EPA MCLGs

[Lester Slaback <Lester.Slaback@NIST.GOV>]

The EPA states in the Drinking Water Standard  that Maximum
Contaminant Level Goals (MCLG) are set at zero based on the linear,
no-threshold cancer risk model for ionizing radiation exposure.  In
this FR notice there is no further discussion beyond this simple
statement.
Does anyone have a reference where this assignment of zero is discussed
further?  Is it basically a court mandate?
Once the MCLG is accepted then the only limit on lowering the
regulatorily enforced MCLs is the technological cost (irrespective of
benefit) of reaching that MCL.  Since the MCLG is zero by definition
all reductions are a benefit.

A related question:  Many toxic elements are essential minerals at
low concentrations.  Based on its chemical properties is there any
data that uranium is essential at some low value?

Disclaimer:  the above are the personal musings of the author, and do not represent any past, present, or future position of NIST, the U.S. government, or anyone else who might think that they are in a position of authority.
Lester Slaback, Jr.  [Lester.Slaback@NIST.GOV]
NBSR Health Physics
Center for Neutron Research
NIST
100 Bureau Dr.  STOP 3543
Gaithersburg, MD  20899-3543
301 975-5810 voice
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