Descriptive Epidemiology of the Principal Asbestos-Related Diseases in Québec, 1981-2004
While awaiting the introduction of the future surveillance system for asbestos exposures and their related diseases, we created the descriptive epidemiological portrait of two of these health problems, malignant mesothelioma and asbestosis. It was constructed using the data from statutory databases available at the ministère de la Santé et des Services sociaux: the Fichier des tumeurs du Québec (tumour registry) for cancer incidence, the Fichier des décès (death registry) for mortality and the Med-Echo registry for asbestosis hospitalizations. Finally, the international comparisons of malignant mesothelioma incidence rates were made using the electronic database of the International Agency for Research on Cancer.
The study area is the Province of Québec. The incidence rates, mortality and hospitalization at the regional level (health region) were compared. The time trends of incidence rates, mortality and hospitalization were analyzed. Standardized rates using the direct method are used for the interregional comparisons, while indirect standardization is used for the international comparisons.
Between 1982 and 2002, 1,530 new cases of malignant mesothelioma of the pleura and 170 new cases of malignant mesothelioma of the peritoneum were diagnosed in Québec. Like many cancers, these diseases are more frequent among people aged 50 and over and among men. Furthermore, among men, the annual incidence rates of malignant mesothelioma of the pleura increased significantly between 1982 and 2002, with an average annual increase of 3.6%. No significant time trend was observed among women. The incidence rates of cancers and malignant mesotheliomas of the pleura are significantly higher in Chaudière-Appalaches, Lanaudière and Montérégie regions among men, and in Chaudière-Appalaches among women. In Chaudière-Appalaches and Montérégie, among men, these results could be explained by prior occupational exposures in the asbestos mines of the Chaudière-Appalaches region, and in the shipyards in Montérégie and Chaudière-Appalaches. For the Lanaudière region, it is possible that the results observed are related to the presence of old shipyards in Montreal and the refineries in Montreal East. However, we cannot exclude that a higher level of clinical suspicion and the presence of specific screening programs in these same regions might explain these observations. Among men, rates lower than the provincial rate are observed in the Bas-Saint-Laurent and Outaouais regions. The lower rates observed in Outaouais might be explained by the cases treated in Ontario and not recorded in the Fichier des tumeurs. Furthermore, the geographical distribution of incidence is not adjusted for residential mobility.
From 1993 to 1997, the Province of Québec showed the highest standardized incidence ratio (SIR) of malignant mesothelioma in Canada, among men and among women. Among women during the same period, only Western Australia and Scotland posted SIRs significantly higher than that of Québec, in the other available cancer registries. Among men, the SIR of malignant mesothelioma in New Zealand, the Netherlands, and in several regions of Great Britain and Australia were significantly higher compared to that of Québec. These international comparisons should be interpreted with caution due to the inherent limitations of their use, given the fact that few national cancer registries are available, that it is not possible to distinguish malignant mesothelioma of the pleura from other mesotheliomas in the aggregated data available and that differences in diagnostic methods could bias the results. However, these results are compatible with asbestos exposure among workers in Québec through mining and industrial activities and in construction. The higher rates observed in Australia might be explained by the preponderance of crocidolite in this country, which is more associated with malignant mesothelioma than chrysotile, the predominant asbestos fibre extracted in Québec. It is also possible that historically, asbestos use was greater in Australia than in Québec.
For the period from 1981 to 2003, 1,059 deaths from cancer of the pleura were recorded in Québec. Of these, almost three times more were among men than among women, and they were more frequent among persons aged 50 and older. Analysis of the annual provincial death rates from cancer of the pleura shows no significant time trend among men or among women. The geographic distribution of death rates for cancer of the pleura indicates that the Chaudière-Appalaches region presented significant excesses among men and women alike. Statistically significant excesses were also observed among men in the Lanaudière and Montérégie regions. These observations are consistent with the situation observed for the incidence of malignant mesothelioma of the pleura.
We also estimated asbestosis incidence using the Med-Echo registry, by taking into consideration the hospitalizations with first mention of asbestosis during the period from 1992 to 2004. In Québec, during this period, 2,072 hospitalizations with first mention of asbestosis were recorded. It was mainly men hospitalized for this disease (25 men for 1 woman). Similarly, the hospitalizations with first mention of asbestosis were mainly observed among people over 60 years of age, and the mean age of these people increased significantly during the period studied. No significant time trend in the estimated rate of hospitalization with first mention of asbestosis was observed among men or women. The geographic distribution of hospitalizations with first mention of asbestosis indicates significant excesses in the Chaudière-Appalaches region among men and women, and excesses for the Estrie and Lanaudière regions among men. These data are consistent with those for the incidence of malignant mesothelioma of the pleura.
In conclusion, the analysis of the data from Quebec health databases enables us to create a valuable epidemiological portrait of asbestos-related diseases. One of the most important data sources is the Fichier des tumeurs du Québec. However, the delays to obtain data are significant and we recommend continuing the current steps to reduce these delays. Second, we recommend carrying out periodic analysis of the trends for malignant mesothelioma of the pleura and cancer of the pleura using the Fichier des tumeurs du Québec, until the future surveillance system for asbestos-related diseases is operational. Finally, despite the limitations of the Med-Echo registry, analysis of hospitalizations with first mention of asbestosis could be continued while awaiting the results of a study to describe the diagnostic criteria for the asbestosis cases in this database.