The Backscatter Machines Safety Debate

[Kaylee]

The political and social issues of backscatter machines are being discussed now in the other JREF forums. I'm hoping that we can discuss the scientific issues of the machines in this one.

The Homeland Security Secretary Janet Napolitano says it's safe, many scientists in related fields say it may not be. Who’s right? And how do people without degrees in science evaluate the conflicting information?

Here’s some of what I’ve read so far:

A letter of concern from a group of scientists at the University of California in San Francisco:
http://www.whitehouse.gov/sites/default/files/microsites/ostp/ucsf-jph-letter.pdf

I really recommend reading it, but for those who won’t -- here’s some of their concerns as summarized by an NPR article:

http://www.npr.org/templates/story/story.php?storyId=126833083

The San Francisco group thinks both the machine's manufacturer, Rapiscan, and government officials have miscalculated the dose that the X-ray scanners deliver to the skin — where nearly all the radiation is concentrated.

The stated dose — about .02 microsieverts, a medical unit of radiation — is averaged over the whole body, members of the UCSF group said in interviews. But they maintain that if the dose is calculated as what gets deposited in the skin, the number would be higher, though how much higher is unclear.

<snip>

For instance, the UCSF scientists, in their letter to Holdren, worry about effects such as melanoma, a dangerous skin cancer; immune-system problems; breast cancer; mutations in sperm cells; and effects on a developing fetus.

The government says that independent testing has proved that the airport scanners are safe. The TSA web site mentions John Hopkin’s University Applied Physics Laboratory as one of the organizations that have evaluated the devices. A Wiki article on back scatter x-rays quotes Dr. Andrew J. Einstein of Columbia Univeristy as saying that the backscatter machines are safe. However, when I googled to get more information as to what John Hopkins APL and Columbia University had to say about the back scatter machines -- I did not find more assurances as I expected:

http://www.cnbc.com/id/40259590

Johns Hopkins University's Applied Physics Laboratory did independent tests — but only to determine how much radiation the devices emit, not to examine safety, said Helen Worth, a lab spokeswoman.

and per a blog
http://myhelicaltryst.blogspot.com/2010/11/tsa-x-ray-backscatter-body-scanner.html

Its also interesting to note that the Johns Hopkins Applied Physics Laboratory criticized other reports from NIST (the National Institute of Standards and Technology) and a group called Medical and Health Physics Consulting for testing the machine while one of the two X-ray sources was disabled (citations at the bottom of the page).

and



http://www.npr.org/templates/story/story.php?storyId=126833083

David Brenner, head of Columbia University's Center for Radiological Research, recently aired his worries before the Congressional Biomedical Caucus.

"There really is no other technology around where we're planning to X-ray such an enormous number of individuals," Brenner told the caucus and congressional staffers. "It's really unprecedented in the radiation world."

Brenner's name carries some clout, because he served on a small group of experts convened in 2002 by the National Council on Radiation Protection and Measurements to write guidelines for the security scanners. He now says he wouldn't have signed the report if he had known the X-ray scanners were going to be used on virtually every air traveler.

<snip>

Brenner says he thinks the danger to most individual travelers is miniscule. But he worries about the unknowns when those very small risks are multiplied times something like 700 million travelers a year.

Recent research, Brenner says, indicates that about 5 percent of the population — one person in 20 — is especially sensitive to radiation. These people have gene mutations that make them less able to repair X-ray damage to their DNA. Two examples are the BRCA-1 and BRCA-2 mutations associated with breast and ovarian cancer, but scientists believe many more such defects are unknown.

"I don't know if I'm one of those 5 percent. I don't know if you're one of those 5 percent," Brenner says, "And we don't really have a quick and easy test to find those individuals."

Children are also more vulnerable to radiation damage, because they have more dividing cells at any time. A radiation-induced mutation in their cells can lead to cancer decades later.

Brenner says the most likely risk from the airport scanners is a common type of skin cancer called basal cell carcinoma, which is usually curable. It often occurs on the head and neck.

The Columbia scientist points out that it would be hard to conceal a weapon on one's head or neck, so he proposes a seemingly simple workaround –- avoid scanning the head and neck.

But TSA officials say that's not practical. Think of the long lines, they say, if the machines had to be adjusted for each passenger's height.

And the American Federation of Government Employees in Congressional testimony on July 21, 2010 brought up some good points. First, here's a summary:

TSA employees want dosimeters (a badge that monitors radiation exposure) -- the TSA says they don’t need them so they will not be issued any AND that TSA employees are NOT ALLOWED to wear dosimeters not issued by the TSA. Who, by the way will not be issuing any.

and

There has been documented cases where TSA employees have been asked by supervisors to engage in unsafe work practices that can increase radiation exposure.

