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

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 also 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 DDrinking water standards then they are obviously set to limit the dose via water [in the case of to humans from the consumption of water (for the WHO values aim seems to be to restrict dose to <0.1mSv/a via drinking water). In the case of wildlife then the organism organisms are permanently in water and potentially getting a dose from sediment perhaps (which may be the largest component of dose to the most exposed organism depending upon the radionuclide).

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).

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