Volume 203 - Issue 6
Pattern of malignant mesothelioma incidence and occupational exposure to asbestos in Western Australia
Authors: Arthur W (Bill) Musk, Nola Olsen, Helman Alfonso, Susan Peters and Peter Franklin
Med J Aust 2015; 203 (6): 251-252. || doi: 10.5694/mja15.00337
Published online: 21 September 2015
Published online: 21 September 2015
The epidemiology of malignant mesothelioma in WA reflect patterns of occupational asbestos exposure of more than 30 years ago
Western Australia has one of the highest rates of malignant mesothelioma (MM) in the world.1 Early cases of MM were predominantly caused by the crocidolite mining operations at Wittenoom.1-3 During the 1950s, Australia had the highest per capita asbestos consumption in the world,2 mostly to manufacture asbestos cement, and there was an increasing number of MM cases in workers using these asbestos products. Production declined rapidly in the 1980s, and all production and importation of asbestos were prohibited from 31 December 2003.
The aim of our study was to describe the pattern of MM incidence in WA in relation to occupational exposure to asbestos.
All incident cases of MM are recorded in the WA Cancer Registry and reviewed by an expert committee (pathologist, respiratory physician, occupational physician, epidemiologist and cancer registrar) to verify the diagnosis. All available exposure information — including medical (often collected for workers’ compensation purposes) and employment records — was examined to determine the most significant occupational exposure likely to be responsible for the disease. The number of cases for each occupational group was expressed as a proportion of all cases for each decade.
There were 1263 confirmed cases of MM between 1962 and 2009 (97% male) in persons who had experienced occupational exposure to asbestos, and a further 75 cases (53% in males) where no exposure could be identified (Box). The total number of cases increased from 57 in the 1960s and 1970s combined, to 211 in the 1980s, 475 in the 1990s, and 595 in the 2000s. The proportions of cases resulting from crocidolite production and transport were highest in the 1960s and 1970s, as were cases in rail workers and plumbers. The proportions linked to asbestos exposure in waterside workers, the armed forces, laggers and insulators, and those working in shipbuilding, asbestos cement production, automotive brake work and non-asbestos mining peaked in the 1990s; the proportions in building and construction workers, electricians, boilermakers and welders, and power station workers were greatest in the 2000s. Overall, the largest proportions of cases were in construction and Wittenoom workers. The proportion of cases with no identifiable exposure was less than previously reported4 and did not differ significantly between decades.
In conclusion, the numbers and proportions of MM cases attributed to occupational asbestos exposure in WA reflect the patterns of asbestos use in the respective occupations more than 30 years ago. Since 1980, an increasing proportion of MM cases has not been linked with occupational exposure to asbestos.5 Occupational exposure nevertheless clearly remains the major cause, and appears likely to be so for many more years. Despite the exponential rise in the risk of MM following exposure to asbestos, decline in the working population at risk and removal of asbestos from construction and industrial equipment suggest that the MM epidemic in WA will be finite.