Now for the long quotes:


http://www.afge.org/Index.cfm/Micro...pdf?Fuse=document&documentID=2485&FileID=2612

Among TSOs, exposure to ionizing radiation has been an issue of great concern from the very beginning of the agency. TSA has held the position that there is no harmful exposure from radiation emissions from the X-ray machines used to view the contents of checked baggage as well as carry-on baggage. TSOs’ concern stemmed from the fact that some of them had worked for the private sector security firms who were doing those jobs before they were federalized in the wake of the terrorist attacks of
September 11, 2001. While they were in the private sector companies, the security officers were provided with dosimeters—devices used to measure the employees exposure to radiation

<snip>

Individual TSOs and AFGE as their representative have asked about a dosimetry program at TSA, but have been denied the dosimeters. TSA’s
position is that the agency has done the necessary testing and is not required by any applicable standards to issue dosimeters to its employees.
While TSA may have done the testing necessary to show that the levels of
radiation emitted from the screening equipment are below action levels, their lack of response and their failure to address employee concerns beg the question, what are they hiding? If the testing has in fact been done, why has TSA been unwilling to share the results with employees, and with us, their representative? We understand some information may be classified as security sensitive, but employees deserve answers.

We urge the Committee to request that TSA provide copies of any studies they have conducted or have contracted with others to conduct. [ed. bold] In order to address our members’ concerns, AFGE has offered to conduct an independent study of radiation emissions and has identified a research team to conduct it. We explored the possibility with TSA, and our offer was declined. AFGE has also been willing to fund the purchase of dosimeters for TSOs since TSA refused to provide them. When they asked if they could wear their own dosimeters, TSOs were told by TSA management that they would not be allowed to wear dosimeters not issued by TSA. TSOs have continued to request dosimeters over the years that TSA has been in
existence, yet TSA has not changed its position.

<snip>


National Institute for Occupational Safety and Health (NIOSH)did observe work practices [ed. in 2003 and 2004] that could increase exposure, such as reaching into the tunnels that carryon baggage goes through or removing the protective lead curtains on the Xray machines. This is a continuing concern based on the reports we received from our members. As recently as last year, members have called AFGE with their concerns when supervisors ordered them to carry out these unsafe work practices.

Congressman Dennis Kucinich has written a letter (Nov 24, 2010) to Transportation Security Administration Chief John Pistole conveying some of his concerns about the backscatter machines. It appears that there is no monitoring program for the machines in place. They are tested once at the factory and once upon installation. He has asked that the TSA to set up a monitoring program for the safety of the TSA employees and the airline passengers.

Also in the Congressman’s letter was a reminder that there can be unexpectedly high dosages of radiation if a machine malfunctions or if there is an operator’s error. Link to the congressman's letter: http://kucinich.house.gov/News/DocumentSingle.aspx?DocumentID=215750

Here’s an example of what has happened in the recent past with medical equipment: http://www.aboutlawsuits.com/radiation-exposure-lawsuit-filed-over-ct-scans-at-la-hospital-6558/

A California man has of has filed a class action lawsuit against Los Angeles’ Cedars-Sinai Hospital on behalf of himself and 206 other patients who were allegedly exposed to radiation overdoses <snip> due to incorrectly administered CT scans at the hospital over an 18 month period.

<snip>

Investigators found that the CT scan machines had been manually manipulated to produce better pictures, inadvertently increasing the amount of radiation exposure.

The hospital says that it has put in place new procedures to prevent over-exposure in the future, including rules that stipulate any changes to the machine’s settings will have to go through the hospital’s head CT technician. The hospital is also providing more training for technicians working with the machine

<snip>

The FDA is investigating whether similar incidents are happening at other facilities, and warns that such incidents may be going unrecognized and unreported, leading to long-term overexposure for patients.

All in all, I'm not convinced about the safety of the backscatter machines. I know that each dose is suppose to be small --- but there doesn't apear to be any monitoring program in place despite the requests of the TSA employees. I'm especially amazed that they are not allowed to bring in their own dosimeters.

Also, it appears that the TSA and the various USA cities' police forces does not plan to limit backscatter machines to airports. There may be plans to install them in other places as well: stadiums, malls, courthouses (ETA: actually there are already in Florida), hospitals, large bridges, and any other sites of large expensive infrastructures that the govt would prefer not to have to replace.

So, its likely that all these small doses can add up -- esp. in the larger cities. I don't think the casual everyday use of backscatter machines are a good idea for health reasons* -- and I'm ready to hear your thoughts. What do you think?



* And other reasons already being discussed in the politics and social issues forums -- we don't have to discuss those reasons here!

ETA: All bolding in the above quotes are mine.

 

[ThunderChunky]

The company really is named Rapiscan? That is hilarious.

You get a dose of radiation just from flying in an airplane.

