RE: Kosov DU - New Scientist Report

["Frame, Paul" <FRAMEP@ORAU.GOV>]

There are a number of Radsafers who are very knowledgeable regarding uranium
inhalation exposures that I would be interested in hearing from regarding
the Rand study.  Forgive the extensive quotations.

>I quote the Rand report on DU:
> 
> "there are no peer-reviewed published reports of detectable increases of
cancer or other negative health effects from radiation exposure to inhaled
> or ingested natural uranium at levels far exceeding those likely in the
Gulf. This is mainly because the body is very effective at eliminating
ingested and inhaled natural uranium and because the low 
> radioactivity per unit mass of natural and depleted uranium means that the
mass of uranium
> needed for significant internal exposure is virtually 
> impossible to obtain."

Given the evidence available from animal studies, this comment strikes me as
being somewhat of an overstatement.

With regard to one of the more important animal studies involving the
inhalation of uranium, the Rand report  states:  "In one animal inhalation
study examining the effects of UO2, no increased mortality was observed at
concentrations of 5 mg UO2/m3 for 5 years (Leach et al. 1970)." 

A problem here is that the Leach study is simply saying that there was no
increased mortality during the five year exposure period. This study did not
address the issue of long term post exposure effects. That such long term
post exposure effects actually occur was reported in a 1973 follow-up study
by Leach et al (1973 Health Physics 25:239-258). In the years following the
exposures lung and lymph node fibroses were observed as well as neoplasms.
The 1973 study emphasizes the "importance of a time factor in tumor
induction and development"  For some reason the Rand study does not mention
this aspect of the follow-up study (as far as I could see). This seems to me
to be a serious omission. Maybe I didn't read the Rand study closely enough
and am missing something however. 

As best as I can determine, the human data on uranium inhalation is
difficult to interpret and most of the animal studies were short term
investigations. 

Thoughts?

Paul Frame
Professional Training Programs
ORAU
framep@orau.gov
http://www.orau.gov/ptp/ptp.htm
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