As part of its anti-terrorism effort,
the federal government is considering a plan to
install X-ray machines in airports -- not just to
screen carry-on bags, as it does already, but to
scan outgoing passengers themselves. The technology
has proven itself in prisons and among Customs and
Border Protection agents who use it to search for
drugs, illegal weapons, and contraband.
But the idea of using it on 700
million American air passengers a year is generating
serious privacy concerns from civil libertarians --
and safety questions among some scientists, who
question whether the risks, however small, outweigh
the potential benefit of catching people hiding
plastic explosives or other dangerous devices.
Citing research from three
organizations of radiation specialists, the
manufacturer of one device, BodySearch, said the
technology is safe, even for children and pregnant
women.
The National Council on Radiation
Protection and Measurements, a nonprofit corporation
chartered by Congress, concluded the technology is
not dangerous because it uses very, very low-dose
"backscatter" X-rays. In medical X-rays, the rays go
all the way through the body and land on film or are
digitized to produce an image; in "backscatter"
imaging, the X-rays bounce back toward the scanner,
penetrating the body only shallowly, producing
ghostly images of the body in all its naked glory --
love handles, under-wire bras, private parts and
all.
For
most people, even for frequent flyers, this low
exposure is probably safe -- it would take at
least 2,500 scans a year to reach the maximum
recommended exposure. (Security personnel would not
be exposed unless they went through the machine.) So
long as the X-ray machine is maintained properly,
the dose from one scan would be about
1,000th
AS MUCH AS A TRADITIONAL chest X-ray.
That’s
"barely measurable," said Dr. Elliot
Fishman,
a radiologist at Johns Hopkins Hospital.
In fact, it’s less than the
background radiation from the cosmic rays that you
get from flying cross country , far less than a
dental X-ray; hundreds of thousands of times less
than a whole body CT scan
and millions and millions of times
less than X-rays used to treat, say, prostate
cancer .
But -- and this is a big "but" – some
people might be at extra risk of radiation-induced
problems.
Even though the risk is “miniscule,”
explained Lee Chin, chief of medical physics at the
Dana-Farber Cancer Institute and Brigham and Women’s
Hospital, “there
may be a finite risk when such a
large population is irradiated."
And people at extra risk may not know
who they are, said David Brenner,
professor of radiation oncology and public health at
Columbia University Medical Center.
The biggest radiosensitive group is
children and fetuses. "I would be uncomfortable in a
scenario where pregnant women were forced to go
through these machines," he said, adding that "women
don’t always know if they’re pregnant."
Others may be extra radiosensitive,
too, including people who carry the breast cancer
genes called BRCA1 and BRCA2, who may not know they
have the genes. And an even bigger risk group is
people who unknowingly carry a mutated gene called
ATM (for ataxia telangiectasia).
David Albright, a physicist and
president of the Washington, D.C.- based Institute
for Science and International Security, a nonprofit,
non-partisan science policy group, said, "If
hundreds of millions of people are scanned with this
device each year, the population dose could reach
levels where a few cancers are possible. Even if
just one person died, is that worth it?"
Balancing these tradeoffs is
difficult and fraught with emotion.
Because “no dose of radiation is
without some risk,” said Dr. Jay Harris, chair of
the department of radiation oncology at the
Dana-Farber and the Brigham, “the benefit of
possibly catching terrorists must be weighed against
the risk to the public and the feasibility of
alternative methods.”
David Ropeik,
director
of risk communication at the Harvard Center for Risk
Analysis, said that radiation is hard to understand,
in part because it is invisible. And people tend to
worry more about hazards they don’t understand or
can't see. Moreover, "any risk imposed on you feels
scarier than a risk you choose yourself," he said.
Others see it differently.
"I would welcome the fact that I am
safer," because the X-rays would make it harder for
terrorists to smuggle bomb-making material onto
planes, said Chris Cagnon
a clinical medical physicist at the David Geffen
School of Medicine at UCLA.
But what would happen, he wondered,
if people began outsmarting the technology? "It
would be easy for people to start wearing clothes
that are hard to X-ray. If so, then, what’s the
point?"
And the fact that radiation experts
have deemed the idea safe does not convince George
Annas,
chair of the department of health law, bioethics and
human rights at the Boston University School of
Public Health.
"Physicists love radiation," he said.
Low doses? "They always say that."
So far, the Transportation Security
Administration, part of the Department of Homeland
Security, is merely "contemplating initiating a
pilot program" to test the machines at airports,
said spokeswoman Yolanda Clark.
Researchers are also looking at
alternatives to X-rays, including high-frequency
microwave screening and trace-chemical detectors
that use a gentle stream of air to dislodge and
collect particles from the person being screened.
As for me, my rational mind says it’s
probably not a problem to walk through a backscatter
X-ray machine. But my gut still says, “No thanks.”
Judy Foreman’s
column appears every other week. Past columns are
available on
www.myhealthsense.com
