Halfmask air-purifying respirators are used by millions of workers to reduce inhaling air contaminants, both chemical (e.g., asbestos, styrene) and biological (e.g., SARS-CoV-2, Mycobacterium tuberculosis). In 2006, the federal Occupational Safety and Health Administration (OSHA) promulgated a standard that gave halfmask respirators an assigned protection factor (APF) of 10. This signified that OSHA assumes a fit-tested and trained wearer will experience a 10% maximum total inward leakage of contaminated air into the facepiece. To derive APF = 10, OSHA analyzed data from 16 workplace studies of the efficacy of halfmask respirators worn against particulate contaminants. In this commentary, I contend that, in considering the data, OSHA made several errors that overstated halfmask respirator efficacy. The errors were (i) failing to properly account for within-wearer and between-wearer variability in respirator efficacy; (ii) ignoring the effect of particle deposition in the respiratory tract; (iii) aggregating unbalanced data within and between studies, and effectively double-counting the data in some studies; and (iv) ignoring the effect that particle size exerts in penetrating respirator facepiece leak paths. The net result is that OSHA's APF = 10 can lead to excessive toxicant exposure for many workers.

中文翻译：

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对职业安全与健康管理局半面罩呼吸器指定防护系数的批评


数百万工人使用半面罩空气净化呼吸器来减少吸入空气污染物，包括化学污染物（例如石棉、苯乙烯）和生物污染物（例如 SARS-CoV-2、结核分枝杆菌）。 2006 年，联邦职业安全与健康管理局 (OSHA) 颁布了一项标准，规定半面罩呼吸器的指定防护系数 (APF) 为 10。这意味着 OSHA 假设经过适合性测试和训练的佩戴者将经历 10% 的最大总吸入量受污染的空气泄漏到面罩中。为了得出 APF = 10，OSHA 分析了 16 项工作场所研究的数据，这些研究涉及佩戴半面罩呼吸器对抗颗粒污染物的功效。在这篇评论中，我认为，在考虑数据时，OSHA 犯了几个错误，夸大了半面罩呼吸器的功效。这些错误是（i）未能正确考虑呼吸器功效的佩戴者内部和佩戴者之间的差异； (ii) 忽略呼吸道中颗粒沉积的影响； (iii) 汇总研究内部和研究之间不平衡的数据，并在某些研究中有效地重复计算数据； (iv) 忽略颗粒尺寸对穿透呼吸器面罩泄漏路径的影响。最终结果是 OSHA 的 APF = 10 可能导致许多工人过量接触有毒物质。