Asbestos and Mesothelioma a briefing document for the Metropolitan Police Prepared by Professor John Cherrie, Heriot Watt University, Edinburgh, UK. Introduction The purpose of this document is to provide a brief introduction to asbestos and the diseases that may be caused by inhaling this mineral dust. The document is intended to inform officers who may have been inadvertently exposed to asbestos during their service. A detailed investigation of the circumstances surrounding these exposures is currently being undertaken by the MPS Safety and Health Risk Management Team, and further advice will be issued once this is complete. Asbestos Asbestos is the name used for a group of naturally occurring fibrous silicate minerals that were exploited commercially because of their: flexibility high tensile strength incombustibility low thermal conductivity and resistance to chemical attack There are six minerals included in this definition; one, chrysotile, is in the serpentine group of minerals, while the others, including amosite, crocidolite, anthophyllite, actinolite and tremolite belong to the amphibole group of minerals. The three types of asbestos that were most commonly used in the UK were amosite (brown asbestos), chrysotile (white asbestos) and crocidolite (blue asbestos). The photographs on the following page show examples of blue and white asbestos fibres magnified on an electron microscope 1. Note, the white bar at the top of each photograph is 50 µm long (roughly 2/1000 of an inch). Human hair has a diameter between about 30 µm to 100 µm. 1 Photographs from http://usgsprobe.cr.usgs.gov/picts2.html 1
Crocidolite (blue asbestos) Chrysotile (white asbestos) None of these minerals are naturally occurring in the UK, at least not in commercially exploitable quantities, and so the material that was used was mostly imported from Australia, Canada or South Africa. In total, over 5 million tonnes of asbestos were imported into the UK during the last century. The peak of asbestos imports into the UK occurred between 1970 and 1975; the use of asbestos is now banned in this country, but there are still a great deal of asbestoscontaining materials in buildings and industrial plant, and contaminating the soil of old industrial sites. Exposure to asbestos at work is regulated by the Control of Asbestos Regulations 2012, which came into force on 6 April 2012. The first set of asbestos regulations was introduced in the 1930s and there were several successive regulations that have progressively tightened the law in this area. Mesothelioma and other diseases caused by asbestos The very properties that made asbestos a valuable raw material also creates problems when it is inhaled. In particular, the ability of the fibres to split along their length into fine fibres that can reach the furthest part of the lung, and the resistance of the fibres to the chemical attack of the lung's defences. Fibres with diameter less than 3 µm will remain suspended in the air for long enough to reach deep into the lung when inhaled. Long thin fibres are just as likely to penetrate into the lungs as short thin ones. 2
Long thin asbestos fibres, once in the lung, are not readily removed. In fact, in sufficient numbers they are able to damage the scavenging cells that arrive to remove them and this leads to a process of 'healing' by scar formation or fibrosis. Unfortunately, scar formation in the lung destroys useful lung tissue and ultimately may result in sufficient damage to impair the lung's ability to take up oxygen. This leads to the person becoming short of breath and, if the disease progresses because of prolonged exposure, may be responsible for his or her death. This is the disease known as asbestosis, and it is only caused by exposure to very high concentrations of asbestos over many years. It has been known from the 1940 s and 1950 s that excessive numbers of asbestos workers die from lung cancer. The risk was such that a man with asbestosis who smoked 20 cigarettes per day had a 50% chance of dying of lung cancer. Someone not exposed to asbestos who smoked 20 cigarettes per day, in contrast, has a 13% chance of dying of lung cancer, which is bad enough! The evidence again suggests that the more asbestos a worker has been exposed to, the greater his risk of lung cancer. However, far and away the main cause of lung cancer is cigarette smoking. Asbestos-related lung cancer probably causes around 1or 2% of all lung cancer deaths in men in Britain, approximately one asbestos-related lung cancer deaths for each mesothelioma that is diagnosed. There is some evidence that the risk of lung cancer is highest with exposure to crocidolite or amosite and to a lesser extent for chrysotile, although there is a great deal of variation in the lung cancer risks between different workplaces that have been studied. Lung cancer usually progresses by spreading to new sites round the body and there are currently no widely used methods for early detection of the disease, although new protocols for screening heavy smokers are currently being assessed. Occasionally patients may be cured by major surgery, but essentially the hope for control of this disease lies in persuading people not to smoke. This applies with special force to people who have been exposed to asbestos. Mesothelioma is a malignant, incurable cancer of the outside lining of the lungs (called 'the pleura') or the lining of the bowels ('the peritoneum'). When it affects the pleura it causes pain in the chest and breathlessness, and the chest X-ray shows signs of fluid and tumour inside the chest wall. It progresses slowly over 1 to 2 years, making the patient suffer more and more pain and malaise, lose weight and 3
