Fwd: Lead Apron Thickness

[Ccja@aol.com]

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Forwarded message:
From:	BERGSAGEL.CARL@SEATTLE.VA.GOV
To:	BERGSAGEL.CARL@SEATTLE.VA.GOV, ccja@AOL.COM
Date: 97-08-07 13:18:13 EDT

Chris,
 
Your email sparked my curiosity.  I was not aware of a regulatory
increase in required lead equivalency for fluoroscopy operator lead
aprons.  I'm sure you've seen this, but NCRP 33 (1968) states in para.
3.1.3(j):  "Protective aprons of at least 0.25 mm lead equivalent should
be worn in the fluoroscopy room by each person (except the patient) whose
trunk is exposed to radiation fields of 5 mR/hr or more."
 
NCRP 102 (1989), para. 3.3.4(p) states "Protective aprons of at least 0.5
mm lead equivalent shall be worn in the fluoroscopy room by each person
(except the patient).  People who must move around the room during the
procedure should wear a wraparound protective garment."
 
Not only is the lead equivalency doubled, but the recommendation has been
tightened from a "should" to a "shall", in NCRP-speak meaning change from
"prudent practice" to "necessary to meet accepted standards of
protection".  I'm not aware that occupational dose limits were reduced
between 1968 and 1989, so I am at a loss as to why the change.  The Army
medical centers I worked at in the 1980s had fluoroscopy users wear two
film badges, one under the apron and a second collar badge outside the
apron.  Even with 0.25 mm lead equivalent aprons, we never picked up any
significant doses recorded on the under-apron dosimeters.
 
Makes you wonder--if science is not driving the NCRP, what is?
 
If you get any insight from any radsafers, I'd appreciate a copy.
 
Carl B.
bergsagel.carl@seattle.va.gov