 

[casebro]

I would have thought by now that somebody has worn a dosimeter through one, then sent it for analysis. I would expect a gazillion investigative reporters to jump at the chance. Is lack of that evidence. evidence of the lack of radiation?

 

[Drachasor]

I would have thought by now that somebody has worn a dosimeter through one, then sent it for analysis. I would expect a gazillion investigative reporters to jump at the chance. Is lack of that evidence. evidence of the lack of radiation?

The radiation has been measured. It's super-tiny. Super-super tiny.

Does it increase the risk of cancer? Yes, but by a very, very, very small amount. An airplane flight of a couple hours by anyone's measure increases the risk of cancer by a much larger amount. There's just some debate on how the two compare, essentially.

So, in a sense, they aren't safe, but in that same sense, an uneventful airplane flight is far less safe.

That said, I favor them switching fully to the radio-based devices as those literally can't ever cause cancer. It's completely physically impossible.

 

[Mikemcc]

Dosimeters have to be used in a controlled way to try and eliminate false readings. For instance a radiation worker from a nuclear power station could conceiveably wear one home, which might have radon gas coming up into it. This would show as a high dose, but would not be due to their work environment, therefore they don't remove them from site.

The level from these machines is vanishingly small. Yes it does add to accumulated dose, but not to a level that is significant. The main arguement is whether the risk from the additional dose is comparable to the risk of being blown up by a terrorist bomb if the scanner was not used.

 

[Cuddles]

Does it increase the risk of cancer? Yes, but by a very, very, very small amount.

Actually, probably not. The evidence suggests that low doses of radiation either have no effect at all, or could even be beneficial. See, for example, figure 9 and table 4 in "Radiation and Reason" by Wade Allison. (I think it's still available free, if not the references for those parts are:
Preston, Dale L. et al (2004) Effect of Recent Changes in Atomic Bomb Survivor Dosimetry on Cancer Mortality Risk Estimates. Radiat. Res. 162, 377–389.

Henriksen, Thormod and Maillie, H. David (2003) Radiation & Health. Taylor & Francis.)

 

[casebro]

Dosimeters have to be used in a controlled way to try and eliminate false readings. For instance a radiation worker from a nuclear power station could conceiveably wear one home, which might have radon gas coming up into it. This would show as a high dose, but would not be due to their work environment, therefore they don't remove them from site.

The level from these machines is vanishingly small. Yes it does add to accumulated dose, but not to a level that is significant. The main arguement is whether the risk from the additional dose is comparable to the risk of being blown up by a terrorist bomb if the scanner was not used.

Yes but , from my reading of threads like this, the exposure always seems to be calculated, not an actual dosimeter measurement.

So far as the usage goes, it doesn't take a rocker scientist to wear one. Janitors at nuke plants seem smart enough, on a par with investigative journalists.

 

[quarky]

Perhaps a naked airline will emerge, making flying fun again.

 

[soylent]

The company really is named Rapiscan? That is hilarious.

I believe it's mean to be pronounced rapi[d]-scan, not rape-i-scan; but the latter is definitely funnier.

 

[elgarak]

Yes but , from my reading of threads like this, the exposure always seems to be calculated, not an actual dosimeter measurement.

1) X-ray sources have very easily defined outputs. If you know how they're build, and how much electrical power they consume, an upper limit to the x-ray radiation can easily be calculated, and be reliable.

2) Measuring doses, and expanding those doses into a dose equivalent (i.e., which biological damage does a certain dose do if it is absorbed by the body), on the other hand, is very tricky. In particular small doses, like the ones here, are very difficult to measure. And you still need to calculate from the dose you have measured at one point in space how much dose equivalent a person would get. The thing is, this will not tell you more than what you can already estimate as upper limit from geometry and math alone, as dosimeters have a quite high error at small doses.

 

[Craig4]

Perhaps a naked airline will emerge, making flying fun again.

There already is one in Germany. That image you're having in your mind of beautiful naked people watching in-flight movies and eating peanuts. Yeah, not so much with that.

 

[Beth]

Thanks for starting the thread. I don't have much scientific knowledge about radiation or dose calculation. I do have some familiarity with assessing the reliability of such machinery and the likelihood of manual overrides to produce better pictures when supervisors pressure them to improve performance.

All in all, even if it is a very safe dose of radiation when used properly, I am quite pessimistic regarding the probability of accidental high doses on occasion. In addition, if I were a regular flyer, I would be quite anxious about getting the additional exposure on a regular basis.

Further, I am concerned when apparently respectable experts in the field are claiming that we don't really know the effects of this particular type of radiation and that the type of radiation can potentially majorly impact the effect.