Malignant mesothelioma cases over 5 decades in Western Australia, according to occupational group
Occupational group |
1960–1979 |
1980–1989 |
1990–1999 |
2000–2009 |
Total |
||||||||||
No. |
% |
No. |
% |
No. |
% |
No. |
% |
No. |
% |
||||||
Wittenoom workers |
31 |
54.4% |
70 |
33.2% |
83 |
17.5% |
82 |
13.8% |
266 |
19.9% |
|||||
Rail workers |
8 |
14.0% |
14 |
6.6% |
36 |
7.6% |
51 |
8.6% |
109 |
8.2% |
|||||
Plumbers |
2 |
3.5% |
6 |
2.8% |
14 |
2.9% |
20 |
3.4% |
42 |
3.1% |
|||||
Asbestos transport |
2 |
3.5% |
6 |
2.8% |
12 |
2.5% |
8 |
1.3% |
28 |
2.1% |
|||||
Non-ABA Wittenoom workers |
0 |
— |
10 |
5.1% |
9 |
1.9% |
12 |
2.0% |
31 |
2.3% |
|||||
Other asbestos work |
0 |
— |
1 |
0.5% |
1 |
0.2% |
0 |
— |
2 |
0.1% |
|||||
Waterside workers |
2 |
3.5% |
15 |
7.1% |
34 |
7.2% |
19 |
3.2% |
70 |
5.2% |
|||||
Armed forces |
0 |
— |
6 |
2.8% |
29 |
6.1% |
27 |
4.5% |
62 |
4.6% |
|||||
Laggers and insulators |
1 |
1.8% |
8 |
3.8% |
21 |
4.4% |
16 |
2.7% |
46 |
3.4% |
|||||
Ship building |
0 |
— |
7 |
3.3% |
17 |
3.6% |
11 |
1.8% |
35 |
2.6% |
|||||
Asbestos cement production |
1 |
1.8% |
2 |
0.9% |
16 |
3.4% |
14 |
2.4% |
33 |
2.5% |
|||||
Automotive (brakes) |
0 |
— |
2 |
0.9% |
11 |
2.3% |
13 |
2.2% |
26 |
1.9% |
|||||
Non-asbestos mining |
0 |
— |
0 |
— |
2 |
0.4% |
2 |
0.3% |
4 |
0.3% |
|||||
Building and construction workers |
2 |
3.5% |
28 |
13.3% |
84 |
17.6% |
175 |
29.4% |
289 |
21.7% |
|||||
Other occupations* |
2 |
3.5% |
11 |
5.2% |
34 |
7.2% |
51 |
8.6% |
98 |
7.3% |
|||||
Electricians |
0 |
— |
2 |
0.9% |
6 |
1.3% |
28 |
4.7% |
36 |
2.7% |
|||||
Boilermakers and welders |
1 |
1.8% |
6 |
2.8% |
16 |
3.4% |
26 |
4.4% |
49 |
3.7% |
|||||
Power station workers |
0 |
— |
1 |
0.5% |
8 |
1.7% |
11 |
1.8% |
20 |
1.5% |
|||||
Pipe fitters |
1 |
1.8% |
2 |
0.9% |
3 |
0.6% |
11 |
1.8% |
17 |
1.3% |
|||||
No identifiable source of asbestos exposure |
4 |
7.0% |
14 |
6.6% |
39 |
8.2% |
18 |
3.1% |
75 |
5.6% |
|||||
Total |
57 |
100.0% |
211 |
100.0% |
475 |
100.0% |
595 |
100.0% |
1338 |
100.0% |
|||||
ABA = Australian Blue Asbestos company. *Occupations that are not covered by the presented list of occupational groups. The bold cells mark the decades with the highest proportion of malignant mesothelioma cases for each occupational group. | |||||||||||||||
Competing interests
No relevant disclosures.
Acknowledgements
This research was supported by the National Health and Medical Research Council (project grant 634458). We acknowledge the following investigators who made a significant contribution to the collection and preparation of the data, as well as to the preparation of earlier drafts of the manuscript: Nicholas de Klerk, Alison Reid, Fraser Brims, Keith Shilkin, Timothy Threlfall and Evelyn Lee.
References
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- Xu Z, Armstrong BK, Blundson B, et al. Trends in mortality from malignant mesothelioma of the pleura, and production and use of asbestos in Australia. Med J Aust 1985; 143: 185-187.
- de Klerk NH, Musk AW. Epidemiology of mesothelioma. In: Robinson BWS, Chahinian AP, editors. Mesothelioma. London: Martin Dunitz, 2002: 339-349.
- Leigh J, Davidson P, Hendrie L, Berry D. Malignant mesothelioma in Australia, 1945–2000. Am J Ind Med 2002; 41: 188-201.
- Olsen NJ, Franklin PJ, Reid A, et al. Increasing incidence of malignant after exposure to asbestos during home maintenance and renovation. Med J Aust 2011; 195: 271-274.