has been implicated as a lung carcinogen (UNSCEAR 2000b).

Of all the studies reviewed above, only seven provide dose-specific estimates of ERR and only one provides an estimate of the EAR. Table 7-2 and Figure 7-1 summarize the results from these studies. In the figure, results are shown for all studies as well as those restricted to an average dose to less than 1 Gy.

In the incidence studies, the ERR/Gy ranges from 0.15 Gy−1 in survivors of HD to 1.4 Gy−1 in patients treated for hemangioma in infancy. In mortality studies, estimates range from 0.00 per gray among tuberculosis patients exposed to fluoroscopy to 0.43 Gy−1 in patients treated with radiation for peptic ulcer. Although risk estimates from these studies vary, confidence intervals are very large and the estimates shown are therefore statistically compatible.

In interpreting the results of these studies, differences in study populations and exposure patterns must be taken into account: the hemangioma study (which had 11 cases of lung cancer) included only patients who were exposed in infancy, while the average age in other cohorts ranged from 28 in tuberculosis patients exposed to fluoroscopic X-rays to 50 years among breast cancer survivors. Exposure rate and exposure pattern also vary across studies, with hemangioma patients having received a low-dose-rate, protracted exposure (over a period of 1 d to more than 2 years) and tubercu-

FIGURE 7-1 Distribution of study-specific estimates of ERR per gray for lung cancer according to average dose to the lung. Results are shown for all studies as well as studies in which the average dose to the lung was less than 1 Gy.

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