|
||||||||||||||
Answer to Question #709 Submitted to "Ask the Experts"Category: Doses and Dose Calculations — Internal dose calculations The following question was answered by an expert in the appropriate field: Q
In determining bioassay results, what approach(es) do you use in establishing background values for 14C bioassays?
A
You know how they say your employees are your best assets. In this case
it is absolutely true. What you need to determine a background for 14C
in urine is a background population that will provide you with
representative data. In this case this population is a group of your
employees who do not handle radioactive materials, your administrative
staff and business managers, or sales people.
You should obtain approximately 20-30 urine samples (24-hour urines if
available) and perform the identical analysis that you plan to perform
on your occupationally exposed employees. Now you have a set of data
which should be fairly representative of your employees. This is your
background data. An alternative to this method would be to buy or make
synthetic urine (yes they make artificial everything these days). The National Institute of Standards and Technology
provides freeze-dried urine samples with toxic substances and other
drug metabolites and may be able to provide standard freeze-dried
urine—phone: 301-975-6776, fax: 301-948-3730, or email: srminfo@nist.gov
for the latest prices. A recipe for synthetic urine is available (done
by Pacific Northwest National Laboratory [PNNL]) Report 6490 (1988)
from the National Technical Information Service,
U.S. Department of Commerce, 5285 Port Royal Road, Springfield, VA
22161. You should now perform the standard statistical analysis on this
data to determine the average background, standard deviation of
background, etc. Plug this into your favorite minimum detectable
activity (MDA) or lower limit of detection (LLD) formulas and Voila.
You have the LLD for your entire process that includes your individual
variations, and all. If you are interested in a very rigorous analysis
(that is, you are a real glutton for punishment) you can check out the
following link for PNNL's Bayesian Analysis Web page to help you determine the appropriate LLD for your samples.
Two references for determining the LLD/MDA can be found in:
Shawn Googins, CHP
Answer posted on 28 February 2001. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.
|
||||||||||||||
| This page last updated 18 December 2009. Ask Question | Search ATE | Site Map | Privacy Statement | Disclaimer | Security Notice | Webmaster | ||||||||||||||
