AIRPORT SCANNERS RADIATION: IS
IT DANGEROUS OR NOT?
There are two types of airport body
The controversial one uses very low
doses of X-rays to scan travelers front
and back and create a "naked" image.
There are currently 206 of these
machines at 38 US airports.
The other type doesn't use X-rays but
instead a technology called millimeter-
wave scanning. There are 167 of
these units at 30 US airports.
Earlier this year, four scientists from
the University of California, San
Francisco, wrote a letter to Presidential
Science Adviser John Holdren raising
concerns about the cancer risks of
exposing hundreds of millions of
travelers every year to airport X-ray
In the letter they said:
Unlike other scanners, these new
devices operate at relatively low beam
The majority of their energy is
delivered to the skin and the
underlying tissue. Thus, while the
dose would be safe if it were
distributed throughout the volume of
the entire body, the dose to the skin
may be dangerously high.
The X-ray dose from these devices
has often been compared in the media
to the cosmic ray exposure inherent to
airplane travel or that of a chest X-ray.
However, this comparison is very
misleading: both the air travel cosmic
ray exposure and chest Xrays
have much higher X-ray energies and
the health consequences are
appropriately understood in terms of
the whole body volume dose.
In contrast, these new airport scanners
are largely depositing their energy into
the skin and immediately adjacent
tissue, and since this is such a small
fraction of body weight/vol, possibly by
one to two orders of magnitude, the
real dose to the skin is now high.
Our colleagues at UCSF,
dermatologists and cancer experts,
raise specific important concerns:
• A) The large population of older
travelers, >65 years of age, is
particularly at risk from the mutagenic
effects of the X-rays based on the
known biology of melanocyte aging.
• B) A fraction of the female population
is especially sensitive to
leading to breast cancer. Notably,
because these women, who have
defects in DNA repair mechanisms, are
particularly prone to cancer, X-ray
mammograms are not performed on
them. The dose to breast tissue
beneath the skin represents a similar
• C) Blood (white blood cells) perfusing
the skin is also at risk.
• D) The population of
and cancer patients (see above) is
likely to be at risk for cancer induction
by the high skin dose.
• E) The risk of radiation emission to
children and adolescents does not
appear to have been fully evaluated.
• F) The policy towards pregnant
women needs to be defined once the
theoretical risks to the fetus are
• G) Because of the proximity of the
testicles to skin, this tissue is at risk
for sperm mutagenesis.
• H) Have the effects of the radiation
on the cornea and thymus been
Holdren's office asked the TSA and the
Food and Drug Administration to
respond. Their eight-page letter to
Holdren was posted on the FDA's
The response, among other things,
First, the letter is correct to note that
the TSA-deployed product is a recent
However, the specification for the x-ray
tube for the deployed model is almost
identical to the original 1991 product.
The stated concern was, "The majority
of their energy is delivered to the skin
and the underlying tissue."
However, the concern that "the dose to
the skin may be dangerously high" is
not supported. The recommended limit
for annual dose to the skin for the
general public is 50,000 µSv. The
dose to the skin from one screening
would be approximately 0.56 µSv when
the effective dose for that same
screening would be 0.25 µSv.
Therefore the dose to skin for the
example screening is at least 89,000
times lower than the annual limit.
Second, radiation safety protection
quantities are stated as 'effective dose'.
NCRP Commentary No. 16 says, "The
purpose of effective dose is to place
on a common scale the radiation
doses: (1) from different types of
ionizing radiation that have different
biological effectiveness, and (2) in
different organs or tissues that have
different radiation sensitivities."
Comparing effective doses from
different sources is appropriate. The
comparison between the effective dose
from cosmic ray exposure or a medical
diagnostic chest x-ray and the effective
dose from a security screening is
intended to be a clear means of risk
Dr. Marc Shuman, a cancer expert and
one of the concerned California
professors, said the four are in the
process of writing a detailed response
to the Department of Health and
Human Services but called the
agency's arguments "seriously flawed."
Shuman said they believe there should
be a moratorium on full-body scanning
until further study is conducted.
Dr. David Brenner is equally
unpersuaded by the government's
response. Brenner is head of the
Center for Radiological Research at
Brenner's complaint is that the
government experts are entirely
focused on the risk of cancer for
"I don't think anybody would argue the
point that the individual risk is small.
Whether it's one in 10 million or one in
100 million, it's very small," he said in
an interview. "But multiply that times
700 million people – the number of
people getting on planes currently –
and that's the public health risk."
