Re: MCLs for Radium in Drinking Water

[Schoenhofer <schoenho@via.at>]

At 16:30 1996-06-10 -0500, you wrote:
>The MCL for Radium in drinking water is 5 pCi/L for Ra-226 "plus" Ra-228.
>
>Why do they have to combine (or "plus") the two isotopes?
>
>==========================================================================

The combination is easily explained: Due to old measurement methods a "gross
radium value" was measured, because the method could not distinguish between
Ra-226 and Ra-228. Taking usual ratios of Ra-226 and Ra-228 in drinking
water into consideration, the value of the "gross radium" of 5 pCi/l assured
that both radionuclides were less than 3 pCi/l each - which is the actual
limit for the single radionuclides. Extreme ratios might occur and then the
value of 5 pCi/l for "gross radium" might not assure that Ra-226 is below 3
pCi/l. You remember that in the case of a "gross radium value" above 5 pCi/l
it is necessary to analyse for the single radium isotopes. 

These values are part of an Interim Drinking Water Regulation. For more
information I recommend the special issue of Health Physics on Radionuclides
in Drinking Water, which was published some years ago. 

The reason, why I post this to radsafe is simply that I would like to ask
you, collegues, whether the proposal put forward by the EPA on radionuclides
in drinking water some years ago is in force now. I remember the value
proposed for radon in drinking water of about 11 Bq/l - which actually would
mean that in many areas the water could not be used for drinking purposes
any more. Direct your information to me or if you think it is interesting
for other radsafers post it to radsafe.

Best regards,

Franz Schoenhofer
Department for Radiochemistry and Radioactivity in Food
Federal Institute for Food Control and Research
Kinderspitalg. 15
A-1095 Vienna
AUSTRIA


>
Schoenhofer
Habichergasse 31/7
A-1160 Wien
Tel./Fax:	+43-1-4955308
Tel.:		+43-664-3380333
e-mail:		schoenho@via.at