Health and Safety
Executive / Commission
Statistics
In populations with heavy asbestos exposures (investigated in epidemiological studies) there have typically been at least as many, sometimes up to ten times as many, excess lung cancers as there have been mesotheliomas. The ratio depends on a range of factors - the most important of which are type of asbestos, level of exposure, age at exposure and smoking - and so one cannot be too precise about the overall ratio. Two lines of argument suggest that the ratio of asbestos related lung cancers to mesotheliomas in the British population as a whole is towards the lower end of the range of 1-10 estimated from the epidemiological studies. Firstly a study of lung cancer mortality in relation to indices of asbestos exposure and smoking habits in the west of Scotland suggested a ratio of around two asbestos lung cancers per mesothelioma for this region - which is known to be associated with fairly high asbestos exposures. Secondly, analyses of mesothelioma deaths in Great Britain by occupation and geographical area suggest that substantial numbers of deaths may have arisen in workers other than those that were most heavily exposed. On this basis HSE has for some years operated a rule of thumb that there are 1-2 asbestos related lung cancers for every mesothelioma death.
More recent evidence suggests that the ratio may be at the bottom end of the range of 1-2. 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).
Finally, a recent analysis of lung cancer mortality for the whole of the Great Britain by occupational group in relation to indices of asbestos exposure and smoking habits suggested that the ratio of asbestos related lung cancer to mesothelioma deaths is between two-thirds and one.
Prior to 2006 lung cancer as a prescribed disease in connection with asbestos exposure has typically given rise to between 50-80 new cases of assessed disablement each year - with the exception of the late 1990s when the annual number of cases was below this level - see Table IIDB05. In addition to lung cancers with accompanying evidence of asbestosis, from April 2006, the criteria for compensation were amended to include lung cancers where individuals were exposed to asbestos in the past in certain high risk occupations. This appears to have increased the number of assessed cases with 190 in 2006 and 195 in 2007, though this still falls far short of the estimated number of annual cases based on the mesothelioma:lung cancer ratio.
Table THORR01 shows reports from the SWORD and OPRA schemes which indicate numbers of a similar order, with 104 estimated cases in 2007. Some of these lung cancers will not have been caused by asbestos and it should be noted that in April 2002 a new method of collecting statistical information on claims and assessments was introduced by the Department for Work and Pensions, making data more accurate.