eventually die. A similar course is followed with peritoneal disease, though here there is pain and swelling in the abdomen. All types of asbestos can cause mesothelioma, although the disease is most clearly associated with exposure to crocidolite and amosite. Although there is good scientific evidence that risk of development of mesothelioma is related to the intensity of exposure, many cases have occurred after relatively short (around 6 months) exposure to crocidolite or amosite. Mesothelioma usually develops between 20 and 50 years after the exposure to asbestos first took place. This explains why the occurrence of the disease has been steadily rising in Britain over the last 40 years, since the peak uncontrolled use of asbestos in Britain occurred during and after the Second World War. The statistics for men and women are shown in the following figure 2. Whether or not someone smokes cigarettes has no effect on the risk of mesothelioma, although as we have seen it does impact on lung cancer risk. Similarly, exposure to non-asbestos dust does not increase the risk of mesothelioma. Several other conditions may affect the pleural lining of the lung as a result of asbestos exposure. They are all relatively benign conditions, though they may be frightening for anyone who is diagnosed with these conditions because of worries that they may develop cancer or mesothelioma. Pleural plaques are one of these conditions. These are harmless scars in the pleura that can be found in almost 2 Data from http://www.hse.gov.uk/statistics/tables/index.htm#lung 4
anyone who has been exposed to asbestos for several years. They often show up on X-ray. More rarely, the pleura scars more extensively (so-called 'pleural fibrosis') and this may cause some difficulty with breathing, If, as is only very rarely the case, it needs treatment, the fibrosis can be removed by an operation. Very occasionally asbestos exposure causes fluid to accumulate around the lung (pleural effusion). This usually goes away by itself, or it can be removed easily with a needle. Recently the World Health Organisation, International Agency for Research on Cancer (IARC) reviewed the evidence for the carcinogenicity of asbestos. They reaffirmed that all types of asbestos can cause cancer, and in addition to mesothelioma and lung cancer they identified two other types of cancer that are associated with asbestos: cancer of the larynx and ovarian cancer. Who is at risk of mesothelioma? Each year in Britain there are more than 2,500 deaths from mesothelioma. There is some variation in the death rate across the country, with the highest risks seen in the North East of England and the West of Scotland. The risk of mesothelioma death is greatest amongst occupations associated with the construction industry, such as carpenters, plumbers and electricians, and about half of the mesotheliomas occurring amongst men born in the 1940s are associated with this type of work. The high risk is due to the extensive use of asbestos containing materials in the construction industry in the 1950, 60s and 70s. However, more than two-thirds of all British men born in the first half of the last century and one quarter of women have at some time worked in jobs where they had exposure to asbestos. There is a very diverse range of occupations where mesothelioma deaths are recorded. For example, in the period between 2002 and 2010, for men, there were 58 mesothelioma deaths amongst secondary school teachers, 12 cases amongst nurses, 12 cases amongst actors, 5 amongst aircraft pilots, 3 amongst professional sportsmen and two in senior officials in national government. In the same period there were four deaths amongst police officers (inspectors and above), and 46 amongst police officers (sergeant and below) 3. 3 Statistics obtained from a report prepared by the Health and Safety Executive entitled, Mesothelioma Occupation Statistics. Male and female deaths aged 16-74 in Great Britain 2002-2010. 5
What is the risk for me? Most people exposed to asbestos, even those exposed to very high concentrations, will not die from an asbestos-related cancer. For example, if a hundred people were exposed identically to very high levels of asbestos for a prolonged period of time then perhaps 10 will eventually die from mesothelioma late in their lives; a slightly higher number might die from asbestos-related lung cancer. Whether or not you get the disease is apparently down to chance. We are all familiar with the ideas of chance, for example through playing the lottery or buying a raffle ticket. Chance is generally described as the odds of something happening and so if you buy a ticket for the UK National Lottery then there is a one in 14 million chance that you will win the jackpot and about a 1 in 1,000 chance of winning a prize with four correct numbers. You should beware however; the scientific way of describing odds is about the probability of something happening which is different from the way odds are used in betting, such as on horse racing. For someone exposed inadvertently to asbestos for a few days or weeks each year the main potential risks to health is mesothelioma or lung cancer. It is often assumed that the risk of any disease is very very low for at least ten years, but thereafter the risk increases and the more time that passes the greater the chance of someone contracting mesothelioma. As we have discussed the risk depend on fibre type, the level of exposure, the duration of exposure and time since first exposure. Based on the available scientific data it is possible to produce mathematical models using these factors to predict the chance that someone will eventually contract mesothelioma. One of these models was developed by two scientists who worked at the British Health an Safety Executive: John Hodgson and Andrew Darnton 4, and it is this model that has been used to illustrate possible risks in this document. The concentration of asbestos in the air is generally measured as fibres/ml, i.e. the number of fibres per millilitre of air. The background levels in cities are very low, but there is generally some asbestos present, perhaps around 0.00005 fibres/ml. The present legal limit is 0.1 fibres/ml, but in the past the limit was higher and it has been progressively reduced; in 1970 the limit was 2 fibres/ml for amosite and chrysotile 4 Hodgson, J. T., & Darnton, A. (2000). The quantitative risks of mesothelioma and lung cancer in relation to asbestos exposure. The Annals of Occupational Hygiene, 44(8), 565 601. 6
