How bulk asbestos identification by PLM works

Polarised light microscopy (PLM) has been the standard method for identifying asbestos fibre type in bulk material samples for several decades. It is relatively affordable, does not require specialist site access, and produces a result that is accepted by licensed contractors, building surveyors, and local authorities. Understanding what the method involves helps you interpret the result correctly and decide whether further investigation is needed.

The three main asbestos fibre types ¶

The three fibre types most commonly encountered in Japanese buildings are chrysotile (white asbestos), amosite (brown asbestos), and crocidolite (blue asbestos). Chrysotile was the most widely used and is found in several products including ceiling tiles, floor tiles, pipe lagging, and textured coatings. Amosite and crocidolite were used in insulation boards and sprayed coatings and are considered higher risk due to their fibre geometry.

PLM can distinguish between these fibre types based on their optical properties under polarised light. The analyst examines the refractive index, birefringence, and extinction angle of the fibres to make the identification. The method is qualitative for fibre type and semi-quantitative for content percentage.

What the result tells you ¶

A PLM result will confirm whether asbestos fibres are present, identify the fibre type or types, and give an estimated percentage content. A result of 'asbestos not detected' means no fibres were identified in the portion of material examined; it does not guarantee the material is entirely free of asbestos, particularly if the material is heterogeneous.

The fibre type and content percentage determine the risk category of the material and the type of licensed contractor required for removal. Your building surveyor or the licensed contractor will use the PLM result to plan the removal method and the required controls.

When you need air fibre counting instead ¶

PLM on a bulk sample tells you what is in the material. It does not tell you how many fibres are present in the air in the room. If you need to assess ongoing airborne exposure, for example during or after removal work, you need airborne fibre counting by phase contrast microscopy (PCM), which requires air sampling equipment and a licensed hygienist.

Lank CoreLab carries out bulk PLM identification only. We do not carry out surveys, air monitoring, or removal work. This means our identification results are independent of any commercial interest in the outcome of the survey.

Bulk asbestos identification costs ¥6,500 per sample with a three working day turnaround. If you have a material that has been flagged by a surveyor and you want an independent identification before commissioning further work, a single bulk sample is a practical starting point.