Committee Examining Radiation Risks of Internal Emitters
(CERRIE)
_________________________________________________________________________
11th Meeting, October 22, 2003 INFO 11- L
Conference Room 8
DEFRA, Ashdown House
123 Victoria Street
London SW1E 6DE
Alpha Radiation from Particulates: Reply from Dr D Kirkland
1. Attached for the Committee’s information is a copy of an email received from Dr D
Kirkland in response to the Committee’s letter of June 10 (also attached for ease of
reference). Dr Kirkland’s comments on the Preliminary report are contained in Paper 11-1.
IF
Oct 2
1
From: dkirkland
To: d.goodhead@har.mrc.ac.uk
Sent: Wednesday, October 01, 2003 12:09 AM
Subject: CERRIE
Dear Professor Goodhead
Thank you very much for CERRIE’s comments about our paper. Unfortunately the work on Table 5
from our earlier paper is still not completed, so the best I can do by Sept 30th is to respond briefly to
some of the points which were raised in the letter from Dr.Fairlie, and to send comments on the
Preliminary Report.(attachment below, also sent by post )
Response to letter
Unattached fraction. There were two reasons why we did not mention this on our paper.
(i) It was not considered, at the time, to be particularly relevant to the hypothesis being presented
(ii) It would have added considerable complication to what was already a fairly lengthy paper.
Further consideration (below) suggests we should perhaps have paid more attention to this matter.
For a given exposure, expressed in WLM, large increases in unattached fraction increase mean alpha
dose to the upper airways markedly, but have little effect on the mean dose to distal lung, the region in
which rats¹ (unlike human) lung tumours originate. For this reason control of unattached fraction
seems relatively unimportant, as Dr R Masse has pointed out (personal correspondence 1989)
However all is not well here, because large changes in unattached fraction do appear to be associated
with large changes in rat cancer risk per WLM. How can this happen, when the dose to the region
where the cancers originate is not changed much? The reason, I suggest, is that a high unattached
fraction requires a low concentration of condensation nuclei, which is exactly what is required for
daughter aggregate T2 sources to form. Thus, increasing unattached fraction, raises the mean dose in
the upper airways , has little effect on the mean dose in the distal lung, and is accompanied by
increases in the number of daughter aggregates in this distal region. The association of increasing lung
cancer risk in rats with increasing unattached fraction appears then to be further evidence implicating
T2 sources as a causative agent in lung cancer. The human situation requires separate analysis.
U miners’ lung cancers
Radon daughter concentrations in miner studies are mean values, some of which are based on only
one measurement per year per mine. (F.Steinhausler,W. Hofmann 1984) As such, they are likely to be
rather poor indicators of the extremes of concentration likely to be experienced at different times and
places under a variety of working and ventilation conditions. The longer miners spend underground
the more likely they are to experience such extremes. At 50% equlibrium, the Radon concentrations in
fissures, mentioned in our paper, convert to 5000 to 50000WL, somewhat more than the 5WL
concentrations in most miner studies referred to in BEIR VI. These extremes values would be rapidly
diluted, of course, but mine shaft Radon concentrations of 2 million Bq per cu.m (equivalent to about
500WL at F=1) have been recorded.eg in Schneeberg in the shaft known locally as the Todesschaft
(Death Shaft).
I hope the above, and the attached comments on the Preliminary Report are helpful.
Yours sincerely
David Kirkland
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Committee Examining Radiation Risks
of Internal Emitters (CERRIE)
_________________________________________________________
c/o Department for Environment,
Food and Rural Affairs
Nobel House, Room 541
17 Smith Square
LONDON SW1P 3JR
Dr David Kirkland June 10, 2003
Ottersgill
Stenness
Orkney
KW16 3HA
Dear Dr Kirkland,
CERRIE Consideration of Kirkland Paper
Further to Professor Goodhead’s letter of March 12 and follow-up email of March 26, the
Committee have recently considered your 10 page paper entitled “Comments on dose, lung
cancer risk and alpha radiation”.
The Committee considered that your paper was indeed very interesting. However the paper
did not discuss the phenomena of attached and unattached fractions, and, as you have
acknowledged, did not yet include the substantial data from radon studies of lung cancer in
rats done by Claire Collier and others at AEAT, Harwell (still unpublished at present). The
Committee also noted that the paper ran counter to well-established miner epidemiological
data which showed an inverse exposure rate effect: the higher the concentration of radon
daughters, the lower the level of health effects per unit exposure. From the BEIR VI report on
cohorts of exposed miners around the world, it could be inferred that there would be few
significant T2 sources according to your criteria. Your paper stated that there would be no T2
sources below a radon1 concentration of 5 Working Levels, but most radon concentrations in
the miner studies were below 5 Working Levels. Nevertheless all the miner cohorts showed
enhanced lung cancers and the risk per unit dose was found to be greatest for the lower
radon concentrations.
Nevertheless the Committee thought your paper was very stimulating and they requested
that I thank you for taking the time and trouble to send them your views. We would very
much invite you to develop and evaluate your hypothesis further in the light of the human
and AEAT rat data and invite you subsequently to seek peer review of your paper.
Yours sincerely
Dr IAN FAIRLIE
Secretariat
1
to be precise, the alpha-emitting progeny of radon
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