Asbestos Occupational Exposures

Asbestos Occupational Exposures

Overview

Inhalation is the most important route of occupational exposure to asbestos.[1] CAREX Canada estimates that approximately 235,000 Canadians are exposed to asbestos in their workplace. Current asbestos-related disease is associated with exposures that occurred 10 to 40 years ago. This is due to the latency period between exposure and onset of disease. The exposure sources were very different at that time than they are now.

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Exposure from more widespread mining and milling, in addition to primary use of asbestos in manufactured products and buildings was most important in the past. According to the Burden of Occupational Cancer in Canada project, past exposures (1961-2001) to asbestos leads to approximately 1,900 lung cancers and 430 mesotheliomas each year [2,3]. This amounts to 8% of all lung cancers and 81% of all mesotheliomas diagnosed annually (almost all of the remaining mesotheliomas are likely due to environmental asbestos exposure). Most asbestos-related cancers occur among workers in the manufacturing and construction sectors. Work-related asbestos exposure resulted in approximately $2.35 billion in costs for newly diagnosed lung cancer and mesothelioma cases in 2011[4].

In contrast, the vast majority of exposure that occurs today is due to contact with older asbestos-containing products, and doing renovation work on buildings and in industrial plants. These exposures can be considered as a kind of secondary exposure from contact with those products and building materials that were made or put in place more than 35 years ago.

Many of the workers currently expected to be exposed work in the construction sector, where exposure occurs from poor exposure control during renovation and refurbishing of old buildings. Exposure in construction workers is difficult to monitor due to the wide variety of worksites and the transient nature of employment for many workers. Despite this, the INSPQ in Quebec released a report on exposures to asbestos in the construction industry.[5]

In addition, exposure may commonly occur among maintenance workers in industries where substantial amounts of asbestos were used in the past (such as smelting, petroleum refining and pulp and paper), as well as automotive brake repair workers, and people that repair and maintain ships.

In some cases, we expect to see exposure today in the same or similar occupational groups as we did in the 1970s (i.e. construction workers, plumbers and pipefitters), albeit at lower exposure levels. In other cases, such as in mining, exposure has been almost completely phased out. Further, the abatement and asbestos remediation industry is an entire category of business with potential for exposure to asbestos that did not exist as a separate profession until the early 1980s.

CAREX Canada estimates that the largest occupational groups exposed are carpenters, construction trades helpers and labourers, electricians, and janitors, caretakers and building superintendents.

Prevalence Estimate

Using an approach that considered historical uses of exposure in Canada to guide exposure assessments for the present day, results indicate that approximately 235,000 Canadians are currently exposed to asbestos in their workplaces, and are primarily male (89%). This estimate includes people with the potential for exposure at work to any form of asbestos likely to exceed the non-occupational background level in dwellings or urban air (usually below 0.001 f/cm3).

The largest industrial groups exposed are construction-related (specialty trades and building construction contribute about 67% of all exposed workers). Other important industries include public administration, schools, and hospitals.

When examining exposure to asbestos by occupation, the largest exposed groups are carpenters (36,000 workers exposed), construction trades helpers and labourers (36,000 workers exposed), electricians (21,000 workers exposed), and janitors, caretakers and building superintendents (18,000 workers exposed).

The number of workers exposed to asbestos increased by approximately 83,000 workers from 2006 to 2016 (a 55% increase). 

Workers exposed to asbestos by industry in 2016

Workers exposed to asbestos by region in 2016

Click the second tab to view total number of workers exposed.

Level of Exposure

In total, approximately 235,000 Canadians are exposed to asbestos in their workplaces. The majority of workers exposed to asbestos are in the low and moderate exposure categories. A significant number of asbestos-exposed workers are at risk for high exposure.

Workers exposed to asbestos by exposure level in 2016

Level of exposure by industry

Identifying industries with either 1) workers exposed to high levels of asbestos or 2) a larger number of workers exposed to asbestos is important in guiding cancer prevention efforts to prioritize exposed groups and target resources most effectively.

The table below shows the number of workers exposed by industry group and level of exposure to asbestos. These results highlight industries with the most number of workers, as well as industries with the highest levels of exposure. For example, in the specialty trade contractors and construction of building industries, a large number of workers are exposed, with many exposures occurring in the moderate and high exposure categories. Depending on the goals of a prevention campaign, exposure reduction in the large industrial group might be a useful strategy, or reducing exposure to those at highest risk of exposure could be seen as a priority.

Workers exposed to asbestos by exposure level and industry in 2016

*Numbers may not add up due to rounding
Methods and Data

Our Occupational Approach page outlines the general approach used to calculate prevalence and exposure level estimates for workplace exposures.

Data Sources

Data used in developing the occupational estimates for asbestos were collected from several sources:

  1. The Canadian Workplace Exposure Database (CWED) contains approximately 6,700 measurements for asbestos exposure. These measurements were collected during the years 1981 to 2004 in Ontario and British Columbia workplaces.
  2. Canadian and US scientific peer reviewed publications that addressed asbestos exposure in Canada and the United States.
  3. Grey literature including technical reports from governments and international bodies.

Prevalence Estimate Method

CAREX defines exposure to asbestos as inhalation at work to levels significantly exceeding non-occupational background levels.

To determine the number of workers potentially exposed to asbestos at work, CAREX occupational exposure experts used methods previously established in other peer-reviewed CAREX projects in Europe. A series of steps were taken to assign exposure proportions to occupations and industries at risk of exposure to asbestos.

  1. Occupations and industries at risk of possible exposure to asbestos were identified using any combination of data sources described above.
  2. The total number of workers in each identified occupation and industry intersection was obtained from Statistics Canada 2016 census data.
  3. A percentage of workers exposed was assigned to that occupation and industry intersection. Percentages were determined by consultation with existing evidence in the data sources, previously established methods from the Europe CAREX estimates and the expert judgement of CAREX occupational hygienists.
  4. The number of workers in the identified group is multiplied by the assigned percentage to calculate the prevalence estimate of workers exposed to asbestos.
Sources

1. National Toxicology Program (NTP). 14th Report on Carcinogens for Asbestos (2016) (PDF)
2. Labrèche F, Kim J, Song C, Pahwa M, Calvin BG, Arrandale VH, McLeod CB, Peters CE, Lavoué J, Davies HW, Nicol AM. “The current burden of cancer attributable to occupational exposures in Canada.” Prev Med 2019;122:128-39.
3. Occupational Cancer Research Centre. Burden of Occupational Cancer (2017)
4. Tompa E, Kalcevich C, McLeod C, Lebeau M, Song C, McLeod K, Kim J, Demers PA. “The Economic Burden of Lung Cancer and Mesothelioma Due to Occupational and Para-Occupational Asbestos Exposure.” Occup Environ Med 2017;74(11):816-822.

  

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