MESOTHELIOMA: Mesothelioma Cases.

Mesothelioma is a formerly rare form of cancer in which malignant (cancerous) cells are found in the mesothelium, a protective sac that covers most of the body's internal organs. It principally affects the pleura (lining of the lungs) and peritoneum (surrounding the lower digestive tract). Most of the people who develop mesothelioma have worked on jobs where they inhaled asbestos particles. Working with asbestos is the major risk factor for mesothelioma. The typically long delay between first exposure to asbestos and death from mesothelioma (seldom less than 15 years, but possibly as long as 60 years) means that deaths occurring now and most of those expected to occur in the future reflect industrial conditions of the past rather than current work practices. This latency period means that the effectiveness of current controls cannot yet be assessed from the mesothelioma mortality figures. A history of asbestos exposure at work is associated with about 80 percent of all cases. However, mesothelioma has been reported in some individuals without any known exposure to asbestos.

Overall scale of disease including trends

Table MESO01 shows that the annual number of mesothelioma deaths in Great Britain has risen fairly constantly since 1968 (the first complete year for which data is available following the introduction of the mesothelioma register in 1967); see also Figure 1. The total number of deaths in 2004 was 1969. . Most of those who die from mesothelioma each year are male: in 2004 there were 1674 male deaths, 85% of the total number. Figure 1 also shows the number of disablement benefit cases made each year for mesothelioma since 1981. The sharp increases in claims registered from 2002 onwards may be due to the introduction of a new method of collecting statistical information in April 2002. Table MESO02 shows the number of mesothelioma deaths in each year in 5-year age groups for males and MESO03 shows the number of mesothelioma deaths in each year in 5-year age groups for females.

Although the vast majority of mesothelioma cases, around 80%, are caused by occupational exposure to asbestos, a relatively small number of deaths each year occur in people with no history of exposure. There is some evidence to suggest that there could be as many as 50-100 of these so called spontaneous mesotheliomas each year.

Fig 1. mesothelioma deaths and disablement benefit cases 1978-2003/4

Note: Data for industrial industries is available for 2005 were as mesothelioma death data is only currently available to 2004.

The number of female mesothelioma deaths has always been much smaller than the corresponding number of male deaths. The proportion of annual deaths which were female has tended to fall since 1968, although there has been a slight increase over the last few years. In the early 1970s over 20% of deaths were female. The proportion fell to 13% in the early 1990s and remains around 15% since then. There were 295 deaths provisionally recorded for females in 2004 compared with 285 in 2003.

Table MESO04 shows numbers of mesothelioma deaths and death rates by age and sex for the twelve three-year time periods from 1968-2004. Death rates for males are also shown in Figure 2. There are large differences in the magnitude of the rates between the different age groups for males, with rates since 1990 in the two oldest age groups (65-74 and 75+) being between 2 and 3 orders of magnitude higher than those in the lowest age category (0-44 years), and following an increasing upward trend over time. In the 55-64 age group, the increase in the rate over time has generally not been as steep as for older age groups, and shows some evidence of a levelling off in recent years. After an increasing trend in the earlier time periods, rates in the lowest two age groups (0-44 and 45-54 years) both show decreasing trends towards the end of the period. This is strongest in the 0-44 age group where the rate starts to decrease during the early 1990s. The pattern of progressively higher rates in older people and a decrease in the rates in younger people is consistent with that expected as the peak of an epidemic is approached. The rates for females over time tend to fluctuate to some extent because of greater statistical variation due to the smaller overall numbers. Rates for females are generally speaking an order of magnitude lower than those for males.

Fig 2. Average annual male mesothelioma death rates per million by age and time period 1968-2003p

Table MESO05 shows standardised mesothelioma death rates per million by 3-year time period, government office region and sex. The period 1990-1992 was taken as the base for standardisation over time and Great Britain for standardisation over region. Thus the standardisation allows for changes in the age-structure of the underlying population over time and between regions. For example, crude death rates tend to increase by a larger amount over time than the age-standardized rates presented due to greater survival of the population in later time periods to ages where the rate of mesothelioma is higher.

For both males and females the rates for Great Britain follow an upward trend over time - reaching 52.7 and 9.7 deaths per million respectively in 2002-2004 compared with 32.1 and 4.7 in 1990-1992. For males, upward trends were evident in the rates over the period for all regions. There is some evidence of rates for the different regions converging over time in that regions with the lowest rates in earlier periods tended to increase most, and those with higher rates increased to a lesser extent. For example, the largest relative increases - over twofold – were in the West Midlands and Wales, the two regions with the lowest rates in 1990-1992. In contrast the smallest relative increase was in Scotland (approximately 30%) which was the region with the second largest rate (after the North East) during the period 1990-1992. Although the numbers of cases are much smaller for females and so the pattern in the rates over time is more erratic, an upward trend is fairly clear in most regions. More detailed mesothelioma statistics by region are available in two separate fact sheets.

Statistics by Occupation

Detailed mesothelioma death statistics for males and females and relative mortality for different occupational groups are available in a separate factsheet (Mesothelioma occupation statistics for males and females aged 16-74 in Great Britain, 1980-2000). This analysis showed that occupations where males had the highest risk of mesothelioma were metal plate workers (which includes shipyard workers) and vehicle body builders (which includes railway carriage and locomotive building). A number of the other high-risk occupations identified are associated with the construction industry, such as plumbers and gas fitters, carpenters and electricians. The analysis also showed that although the total number of male mesothelioma cases has increased almost three-fold since the early 1980s, in most cases proportions of mesothelioma deaths across occupational groups have remained stable over time. Occupations identified as relatively high risk for females included metal plate workers, chemical workers (which includes those classified as "process workers"), plastics workers and other foremen/labourers (which includes those classified as "factory workers").

Statistics by Industry

Table IIS10 shows the analysis of average rates of new assessments for disablement benefit cases in 2003-2005 by industry, and shows that, with a rate of 32.0 cases per 100 000 employees per year, the construction industry (including insulation and asbestos removal workers) had the highest rate, followed by extraction, energy and water supply industries with an annual rate of 9.4 cases per 100 000 employees.

Estimation of the future burden of mesothelioma deaths

Updated statistical modelling of mesothelioma deaths during the period 1968-2001 in males aged 20-89 was used to produce an estimate of the future peak number of mesothelioma deaths to males and females of all ages:

The annual total number of mesothelioma deaths in Great Britain is currently predicted to peak at a level of 1950 to 2450 deaths during the period 2011 to 2015.
The updated modelling suggests that annual total number of mesothelioma deaths to males aged 20-89 in Great Britain will peak at a level of 1650 to 2100 deaths during the period 2011 to 2015.
The annual total number of mesothelioma deaths to females in Great Britain is predicted to peak at a level of 250 to 310 deaths, though this estimate is more uncertain since it is derived by simply applying the results for males to the average proportion of deaths among females.
Around 10 mesothelioma deaths among males aged 90 or over are expected to occur annually during the period of the peak – although this is very uncertain.

Although these projections rest on a number of uncertain (and largely unverifiable) assumptions, the timing and scale of the maximum annual death toll is not highly sensitive to these uncertainties. What is highly uncertain, is the rate at which the numbers will fall after this peak is reached. More information about the methodology for predicting future numbers of mesothelioma deaths is available in the factsheet: