Low-level Rn exposure and lung cancer

[Steven Dapra <sjd@swcp.com>]

March 31



	One of the fundamental rules of toxicology (if not <the> fundamental rule)

is that "the dose makes the poison."  It seems that this is generally true

of exposure to radiation as well.



	While doing some library research on radon and lung cancer I found that

this rule might not apply for radon exposure and lung cancer.  According to

Lubin (1994), " . . . the exposure-response relation declined with

increasing exposure rate or decreasing exposure duration, implying that for

equal total exposure, a higher risk for lung cancer is experienced by those

who accumulate exposure at a lower exposure rate and over a longer period

of time."  (This is quoted from p. 324, col. 2 of an "Invited Commentary"

wherein Lubin analyzed and discussed approximately 20 papers studying lung

cancer and radon exposure.  He also drew on other germane research findings.)



	In another paper (Darby et al. 1998) we read (p. 405, col. 1):  " . . .

greater risks are associated with exposures occurring at a low exposure

rate and spread over a long duration than for exposures occurring at a high

exposure rate with short duration [citations omitted]."



	Why does it seem - at least for radon exposure - that lower exposure

levels lead to a higher risk of cancer?  Does this phenomenon show up for

exposure to any other type of radiation exposure?  Please note that I do

not want to instigate a debate about LNT.  I only would like to know why

this anomaly shows up in the case of radon exposure.  You may reply via

RADSAFE or via private e-mail, whichever is more convenient.



Steven Dapra

sjd@swcp.com



REFERENCES



Darby, S. et al.  Risk of lung cancer associated with residential radon

exposure in south-west England:  a case-control study.  British Journal of

Cancer.  78(3):394-408; 1998.



Lubin, J. H.  Invited Commentary:  Lung Cancer and Exposure to Residential

Radon.  American Journal of Epidemiology.  140(4):323-332; 1994.









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