It remains uncommon knowledge that there are two distinct types of asbestos fibre, amphibole and serpentine. They differ in the structure of their mineral crystals, one being based on iron silicates and one being a magnesium silicate.

In simple terms, the types which we see being spoken about within industry and construction are blue, brown and white.  Of these blue and brown are of the amphibole type and are known to cause the disease mesothelioma while white asbestos is quite a different matter, having no clear cases of exposure which have been reliably linked to cancers.

The HSE has agreed that white asbestos is at least an order of magnitude less dangerous than blue and brown asbestos and recently the media have revived the story of asbestos as the National Farmers Union and one of its members mounts a legal challenge aimed at the Department for Work and Pensions arguing that implementation of new regulations face farmers (among others) with a very significant and, arguably, unjustifiable bill amounting to nearly £6bn.

So, the question must be, what is the truth behind this?

Basis in scientific fact

As is often the case, the argument from a scientific basis is really quite clear.  Large amounts of asbestos are in place on farms, as well as on many industrial sites, most commonly as corrugated cement roofing sheets (often referred to as ‘big six’) which does contain asbestos material which is typically white and in a concentration of about 8-12%.  As these materials were manufactured some time ago by a variety of  producers to an approximate formula we cannot be sure on actual figures in the sheets which we see in use and herein lies the crux of the problem.

Uncertainty gives rise to risk

During the production process an amount of white asbestos would have been added to the cement mix for these roofing sheets and their associated rainwater goods.  But, this level of concentration could vary widely.  In addition, should white asbestos have been in short supply, it was not uncommon for a blue or brown asbestos type to have been substituted giving rise to a far greater risk.  Typically, samples are obtained by specialist consultants before any dismantling and sheets are taken down whole and under wetted conditions to prevent the spread of fibres, but, without sampling all of the sheets how can we be sure that the risk is controlled and therefore, how can we be assured that our controls are adequate.

No safe limit

It seems that science can reliably tell us that white asbestos is relatively harmless and easily metabolised by the human body once it enters the lungs but what it cannot tell us, despite many years of research, is what constitutes and significant level of asbestos exposure.  Past cases have shown that those with relatively limited exposures may well go on to develop mesothelioma whilst, in some circumstances, those with a far higher exposure level can remain well – the exceptions prove the rule but no one is capable of saying that exposure to relatively few fibres is safe.

The real situation

Under laboratory conditions we must accept the following;

• White asbestos is unlikely to cause mesothelioma and is capable of being metabolised within the lungs (even glass, mineral wool and carbon fibres can be broken down in the lungs and do not give rise to mesothemiolma from research conducted)
• White asbestos is at least one order of magnitude less dangerous that its amphibole cousins;
• White asbestos used in roofing sheets, rainwater goods and similar asbestos containing materials (ACM’s) is trapped within a cementatious matrix and fibre release can only occur through damage;
• Good techniques involving removing sheets whole and using a wetting agent can reliably control risk to acceptable levels.

In the real world we must make allowances for these facts;

• The type and concentration of asbestos within roofing sheets, rainwater goods and similar ACM’s is variable and unknown;
• There is no accepted safe level of exposure to amphibole asbestos fibres;
• Techniques and controls which are adequate for controlling exposure to white asbestos are likely to be quite inappropriate for blue and brown asbestos.

In conclusion

The question which remains is would we choose to take the chance with our loved ones that exposure to white asbestos is likely to be OK given that the far more dangerous amphibole types are possibly present?

Given that there is no accepted safe level of exposure I would personally say I would not.  However, if the choice between leaving the sheets in place, provided they remain in good condition, and removing them is given – then any regulations which require this would certainly not have our backing or that of any other sane, and scientifically minded, safety consultant.

Clients:  If you have a specific question on this matter please telephone your retained safety consultant on 01453 800100