Hyping Health Risks by Geoffrey C. Kabat

Author:Geoffrey C. Kabat
Language: eng
Format: epub
Tags: Medical/Health Care Delivery
Publisher: Columbia University Press
Published: 2011-11-18T05:00:00+00:00

BEIR VI

Eleven years after the publication of the BEIR IV report, in 1999 a second report from the National Research Council entitled Health Effects of Exposure to Radon, provided a new, updated analysis of the miner data, this time based on 11 cohorts and including 68,000 miners and 2,700 cases of lung cancer, as compared to the 4 cohorts and 360 lung cancer deaths in BEIR IV.64 The large increase in the available data permitted a refinement of the model developed in the earlier report.

After extensive analysis, BEIR VI concluded, on the basis of what was known from studies of underground miners and an understanding of genomic damage caused by alpha particles, that exposure to residential radon is “expected to be a cause of lung cancer in the general population.”65 The analysis further indicated that there was a “synergistic effect” of radon together with smoking, although the precise nature of the interaction—whether “multiplicative” or “sub-multiplicative”—could not be determined. Most importantly, the committee estimated that between 15,400 and 21,800 lung cancer deaths per year in the United States could be attributed to domestic radon exposure, although the authors indicated that, given the uncertainties in the analysis, the actual number of deaths could be between 3,000 and 33,000. (The authors also estimated that between 2,100 and 2,900 of the lung cancer deaths caused by radon occur in never smokers.) These numbers, the committee noted, make radon “the second leading cause of lung cancer” after cigarette smoking.66

For all the sophisticated statistical modeling provided in the report, two major problems cast doubt on the ability make accurate estimates of the effects of radon at residential levels based on the miner data. These are the dearth of data on miners exposed at low radon levels and the powerful effect of smoking.

The core of the report consists of two components: (1) the extrapolation of the miner data from the 11 cohorts down to the levels encountered in homes and (2) the meta-analysis of the available case-control studies of residential radon. Each of these topics was addressed in a paper in the Journal of the National Cancer Institute published in the mid-1990s,67 and the results were presented in greater detail and in updated form in the 1999 report. I will refer both to the papers and to the report.

The analysis of the combined miner data from the 11 cohorts showed that cumulative radon exposure in miners was directly related to risk of lung cancer—in a linear manner—in both ever smokers and never smokers (fig. 5.1). In addition, based on theoretical considerations, the committee posited that there was no threshold, i.e., no level below which radon would not affect the risk of lung cancer, although it acknowledged that the existence of a threshold could not be ruled out. Application of the “linear no threshold model” to the miner data implied that even at the low levels encountered in most homes, radon exposure would carry some risk.68

In addition to analyzing the full range of the miner data (ranging from

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