And Brenner says there's reason to
think the radiation dose delivered per
scan is about 10 times higher than the
It comes from a paper by Arizona State
University physics professor Peter Rez
that is scheduled to appear in a journal
called Radiation Protection and
Rez says he was skeptical that the X-
ray dose the government claims for the
machines – about 1/10,000th of a
chest X-ray — could produce a usable
image at all. He calculated backward to
figure out how big an X-ray dose would
be needed to get the kind of images
the machines produce.
Rez agrees the individual risk is still
negligible. "It's a 1-in-20-million chance
of dying from radiation for each scan,"
he says. "Your chances of being struck
by lightning in the US in any year is 1
But the probability of being blown up in
an airplane by a terrorist is around 1 in
30 million. So the risk from the scan is
about the same as the thing you're
trying to prevent."
Brenner says if Rez's dose calculation
is right, pilots and very frequent fliers
could exceed the recommended
annual radiation dose limit of 250
microSieverts. That would require
going through the scanner 250 times,
by Rez's dose calculations, rather than
2,500 times, by the government's
The result, he maintains, is "you will
end up with some number of cancers
coming out of each year's scanning
operations." Applying it to the 125,000
commercial airline pilots and perhaps
125,000 other flight personnel, each
averaging 250 scans per year,
Brenner estimates "there might be five
cancers, or two fatal cancers, resulting
from a year's worth of X-ray screening"
among airline personnel.
This could all be avoided, Brenner
says, if the government relied entirely
on the millimeter-wave scanners
instead of the X-ray scanners.
By the way, you might be wondering:
Can the average traveler standing in a
security line tell the difference?
Yes, a TSA spokesman says. The X-
ray type is blue and has two walls. The
millimeter-wave machine is grayish-
white and is more cylindrical.
Could airport scanners give too much
Dr Gupta's answer for CNNHealth:
TSA is using two types of screening
One, the millimeter wave imaging
machine, uses radio frequency energy
to image the body. According to the
TSA these deliver 10,000 times less
energy than your cell phone.
The other type of machine,
backscatter X-ray, is what has people
talking because these units rely on X-
These X-rays are very low level, they
bounce radiation off the skin and back
to the machine. This is how authorities
can scan for dangerous items under
someone's clothes. But this also
means the radiation is at very low
levels. It's bouncing off the skin, not
penetrating it or your organs. This is
unlike a medical X-ray which is a
higher level radiation penetrating the
skin to see bones and other tissue.
In fact, passing through this
backscatter X-ray scanner actually
exposes you to a hundred times less
radiation than a flight from say Boston
to Los Angeles. When you fly you are
exposed to cosmic rays so the
backround radiation is higher at higher
altitudes. This is is the same reason
people in Denver are exposed to more
radiation per year than, say, folks
living in Miami, because Denver is at
The American Cancer Society told us
that because the radiation levels being
reported are low, its experts don't see
this being a serious issue for
Response by Peter Rez, physics
Dr Gupta's comments are incorrect.
The X-ray scanning machines use the
same 100kV X-ray generator as a CT
machine or other hospital X-ray
To say that in one case the X-rays
bounce off the clothing while in the
other case they penetrate the body is
physical nonsense. The dose is lower
than a CT machine because the beam
is tightly collimated (or focused into a
My calculations indicate that it is still
much higher than the manufacturers
claim, somewhere between 5 times
greater to 50 times greater depending
on image quality.
Another issue is that these machines
are not very useful for their intended
purpose, they would have difficulty
detecting even large amounts of some
explosives such as TATP.
RADIATION SICKNESS: NEW
Japan's nuclear emergency highlights
a big medical gap: Few treatments
exist to help people exposed to large
amounts of radiation.
But some possibilities are in the
The US federal Biomedical Advanced
Research and Development Authority,
or BARDA, funds late-stage research
of products the US government deems
most likely to pan out.
BARDA has invested $164 million for
research into anti-radiation treatment
candidates since 2008, and $44 million
for radiation testing — in hopes of
adding such products to the nation's
emergency medical stockpile soon.
Part of the challenge is radiation's
variety of injuries — burns, bone
marrow and gastrointestinal damage,
lung scarring, the later-in-life cancer
risk. Yet outside of an immediate blast
zone where open wounds and burns
make injury clear, there's no fast way
to tell who got a huge dose.
Those Geiger counter-style monitors
used on power-plant workers in
Japan? They detect contamination on
clothing or skin that might not enter the
body, not what the body has absorbed,
says medical physicist David Brenner,
director of Columbia's Center for
Brenner's team built a robotic machine
named RABiT -- for "rapid automated
biodosimetry tool" — that can analyze
those bloodspots quickly. The eventual
goal is to be able to test 30,000 blood
samples in a day. Brenner is working
with Northrop Grumman to make the
machinery smaller, even portable.
