Health and Safety Executive

Asbestos related disease statistics: frequently asked questions and answers

Last updated October 2009

What is asbestos?

Asbestos is the generic term for a wide range of naturally occurring minerals that crystallise 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.

Why is it a problem?

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 air. 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 Control of Asbestos Regulations 2006 brought together three previous sets of Regulations covering the prohibition of asbestos, the control of asbestos at work and asbestos licensing together with a ‘duty to manage asbestos’ for those responsible for non-domestic premises.

Why was asbestos used so extensively if it is such a hazard?

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. Some kinds of asbestos 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.)

What diseases are caused by asbestos exposure?

As asbestos fibres accumulate in the lungs, several diseases may occur:

Two principal kinds of cancer:

  • Mesothelioma is a cancer of the pleural and peritoneal lining and is considered to be almost exclusively related to exposure to asbestos. It is almost always fatal with those affected usually dying within 1 or 2 years of diagnosis. Mesothelioma has a long latency period (i.e. the time between initial exposure and the onset of the disease) that is typically between 30 and 40 years.
  • Lung Cancer is a malignant tumour of the bronchi - the tubes carrying air to and from the lungs. The tumour grows through surrounding tissue, invading and often obstructing air passages. Again, the disease has a long latency period - typically at least 20 years.

Non-malignant lung diseases:

  • Asbestosis is a scarring of the lung tissue. This scarring impairs the elasticity of the lung, restricting their expansion and hampering their ability to exchange gases. This leads to inadequate oxygen intake to the blood. It is a slowly progressive disease with a latency period of 15 to 30 years.
  • Diffuse pleural thickening is a non-malignant disease in which the lining of the lung (pleura) becomes scarred. If it is extensive then it, too, can restrict expansion of the lungs and lead to breathlessness. It normally takes at least 10 years after the first exposure to develop asbestos related pleural disease. The disease is a chronic condition with no cure.
  • Small areas of scarring are called pleural plaques. They do not cause symptoms.

How many mesothelioma deaths are there each year?

  • The annual number of mesothelioma deaths has increased considerably over the period for which statistics are available, reaching 2156 deaths in 2007, the latest year for which data are available, compared with 153 in 1968.
  • The expected number of deaths amongst males is predicted to increase to a peak of 2038 (90% prediction interval: 1929 to 2156) in the year 2016.

How many asbestos-related lung cancer deaths are there each year?

  • Lung cancer deaths caused by asbestos are clinically indistinguishable from those caused by other agents such as tobacco smoke. This means the number of cases cannot be determined by direct counting and must therefore be estimated.
  • Because of improving evidence, our "best estimate" of the annual number of asbestos-related lung cancers has been revised over the years from "about two lung cancer deaths per mesothelioma each year" before the early 1990s to "one or two" and then to "around one" more recently.
  • In the past our estimates have largely been based on comparisons of numbers of mesothelioma deaths in studies of groups of asbestos-exposed individuals with numbers of ‘excess’ lung cancers in those groups (how many more lung cancers were observed than would have been expected in the groups if there had been no asbestos exposure). Estimates produced on this basis have always been regarded as uncertain (and still are).
  • Recent research estimated the ratio of asbestos-related lung cancer deaths to mesotheliomas by developing a statistical model for lung cancer mortality within the British working population in terms of asbestos exposure and smoking habit [1]. This suggests a ratio in the range 0.7 to 1 - in other words rather fewer lung cancers than mesotheliomas. However, in view of the uncertainties in the totality of the epidemiological evidence "around one asbestos-related lung cancer per mesothelioma" is still a reasonable view.
  • Asbestos is a more potent cause of mesothelioma than lung cancer and smoking is thought to interact with asbestos exposure in the causation of lung cancer. Thus going forward in time the ratio of lung cancers to mesotheliomas is likely to fall, because the mesotheliomas will increasingly be generated by low exposure levels of asbestos that are less likely to cause lung cancer and because smoking levels have fallen since the 1960s (factors that, together, mean fewer lung cancers per mesothelioma).

So what does HSE now think the current annual total number of asbestos related cancer deaths is?

