RE: Depleted Uranium vs. Tungsten -Reply

[rkathren@tricity.wsu.edu (Ron L. Kathren)]

At low enrichments, chemical toxicity of uranium (more specifically kidney
toxicity0 is predominant andgreatly exceeds the radiotoxicity; this is
certainly tthe case for both natural and depleted uranium.  Radiotoxicity
does not become controlling until enrichments of several per cent are
reached; the exact enrichment at which this occurs depends upon what
assumptions are used regarding the U-234 content of the enrichment.  The
transition point is typically and conservatively considered to be somewhere
in the vicinity of 5-10% by weight, although I have seen higher values.  So
it really doesn't matter whether the TLV-TWA was for depleted (0.2%) or
natural (0.7%) U; For these materials the radiological contribution (and
hence risk) to the overall toxicity is so small reltative to the chemical
toxicity that it can be ignored for all practical purposes.  Hence the
TLV-TWA for the two materials should be the same.


Ronald L. Kathren
Professor and Director
United States Transuranium and Uranium Registries

  At 02:46 PM 1/23/98 -0600, Zack Clayton wrote:
>ACGIH's 1997 TLVs and BEIs  guide lists the TLV-TWA for
>uranium as 0.2
>mg/m^3 and the TLV-TWA for tungsten as 5 mg/m^3 for soluble
>variants and
>1 mg/m^3 for insoluble variants. The TLV-STEL values for each
>show a similar ratio.
>
>This is good info, BUT --  The question as phrased regarded 
>chemical toxicity.  What part of the risk in the TLV-TWA
>calculation is due to the radiological component of uranium?
>Other than the fact that I don't really think you can separate the
>two risk components for U in the real world, it is an intersting
>academic exercise.  It also begs the question of was this
>TLV-TWA for natural or depleted U?
>
>Zack Clayton
>zack.clayton@epa.state.oh.us
>
>