Brenner says federal approval is still a
few years away but that the prototype
could be used in an emergency if
health officials shipped blood samples
to his lab.
What about treatments?
Cells in the bone marrow and GI tract
are extremely vulnerable to radiation.
They overreact to what should be
reparable damage and commit cellular
suicide, says Dr. Andrei Gudkov of the
Roswell Park Cancer Institute.
Gudkov's team created a drug based
on a protein from normal gut bacteria,
named flagellin, that blocks some of
the cellular destruction and also
stimulates recovery of remaining cells.
It dramatically improved the survival of
monkeys treated up to 48 hours after
they were zapped. And safety testing
in 150 healthy people so far suggests
the main side effect is a flulike
reaction, Gudkov says. Cleveland
BioLabs Inc. is doing further work
needed for Food and Drug
Since the atomic bombings against the
cities of Hiroshima and Nagasaki in
Japan during World War II, radiation
exposure to large populations has
been largely limited to industrial
accidents, such as the April 1986
event at the Chernobyl Nuclear Power
Plant in the Ukraine.
The effects of radiation exposure
manifest quickly and depend on a
variety of factors, including the dose
absorbed by different parts of the body:
Chromosome damage in circulating
lymphocytes, nausea, headache,
vomiting, fatigue, weakness, infection,
fever, bleeding, wound and burn
morbidity, skin effects, loss of fluids;
anorexia; ulceration; death of crypt
cells, bloody diarrhea; gastrointestinal
ulcerations; infections; hemorrhage;
marrow hypoplasia; death.
Acute radiation syndrome [ARS], is
caused by exposure to a high dose of
radiation over a short period of time,
usually in a manner of minutes. The
cells that are lost the earliest following
exposure are rapidly dividing
hematopoietic stem cells and
progenitor cells of the bone marrow
that are highly sensitive to the effects
There are no approved products to
treat or prevent ARS.
Potassium iodide [KI] was approved by
the FDA in 1982 to reduce the risk of
thyroid cancer in radiation
emergencies involving the release of
radioactive iodine. For example, the
Chernobyl reactor accident resulted in
massive releases of I-131 [radioactive
iodine] and other radioiodines.
Beginning approximately 4 years after
the accident, a sharp increase in the
incidence of thyroid cancer among
children and adolescents in areas
covered by the radioactive plume was
However, it is important to note that KI
cannot protect against any other
causes of radiation poisoning, nor can
it provide any degree of protection
against dirty bombs that produce
radionuclides other than isotopes of
Experimental drugs and procedures:
Congress passed the Project
BioShield Act in July 2004.
Several companies developing product
candidates for the treatment and/or
prevention of ARS have received
government awards under the Project
Aeolus Pharmaceuticals, Inc. Product:
Cellerant Therapeutics, Inc. Product:
Cleveland BioLabs, Inc. Product:
Derma Sciences, Inc. Product: DSC127
Osiris Therapeutics, Inc. Product:
Prochymal Received a $224.7 million
contract, including purchase options,
from the United States Department of
Defense (DoD) to develop and
This treatment is to utilise stem cells
that had been isolated from bone
marrow in an adult.
It is thought that this process will
restore the lining in the gut by
repairing the damage. Prochymal is
also purported to rejuvenate the blood
and repair damage to the skin.
After the stem cells are isolated from a
donor, they can be expanded, allowing
for thousands of doses to be produced
from just one donation.
These stem cells work to reduce
inflammation that is responsible for a
great deal of the tissue damage that
happens after radiation exposure.
Another benefit is that the stem cells
also operate at a cellular level to
encourage the formation of new tissue
from the release of special growth
The European Group for Blood and
Marrow Transplantation (EBMT) has its
headquarters in Barcelona, Spain.
Reacting to the Japanese nuclear
emergency, EBMT contacted all its
536 centres by email, asking them if
they would be able to treat patients
suffering from radiation exposure.
The EBMT has about 2,500 specialist
doctors who can treat people with
bone marrow problems.
The group drew up plans for treating
radiation victims after the terror attacks
of 11 September 2001.
All six of the Fukushima plant's
reactors are experiencing problems
following the earthquake and tsunami,
in which an estimated 10,000 people
It is not clear how many victims will
need help, but there is concern for the
50 or so engineers that are battling
around the clock to stop a major
The head of EBMT's Nuclear Accident
Committee, Professor Ray Powles, told
the press that they were working on
the possibility they may have to treat
200 people or more.
Powles said governments and
hospitals would be prepared to ease
restrictions on immigration and costs of
transport and treatment.
He predicted that some patients might
need bone marrow transplants, while
others might just need antibiotics or
they might need antibiotics and other
drugs as well as blood and platelets.
It's not that dissimilar to treating