Low Positive Doses in Personnel Monitoring

["Sue M. Dupre" <dupre@Arundel.Princeton.edu>]

Good morning!  I've just been handed responsibility for the routine 
management of our personnel monitoring program, and I'm giving some 
consideration to different ways of handling some aspects of the 
program.  For instance, we've been discussing the problem of those 
ever-present low positives, positives on the order of 10 or 20 or 30 
mrem. I presume that we all are suspicious of doses that are close to 
minimum detectable levels, that we've all seen cases in which a dose 
is reported but the badge wasn't worn, for instance.  Assuming that 
you've dealt with the vendor to eliminate factors such as control badge
problems,  then how do you proceed?

1)  Do you do some sort of followup action on ALL positives,  e.g., 
sending out a questionnaire to collect information so you can 
determine whether the dose is likely to be real.  If so, do you do this 
because of regulatory concerns, liability concerns,  because you hate 
inaccuracy, or for some other reason? 

2)  Do you set a limit below which you ignore low positives and only 
do investigations of higher doses (this would mean that you accept 
the low positives as reported)?  

How would you assign dose in the following scenario?  Researcher A 
is reported to have received 30 mrem in one period, but in the followup 
questionnaire says that he did not use radioactivity during the period 
in question, though other people in the lab used P-32.  Researcher B 
who is also reported to have received 30 mrem says that she used S-35 and works 
in a lab in which only S-35 is used.  Staff member C is a support staff
member (maybe a janitor, but let's not get into the issue of whether 
janitors and other similar support staff should be badged) who is 
reported to have received 30 mrem;  Person C works in the same 
building as researchers A and B and regularly passes through labs in 
which many common radioisotopes including P-32 are used. 

It has been suggested to me that we tell the researcher what dose 
they are believed  to have received (either based on the reported dose 
or based on our conclusion following investigation) and ask them to 
confirm that they could have received such a dose but I suspect that a
very high percentage of researchers do not have a sufficient 
understanding of how the radioactivity they work with or around 
relates to doses actually received for this to be realistic and practical.   
Any reaction?

I'll be grateful for any information and comments you have to share.  
I will summarize later the gist of the information I receive from you 
all.  Please feel free to call me if it's more convenient.  Thanks!

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@princeton.edu
Phone:  (609) 258-6252
Fax:    (609) 258-1804

Visit the OHS Web site at http://www.princeton.edu/~ehs