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Re: More on DU
At 09:50 08/06/99 -0500, you wrote:
>
> Keith Bradshaw wrote:
>
> >>I calculated an Annual Limit of Intake (inhalation) of 32Bq, which
> corresponds to 2100microgram of DU for members of the public (1mSv/yr
> limit). At 2000 hr per year and a breathing rate of 1.2m3/hr, you
> obtain a Derived Air Concentration (DAC) of 0.013 Bq/m3 which
> corresponds to 0.88microgram/m3. This is a factor of 227 times more
> restrictive than the ACGIH limit.<<
>
> There are several points I would like to make. First the ACGIH limit
> quoted in the RAND report is an occupational limit and not a limit for
> the general public. It is based primarily on chemical considerations.
> The DAC (occupational) for insoluble depleted uranium with the mix
> quoted is approximately 0.7 Bq/m3 which is approximately 0.05
> milligrams/m3 for an ALI of approx 100 milligrams.
That's for an annual limit of 50mSv. I think the occupational limit in UK
is 20mSv. As you point out, I've calculated it for members of the public,
which in the UK have a limit of 1mSv/y. In the US, I believe dose limits to
members of the public are even more stringent, 0.15mSv/y for EPA regs on
the nuclear fuel cycle. Anyway, this is what I wanted to get to the bottom
of. I'm not actually interested in this from the Gulf War Syndrome angle.
>
> Second point and perhaps more germane to the discussion is the
> difference between the risk associated with a calculated dose and the
> actual risk of the exposure. The RAND report also made the point and
> I will quote from the report, "Although any increase in radiation to
> the human body can be calculated to be harmful from extrapolation from
> higher levels, 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 in the Gulf."
Perhaps, but exposure limits have been set and it's our statutary duty to
both keep below them AND to clearly demonstrate that we are keeping below
them. From the sound of things, this has not been done in the Gulf War.
>
> Third the statement Keith Bradshaw made:
>
> >>>"The consensus of sensible replies seems to be that the limit of
> 200microgramU/m3 set by the American Conf. of Gov. Induustrial
> Hygenists is based on chemical toxicity. The Rand report says this
> limit applies to both soluble and insoluble forms." <<
>
> Is incorrect. The RAND report on page 11 makes a clear distinction
> between soluble (0.05 ug/m3) and insoluble (0.2 ug/m3) uranium
> standards.
Under 'Chemical Toxicity Guidelines for Uranium in Air' quote: "The [ACGIH]
adopted the maximum permissible concentration of 200ug/m3 for soluble
uranium along with a permissible concentration of 200ug/m3 for insoluble
natural uranium (ACGIH, 1993)."
This is one of the things I wanted cleared up. I have not found the bit on
"page 11" probably because the pagination is a bit out on my copy. Do you
mean 'mg' for 'ug' above? If so, the 0.2mg/m3 of insoluble U (class Y)
works out to a dose of approx. 400mSv/y
(200ug*0.0253Bq*1.2m3/h*2000h*3.3e-05Sv/Bq).
>
> Finally, perhaps my eyes are getting old, but I cannot find where the
> RAND report stated that protection from the chemical risks would
> automatically protect from radiation exposures.
>
Quote: "Under exposures at or near the maximum permissible concentration in
air, the amount of uranium present in the lung or kidney or the amount in
bone will never, with natural uranium, constitute a radiological hazard."
Actually, the Rand report is quoting Hodge et al (1973) here, and I
apologise because this DOES refer only to SOLUBLE uranium, which I missed
before :)
Regards
Keith
--------------------------------------------------------------------------
Keith Bradshaw
01703 596600 OR 596587
Geosciences Advisory Unit
School of Ocean and Earth Sciences
Southampton Oceanography Centre
European Way
SOUTHAMPTON
SO14 3ZH
UK
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