Clear and simple detection of asbestos stained with two dyes for building materials collected from disaster and demolition sites using a stereomicroscope.

Whenever houses are demolished or disasters occur, large quantities of building materials are discharged, which may contain asbestos. To prevent the damage caused by asbestos exposure, a rapid asbestos presence confirmation method is required at demolition sites or temporary disaster storage sites. It is difficult to confirm the presence of asbestos in waste building materials by simple observation. However, it can be confirmed by staining the materials with two dyes: methylene blue (MB) with positive charge, and erythrosine (RED-3) with negative charge, and using a stereomicroscope. The method was applied to samples collected from disaster and demolition sites. Asbestos was stained violet or reddish-purple, and the base material of the building materials remained blue. Using this method, even amateur workers can detect asbestos by means of an image in a different color than the building substrate. Furthermore, the present method detected asbestos more explicitly than the official method (JIS A 1482, 1483; detection limit is < 0.1%) recommended by the Japanese government. This cost-effective method is suitable for detecting asbestos at disaster and demolition sites. The mixture of MB and RED-3 formed nanoparticles of size 151 nm and surface charge of -34 mV that selectively stained asbestos. The staining mechanism was discussed.