Asbestos: Current Knowledge on the Exposure and Diseases of Workers and the General Population in Québec from 2003 to 2009

This document reports on the Québec data acquired since 2003 on asbestos exposure and asbestos-related diseases, both among workers and in the general population. However, the aim is not to update the knowledge on asbestos as such. This report also summarizes the status of the Québec surveillance system for asbestos exposures and asbestos-related diseases, which will be introduced by the Institut national de santé publique du Québec (INSPQ), as a result of the adoption of the Policy concerning the increased and safe use of chrysotile asbestos in Québec.

The most recent data (2004) on environmental exposure to asbestos in outdoor air identified no asbestos fibres in Montréal and in the city of Québec. However, in Thetford Mines, the average airborne asbestos concentration was 0.0043 fibre/ml (f/ml) by transmission electron microscopy (TEM). This concentration was 215 times higher than that obtained in the air outside buildings involved in litigation regarding the removal of asbestos-containing materials (ACM) in the United States. Between 1998 and 2005, in the city of Asbestos, average concentrations ranged from 0.003 to 0.007 f/ml, although we do not know if these were of asbestos fibres, since the analytic method was not specified.

No publication later than the year 2000 has been found on the exposure levels of asbestos miners in the areas of Thetford Mines and Asbestos.

With respect to the industrial sector, at the end of 2009, nine Québec factories were identified in which asbestos was used in the manufacturing process or in which workers handled asbestos-containing products. None of the factories used asbestos safely in accordance with one or more criteria defined a priori. These findings show the importance of exposure surveillance among workers in these workplaces.

Material characterization data obtained in 2009 were collected at high-risk construction sites. Of the 2,475 samples that contained asbestos, 75% contained chrysotile only, 15% chrysotile in the presence of other types of asbestos fibre and 10% amphiboles only (i.e. the asbestos family that excludes chrysotile). In another study, 1,251 material samples contained amphiboles only and 10,538 other samples chrysotile alone (95%) or a mix of chrysotile and amphiboles (5%). Therefore, we find chiefly chrysotile in the on-site materials in the buildings studied.

Of the 3,000 air samples collected during work on high-risk construction sites, 43% had concentrations higher than or equal to 1 f/ml, which is the occupational exposure limit value for chrysotile asbestos in Québec. These results show the importance of enforcing the exposure control measures prescribed in the regulations. Of the 2,626 air samples collected in changing rooms on construction sites, during asbestos removal work, 77% had fibre concentrations equal to or higher than 0.01 f/ml compared to 14% in adjacent areas (0.01 f/ml is the threshold level required by regulation before dismantling the sealed enclosures within which demolition work takes place).

With respect to asbestos-related diseases, from 1982 to 2002, 1,530 people (1,210 men and 320 women) received a new diagnosis of pleural mesothelioma in Québec. During that study period, the annual age-adjusted incidence rates increased significantly among Québec men, with an average annual growth rate of 3.6%. At the regional level, the standardized incidence rates for pleural mesothelioma were significantly higher among men and women in the Chaudière-Appalaches region, and among men in the Montérégie and Lanaudière regions. Between 1982 and 2002, 170 Quebeckers were diagnosed with a peritoneal mesothelioma (98 men and 72 women).

Between 1992 and 2004, 2,072 people (1,993 men and 79 women) were hospitalized with first mention of asbestosis as the primary or secondary diagnosis. Significant excess hospitalizations for asbestosis were observed among men and women in the Chaudière-Appalaches region and among men in the Estrie and Lanaudière regions.

An estimation of lung cancer and mesothelioma risk among residents in the city of Thetford Mines was carried out using two approaches, one based on the Berman and Crump model and the other on the guidelines of the Ministère de la Santé et des Services sociaux. Depending on the approach used, the lifetime excess mortality for these two cancers ranged from 8.2 to 125 per 100,000 persons residing in Thetford Mines with a continuous lifetime exposure to asbestos.

Few studies have documented asbestos-related diseases among Québec workers. A 2009 publication described all new cases of asbestos-related diseases recognized as occupational lung diseases by the Comité spécial des maladies professionnelles pulmonaires (CSMPP-special committee on occupational lung diseases) between 1988 and 2003. During this period, 1,348 workers had 1,512 diseases. The workers were chiefly exposed in the construction industry and in the maintenance and repair of asbestos-containing products or structures (49.4%), thereby surpassing the number of workers exposed in mines (29.1%).

Mesothelioma and asbestosis cases recognized as occupational diseases by the CSMPP represent respectively 21.4% of pleural mesothelioma cases registered in the Fichier des Tumeurs du Québec (tumour registry) and 35% of persons hospitalized with mention of asbestosis registered in the MED-ÉCHO system (Maintenance et exploitation des données pour l'étude de la clientèle hospitalière - maintenance and use of data for the study of the hospital clientele).

With respect to asbestos exposure, the surveillance system to be introduced by the INSPQ will prioritize exposure surveillance of miners, workers who transform and process asbestos and construction workers, and the surveillance of environmental exposure to asbestos in the cities of Thetford Mines and Asbestos.

With respect to disease surveillance, the system will prioritize the surveillance of asbestosis, pleural and peritoneal mesothelioma and asbestos-related lung cancer, which are notifiable diseases since 2003. As these diseases are under-reported, a pilot study with the aim to facilitate the reporting of these notifiable diseases by physicians will be introduced in two Québec hospitals. If the pilot study proves effective in identifying and reporting cases, this approach, which requires the collaboration of medical archives departments, would be proposed in all Québec hospitals.

Louise De Guire
M.D., Institut national de santé publique du Québec
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