Evaluating impacts of occupational exposure limits for silica using g-estimation

 描述(由申请人提供)：当健康状况不佳的工人减少接触，而健康的工人没有，即使接触会导致疾病，也很难检测出两者之间的联系。这种健康的工人幸存者偏见在研究长期职业暴露与慢性病之间的关系时尤其成问题。使用常规回归分析对健康工人的幸存者效应没有令人满意的解决方案。幸运的是，已经开发出了消除这种偏见的替代方法；直到最近，这些“g-方法”才被应用到职业环境中。我们的团队成功地将它们应用于一项大型死亡率研究，并为使用更传统方法的研究人员未能找到的关系找到了明确的证据。最近的工作将这些方法的使用扩展到持续暴露，我们已经开发了一种公共卫生方法，明确评估实施新暴露限制的影响。硅藻土行业的工人暴露在结晶二氧化硅中，这会导致矽肺和其他非恶性呼吸道疾病，现在被归类为致癌物质。以前对硅藻土工人队列的分析没有调整健康工人幸存者的偏见。由于竞争风险的审查，相对较弱的肺癌结果和对心血管结果的保护性估计可能会进一步偏向。因此，我们的目标是应用g-方法来解决这两个偏差来源，希望这样做将使我们能够发现结晶二氧化硅与肺癌、COPD和心脏病死亡率之间因果关系的更明确证据。一般行业允许的二氧化硅暴露限值(PEL)为100微克/立方米，自1971年以来一直有效，从未更新过；然而，2014年3月就一项拟议的联邦标准举行了听证会，该标准引入了新的PEL为50微克/立方米。我们将评估拟议的可吸入结晶二氧化硅暴露限值的潜在影响，方法是 挽救生命的年数，评估干预措施的效果，而不是比较不同接触史的工人群体。该项目涉及采矿部门和癌症、生殖和心血管疾病NORA跨部门计划。其严格的分析方法将为吸入二氧化硅的影响提供更明确的流行病学证据，使用一种易于向政策制定者和普通公众传达的指标，根据职业暴露限制的影响制定结果。这与NIOSH的R2P倡议直接相关。成果和产出将包括在同行评议期刊上发表的科学研究论文和在会议上的陈述。通过减少工作场所暴露的病因学研究中的偏差和评估职业暴露限制的潜在影响，该项目将导致更好地控制职业健康危害。

 DESCRIPTION (provided by applicant): When workers with poor health decrease their exposure but healthy workers do not, it becomes difficult to detect an association even when exposure causes disease. This healthy worker survivor bias is particularly problematic in studies of relationships between long-term occupational exposures and chronic diseases. Satisfactory solutions to the healthy worker survivor effect using conventional regression analysis do not exist. Fortunately, alternative methods have been developed that do eliminate this type of bias; only recently have these "g-methods" been applied in an occupational setting. Our group successfully applied them to a large mortality study and found clear evidence for relationships that had eluded researchers using more conventional methods. Recent work extends the use of these methods to a continuous exposure, and we have developed a public health approach that evaluates explicitly the impacts of enforcing new exposure limits. Workers in the diatomaceous earth industry are exposed to crystalline silica, which causes silicosis and other non-malignant respiratory diseases and is now classified as a carcinogen. Previous analyses of cohorts of diatomaceous earth workers have not adjusted for healthy worker survivor bias. Relatively weak lung cancer results and protective estimates for cardiovascular outcomes may be further biased due to censoring by competing risks. We therefore aim to apply g-methods to address these two sources of bias in hopes that doing so will enable us to uncover clearer evidence of causal relationships between crystalline silica and mortality from lung cancer, COPD, and heart disease. A general industry permissible exposure limit (PEL) of 100µg/m3 has been in effect for silica since 1971 and has never been updated; however, hearings were held in March 2014 regarding a proposed federal standard that introduces a new PEL of 50µg/m3. We will evaluate the potential impact of the proposed exposure limit for respirable crystalline silica by estimating years of life saved, evaluating effects of interventions rather than comparing groups of workers with different exposure histories. This project addresses the Mining Sector and the Cancer, Reproductive and Cardiovascular Disease NORA cross-sector program. Its rigorous analytical methods will provide clearer epidemiologic evidence for the effects of inhaled silica, framing results in terms of impacts of occupational exposure limits using a metric that is easy to communicate to policymakers and the general public. This is directly relevant to NIOSH's r2p initiative. Outcomes and Outputs will include scientific research papers in peer-reviewed journals and presentations at conferences. By reducing bias in etiologic studies of workplace exposure and evaluating the potential impacts of occupational exposure limits, the project will lead to better control of occupational health hazards.