Abstract

Asbestos is responsible for more than 85% of occupational disease-related deaths, according to CNESST occupational injury reports between 2010 and 2019. Although asbestos use is now banned in Canada and some 60 other countries, it is still present in many products and materials installed before this ban.

In a context of prevention, it is important to be able to determine the presence of asbestos in materials or in the air, to identify the types of asbestos present and to determine their concentration. Depending on the type of sample and the information required, various analysis techniques exist, each with its own advantages and disadvantages. Sometimes it is necessary to combine several techniques to obtain the required information.

L’IRSST proposes three reference methods to analyze asbestos, two using optical microscopy (OM) and one using transmission electron microscopy (TEM). Optical microscopy is an indispensable tool for asbestos analysis. This fast and inexpensive technique can be used to estimate the quantity as well as the types of asbestos found when the two techniques are used, i.e., phase-contrast optical microscopy (PCOM) and polarized light optical microscopy (PLOM).

Transmission electron microscopy is recognized as being the most complete technique for identifying asbestos fibres because it can be used for morphological, chemical and crystallographic analysis. Moreover, its high image resolution makes it possible to observe the small diameter fibres that are often invisible in optical microscopy. However, transmission electron microscopy is a very expensive, complex and time-consuming technique, and the samples are not very representative because of their small size (3mm grid). There is an intermediary technique, scanning electron microscopy (SEM), which could become a complementary and advantageous solution. Despite some limitations, the use of scanning electron microscopy for asbestos analysis is of particular interest because it is simpler and faster to use than transmission electron microscopy, achieves higher resolution than OM and offers the possibility of automation.

The general objective of this activity is to evaluate the imaging performance of three types of detectors for the analysis of asbestos fibres using scanning electron microscopy. The experimental parameters will be optimized for each of the three detectors in order to identify their respective limits and their potential applications for the observation of asbestos fibres.