Modifications to the membrane filter method with phase-contrast microscopy (PCM) for fibre-counting to support a new occupational exposure limit value.

IF 1.8 4区医学 Q3 PUBLIC, ENVIRONMENTAL & OCCUPATIONAL HEALTH

Annals Of Work Exposures and Health Pub Date : 2025-07-15 DOI:10.1093/annweh/wxaf032

Martin Harper, Thomas W S Pang

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Abstract

The occupational exposure limit value (OELV) currently in force for the concentration of asbestos fibres in air in most of the world is 0.1 f cm-3. This value has been considered in some methods as the limit of detection (LOD) for the membrane filter method with phase-contrast microscopy (PCM). There is a directive within the European Union (EU Directive 2023/2668) to lower the OELV in member States to 0.01 f cm-3 from 21 December 2025. In the EU, OELVs are established with specific requirements for the expanded uncertainty around the target value, and to meet those requirements the OELV should not be a simple LOD. A value of approximately one-half of the OELV, if determined accurately, can give reasonable assurance of compliance with the OELV. There are several options available which can allow modification of the membrane filter method with PCM to measure 0.005 f.cm-3 as a time-weighted average (TWA) over a period of hours. As there will be fewer fibres on a sample, greater precision in counting is required. To achieve greater precision, (i) the filter background must be below 2.5 f.mm-2, which is achievable where filters are manufactured in a clean environment, (ii) microscopists must receive training and evaluation, e.g. through participation in a proficiency test program, and (iii) the sample size for counting will need to be increased by increasing the volume of air sampled and counting additional graticule areas. These modifications to the methods, taken together, should allow accurate measurements at 0.005 f cm-3, thus demonstrating compliance with an OELV of 0.01 f.cm-3 for a 4-h or 8-h TWA sample. Although these changes bring some additional cost in sampling and analysis, the PCM method could be retained. Continuing with the PCM methods has the advantages of low cost, capability for on-site analysis, and traceability to risk assessments based on prior PCM data.

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修改膜过滤法与相衬显微镜（PCM）的纤维计数，以支持新的职业暴露限值。

目前世界上大多数地区空气中石棉纤维浓度的有效职业接触极限值（OELV）为0.1立方厘米。这个值在一些方法中被认为是相衬显微镜（PCM）膜过滤法的检测限（LOD）。欧盟有一项指令（欧盟指令2023/2668），从2025年12月21日起，将成员国的OELV降至0.01英尺厘米-3。在欧盟，OELV是根据目标值周围扩展的不确定性的特定要求建立的，为了满足这些要求，OELV不应该是一个简单的LOD。如果确定准确，则OELV的大约一半的值可以合理地保证OELV的遵守。有几种可用的选择，可以允许修改膜过滤方法与PCM测量0.005 f.cm-3作为时间加权平均值（TWA）在一段时间内。由于样品中的纤维较少，因此需要更高的计数精度。为了达到更高的精度，(i)过滤器背景必须低于2.5 f.mm-2，这在清洁的环境中制造过滤器是可以实现的；（ii）显微镜师必须接受培训和评估，例如通过参加熟练程度测试程序；（iii）计数的样本量需要通过增加采样的空气量和计数额外的光栅面积来增加。这些方法的修改，加在一起，应该可以在0.005 f cm-3下进行精确测量，从而证明对4小时或8小时TWA样品的OELV符合0.01 f cm-3。虽然这些变化带来了一些额外的采样和分析成本，但PCM方法可以保留。继续使用PCM方法具有低成本、现场分析能力和基于先前PCM数据的风险评估的可追溯性等优点。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Annals Of Work Exposures and Health Medicine-Public Health, Environmental and Occupational Health

CiteScore

4.60

自引率

19.20%

发文量

期刊介绍： About the Journal Annals of Work Exposures and Health is dedicated to presenting advances in exposure science supporting the recognition, quantification, and control of exposures at work, and epidemiological studies on their effects on human health and well-being. A key question we apply to submission is, "Is this paper going to help readers better understand, quantify, and control conditions at work that adversely or positively affect health and well-being?" We are interested in high quality scientific research addressing: the quantification of work exposures, including chemical, biological, physical, biomechanical, and psychosocial, and the elements of work organization giving rise to such exposures; the relationship between these exposures and the acute and chronic health consequences for those exposed and their families and communities; populations at special risk of work-related exposures including women, under-represented minorities, immigrants, and other vulnerable groups such as temporary, contingent and informal sector workers; the effectiveness of interventions addressing exposure and risk including production technologies, work process engineering, and personal protective systems; policies and management approaches to reduce risk and improve health and well-being among workers, their families or communities; methodologies and mechanisms that underlie the quantification and/or control of exposure and risk. There is heavy pressure on space in the journal, and the above interests mean that we do not usually publish papers that simply report local conditions without generalizable results. We are also unlikely to publish reports on human health and well-being without information on the work exposure characteristics giving rise to the effects. We particularly welcome contributions from scientists based in, or addressing conditions in, developing economies that fall within the above scope.