Bulk sample at low magnification.
Asbestos is a well-known health hazard. The European Directive
on the classification and labelling of dangerous products could
not be applied to asbestos because there was no method to reliably
measure low asbestos contents in such materials. Pooling and evaluating
existing techniques from across the EU provided the first step towards
finding a suitable test. By developing a simplified procedure, based
on optical microscopy, the project team produced an improved method
for identification. This inexpensive test can be used wherever asbestos
is a hazard.
Nearly everybody has heard of asbestos: an amazingly fire-retardant material seized by the construction industry with much fervour. Sadly its glory days did not last. As with those other infamous substances such as DDT and thalidomide, asbestos too had unforeseen problems. Initially, it was identified as a cause of lung disease, scarring lung tissue. Later, it proved to be a Category 1 carcinogen, affecting both the lungs and their lining. Today, the Berlaymount building, the former seat of the European Commission, in Brussels, stands testament to asbestos' fall from grace.
In an attempt to lessen the risks of hazardous substances, the European Union implemented two Directives. Both insist on labelling if a given substance or preparation contains more than 0.1% carcinogen by weight. It sounds simple enough, but with asbestos it is not quite that straightforward.
A preliminary European survey showed that when laboratories measured asbestos content samples, the results varied enormously across the continent and even within individual countries. This would inevitably set back the whole process of adopting and implementing the asbestos labelling Directives.
A common thread
What was the result? A project supported by the European Commission's Measurements and Testing programme brought together a team of researchers to rectify the situation. Perhaps these researchers could, collectively, do something about it. Collation and evaluation of regional and national assessment methods began. This formed the backbone of a coherent testing strategy which emphasised quality and accuracy.
The solution the partners came up with was a plan to develop a robust and efficient analytical method to identify and measure asbestos. Chemical analysis was simply not an option. Asbestos by its very nature is harmful because it is fibrous, so only through using ordinary optical microscopes could its shape be cheaply and effectively determined.
The team aimed high and they wanted to be able to say with 90% probability that their estimates were correct within a factor of two. This was a challenging task, considering that recognising fibres under a microscope amongst masses of other particles is extremely difficult and not comparable to the "normal" chemical tests and other measurements. To achieve this they simultaneously needed to know whether and to what extent sample preparation could trick them into underestimating the true asbestos content. By forming a partnership of key players in each relevant field, the project team created a synergy that put the project on the road to success.
The shape of things to come
Starting at the beginning of the testing process, there was a need for a pre-preparation method. Unfortunately no one single method fitted the bill for the vast array of materials that may have to be tested.
So, another direction was chosen. Rather than use only one method, they tailored or developed a number of simple steps that borrowed from existing techniques.
The first step involved concentrating the material. The precise mechanism depended on the type of carrier substance or asbestos - not an easy task given that the test matter can vary from liquid to solid. The concentrate was then subjected to a standard test. This crucial step would force the material to reveal the true level of danger: its potential to release hazardous asbestos fibres. Standard techniques were too harsh so the partners developed a gentler method. The danger of overgrinding would destroy the fibres but too little grinding would not yield particles of the right dimension.
Hazard a guess?
Shape is a defining characteristic of asbestos. This is where microscopy is needed. Traditionally, asbestos fibre volume is calculated by assuming either a circular or square cross-section. In truth, the reality can be somewhat different and this can cause problems. The researchers lessened the margin of error by developing theoretical and experimental methods for approximating the fibres' true shape and volume, including an efficient counting scheme and an improved eye-piece graticule for the microscope.
A commercial firm has the task of producing the graticule and supplying it. As the technique depends on the graticule, the information documenting the method tells the reader where and how to obtain the graticule.
But how good was the technique? To find out, 37 laboratories across the EU tested this asbestos identification method. Overall, there were no false negatives and only two false positives. So far, so good. And the quantification? In a two-step interlaboratory comparison of 12 centres, only one came close to the right answer; the rest varied. This result came from a very experienced laboratory which suggests that with due care and attention, and a bit more practice, the results will be more precise. This means that it is increasingly possible to avoid more costly means of analysis, such as electron microscopy, until a much later stage.
The simplicity of this technique makes it accessible not only to the majority of laboratories in the EU Member States but potentially it could also be used in many developing countries. All that is needed, in theory, is the right training and a bit of experience. Along with the published scientific papers, the extensive network of key public and private research centres across Europe, which participated in the comparative studies, will provide the impetus for the knowledge to spread. Industry was also active in the comparison and similarly this will guarantee that the results reach the right people in the right sector.
For the partners, each has grown from the experience and learnt from one another. It has stimulated new directions of investigation, such as improved statistical methods for estimating the volume of asbestos and being better equipped to deal with asbestos contaminated soils, buildings, etc. For the first time, a method has been developed which meets the requirements of applicability to a wide range of materials. The legislation now becomes feasible.