From: bbaker@cscns.com (Brian Baker)
Subject: Brehmstrehhlung X-rays
Organization: Community_News_Service
X-Newsreader: TIN [version 1.1 PL8]
Date: Mon, 25 Jan 1993 01:39:27 GMT


Ok, I chalk this post up to too many people in the biotech business
not knowing enuff chemistry.... (sarcastic joke, no offense meant!)

I just graduated with a BS in Biochemistry, got my first job in 
Denver doing RFLP for paternity analysis and trying to perfect a
non-isotopic method of doing genomic Southern blots.

Anyway, a couple of the guys in the lab are doing dot blots in attempts to
detect CMV virus and do HLA typing.  They started with 5 millicuries of
32-p (now they're up to 10 or 15).  They're working behind 1/2" plexiglass,
which is sufficient to 
block all betas coming from the source.  However, one guy took the geiger
counter in front of the screen and noticed a few thousand counts.  I 
told him it was somthing along the lines of X-rays coming from the plexi-
glass.  This person has since talked with a couple of people (a state of
Colorado Radiation Safety officer and some guy at Amersham I believe) and
now is convinced (and has others in the lab convinced) that working with
32-p behind plexiglass is very dangerous because of the X-rays coming 
off.  They have scavanged some lead bricks from an old scintillation 
counter and won't work without stacking the lead in front of the shields
(this lead is about three inches thick and VERY heavy).  I do my work 
with a max of 0.5 mCi (usually .25 tho) and they call me crazy when I 
don't put the lead in front of me.  A guy who sits at a desk about 
twenty feet away from the 32-p room is worried about X-rays bombardidng
him while he's at his desk.  The way I understand this is:

	1)  The X-rays are caused by betas being deflected by lead
	    in the plexiglass, which causes a rapid change in velocity
	    and a subsequent X-ray

	2)  These X-rays are of low energy (compared to X-rays you get
	    at the hospital) and the extinction coefficient is only
	    a few feet or so

	3)  5 millicuries, which is a large amount of 32-p, will not
	    generate enuff X-rays from plexiglass to be concerned about,
	    certainly .5 mCi behind 1/2" plexiglass is safe

Oh yeah...this same person claims X-rays to be 'ionizing radiation'
Now I  had a pretty good Nuclear/Radiochemistry class and I certainly 
don't remember X-rays being classified as ionizing radiation.  This person
also claims X-rays and Gamma rays to be "almost" the same.

So my questions are....

->	Are these Brehmstrahlung X-rays something to be concerned about?
->	What is the mCi limit of a high energy beta emitter (such as
		32-P) which will produce a harmfull level of X-rays from
		plexiglass (or very thin lead shielding)
->	Am I way off base in saying this guy should learn the facts before
  	 	causing unnecessary worry?
->	Just what is the ionizing potential of a Brehmstrallung X-ray?
->	What is the ionizing potential of a higher energy X-ray?
->	I was taught you would get more X-ray dosage from a transcontinental
	  	flight then you would from being exposed to a high level
		Brehmstrallung X-rays.  Is this true?

Thanks for any help in this matter.  If I'm full of it, please let me know.
I don't get the time to read any newsgroups anymore, so please mail any
responses to me ( bbaker@cscns.com ).  Oh yeah... the text I had in 
college went by the name FKMM (after its authors, Friedlander, Kennedy,
and two other guys).  I sold it back and now can't find a copy anyhere.
Can anyone recommend a good text on Nuclear and Radiochemistry that would
help us in matters like these?

Thanks for the help......

	-Brian Baker     Immunological Associates of Denver
	 bbaker@cscns.com    (303) 301-6027 (work) 
			     (719) 637-1140