Absolute Risk Factors Five and More Years After Start of Uranium Mining
Radon Exposure Category (WLM)
Average Exposure (WLM) [1]
Person-Years at Risk (PYR) [2]
Total Exposure (WLM x PYR) TE = [1] x [2]
Lung Cancers Observed [3]
Lung Cancers Expected [4]
Excess Lung Cancers EC = [3] - [4]
Absolute Risk Factor (Excess cancers per WLM per million men per year) ARF = ( EC x 1,000,000 ) / TE
under 120
60
5530.11
332,000
5
1.84
3.16
9.5
120-359
240
6225.32
1,490,000
9
1.99
7.01
4.7
360-839
600
7006.03
4,200,000
13
2.52
10.48
2.5
840-1799
1,320
5730.88
7,560,000
11
2.26
8.74
1.2
1800-3719
2,760
3131.09
8,640,000
20
1.27
18.73
2.2
over 3720
4,000
901.38
3,610,000
10
0.41
9.59
2.7
Total
900
28524.81
25,800,000
68
10.29
57.71
2.2
Notes
The data for this table are taken from Radon Daughter Exposure and Respiratory Cancer, Quantitative and Temporal Aspects, Joint Monograph Number 1, (1971), National Institute for Occupational Safety and Health and National Institute of Environmental Health Sciences.
Because of the small number of cancers observed in the lowest Exposure Category (under 120 WLM) the first risk factor in the last column is more dubious than the other entries in the last column. With longer follow-up times, however, that first risk factor can only get worse: that is, larger -- not smaller -- if more lung cancers develop.
The absolute risk model, used in this table, measures the excess cancers in the entire population exposed, and assumes that any numerical increase in the (absolute) rate of cancer incidence will be proportional to the excess radiation exposure.
The first column and the last column are the important ones to study. Notice that the over-all average of 2.2 excess cancers per WLM per million men (at the bottom right corner of the table) tends to ignore the low-exposure data as expressed by the first entry in the last column. Indeed, the last four risk factors listed (average = 2.15) -- corresponding to larger exposures -- are less than a quarter of the first risk factor (9.5) , which corresponds to the smallest exposures.
