Lubin J H, Samet J M, Weinberg C
National Cancer Institute, Epidemiologic Methods Section, Rockville, MD 20892.
Health Phys. 1990 Dec;59(6):807-17. doi: 10.1097/00004032-199012000-00004.
Recent data on indoor air quality have indicated that Rn (222Rn) and its decay products are frequently present in domestic environments. Since studies of Rn-exposed miners have established that Rn decay products are a lung carcinogen, their presence in indoor air raises concerns about an increase in lung cancer risk for the general population. To directly evaluate lung cancer risk from domestic exposure to Rn and its decay products, as well as to evaluate risk assessments derived from studies of Rn-exposed underground miners, several epidemiologic studies of indoor Rn exposure have been initiated or are planned. This paper calculates sample sizes required for a hypothetical case-control study to address several important hypotheses and shows the impact of several difficult problems associated with estimating a subject's Rn exposure. We consider the effects of subject mobility, choice of the exposure response trend which is used to characterize an alternative hypothesis, and errors in the estimation of exposure. Imprecise estimation of Rn exposure arises from errors in the measurement device, exposure to Rn decay products from sources outside the home, inability to measure exposures over time in current as well as previous residences, and the unknown relationship between measured concentration and lung dose of alpha energy from the decay of Rn and its progeny. These methodological problems can result in large discrepancies between computed and actual study power. Failure to anticipate these problems in the design of a study can result in inaccurate estimates of power. We conclude that case-control studies of indoor Rn and lung cancer may require substantial numbers of subjects in order to address the many questions of importance that burden current risk assessments with uncertainty. We suggest pooling data from studies with the largest numbers of cases and with the most precise estimates of Rn exposure as the best approach for meeting present research needs.
近期有关室内空气质量的数据表明，氡（222Rn）及其衰变产物经常存在于家庭环境中。由于对接触氡的矿工的研究已证实氡衰变产物是一种肺癌致癌物，它们在室内空气中的存在引发了对普通人群肺癌风险增加的担忧。为了直接评估家庭接触氡及其衰变产物导致的肺癌风险，以及评估从接触氡的地下矿工研究得出的风险评估，已经启动或计划开展多项关于室内氡暴露的流行病学研究。本文计算了一项假设的病例对照研究为解决几个重要假设所需的样本量，并展示了与估计受试者氡暴露相关的几个难题的影响。我们考虑了受试者流动性的影响、用于描述替代假设的暴露反应趋势的选择以及暴露估计中的误差。氡暴露的不精确估计源于测量设备的误差、来自家庭外部来源的氡衰变产物暴露、无法测量当前以及以前住所随时间的暴露情况，以及测量浓度与氡及其子体衰变产生的α能量的肺部剂量之间的未知关系。这些方法学问题可能导致计算出的研究效能与实际研究效能之间存在很大差异。在研究设计中未能预见这些问题可能导致对效能的不准确估计。我们得出结论，室内氡与肺癌的病例对照研究可能需要大量受试者，以便解决许多重要问题，这些问题使当前的风险评估充满不确定性。我们建议将来自病例数量最多且氡暴露估计最精确的研究数据合并起来，作为满足当前研究需求的最佳方法。
