CASITILE, THE NEW ASBESTOS (Revised) Page 3: The Sources of Misunderstanding (cont.)
Manufacturing products from the three commercial types of asbestos was a thriving industry for nearly a century following the discovery of large mineral deposits in the nineteenth century; by 1900 asbestos was being used in over 3000 products. The use of amphiboles decreased rapidly, mostly through legislation and because of the health effects, from the 1970s. All these products can be classified into two types. The first consists of those, such as asbestos cement, which encapsulate the mineral fibres within a matrix to give a product with a density greater than 1 g/ml (these are known as High Density Products). The second group includes low density insulation boards, textiles and uses such as asbestos pipe lagging applied using raw mineral fibres. These lower density products typically have a density less than 1g/ml.
Studies over many years on both amphibole and serpentine asbestos fibres have examined their physico-chemical properties and their effects on health. It is now established and well known that amosite and crocidolite in their raw form are potentially very hazardous to human health. It is also generally accepted that chrysotile is very significantly less hazardous, posing no measurable risk to human health at present day mandated permissible exposure levels in the workplace (Hodgson and Darnton, 2000). So great is this disparity that amosite has been estimated to pose a health risk 300 times that of chrysotile, and that of crocidolite 500 times greater (Hodgson and Darnton, 2000). Figures, which incidentally, are considered by many scientists to over-estimate the dangers from chrysotile by a factor of 2 or more.
By 1985 the use and supply of amosite and crocidolite were banned. In November 1999 the use of chrysotile in all building materials and virtually all manufacturing processes was also banned, by the Health and Safety Commission (HSC).
Although no new asbestos products are now manufactured in the UK, many asbestos containing materials (ACMs) remain in millions of the nation’s buildings and products. Current legislation demands that any existing ACMs, except in privately-owned domestic premises, must be identified and managed.
By far the most commonly used ACM is chrysotile asbestos cement (AC), which current regulation now places on a par with all other ACMs. But around 200 studies have shown that the health risks from exposure to any chrysotile fibres released during the use and handling of this High Density Product (HDP) are extremely low (Hoskins and Lange, 2004). The common factor from all major recent studies is that chrysotile HDPs present no measurable risk to health.
In the manufacture of chrysotile AC, it is common practice to use a machine to render down the cement sheets from faulty production into a dust for re-use in later batches. Air monitoring tests carried out in the Lusalite factory in Portugal have shown that no actionable levels of chrysotile fibres were being emitted through this process, despite the aggressive and violent reduction of the sheets in an unenclosed machine (Health and Safety Department, Lusalite). Similar official tests conducted in the UK, to examine the effect of crushing cement sheeting using a JCB digger driven over piles of chrysotile asbestos cement roofing sheets, confirmed that no actionable level of airborne chrysotile fibres were detected.
Herein lies the problem. The authorities make a most fundamental mistake by transposing the risks posed by exposure to raw fibres onto the products made from them. This is scientific nonsense and shows a complete disregard for the many risk assessments that have been made. It is an application of the precautionary principle to attribute the health risk posed by a raw material to products made from it. That is, it is hazard rather than risk based. If this approach were taken for every potentially hazardous material, no product would be left unregulated (nickel, for instance, is officially classified, like asbestos, as a Class One carcinogen, yet it is used to make euro coins).
Among issues studied by research on fibre release from HD products has been the question of whether the chrysotile fibres undergo chemical change when they are used in ACMs and if so how does this affect their properties. Where chrysotile is used in asbestos brake linings, for instance, it has been shown that heating the material (as occurs where the brakes are used) causes the chrysotile fibres to alter their chemistry and structure, transforming them into a different mineral: an olivine known as Forsterite (Mg2 Si2 O4).
Until recently, though less well documented, has been the question of whether a similar process occurs when raw chrysotile is added to cement. In light of the abundance of asbestos cement, by far the commonest use of asbestos in the built environment, this question becomes one of the greatest importance. This review aims to summarise the answers given by recent research, and to discuss their implications.