RE: maximum permissible limits

["Wes Van Pelt" <WesVanPelt@ATT.NET>]

Franz and All,



Yes, this is a very important concept. That is, how much below the

regulatory limit (1 sigma, 2 sigma?) must your assessment be to be assured

that you are in compliance?



I recently ran the US NRC's DandD code that calculates the dose from a given

concentration of contaminant. The code (version 2) gives the dose at the

90th percentile. Furthermore, as a bottom line, it gives the upper 95%

confidence limit of the 90th percentile! The code does not even give the

50th percentile which would be the unbiased value. This code forces the user

community to report a dose that is very much higher than the unbiased

expectation value of the statistical distribution. This is like adding

another layer of ALARA on top of the normal ALARA.



Anyone else notice the strong bias in DandD toward reporting a dose at the

uppermost statistical boundary?



Beat regards,

Wes

Wesley R. Van Pelt, Ph.D. CIH, CHP

Wesley R. Van Pelt Associates, Inc.

Radiation Safety and Environmental Radioactivity

WesVanPelt@att.net



-----Original Message-----

From: owner-radsafe@list.vanderbilt.edu

[mailto:owner-radsafe@list.vanderbilt.edu]On Behalf Of Franz Schoenhofer

Sent: Friday, July 26, 2002 1:59 AM

To: radsafe@list. vanderbilt. edu (E-mail)

Subject: Fw: maximum permissible limits



I have only received two comments on my question, which did not answer it. I

do believe that this question must be of really fundamental interest to

anybody, who is checking data for compliance with legal prescription.

Please, if you do not want to answer to the list, answer to me personally.

So I post my question once again.



Franz





>This comment raises for me a very important question: What is the

criterion,

>whether a maximum permíssible concentration has been exceeded? There are

two

>extremes possible: Is it, that the measured value plus x sigma has to be

>below the MPC or is it that the measured value has to be below the MPC plus

>x sigma? The latter criterion is used in most regulations in Austria

>regarding contaminants in food (x=2). The criterion defined by the Austrian

>Standardisation Organisation (which has to be regarded as a recommendation

>and has no real legislative power) is coherent with the first extreme. I

>wonder, what the legislation is in other countries.

>

>Best regards,

>

>Franz





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