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Re: P-32 and Skin Burns


Check out Table 4.3 and accompanying text in NCRP Report No. 111 "Developing Radiation 
Emergency Plans for Academic, Medical or Industrial Facilities", published in 1991.  
With a few caveats, the skin contamination dose equivalent rate for P-32 (at a depth of 
7 mg/cm-2) is 2397 mSv (240 rads) per hour per MBq of P-32 distributed over 1 square 
centimetre of skin (appropriate for "infinite area" sources with average radii larger 
than the range of the radiation in water).   For point sources (like hot-particles) on 
the skin, the dose rate per MBq is considerably higher. For the information of our 
American colleagues, 1 MBq is equal to 27 uCi.

Obviously, the skin dose is highly dependent on the amount of activity deposited and the 
length of time it is resident. So an undetected splash or smear of P-32 on skin which is 
not washed for some hours after the contamination event (assuming that people bathe or 
shower once daily) could give one heck of a dose - certainly more than the annual dose 
limit.   In Canada, the current annual skin dose limit for officially 
designated radiation workers is 750 mSv, and will be reduced to 500 mSv with the 
adoption of proposed new  regulations.

You should also reference "Medical Effects of Ionizing Radiation" by Mettler and Mosely 
(Grune & Stratton 1985)- pages 126 - 130. It gives the following values for high 
energy beta radiation from radionuclides on the skin surface: threshold erythema, 5-15 
Gy (500-1500 rads); dry desquamation 17 Gy (1700 rads); bullous epidermatitis 72 Gy 
(7200 rads).  

Many years ago (before my time) in our facility, a radiopharmacy tech 
accidentally splashed liquid Mo-99 in acid solution onto the anterior aspect of her 
lower leg - which she unfortunately was unaware of  - and it was missed with routine 
frisking. Mo-99 has numerous emissions, among them, a 1.2 MeV beta as well as wome high 
energy gammas.  I understand that she developed a burn-like lesion on the the skin 
within a day or so which ulcerated and took a long time to heal. The acid chemical 
carrying the Mo-99 was fairly strong, which is likely why she developed symptoms so soon 
-  and after much analysis,  it was determined to be a combined acid/radiation skin 
burn. As soon as she complained of the initial symptoms, major effort was taken to 
assess the amount of Mo-99 activity in the skin lesion, and estimate the radiation dose. 
   There is no doubt that the radiation dose delivered was significant, and probably had 
a lot to do with exacerbating the acid burn and the prolonged healing time.  I never 
delved into all the details about the incident, but understand that the national 
regulatory authority was involved in the subsequent investigation.

So we take skin contamination VERY seriously! 

Karin Gordon
Radiation Safety Officer	voice	(204) 787-2903
Health Sciences Centre		fax	(204) 787-1313
Winnipeg, Manitoba, Canada	e-mail 	kgordon@cc.umanitoba.ca


Sue M. Dupre wrote:
> Good morning:
> This morning I encountered a faculty member who, mostly good-
> naturedly, has a soapbox he likes to pound about mindless radiation
> bureaucrats.  During his usual speech, he said there's no isotope use
> here on campus that can cause any harm to anyone (he's a H-3 user
> but he specifically referred to the P-32 users - and he wasn't
> interested in cancer risk).  I said, well, no, some researchers do
> use enough P-32 to cause skin burns under the wrong circumstances
> and that I could imagine scenarios involving millicurie users of P-32
> getting a microcurie droplet of P-32 on the skin, not surveying, and
> ending up with a skin burn.
> Although this scenario is an easy one to imagine, it must be really very
> rare in occurrence because, as best as I can remember, I've never heard
> anyone anywhere describe such an incident.  So my question: do any
> of you have knowledge, personal or anecdotal, of incidents resulting
> in P-32-induced skin burns?  Feel free to respond to me personally at
> dupre@princeton.edu - I'd be glad to summarize (without referring to
> specific institutions) the responses I get.  Thanks for satisfying my
> curiosity!
> Sue M. Dupre, Health Physicist
> Office of Occupational Health and Safety
> Chemical Sciences Building/Forrestal Campus
> Princeton University
> Princeton, NJ  08544-0710
> E-mail: dupre@arundel.princeton.edu
> Phone:  (609) 258-6252
> Fax:    (609) 258-1804