Table of Contents
PL-1-02 Claudio Bianchi
Geography of Mesothelioma: An Overview
Claudio Bianchi, Tommaso Bianchi
Center for the Study of Environmental Cancer – Italian League against Cancer, Monfalcone,
The principal feature in mesothelioma geography is the lack of data. Reliable figures on the
incidence/mortality of/from mesothelioma are available for about 15% only of the world population.
In particular, mesothelioma epidemiology is scarcely known for a majority of the big asbestos
producer/consumer countries. Where data are available, marked variations in incidence are
observed. During the last decades mesothelioma incidence showed a progressive increase in
various industrialized countries, reaching the highest values in Australia, Belgium, and the UK. In
such countries, annual crude incidence rates are around 30 cases per million. At the other extreme,
crude incidence rates of 0.6 and 0.7 cases per million are reported respectively from Tunisia and
Morocco. Japan showed a tremendous rise in mortality from mesothelioma during the last few
years. In all the countries a high ratio pleural/peritoneal is generally observed. Incidence is
markedly higher among men than among women, and it varies substantially from one occupational
category to another. Some occupational groups (for instance maritime trades, non asbestos textile
industries) have only recently been recognized as categories at risk for mesothelioma. At the
national level, wide variations are observed among the different areas. The above characteristics
may largely be explained by differences in the asbestos use. The latency periods (time intervals
between first exposure to asbestos and diagnosis of mesothelioma) are considerably longer than
previously reported and currently appreciated. In large series mean latency periods were around
50 years. An inverse relationship between intensity of exposure to asbestos and duration of latency
period has been observed. Predictions on the future trend of the mesothelioma epidemic should take
into account the fact that generally latency periods are longer than 20-30 years. The mesothelioma
wave consequent to the very high world asbestos consumption that occurred in the1970s has yet to
Numerous studies have recently been devoted to mesothelioma epidemiology1-11. Nevertheless, for
a vast majority of countries, data on mesothelioma incidence/mortality are not available. In
particular, mesothelioma epidemiology is scarcely known for various of the major asbestos
producers, such as the Russian Federation, China, Kazakhstan, Brazil, and Zimbabwe. In addition,
the situation is unknown for some major asbestos consumers, such as Thailand. Data are only
available for about 15% of the world population. The degree of reliability such data show, varies
substantially from one country to another. In fact, for some countries (e.g. Australia, Scandinavian
countries, UK), the data are based on cancer registries or mesothelioma registries. In other
countries, however, only limited parts are covered by registries, or mortality data only are available.
Where incidence is known or may be estimated with some reliability, the rates are extremely
various (Fig. 1). The highest values are reported or estimated for Australia, Belgium, and the UK.
In such countries the annual crude incidence rates are around 30 cases per million. The Netherlands
also show high incidence (21 cases per million). A second group of countries is characterized by
crude incidence rates comprised between 11 and 20 cases per million. This group includes various
countries of Western and Northern Europe (France, Germany, Italy, Scandinavian countries), and
New Zealand. Incidence rates below 11 cases per million are reported or estimated for many
countries of Europe (Central and Eastern Europe, Iberian peninsula, Ireland), of North America
(Canada, USA), Asia (Cyprus, Israel, Japan, Turkey), and Africa (Morocco, Tunisia). In a majority
of countries mesothelioma incidence showed a progressive increase during the last decades. In
particular, such increase was tremendous in Japan6. The lowest crude incidence rates are estimated
for Morocco (0.7 cases per million), and for Tunisia (0.6 cases per million).
The principal primary site of mesothelioma is the pleura, cases originating from peritoneum being
only a small percentage. The pleura/peritoneum ratio is 13:1 in Australia11; 8:1 in Japan6, and 7.3:1
in Sweden8-9. Mesothelioma incidence is markedly higher among men than among women. This
fact has consistently been confirmed by studies conducted in Europe7, 9, 10, Québec4, USA5,
Australia11, and Japan6. Incidence substantially varies from one occupational category to
another11-12. In The Netherlands, Burdorf et al.12 have estimated that in the insulation industry, the
overall risk of mesothelioma was 5 out of 100 workers, and in the shipbuilding industry, 1 out of
100 workers; in the construction industry the risk was by far lower (7 per 10,000 workers). Some
occupational groups have only recently been recognized as categories at risk for mesothelioma.
Epidemiological studies conducted in Finland13, Iceland14, and Sweden9 confirmed the risks
existing among seafarers. Studies conducted in Italy15 show a previously unrecognized risk among
non-asbestos textile industry workers. A striking feature in mesothelioma epidemiology is the
strong heterogeneity in distribution at a national level. Italy offers a good example of such an
irregular distribution16 (Fig. 2).
When the principal characteristics of mesothelioma epidemiology are considered in the frame of
asbestos use history, a clear relationship emerges between asbestos consumption and mesothelioma
incidence17-19. Moreover the mesothelioma distribution in a given country reflects the location of
the asbestos using industries. Again Italy represents a clear example. In Italy, shipyard and port
areas as well as asbestos industry areas show the highest mortality rates from pleural cancer
(Fig. 2). Interestingly, in some provinces of Northern Italy with large shipyards (Genoa, Trieste, La
Spezia), the high mortality rates from pleural tumors were already reported in the period 1969-
197520. The marked gender difference, generally observed in mesothelioma incidence, is also
adequately explained by differences in exposure to asbestos the two sexes had in various countries
in the past10, 21. In many mesothelioma series, the percentages of asbestos-related cases among
women are markedly lower than the cases among men. In fact, major difficulties are often
encountered in reconstructing occupational and social histories in women21. However, when
objective markers of asbestos exposure (pleural plaques, lung asbestos bodies) are investigated, a
relationship asbestos–mesothelioma may be established also among women21. In interpreting the
relationship asbestos–mesothelioma, it should be remembered that in mesothelioma, latency periods
(time intervals between first exposure to asbestos and diagnosis of the tumor) may be considerably
longer than previously reported and currently appreciated. In large series mean latency periods of
50 years have been reported22-24. Discrepancies among the values of latency periods in the various
series may be explained by the fact that latency periods at least partly depend on the intensity of
asbestos exposure22-24. People severely exposed to asbestos such as insulators show latency periods
of about 30 years22-23. At the other extreme, occupational groups with less heavy exposures, such as
sailors, show mean latency periods of 55 years (Figs. 3-4). Given these premises, it is clear that the
effects of the highest world asbestos consumption, occurring in 1970s, remain to be seen.
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■ 0.6-10 cases per million ■ 11-20 cases per million ■ 21-30 cases per million ■ no data available
Fig. 1. Estimated annual crude incidence rates of mesothelioma
Standardized rate per 100,000 (fig. based on data by Mastrantonio et al., 2002).
= 4-12 cases per 100,000 = 1-4 cases per 100,000 < 1 case per 100,000
Fig. 2. Mortality from pleural cancer among men in
Fig. 3. Latency periods in 400 cases
Fig 3. Latency periods in 400 cases of pleural
mesothelioma, Trieste-Malfacone area, 1968-2001
Fig. 4. Latency periods by occupation in 400 cases
Fig.4. Latency periods in 400 cases of pleural
mesothelioma by occupation, Trieste-Malfacone