Wilson Richard, McConnell Ernest E, Ross M, Axten Charles W, Nolan Robert P
Department of Physics and the Center for Risk Assessment, 9 Oxford Street Rear, Harvard University, Cambridge, MA 02138, USA.
Regul Toxicol Pharmacol. 2008 Oct;52(1 Suppl):S232-45. doi: 10.1016/j.yrtph.2007.11.005. Epub 2007 Nov 28.
In the early 1970s, it became a concern that exposure to the mineral fibers associated taconite ore processed in Silver Bay, Minnesota would cause asbestos-related disease including gastrointestinal cancer. At that time data gaps existed which have now been significantly reduced by further research. To further our understanding of the types of airborne fibers in Silver Bay we undertook a geological survey of their source the Peter Mitchell Pit, and found that there are no primary asbestos minerals at a detectable level. However we identified two non-asbestos types of fibrous minerals in very limited geological locales. Air sampling useful for risk assessment was done to determine the type, concentrations and size distribution of the population of airborne fibers around Silver Bay. Approximately 80% of the airborne fibers have elemental compositions consistent with cummingtonite-grunerite and the remaining 20% have elemental compositions in the tremolite-actinolite series. The mean airborne concentration of both fiber types is less than 0.00014 fibers per milliliter that is within the background level reported by the World Health Organization. We calculate the risk of asbestos-related mesothelioma and lung cancer using a variety of different pessimistic assumptions. (i) that all the non-asbestos fibers are as potent as asbestos fibers used in the EPA-IRIS listing for asbestos; with a calculated risk of asbestos-related cancer for environmental exposure at Silver Bay of 1 excess cancer in 28,500 lifetimes (or 35 excess cancers per 1,000,000 lifetimes) and secondly that taconite associated fibers are as potent as chrysotile the least potent form of asbestos. The calculated risk is less than 0.77 excess cancer case in 1,000,000 lifetimes. Finally, we briefly review the epidemiology studies of grunerite asbestos (amosite) focusing on the exposure conditions associated with increased risk of human mesothelioma.
20世纪70年代初，人们开始担心，接触明尼苏达州银湾加工的与铁燧岩矿石相关的矿物纤维会导致包括胃肠道癌症在内的石棉相关疾病。当时存在数据空白，但现在通过进一步研究已大幅减少。为了进一步了解银湾空气中纤维的类型，我们对其来源地彼得·米切尔矿坑进行了地质调查，发现没有可检测水平的原生石棉矿物。然而，我们在非常有限的地质区域中识别出了两种非石棉类型的纤维状矿物。为进行风险评估进行了空气采样，以确定银湾周围空气中纤维的类型、浓度和尺寸分布。大约80%的空气中纤维的元素组成与镁铁闪石-铁闪石一致，其余20%的元素组成在透闪石-阳起石系列中。两种纤维类型的平均空气浓度均低于每毫升0.00014根纤维，这处于世界卫生组织报告的背景水平之内。我们使用各种不同的悲观假设来计算石棉相关间皮瘤和肺癌的风险。（i）所有非石棉纤维与美国环境保护局综合风险信息系统清单中列出的石棉纤维具有同等效力；计算得出银湾环境暴露导致石棉相关癌症的风险为每28500个寿命中有1例额外癌症（或每100万个寿命中有35例额外癌症），其次，与铁燧岩相关的纤维与温石棉（效力最低的石棉形式）具有同等效力。计算得出的风险在每100万个寿命中少于0.77例额外癌症病例。最后，我们简要回顾了铁闪石石棉（铁石棉）的流行病学研究，重点关注与人类间皮瘤风险增加相关的暴露条件。
