[ RadSafe ] TFP - next questions

Wed Jan 4 16:27:22 CST 2006

Hi James - 

Interesting sample preparation and analysis description. Two potential  error 
factors that do  not appear to be addressed in  
http://mtafund.org/prodlib/radiation_health/final_report.pdf
are  chemoluminescence and K-40 LSA correction, either of  which can easily 
produce a 'false positive' for Sr-90/Y-90  presence. If the Report failed to 
account for either of these  factors, the Report ought to be dismissed on these 
bases alone.

Another problem is the absence of comparative sample media to help  
understand and  correlate the study results. If we assume that  Sr-90 in teeth ought to 
correspond with Sr-90 in bone from the same  individual, too, then bone 
sampling and analysis should be part of this  particular study. 

Since ethics would eliminate sampling bone from live humans from whom Sr-90  
was (supposedly) found in their teeth, then animals could be selected  that 
were alive at the same time in the same vicinity, particularly voracious  
farmland grazers like dairy cows. A brief scan of the Report finds  much verbiage 
about Sr-90 in teeth and bone, but not from the same  person or animal or the 
study locale. Nor does the Report provide any  attempt to affirm any data 
commonalities between humans and animals in  its sampling locale.

Finally, the claim by the Report that the data shows more Sr-90 in  teeth 
near nuclear power plants than elsewhere seems to be a weak correlation at  best, 
and utterly lacking of any objective  merit proving causation.

Use of this Report to formulate public safety policy would seem to be  unwise.

Secular equilibrium is the relationship of a very short-halflived  
radioactive daughter product relative to its long-halflived parent radionuclide.  In the 
context of the tooth sample discussion below, a daughter in secular  
equilibrium with its parent, like Y-90 is with Sr-90 when ingrowth of  the former is 
complete, have equal radioactivity levels to each  other.

Steve
Steven R.  Frey

In a message dated 1/4/2006 4:01:06 P.M. Eastern Standard Time,  
james at bovik.org writes:

> At  some point several years ago, there was a semi-detailed
> description of  the method being used by the tooth fairy
> project to analyze teeth for  Sr.  Can anyone point me to this post?

The following is quoted  from pp. 23-24 and 49 of:
http://mtafund.org/prodlib/radiation_health/final_report.pdf

"Upon  receipt of envelopes containing teeth, RPHP data managers assign 
a unique  control number to each tooth and logs it into a computerized 
data base.  Teeth are periodically sent in batches to REMS, Inc., a 
radiochemistry  laboratory in Waterloo, Ontario, Canada. Laboratory 
personnel document  Sr-90 concentrations by separately measuring Sr-90 
activity (in  picocuries) and calcium mass (in grams) in the teeth. 
REMS personnel,  headed by radiochemist Dr. Hari Sharma, are blinded 
from any information  about each tooth.

"A tooth is dried for 12 hours at 110 degrees  centigrade, then ground 
to a fine powder.  Approximately 0.1 gram of  the powder is weighed in 
a vial, then digested for a few hours with 0.5  milliliter of 
concentrated nitric acid along with solutions containing 5  milligrams
of Sr2+ and 2 milligrams of Y3+ carriers at about 110 degrees  
centigrade on a sand bath. The solution is not evaporated to dryness.  
The digested powder is transferred to a centrifuge tube by rinsing  
with tritium-free water. Carbonates of Sr, Y, and Ca are precipitated  
by addition of a saturated solution of sodium carbonate, then  
centrifuged. The carbonates are repeatedly washed with a dilute  
solution of sodium carbonate to remove any coloration from the  
precipitate. The precipitate is dissolved in hydrochloric acid, and  
the pH is adjusted to 1.5 to 2 to make a volume of 2 milliliters, of  
which 0.1 milliliter is set aside for the determination of calcium.  
The remaining 1.9 milliliters are mixed with 9.1 milliliters of  
scintillation cocktail Ultima Gold AB, supplied by Packard Bioscience  
BV in a special vial for counting. A blank with appropriate amounts 
of  Ca2+, Sr2+, and Y3+ is prepared for recording the background.

"The  activity in the vial with the dissolved tooth is counted four 
times, 100  minutes each time, for a total of 400 minutes, with a 
Wallac WDY 1220X  Quantulus low-level scintillation spectrometer. 
The spectrometer has  special features so that the background 
count-rate in the 400 to 1,000  channels is 2.25 plus or minus 0.02 
counts per minute. The background has  been counted for over 5,000 
minutes so that the error associated with the  background measurement 
is about 1 percent . The overall uncertainty or one  sigma associated 
with the measurement of Sr-90 per gram of calcium is plus  or minus 
0.7 picocuries per gram of calcium.

"The efficiency of  counting was established using a calibrated 
solution of Sr-90/Y-90  obtained from the National Institute of 
Standards and Technology, using  the following procedure. The 
calibrated solution is diluted in water  containing a few milligrams 
of Sr2+ solution, and the count-rate from an  aliquot of the solution 
is recorded in channel numbers ranging from 400 to  1,000 in order to 

determine the counting efficiency for the beta  particles emitted by 
Sr-90 and Y-90. It is ensured that the Y-90 is in  secular 
equilibrium with its parent Sr-90 in the solution. The counting  
efficiency was found to be 1.67 counts per decay of Sr-90 with 1.9  
milliliters of Sr-90/Y-90 solution with 25 milligrams of Ca2+, 5  
milligrams of Sr2+, 2 milligrams of Y3+, and 9.1 milliliters of  the
scintillation cocktail.

"The calcium content was determined  using a Varian A-A 1475 atomic 

absorption spectrophotometer by flame  spectroscopy at a wave length 
of 422.7 nanometers, using acetylene plus  air as fuel."

Please see also:
http://dx.doi.org/10.1016/S0048-9697(03)00439-X

Sincerely,
James  Salsman

P.S. What is "secular equibrium"?  It sounds like  something that 
might happen on Dick Cheney's secret energy task  force.
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