Re: Airport screening and medicine

[JGinniver@AOL.COM]

Reuven,

I'd like to discuss a couple of the points raised in your e-mail. I've copied 

bits of your e-mail and added my questions alongside in italics





> For a continuous flight of 365 days,

> 

Did you mean 365 working days , each of 8 hours, or 265 days x 24 hours?   On 

this note it is my understanding that aircrew (including cabin staff) don't 

even spend a full 2000 working hours in the air, I believe that rules on 

rostering etc. generally limit aircrew (even longhaul) to less than 1000 hours in 

the air.

>  the total radiation exceeds the

> OCCUPATIONAL

> limit of 5 Rads.

> 

Should this have been 'the OCCUPATIONAL limit of 5 REM"?   It's important as 

a large fraction of the dose received by aircrew comes from charged particles 

(some of which are quite exotic) rather than just X or Gamma photons.   As a 

result specialist dosemeter have had to be developed to measure the doses 

received by aircrew.   If your interested an internet search for TEPC (Tissue 

Equivalent Proportional Counter) should bring up some worthwhile hits.   Work in 

the UK has been led by the National Physical Laboratory   (NPL) and the National 

Radiological Protection Board   (NRPB) with the support of some European 

Airlines to provide better information for use in computer codes to estimate 

aircrew doses.



>  This certainly is a point of concern to women employed by

> the airlines, as can be verified by innumerous publications.

> 

While it may be a point of concern to women (and men) employed as aircrew, 

I'm unaware of any peer-reviewed study that has found increase cancer risks for 

aircrew (other than skin cancers for which there may be other confounding 

factors)

> 

> Besides, I do not subscribe to the Hormesis theory that will soon find

> (paid?) followers here and elsewhere, that advocates low (how much is LOW?)

> X-Ray radiation is actually beneficial.

> 

> 

I have to admit that that while not a convert to Hormesis I have read some 

interesting publications on the subject and enjoy the discussions that take 

place on Radsafe.   To be honest while I may not be looking to take my daily dose 

of radiation to remain healthy I am certainly not a subscriber to the Linear 

No Threshold theory which has resulted in the   requirement for a grossly 

disproportionate amount of time, money and effort   to be spent reducing doses to 

as near zero as possible.   I personally believe that there is sufficient 

epidemiological evidence to indicate that current levels of occupational exposure 

do not result in much, if any real increase in risk to the workers.   As an 

example all classified radiation workers in the UK are invited to participate in 

a voluntary study which looks at whether there are any identifiable increases 

in cancer incidence in these workers compared to UK population.   This study 

(the National Registry of Radiation Workers - NRRW) has been running for a long 

time in the UK and every 5 years or so the data is reviewed.  It is my 

understanding that the only cancer where there may have been a statistically 

significant increase was for prostate cancer.   But I believe that even this 

statistically significant finding wasn't present in the last analysis.   Bearing in 

mind that this study includes about 120,000 current or former radiation workers 

with lifetimes doses from microSeiverts to hundreds of milliSeiverts (and may 

be even Seiverts of dose).   I'm happy to say to people that, current 

occupational doses particularly in the nuclear industry are unlikely to increase their 

risk of getting cancer.   However as far as providing advice to workers I'm 

required (by my employer) to quote the increased risks of cancer based on the 

LNT theory and the UK NRPB risk estimates, which have been made slightly (20%) 

more pessimistic than those of the ICRP.



What I always find interesting is that, in the UK at least, the reduction in 

worker doses in the nuclear industry is not mirrored   in a reduction in the 

use of radiation and radioactivity in medicine.   Even simple things like 

changing to more modern films with higher films speeds is often neglected even 

though this is often cost neutral and could halve the doses received by patients 

being radiographed.   



For me radiation and radioactivity continue to have important uses in modern 

society.   We should not be aiming to achieve zero doses, we should be looking 

to minimise these to sensible amounts that allow practices to continue, and 

to use advances in science, where it is sensible and cost effective to do so, 

to minimise peoples exposure.



I'd be interested in your responses.



Warmest regards,

Julian