Cancer Risk In Czech Uranium Miners

目的：我们调查了大量地下铀矿工人的癌症发病率，这些矿工大多是在矿山暴露水平相对较低的情况下受雇的。除了提供关于低水平暴露的数据，通过研究癌症事件而不是死亡率和收集关于吸烟和粉尘暴露的数据，我们的研究应该提供与氡暴露有关的风险的更完整的情况。程序和技术：我们研究了来自捷克共和国Pribram的男性铀矿工人，他们在1976年1月1日之前至少在地下工作了一年，并于1977年1月1日在捷克共和国活着。我们对1945年至1992年的行业记录进行了计算机化处理，那时采矿已经停止。现有的数据包括在出生时分配的唯一识别号码以及在矿山工作的开始和结束日期。1977年1月1日，除2.7%的合格矿工外，所有符合条件的矿工都使用了许多来源来确定他们的重要身份和居住地，包括居民登记、铀工业记录、重要记录以及捷克和斯洛伐克的癌症登记。在18,985名矿工中，发现有16,434人符合条件，并通过将计算机化的矿工数据库与捷克癌症登记处（1976年以来的记录是计算机化的）、Pribram地区癌症登记处（1976年以来的纸质记录）、斯洛伐克癌症登记处以及捷克和斯洛伐克联合登记处、死亡证明和铀工业记录联系起来，跟踪调查癌症发病率和死亡率，直至1992年12月31日。更详细的暴露数据，包括工作地点和相关氡水平、吸烟、粉尘和伽马辐射的每日记录，来自2000人分层随机样本（按年龄和采矿年限分层），以及用于病例队列分析的所有癌症病例。癌症随访一直持续到1998年，以增加除肺癌外其他部位患癌症的矿工人数。已获得这些新增矿工的详细接触数据，目前正在计算机化和核查记录。成就：对1992年以前的癌症发病率和死亡率进行了估计，并与整个捷克共和国的发病率和普里布拉姆地区的发病率进行了比较。还通过比较氡暴露量较高的矿工的癌症发病率与氡暴露量最少的矿工的癌症发病率，对矿工的癌症风险进行了评估。752名矿工被诊断出患有肺癌。56%的矿工在1960年以后开始采矿，当时工业卫生措施大大减少了氡暴露。72%的队列患者的累积暴露量小于50 WLM。与捷克共和国的发病率相比，矿工患肺癌的风险是后者的两倍多。虽然低于5个WLM的矿工的风险没有增加，但所有较高暴露类别的风险都显著增加，并随着剂量的增加而稳步增加。年龄和日历年调整相对风险比较暴露矿工少于5 WLM显示类似的趋势。病例队列分析的初步结果证实，与氡有关的风险不能用吸烟或在矿井中职业性接触粉尘来解释。1100名矿工被诊断为肺癌以外的其他部位的癌症。所有非肺癌的总体标准化发病率略有升高。与地下工作的持续时间或累积工作水平暴露月数没有一致的趋势。然而，某些癌症的风险增加了。例如，白血病的发病率增加了50%，这在统计上是显著的，并且在超过50 WLM的所有暴露水平下，风险都会增加。除了剂量大于200wlm外，肾癌的风险总体上没有增加。喉癌、胰腺癌、肝癌、胃癌、结肠癌和直肠癌的标准化发病率也显著增加，但缺乏一致的剂量-反应趋势，表明辐射以外的因素。我们的数据提供了更多暴露水平的必要信息，更能反映在住宅中发现的暴露。我们是第一个研究癌症发病率而不是死亡率的人，当使用发病率或死亡率数据时，我们将有机会直接比较结果。由于我们有关于矿井中吸烟和其他暴露的数据，我们也将能够探索潜在混杂因素的影响——这在大多数队列中是不可能的。

Aims: We investigated cancer incidence in a large cohort of underground uranium miners largely employed when exposure levels in the mines were relatively low. In addition to providing data on low-level exposures, by studying incident cancers rather than mortality and collecting data on smoking and dust exposure, our study should provide a more complete picture of the risk associated with radon exposure. Procedures and techniques: We studied male uranium miners from Pribram, Czech Republic, who had worked at least one year underground prior to January 1, 1976, and were alive and living in the Czech Republic on January 1, 1977. We computerized industry records from 1945-1992, when mining ceased. Available data included a unique identification number that is assigned at birth and start and stop dates of employment in the mines. Many sources were used to establish vital status and residence on January 1, 1977 for all but 2.7% of eligible miners, including a register of inhabitants, uranium industry records, vital records, and the Czech and Slovak cancer registries. Of 18,985 miners, 16,434 were found to be eligible and were followed for cancer incidence and mortality through December 31, 1992 by linking the computerized miner database with the Czech cancer registry (for which records were computerized since 1976), the Pribram region cancer registry (paper records from 1976), the Slovakian cancer registry and a combined Czech and Slovakian registry, death certificates, and uranium industry records. More detailed exposure data, including daily records of work location and pertinent radon levels, smoking, dusts, and gamma radiation were obtained for a 2,000-person stratified random sample (stratified on age and decade of mining) of the cohort and all cancer cases for use in case-cohort analyses. Cancer follow-up was extended through 1998 to increase the number of miners with cancers of sites other than the lung. Detailed exposure data have been obtained for these additional miners and records are now being computerized and verified. Accomplishments: Cancer incidence and mortality rates though 1992 have been estimated and compared with rates for the general Czech Republic and with rates for the Pribram region. Cancer risk among miners also has been evaluated by comparing cancer rates among miners with higher exposures to the rates among miners with the least amount of radon exposure. Lung cancer was diagnosed in 752 miners. Fifty-six percent of miners began mining after 1960 when industrial hygiene measures substantially reduced radon exposure. Cumulative exposure was less than 50 WLM for 72% of the cohort. Compared to incidence rates for the Czech Republic, miners had a more than two-fold risk of developing lung cancer. Although risk was not increased for miners with fewer than 5 WLM, the risk was significantly increased at all higher exposure categories and increased steadily with dose. Age- and calendar year-adjusted relative risks comparing exposed miners to those with fewer than 5 WLM showed a similar trend. Preliminary results from the case-cohort analysis confirm that the radon-associated risks are not explained by smoking or by occupational exposure to dusts in the mines. Cancer of sites other than the lung was diagnosed in 1100 miners. The overall standardized incidence for all non-lung cancers was slightly elevated. There were no consistent trends with duration of underground employment or cumulative working level months of exposure. Risk was increased, however, for specific cancers. For example, there was a 50% increase in leukemia, that was statistically significant, and risk was increased at all exposure levels above 50 WLM. There was no overall increase in risk for kidney cancer, except at doses greater than 200 WLM. Significantly increased standardized incidence ratios were also found for cancers of the larynx, pancreas, liver, stomach, and colon and rectum, but the absence of consistent dose-response trends points to factors other than radiation. Our data provide much needed information on exposure levels that are more reflective of exposures found in residences. We are the first to study cancer incidence rather than mortality and will have the opportunity to directly compare the results when incidence or mortality data are used. Since we have data on smoking and other exposures in the mines, we will also be able to explore the influence of potential confounders - something that has not been possible for most cohorts.