Health and Safety
Executive / Commission
Statistics
Last updated August 2007
Asbestos is a term used for a number of naturally occurring minerals that have crystallised to form long thin fibres and fibre bundles. Most common is the serpentine group, which includes chrysotile (white asbestos) and which has been the most frequently mined. A second asbestos group known as the amphiboles includes crocidolite (blue asbestos) and amosite (brown asbestos). The fibres have high tensile strength, and chemical, electrical and heat resistance - properties that made asbestos extremely useful as a building/insulation material. Asbestos has been used extensively in Great Britain and throughout the world.
Although asbestos is a hazardous material it can only pose a risk to health if the asbestos fibres become airborne and are then inhaled. Therefore, most asbestos materials pose little risk unless they are disturbed in some way that allows the fibres to be released into the atmosphere. Inhalation of asbestos fibres can lead to serious diseases such as lung cancer, mesothelioma (a cancer of the linings of the lungs – the pleura or lower digestive tract – the peritoneum) and asbestosis (a chronic fibrosis of the lungs). Many cases of these diseases occurring now are a result of exposure in industries that used asbestos extensively in the past. However, the fact that asbestos was also installed in many buildings means that a wider range of people still have the potential to be exposed – particularly building and maintenance workers. For this reason the latest revision of the Control of Asbestos at Work Regulations introduced (from May 2004) a new duty on those responsible for non-domestic premises to manage the asbestos contained in them.
The asbestos minerals ability to resist high temperatures is what made it so useful. Asbestos is ideal for any process involving the conservation or preservation of heat. The fibre gives protection against fire, corrosion, cold, acids, alkalis, electricity, noise, energy loss, vibration, salt water, frost, dust and vermin. For a long time the dangers of asbestos use were not widely understood. Asbestos related disease generally takes many years – often several decades – to develop after exposure. Thus, the scale of the health risks were only becoming known after asbestos had already been widely used and many people had already been exposed. Who is currently at risk of being exposed to asbestos? If disturbed, asbestos material may release asbestos fibres which can be inhaled into the lungs. The fibres can remain there for a long time as they are not easily destroyed or degraded. Asbestos material that would crumble easily if handled, or that has been sawed, scraped, or sanded into a powder, is more likely to create a health hazard. Persons most likely to be currently exposed to asbestos are those working in building and maintenance trades, and to a lesser extent those involved in asbestos removal (where risks potentially exist unless rigorous precautions are taken.)
As asbestos fibres accumulate in the lungs, several diseases may occur: Two principal kinds of cancer:
Non-malignant lung diseases:
In 2005 (the latest year with published data) there were 2037 mesothelioma deaths. Adding an equivalent number of lung cancers brings the total to 4074. Using this exact figure would imply much more accuracy than is truly the case. Even rounding to the nearest hundred 4100 overstates our certainty if it is taken to imply the true number is larger than 4050 and is smaller than 4150. Thus we suggest "around 4000" is the best available simple formulation.
Based on an analysis of the deaths from 1980 – 2000 the ten occupations found to have the highest risk of mesothelioma for males were Metal Plate Workers, Vehicle Body Builders, Plumbers and Gas Fitters, Carpenters, Electricians, Sheet Metal Workers, Electrical Plant Operators, Production Fitters, Construction Workers, and Electrical Engineers [3]. Because of the long latency period of mesothelioma (between 15 and 60 years) these results generally relate to exposures before the 1980s. These and other high-risk occupations can generally be associated with three broad areas of past asbestos use: shipbuilding, railway carriage and locomotive building, and the installation of lagging or other insulation materials in buildings or industrial plant. However, over 25% of those dying from mesothelioma had worked in the building or maintenance industry, an area of exposure we cannot be sure has been eliminated.
Much has been done to control the risk from asbestos. The use, supply and importation of asbestos and asbestos products has been banned for all but a few exceptions by the Asbestos (Prohibition) Regulations. Work with asbestos generally requires a licence and the use of strict control measures, including personal protective equipment such as respirators. The fact that a wide range of people now have the potential to be exposed to asbestos – particularly workers involved in building maintenance – led to the latest revision of the Control of Asbestos at Work Regulations which introduced (from May 2004) a duty on those responsible for commercial premises to manage the asbestos contained in them.
High-risk areas tend to be those containing, or near to, industrial sites where asbestos was used extensively in the past – for example, shipyards, asbestos manufacturing factories and railway engineering works [3]. This will usually mean that the area has a higher proportion of people who have worked in these industries than the average for the country, and excess mesotheliomas are likely to occur in people who have worked in them. In some cases there may have been a general environmental risk in places close to these sites in the past. Individual risk has more to do with occupation rather than geographical location of residence. Nowadays, those working in building maintenance trades are likely to be at highest risk.
This most likely means that your area had a relatively low number of mesotheliomas. The geographical distribution of mesothelioma deaths is affected by the fact that death certificates (upon which statistics are based) only record the last address of residence. Thus people may have had heavy exposures to asbestos in the past in the traditional high-risk industries located within certain geographical areas, and then moved to areas of a relatively lower risk before dying from mesothelioma. Also, the effect of the risk of more general exposures across a wider range of occupations (e.g. exposure to maintenance workers in buildings) is likely to affect all geographical areas and is thus likely to be most noticeable in those that have traditionally been of lowest risk.
This doesn’t necessarily mean all workers in the occupation have a high risk. What the analysis of occupational groups demonstrates is which occupations on average have a higher risk associated with working in them. The true nature of any risk will crucially depend on the timing and amount of asbestos inhaled. In any case, since mesothelioma has a long latency and because death certificates (upon which statistics are based) only record the last occupation of the deceased, the occupation recorded may not be the one that resulted in the asbestos exposure. Consequently, part of the risk for a given occupation may be because workers exposed in other jobs have moved into this line of work towards the end of their careers.
Though chrysotile (white asbestos) has been used most widely, the greater potency of amphibole (blue and brown) asbestos to cause illness is generally recognised. Hodgson and Darnton in their scientific paper (2000) estimated the risk of mesothelioma and lung cancer by asbestos fibre type for a range of different exposure scenarios [2]. This analysis suggests that on average blue asbestos has a risk about 500 times that of white asbestos for mesothelioma and 10-50 times as high for lung cancer. The equivalent risk ratio for brown asbestos is 100 for mesothelioma and the same as blue (10-50) for lung cancer.
There is a lack of scientific consensus as to whether there exists a threshold of exposure to asbestos below which a person is at zero risk of developing mesothelioma. However, there is evidence from epidemiological studies of asbestos exposed groups that any threshold for mesothelioma must be at a very low level – and it is fairly widely agreed that if a threshold does exists then it cannot currently be quantified. For practical purposes HSE does not assume that such a threshold exists.
The situation for lung cancer and asbestosis is uncertain. Arguments for a threshold for lung cancer are based on the notion of the carcinogenic process being an extension of the chronic inflammatory processes producing fibrosis. It is generally recognised that heavy doses of white asbestos are required to produce clinically significant lung fibrosis. However, the situation for blue and brown asbestos is more uncertain and fibrosis has been observed at much lower exposures. This also suggests that if a threshold for lung cancer does exist for blue and brown asbestos it must be at a very low level indeed.
It is widely accepted that tobacco smoke interacts with asbestos in the causation of lung cancer. This means that the risk of lung cancer for a smoker exposed to asbestos is greater than the sum of the individual effects due to smoking and due to asbestos.
