mortality, according to the projection model used. The linear model (L-L)** predicts increases of about 1 percent to 3 percent (about 1,700-5,000 cancer cases) over the normal expectation^depending on the projection model. The pure quadratic model (Q-L)*** predicts increases of about 0.06 to 0.2 percent (about 100-300 cancer cases) over the normal expectation of cancer mortality, according to the projection model used. The calculations are summarized in Table B-l taken from the BEIR III Report (NAS-BEIR, 1980). The upper and lower limits of these cancer mortality-risk estimates suggest a wide range of values which may differ by as much as an order of magnitude. The uncertainty derives mainly from the dose-response models used, from the alternative absolute and relative projection models, and from the sampling variation in the source data. The lowest risk estimates—the lower bound of the range—are obtained from the pure quadratic model; the highest—the upper bound of the range—from the linear model; and the 1 inear-quadratic model provides estimates intermediate between these two extremes. For continuous lifetime exposure to one rad per year, the increase in cancer mortality, according to the 1 inear-quadratic dose-response model (LQ-L), ranges from about three percent to eight percent (about 5,000-13,000 cancer cases) over the normal expectation, depending on the projection model. The linear model (L-L) predicts increases of about 7 percent to 18 percent (about 11,000 to 30,000 cancer cases) over the normal expectation. The quadratic dose-response model (Q-L) cannot be applied to this calculation. The calculations are summarized in the BEIR III Report (NAS-BEIR, 1980). The calculations for continuous exposure to one rad per year from the BEIR III Report (NAS-BEIR, 1980) segments the population into several age intervals, viz. 20-65 years, 35-65 years, and 50-65 years, exemplifying conditions of occupational exposure over a working career. For the increasing age groups, much of the variation in cancer risk estimates is due to the total dose received for the different periods of continuous exposure. The excess cancer mortality decreases with increasing age interval due almost completely to the total dose received rather than on the projection model used. For exposure at 35-65 years and 50-65 years, the two projection models give nearly identical results. **Linear (L) for low-LET radiation, linear (L) for high-LET radiation. ***Quadratic (Q) for low-LET radiation, linear (L) for high-LET radiation.
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