All in all, I find it quite disquieting that these machines will be placed in many large public spaces. On the other hand, I find the terrorism occurring around the world terrifying to contemplate. Mostly I ignore it but I can honestly say that the it has crossed my mind that the more we clamp down on air travel, the more likely we are to experience terrorists acts elsewhere. We've been lucky and alert for close to ten years now, but I can well imagine the bombing of an arena filled with thousands.

On the whole, I think I'd prefer just the fear of the terrorists. I don't really want to fear my government too. My only comfort is I rarely travel and don't get out much, so it won't directly affect me much. It's small comfort, but it's all I got.

 

[Drachasor]

Further, I am concerned when apparently respectable experts in the field are claiming that we don't really know the effects of this particular type of radiation and that the type of radiation can potentially majorly impact the effect.

There's not one expert claiming this radiation is significantly dangerous as far as I have read.

 

[casebro]

There's not one expert claiming this radiation is significantly dangerous as far as I have read.

And I haven't read of any actual dose received. Only calculations of what the machines put out, they think. The calculations seem to be low figures based on what they think is absorbed by clothing, wasted, etc. None have quoted an actual measurement taken at the skin, extrapolated to the total of skin surface area to attain a total exposure.

It takes a pretty good 'ping' to get a sonar return.

Or, compare to ultrasound, the pick up has to be right on the skin, in fact a grease has to be applied to get good conduction

 

[Drachasor]

And I haven't read of any actual dose received. Only calculations of what the machines put out, they think. The calculations seem to be low figures based on what they think is absorbed by clothing, wasted, etc. None have quoted an actual measurement taken at the skin, extrapolated to the total of skin surface area to attain a total exposure.

There have been studies where the output is measured (John's Hopkins is an example in the OP). What people need to bear in mind is that even if you multiply the radiation by 10 or 50 (more than taking account skin absorption and so forth), it is still very tiny and a few hours of flight will give you more radiation.

Again, no scientists think it is actually that dangerous.

It takes a pretty good 'ping' to get a sonar return.

Or, compare to ultrasound, the pick up has to be right on the skin, in fact a grease has to be applied to get good conduction

Err, such technologies work on a completely different mechanism...how is that related at all?

 

[elgarak]

One of the big problems with radiation: There is no 'safe' level.

We know which dose will kill.

We know there's a certain amount of radiation naturally occurring with a certain amount of cell damage. This may cause some cancers, but may also be necessary for a certain amount of evolutionary forcing. How much above this (non-constant in space or time) background, but below the lethal dose, is 'dangerous'? There's no clear answer to that.

 

[Drachasor]

One of the big problems with radiation: There is no 'safe' level.

We know which dose will kill.

We know there's a certain amount of radiation naturally occurring with a certain amount of cell damage. This may cause some cancers, but may also be necessary for a certain amount of evolutionary forcing. How much above this (non-constant in space or time) background, but below the lethal dose, is 'dangerous'? There's no clear answer to that.

There actually is some evidence that a small amount above background is helpful, as someone pointed out. We do know quite a bit about radiation damage in general. Beyond that, when you compare the radiation from these machines to background and what airline passengers get...it is very tiny. Freaking out about it is tantamount to hysteria.

 

[Beth]

There's not one expert claiming this radiation is significantly dangerous as far as I have read.

Right. They are saying it hasn't been studied and we don't know how safe or dangerous it actually is. I'm not particularly comfortable with the idea of exposing millions of citizens, some of them quite frequently, to radiation when no one appears to know what the actual effect of it might be. It is also disquieting that the actual levels of radiation are not being measured and the results publicly released.

I haven't looked into it, but is there any information being released on maintenance and calibration of these machines? If one malfunctions by emitting too much radiation, will operators be able to tell and shut it down until it's fixed?

 

[Kaylee]

I haven't looked into it, but is there any information being released on maintenance and calibration of these machines? If one malfunctions by emitting too much radiation, will operators be able to tell and shut it down until it's fixed?

There may not be a monitoring program in place. In Congressman Dennis Kucinich's letter to Transportation Security Administration Chief John Pistole, dated Nov 24, 2020, he asked the TSA to set up a monitoring program for the safety of the TSA employees and the airline passengers.

 

[Kaylee]

It is also disquieting that the actual levels of radiation are not being measured and the results publicly released.

I'd like to know what the range of radiation being released is for each model that has been sold to the govt and put into use.

Specifically I'd like to know the lower limits, upper limits, and typical usage limits for several areas around the machine. That is where its targeted (the airline passenger), near the operator (TSA employee) and several areas where bystanders could be waiting (airline passengers waiting at the checkpoint). How far away does one have to be so they get no effects of the radiation at all?

It's possible that some of this information may be available on technical specification sheets* that may be on the vendor's web sites -- but it would also be nice if this information was available on an independent 3rd party's web site.


*Its on my list of things I intend to google for ..