the
of a cell, called double-strand breaks (DSB), the cells are
changed into a slightly different cells, which are called
While uncommon, these mutations are associated with an increased
cancer. When a large number of cells in one organ are damaged,
lung cancer radiation, for instance, the body has no choice
repair the DSBs, or the organ could fail, Lobrich says.
But with low-dose radiation, he says, only a few cells are
damaged in a
given organ due to the small amount of radiation. The body
basically decide it's better to let those few cells die and
by the division of existing healthy cells in the body than
to repair the
DSB's and increase risk for a mutation. "I find this
latter a more
intriguing idea," he says. "If you believe in the
logic of nature, you
would expect the body to behave exactly this way, to refrain
to avoid the risk of mutations."
"This study is very significant," says Timothy
Jorgensen, an associate
professor of radiation medicine at Georgetown School of Medicine
Washington, D.C. Jorgensen says that risk assessment of the
radiation has been made from extrapolating how much damage
occurs during high-dose radiation and assuming that cell damage
repair follows the same pattern when radiation doses are lower.
this study suggests that the mechanism is different, and changes
we think about how radiation works," he adds.
The question, Lobrich says, will be the subject of further
In the meantime, Lobrich and other doctors say, don't stop
diagnostic X-rays you need. "I don't want people to get
the idea that
X-rays are dangerous, because we are all exposed to low doses
and they are therapeutic, helping to prevent illness,"
says Richard B.
Setlow, a senior biophysicist at the Brookhaven National Laboratory.
Setlow brought the study to the attention of the National
Sciences, which publishes Proceedings.
Lobrich recommends having medically necessary X-rays, but
some caution. "If there is a hereditary indication for
breast cancer risk, like having a mother and/or grandmother
breast cancer, have the mammography exams done and don't worry
about the radiation risk," he says. "But if the
radiologist is about to
take another, or a third image of your chest because he didn't
quality of the first picture, stop and ask for a medical indication."
Lobrich adds that dental X-rays carry little risk because
not very likely to cause cancer in that part of the body.
For the study, scientists exposed human cell cultures in
to X-ray levels similar to those in a standard dental exam.
It was the
first time a study has been done of cell damage following
low doses of
radiation, Setlow says. Previously, assessments of cell damage
estimated based on higher doses of radiation. Using a fluorescent
marker, the scientists noted the DSBs in the DNA of the cells
the radiation and monitored them to see how long it took for
to repair themselves after radiation.
"Usually DSBs are repaired within a few hours after
Lobrich says, "but we observed that DSBs induced by very
remained unrepaired for many days. And even two weeks after
radiation, most of the induced DSBs were still present."
The National Institutes of Health has a thorough explanation
radiation and its effects. More information about radiation
risks can be
found at the Environmental Protection Agency.
Richard B. Setlow, Ph.D., senior biophysicist, Brookhaven
National Laboratory, Upton, N.Y.; Markus Lobrich, Ph.D., professor
radiation biology, Saarland University, Homburg, Germany;
Jorgensen, Ph.D., associate professor of radiation medicine,
School of Medicine, Washington, D.C.; March 31-April 4, 2003,
Proceedings of the National Academy of Sciences
Copyright © 2003 ScoutNews, LLC. All rights reserved.
May Cause Alzheimers
Talking on cellphones is the leading cause of crashes caused
distraction, according to the California Highway Patrol. Maybe
because new evidence shows that cellphones may trigger the
of Alzheimer's disease. Studies of rats in Sweden found that
from mobile phones damages areas of the brain associated with
memory and movement, but so far, no one has found conclusive
that cellphones damage the human brain. It's a long-running
between people who want to talk and drive and other drivers
they wouldn't, and people who say cellphones are safe to use
who think they're turning our brains into Swiss cheese. Leif
experimented on rats aged between 12 and 26 weeks old, when
are in the same stage of development as human teenagers. The
exposed to two hours of radiation of the same kind emitted
phones. When their brains were examined under a microscope
later, they had many dead brain cells. "A rat's brain
is very much the
same as a human's," says Salford. "We have good
reason to believe that
what happens in rat's brains also happens in humans."
He also thinks cellphones could set off Alzheimer's disease
people. "What we are saying is those neurons that are
already prone to
Alzheimer's disease may be stimulated earlier in life,"
"However, this theory is hypothetical. We do not have
evidence yet that
the human brain is affected in this way. "We cannot exclude
some decades of often daily use, a whole generation of users
negative effects maybe already in their middle age."
In California, talking on cell phones is the leading cause
crashes that can be blamed on distracted drivers. "I
didn't think cell
phones would be the highest category,'' says Spike Helmick,
California Highway Patrol. "But I was wrong. We have
to be concerned.''
When state officials studied what distracted drivers in 9,000
cellphone use was the cause of 891 of them, almost one in
10. This was
followed closely by fumbling with the radio or CD player,
in 768 crashes. Disciplining kids in the car, eating and smoking
other leading causes, but were far behind the first two.
However, most crashes aren't caused by driver distraction.
Out of the
522,562 crashes in California in 2001, only 51,107 were due
inattention. Speeding is the cause of most crashes.
But highway patrol spokesman Tom Marshall thinks the number
caused by cellphones is much higher. He says, "Any right-minded
knows a driver probably won't 'fess up to the fact he was
on a cell phone.''
Retired Sgt. Bruce Raye says he never handled an accident
cellphone during his 10 years in the San Jose police traffic
But he also said that such reports could be low because officers
remember to ask about a cellphone, due to all the other information
they're required to put in an accident report. "You can't
get them to
write the correct court date on a ticket, let alone remember
if a cell
phone was related to the accident,'' he says. "There
are probably many
more accidents where cell phones contributed.''
But driver Andrea Puck of Santa Clara says, "If the
risky behavior truly
is the conversation, then banning the device is as ridiculous
conversation while driving. If you really want to get rid
distractions while driving, ban children from cars.''
Maybe we should stick to ESP. The U.S. government tried it
success, although they're keeping it a secret.
Don't use your cellphone just to make calls use it to attack
cellphones! The design firm Ideo has invented cellphones that
people from making unnecessary calls or zap other cellphone
talk too long or too loudly in public. One design comes with
plates attached to it that can send an increasing electric
shock to the
people you're talking to. Another phone is shaped like a musical
instrument. "It looks like a snake that has swallowed
a mobile phone,"
says designer Graham Pullin. In order to make a call, you
have to stand
up and play a tune on the musical phone. "It seems inconceivable
someone would stand up and play it in the middle of a crowded
so it is a good litmus test about where it is appropriate
to make a
call," Pullin says. Then there's the catapult phone,
which allows users
to aim their phone at someone talking on another phone nearby
and send a
sound that disrupts their conversation. Maybe the best design
is a quiet
phone that allows you to have a silent conversation. Instead
speaking, you simply press a button to reply "yes"
or "no" the person on
the other end of the line.
We have to admit we like the catapult phone best. Now can
a zapper for those loud "boom box" car radios? There
are certain people
we can always talk to quietly, without disturbing anyone else.