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Technical issues related to the ERICA Tool (on Facilia website)

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Posted: 05/03/2012
From:
Phil Crouch
Australia

ERICA EMCLs

Question:
I have done a freshwater assessment with natural (U series) radionuclide concentrations of about 0.2 Bq/L. This is around half of our drinking water standard, but when I put it into ERICA I get a number of organisms with dose rates up to 200 - 300 microGy/h, and hence well over the ERICA default screening level. It seems very odd that there should be a result like that from water meeting drinking water standards, and I was wondering if you have any comments.

Answer:
We had noticed this for a few radionuclides although the discussion has never been had.

For instance the Am-241 EMCL is considerably below the WHO Guidance Level of 1 Bq/l (although the WHO GL for U-238 is 10 Bq/l).
There are some ‘oddities’ between drinking water GLs and the concentration in water which would produce human food which would not be allowed into the foodchain, e.g. at 10 Bq/l of Cs (the WHO GL) the concentration in fish would be 25,000 Bq/kg.

Not having had much to do with drinking water standards then they are obviously set to limit the dose via water [in the case of the WHO values seems to be to restrict dose to <0.1mSv/a via drinking water). In case of wildlife then the organism are permanently in water and potentially getting a dose from sediment perhaps the largest component of dose.

That said we are aware that some of the ERICA EMCLs are unrealistically low, there are a few freshwater ones which are below natural background concentrations. Some of this is probably due to the pdf assigned to the sediment-water distribution coefficient (another example you’ve already come across is the prevalence of lichen as a limiting organism in terrestrial ecosystems).

Answered by Nick Beresford (CEH) and David Copplestone (Stirling University) 2/03/2012

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Posted: 24/02/2012
From:
Chantal Medri
Canada

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