and 0.2 fibres/ml for crocidolite. Typical levels in dusty construction sites in the 1960s could have been 10 or 20 fibres/ml. If we take as an example someone who worked as a carpenter from 1960 at age 20 to 1970 and was exposed to amosite asbestos each working day at 10 fibres/ml then their estimated risk of eventually dying from mesothelioma would be around 1 in 6. If there were 100 young carpenters exposed in the same way as this man then we might expect 17 to die from mesothelioma. This is a very high risk and it is the reason that so many carpenters die from this disease between 2002 and 2010 there were almost 860 mesothelioma deaths amongst those employed in the occupation. If instead of being 20 when he did this work our carpenter had been 50 then the risk would have been lower, around 13 in 100. You can see how age is a determinant of risk and this is because there is less time for the cancer to develop amongst older people. Consider now someone exposed to amosite asbestos at 1 fibre/ml for one day every month from 1980 (age 30) to 1990. In this case his estimated risk would be around 5 in 10,000. If the level of exposure had been lower, for example at the current legal limit of 0.1 fibres/ml, then the risk would have been around 1 in 10,000. These risks are much lower than in the first example with the carpenters, reflecting the lower exposure and the lesser frequency of exposure. For example, if all serving officers in the Metropolitan Police were exposed in this way at 0.1 fibres/ml then it might be expected that three would eventually die from mesothelioma in their old age. The investigation of the sites where officers may have been inadvertently exposed to asbestos while involved in firearms training in MPS buildings is in progress. At this stage it is not possible to be definitive about any risks, but further information will be available once these investigations are complete. Health counselling and disease screening Asbestos workers must have health surveillance by law, but the advantage of surveillance for others exposed to asbestos is less certain. This is particularly the case because of the difficulty in detecting the disease through any screening programme and the generally poor prognosis for someone who has a diagnosis of mesothelioma or lung cancer. 7
Anyone who is inadvertently exposed to asbestos will be anxious about what effects it might have on his or her health; this is completely understandable. However, it can help to have some better idea of the risks to understand the chance that some sort of harm may occur. In these sorts of circumstances it is best for the employer or other responsible party to thoroughly investigate the circumstances of the exposure and particularly identify the possible level and duration of exposure, fibre type and identify who may have been exposed. Armed with this information it is possible to make an estimate of the risk using the methods described earlier. This process is underway in relation to the possible exposures amongst MPS officers who undertook firearms training on sites where asbestos may have been present. Once these investigations are complete it will be possible to provide specific advice to those involved. The Health and Safety Executive advises that if you are concerned about an inadvertent asbestos exposure at work then you should consult your GP (or the company occupational health service). It may be that your healthcare provider will offer to test your lung function or to ask about your respiratory health. The main purpose of these tests is to reassure you that your health has not been damaged in the short-term by the exposure, but they cannot detect mesothelioma or other cancers. You may ask for a note to be made in your personal health records about the possible exposure, including when it happened, how long it lasted, the type of asbestos and possible exposure levels (if known). HSE does not advocate routine chest X-rays for people who have had an inadvertent exposure to asbestos, because of the long time-lag between exposure and any risk of disease and because X-ray examinations cannot determine whether the person inhaled asbestos. Smoking cigarettes is the main cause of lung cancer and people who have been exposed to asbestos and are smokers have a much greater risk of contracting lung cancer. If you are a smoker and are concerned about your risk of lung cancer in the future then the best option is to quit smoking. The risk of mesothelioma is not affected by smoking status or exposure to non-asbestos dust. Steps are being taken to offer health counseling and screening to officers based on the final outcome of the investigations being undertaken by the MPS Safety and Health Risk Management Team. 8
Further information There is more information about asbestos and mesothelioma on the website of the Health and Safety Executive: http://www.hse.gov.uk/asbestos/ Further information about mesothelioma is available on the Cancer Research UK website: http://www.cancerresearchuk.org/aboutcancer/type/mesothelioma/about/mesothelioma-risks-and-causes On the NHS site: http://www.nhs.uk/conditions/mesothelioma/pages/definition.aspx And the British Lung Foundation site: http://www.blf.org.uk/page/mesothelioma About the author Professor John Cherrie is a scientist who works at Heriot Watt University and at the Institute of Occupational Medicine (IOM) in Edinburgh. He has worked on several research projects investigating the risks of asbestos-related diseases and has prepared reports for civil court cases on asbestos. His email address is j.cherrie@hw.ac.uk Telephone: 07796261688 9