In 2007 (the latest year with published data) there were 2156 mesothelioma deaths. Simply adding an equivalent number of asbestos-related lung cancers brings the total to 4312, though clearly such a figure implies much more accuracy than is truly the case. For example, it is arguable that perhaps 100 mesotheliomas each year are not caused by asbestos. Furthermore, if the number of asbestos related lung cancer deaths was indeed less than the number of mesotheliomas this would imply a lower figure still - perhaps lower than 4000. On the other hand, it is likely that a relatively small number of other cancer cases - including some stomach and laryngeal cancers - each year are caused by asbestos and so including an estimate for these would tend to increase the overall number. Given these uncertainties we suggest "around 4000" is the best available simple formulation for the current annual total number of asbestos-related cancer deaths.

How many cases of non-malignant asbestos-related disease are there each year and what are the trends over time?

  • There were 96 deaths in 2007 where asbestosis is described as the underlying cause of death on the death certificate.
  • The annual number of new cases of asbestosis according to the Department of Work and Pensions (DWP) Industrial Injuries and Disablement Benefit (IIDB) scheme (which compensates workers for prescribed occupational diseases) has risen erratically since the early 1980s, with the trend strongly increasing since the early 1990s reaching the current level of 795 in 2007. This is likely to be an underestimate of the total number of cases.
  • There were 400 new cases of disablement benefit for diffuse pleural thickening in 2008.
  • The trend in diffuse pleural thickening has increased over recent years, although this may be partly or wholly explained by the acceptance of claims under the IIDB scheme for unilateral (affecting only one lung) cases and other changes in data collection methods.

Which occupations are associated with the highest mesothelioma risks?

Based on an analysis of the last recorded occupation for mesothelioma deaths during 2002 - 2005, the ten occupations found to have the highest risk of mesothelioma for males were Carpenters, Plumbers, Electricians, Labourers in Other Construction Trades, Metal Plate Workers, Pipe Fitters, Construction Operatives, Managers in Construction, Construction Trades and Energy Plant Operatives. The occupations most frequently recorded on deaths certificates of men dying from mesothelioma today include may that are associated with construction and building maintenance trades, highlighting the important role of past exposures to “end users” of asbestos containing materials in the building industry.

What is being done to reduce risks from asbestos?

Much has been done to control the risk from asbestos. 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 - has led to the latest set of Regulations - The Control of Asbestos Regulations 2006.  This came into force on 13 November 2006 (Asbestos Regulations - SI 2006/2739) and brings together three previous sets of Regulations covering the prohibition of asbestos, the control of asbestos at work and asbestos licensing. The Regulations prohibit the importation, supply and use of all forms of asbestos and they continue the ban introduced for blue and brown asbestos in 1985 and for white asbestos in 1999. They also continue to ban the second-hand use of asbestos products such as asbestos cement sheets and asbestos boards and tiles; including panels which have been covered with paint or textured plaster containing asbestos.

The Asbestos Regulations also include the ‘duty to manage asbestos’ in non-domestic premises. Guidance on the duty to manage asbestos can be found in the Approved Code of Practice The Management of Asbestos in Non-Domestic Premises, L127, ISBN 9780 7176 6209 8 and from the link duty to manage.

My local/unitary authority area was identified as having a high risk of mesothelioma. Does this mean there is a problem in my area or that I am at higher risk of being exposed to asbestos?

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.

The number of mesotheliomas in my local/unitary authority area increased relatively more rapidly than the number for Great Britain as a whole. Does this mean my area has an asbestos problem?

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.

My occupation was identified as high risk. Does this mean that I should be worried about developing asbestos related disease?

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.

How do the risks from exposure to different kinds of asbestos differ?

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.

Is there a safe level of exposure below which there is no risk?

Mesothelioma

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.

Asbestosis and lung cancer

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.

The main cause of lung cancer is smoking. How great is the combined risk of lung cancer due to asbestos exposure and smoking?

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.

References

  1. Darnton AJ, McElvenny DM, Hodgson JT (2005). Estimating the Number of Asbestos-related Lung Cancer Deaths in Great Britain from 1980 to 2000. Ann. occup. Hyg., Oxford University Press. pp. 1-10
  2. Hodgson, JT & Darnton, A (2000). The Quantitative Risks of Mesothelioma and Lung Cancer in Relation to Asbestos Exposure. Ann. occup. Hyg., Vol. 44, No. 8, pp. 565-601
  3. McElvenny, DM, Darnton, AJ & Price, MJ (2005). Mesothelioma Mortality in Great Britain from 1968 to 2001. Occupational Medicine; 55: pp. 79-87 Page 7 of 7

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Updated 19.10.09