Scanner Radiation Fears

This is a bit on all you want toknow about scanners.  Most of us will beexposed to this device rarely, but a minority will be exposed many times.  We may be reassured that there is no risk andthe risk mat be minimal but doubt and potential legal liability willcontinue.  I think passports should havea radiation counter built in.  That wayeveryone can check his exposure.

We likely should do the same withcell phones.  The science for radiationis affected by the natural counter activity associated with low exposure.   Statistical work and experimental design mustcorrect for the effect and I do not think anyone has done so.  The real work has to be done with subjectswith excessive exposure.

Some good work is been done onthis and I hope to report on it.

Full-body scanners: we reveal all

18:08 18 November 2010 by JustinMullins

For similar stories, visit the Crime andForensics Topic Guide

http://www.newscientist.com/article/dn19746-fullbody-scanners-we-reveal-all.html

The recent release of pictures taken by full-body scanners has outragedthe travelling public and focused attention on the risks the devices may carry.New Scientist deals with the concerns

What are full-body scanners?

Remember the X-ray specs of science fiction comics that would let peoplesee through walls and clothing? Full-body scanners are a bit like them. Thescanners take advantage of the fact that at certain wavelengths,electromagnetic waves can pass through clothes but not through the skin, metalor substances such as drugs and explosives.

If your eyes were sensitive to these wavelengths like the scanners,every person you meet would appear naked, with pens, coins, belt buckles andthe like magically festooned about their person. You would also be able to seeif they were carrying a knife, gun or explosives.

What are the health concerns surrounding them?

There are two main types of full-body scanner. One uses X-rays whilethe other uses lower-energymillimetre wavelengths. X-rays are hazardous because their photons haveenough energy to ionise atoms and break chemical bonds. That can cause damageto DNA that subsequently leads to cancer. The machines are deemed safe becausethe total dose that someone receives during a scan is tiny.

However, earlier this year, a group of scientists at the University of California,San Francisco, raised a number of concerns over X-ray scanners. They said theX-rays they use are low energy to ensure they bounce only off skin rather thanpassing through the body, to produce an image focused on objects concealedbeneath clothes. This means that the entire dose that the person being scannedreceives is concentrated on the skin rather than spread throughout their body.That could mean the skin receives a dose that is one or two orders of magnitudemore than expected.

To many observers, the response of the US Food and Drug Administration failed toproperly address these concerns.

Are there health concerns surrounding millimetre-wave scanners?

In theory, these ought to be safer than X-rays because millimetrephotons do not have enough energy to break chemical bonds. Last year, however,researchers at Los Alamos National Laboratory in New Mexico suggested that these low energyphotons could damage DNA in an entirely novel way. They say that while thesephotons cannot break DNA, they can shake it. This shaking may be so strong thatit unzips the two strands in DNA, interfering with the genetic machinery thatkeeps cells working and healthy.

The team at Los Alamos did their calculations for submillimetre orterahertz waves,  whose photons areslightly more energetic than those of millimetre waves. Their results areprobabilistic rather than deterministic, they say. This explains why someexperiments show that terahertz waves can damage DNA while other, practicallyidentical studies show nothing.

While terahertz full-body scanners are not yet widely used, the workdoes show that the effects of electromagnetic waves on DNA are not fullyunderstood.

Are there alternatives to full-body scanners?

Travellers can opt out of being scanned and choose to be friskedinstead. In the US,one group is hoping to highlight the controversy over full-body scannersby encouraging everyonetravelling on 24 November to elect to be frisked.

What about privacy concerns?

The USTransportation Security Administration admits that the scanners have theability to store and print images. But it says this capability is used onlywhen the machines are tested and is switched off at all other times. Criticspoint out that it isn't clear how difficult it is to reactivate this capabilityor how the TSA prevents employees from recording the images with another devicesuch as a cellphone camera.

Earlier this week, hundreds of images taken by a body scanner used by marshals at acourthouse in Florida appeared on the internet. The TSA says it would beimpossible for a similar leak to occur from airport scanners. It's fair to saythe public is yet to be reassured.