Radon and Lung Cancer - Response to Helmuth Lau

[Bill Field <bfield@dexter.pmeh.uiowa.edu>]

At 06:30 PM 2/25/97 -0600, Helmuth Lau requested information  concerning:

1. What is the cheapest, but still effective way to measure radon in air.
2. What are the harmful effects of radon and its progeny to human health and what are the studies that show that up.


Response to Helmuth Lau:

1. The type of detector you purchase depends on whether   you need a short term or long term measurement.  Charcoal canister type detectors perform fairly well for short term radon testing.  Alpha track detectors would be preferred for longer term testing.  Contact me directly and I can give you the name of some vendors that may be able to help you.

2. Concerning the harmful effects of radon progeny to human health:

a) Radon is a lung carcinogen.  In the United States radon (and radon progeny) provides the primary source of ionizing radiation exposure, imparting a greater effective dose equivalent to the average individual than other natural and man-made sources combined (NCRP 1987).

b) Lubin et al. found in a 1994 joint analysis of 11 underground miner studies a linear relationship between cumulative exposure to radon (and its progeny) and lung cancer.  The reference is Lubin et al., Radon and Lung Cancer Risk: A Joint Analysis of 11 Underground Miner Studies, National Institutes of Health, U.S. Department of health and Human Services, Public Health Services, NIH Publication No. 94-3644, 1994.  The references for all the major miner studies, you are interested in, are listed in this publication.

c) The risk estimates provided by the miner studies can not be extrapolated to the general population with certainty, because of inherent differences between the mining population and general population as well as differences between the mine and home environment.  Therefore, numerous epidemiologic investigations, using either ecologic or case-control designs, have attempted to directly examine the relationship between indoor radon exposure and lung cancer.

d) Over 20 ecologic studies have been published since 1981.  These studies generally attempted to correlate geographically based lung cancer rates with mean radon concentrations from a geographic area.  Stidley and Samet reviewed 15 ecologic studies and concluded that ecologic studies cannot accurately measure the lung cancer risk associated with indoor radon exposure (Reference available on request).  The ecologic study should be merely used to generate hypotheses.  It has major limitations including difficulty in assessing exposure, controlling for smoking status, etc.

Regarding Dr. Cohen's studies - They are ecologic in nature.  He should be credited with at least trying to adjust for the many confounders that plague these types of studies.  But, no matter how you try to adjust on an aggregate level, huge misclassifications occur. For example, can you imagine the misclassification that occurs by trying to adjust for smoking rates on a county level using tobacco sales taxes.  How do you interpret these taxes?  Do they indicate 1000 people smoked 1 pack a day or 500 people smoked 2 packs a day.  I think Dr. Cohen himself would agree that the case-control study design is preferable to the ecologic study design to determine the risk posed by radon exposure.  Dr. Cohen's goal in his studies is not to look at the risk posed by radon exposure, but rather to examine the validity of the LNT theory.  Hopefully, he will see this posting and verify this statement.

e) The case-control study design overcomes many of the limitations ofologic studies and has been used to examine the relationship between radon exposure and lung cancer (References available on request).  The major case-controls studies completed to date have been inconclusive for several reasons including: study performed in low radon area, inadequate sample size, poor dosimetry, etc.  Some of the studies showed positive associations with dose response relationships, while others failed to find any significant increases in risk.  There are currently major studies underway in Europe, China and the United States (Iowa, Connecticut, Utah & Missouri).  A few of these studies have sufficient power to stand on their own merits.  In addition, an International pooling effort of residential radon studies is underway which will combine data from similar studies (reference available on request).  However, each study should be viewed on its own merits.  Hopefully, the scientific community will take the time to read the studies and judge them on their merits before deciding whether or not radon is a hazard at concentrations found in residential areas.

I apologize for the length of this posting, but I thought Helmuth Lau deserved an answer to his questions.  Please contact me directly for any references you may need to support claims made above.

Bill Field






^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
R. William Field, Ph.D.
Department of Preventive Medicine
Division of Epidemiology
N222 Oakdale Hall
University of Iowa
Iowa City, Iowa 52242

319-335-4413 (work)
319-335-4747 (fax)
bill-field@uiowa.edu (email)
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