Chrysotile: New Exposure Indices and Cancer Epidemiology

描述：石棉被归类为明确的人类致癌物质，根据美国现行法规，所有形式的石棉都被视为同等危险。温石棉是最常用的石棉形式，尽管温石棉在美国的使用受到限制，但由于大量的就地纤维，维修人员和建筑物居住者继续暴露在石棉中，而且在发展中国家的使用正在增加。尽管积累了科学证据，但关于石棉的致癌性，特别是温石棉的致癌性，仍有一些问题尚未解决。一些研究人员认为，与接触温石棉相关的癌症风险比接触闪石形式的石棉低得多。在接触温石棉的工人中，纺织工人患肺癌的极高风险与矿工和磨坊工人的低得多的风险之间也存在着一种无法解释的对比。这些争议很难解决，因为只有少数独立研究有足够的暴露反应信息。为了解决有关温石棉的公开问题，我们建议对北卡罗来纳州四家石棉纺织厂的5818名工人进行历史队列研究，这些工厂有大量的石棉暴露数据，但从未对癌症发生进行研究。这项流行病学研究的主要目标是：1)使用基于纤维浓度的已建立的指标和新的指标来估计纺织工人接触温石棉的风险，新指标使用透射电子显微镜来说明纤维的分布、尺寸和表面积；2)描述累计接触温石棉与肺癌死亡率之间的定量关系，同时控制潜在的混杂职业暴露；以及3)还评估与新的石棉暴露指标相关的肺癌风险，包括测量纤维尺寸分布、纤维尺寸和纤维表面积。对这一新人群进行良好的流行病学调查将提供急需的信息，以帮助回答有关先前研究的概括性以及温石棉的相对危险性的问题。此外，使用更充分地考虑石棉纤维长度和宽度的双变量分布的暴露指数对肺癌道德进行研究，将为所有形式的石棉以及人造矿物纤维的风险评估提供新的数据。

DESCRIPTION: Asbestos is classified as a definite human carcinogen, with all forms treated as equally hazardous under current US regulations. Chrysotile is the most commonly used form of asbestos and, while use of chrysotile is restricted in the US, maintenance personnel and building occupants continue to be exposed due to the vast quantities of in-place fiber and use in developing countries is increasing. Despite the accumulated scientific evidence, a number of questions remain unresolved concerning the carcinogencity of asbestos in general and chrysotile in particular. Some researchers argue that the cancer risk associated with exposure to chrysotile is much lower that that for amphibole forms of asbestos. Among workers exposed to chrysotile, an unexplained contrast also exists between the extremely high risk of lung cancer among textile workers and the much lower risk among miners and millers. These controversies are difficult to resolve because only a handful of independent studies have adequate exposure-response information. To address open questions about chrysotile, we propose a historical cohort study of 5818 workers at four North Carolina asbestos textile plants that have extensive data on asbestos exposures but where cancer occurrence has never been studies. The principal goals of this epidemiology study are: 1) To estimate textile workers' exposures to chrysotile asbestos using both established indicators based on fiber concentration and new indicators, which use transmission electron microscopy to account for fiber distribution, dimensions, and surface area; 2) To characterize the quantitative relationship between cumulative exposure to chrysotile and lung cancer mortality while controlling for potentially confounding occupational exposures, and 3) To also evaluate the risk of lung cancer with respect to new indicators of asbestos exposure, including measures of fiber size distribution, fiber dimensions, and fiber surface area. A well-conducted epidemiologic investigations of this new population would provide information badly needed to help answer questions concerning the generalizability of previous study, and about the relative hazardousness if chrysotile. Furthermore, research on lung cancer morality using exposure indices that account more fully for the bivariate distribution of asbestos fiber length and width would provide new data relevant to risk assessments for all forms of asbestos as well as man-made mineral fibers.