Occupational Risks for Asbestos-related Disease

Asbestos Exposure: Past and Present

Asbestos is a group of naturally occurring mineral fibres and was widely used in insulation and other building materials from the 1930s to the 1980s. In 2018, Canada banned the import, manufacture, sale, trade or use of asbestos and asbestos-containing products, with some exceptions. However, asbestos is still present in many older homes and buildings due to its historical widespread use [1].

Exposure to asbestos can cause mesothelioma, lung cancer, and asbestosis, as well as laryngeal, ovarian, and gastrointestinal tract cancers [2]. The primary route of exposure is through inhalation of asbestos fibres. Asbestos-related diseases take 10-40 years to develop so many recent and emerging cases are related to past working conditions [3].

A study of occupational cancer burden conducted by the Occupational Cancer Research Centre found that 7.8% of lung cancer and 80.7% of mesothelioma diagnosed annually in Ontario were attributed to occupational exposures to asbestos. The study also reported that 30% of the cancers caused by occupational exposure were among former manufacturing workers and an additional 25% among former construction workers [4]. 

Construction trades workers are still at risk of exposure when working in older buildings through maintenance of equipment in areas containing asbestos, or when renovating or demolishing old buildings. Insulators may be exposed to asbestos when they remove or replace old insulation [2,4]. Pipefitters and plumbers may be exposed when fixing older pipes or when installing new ones in areas that contain asbestos. Boilermakers and related workers may be exposed to asbestos when working with older boilers in buildings and ships that were often insulated with asbestos-containing material and connected to pipes for transferring steam that were insulated with asbestos. Many other building trades are also at risk of encountering asbestos. Similarly, firefighters also have increased risks of asbestos exposure when fighting fires in older buildings as asbestos fibers can be released into the air [2,4].

Asbestos-Related Disease

Mesothelioma is an aggressive and highly fatal cancer that occurs in the lining of the lungs or abdomen and is primarily caused by exposure to asbestos. Approximately 80-85% of mesothelioma cases are attributable to occupational asbestos exposure [5-7]. It is estimated that annually in Ontario 140 mesotheliomas are a result of occupational exposure to asbestos and approximately 55,000 workers are still exposed to asbestos [Figure 1] [4-5]. Mesothelioma has very poor survival; In Ontario, median survival between 1993 and 2017 was 8.6 months, with 38% survival at one year and only 4.7% at five years [5].

Figure 1. Number of mesothelioma cases in Ontario, 1992-2017 [5]

 

Asbestosis is a serious disease characterized by lung tissue scarring caused by inhaling asbestos fibres. Symptoms include difficulty breathing, coughing, and in severe cases heart enlargement, disability, and death [3].

Asbestos is one of the most important causes of lung cancer after cigarette smoking. There is evidence that asbestos exposure and cigarette smoking have a positive synergistic interaction, with both additive and multiplicative effects on lung cancer risk [8]. In Ontario, occupational exposure to asbestos causes 630 lung cancers annually[4].

Occupational Disease Risks

The ODSS was used to detect risks of disease across hundreds of industry and occupation groups. Worker groups with higher risks of asbestos-related disease are highlighted here. The following results show the % increase in risk among groups of workers by industry or occupation compared to all other workers followed in the ODSS.

 

Asbestos mining

Asbestos mining was a small industry in Northeastern Ontario that predominantly operated from 1950-1978 [9-10]. Only a small group of these miners were captured in the ODSS. However, this small group demonstrated a dramatically higher risk of mesothelioma compared to other workers. This is expected as these workers had very high levels of exposure to asbestos. Lung cancer risk was also 393% higher for asbestos miners compared to other workers in ODSS.

Occupation Increased risk
Mesothelioma Asbestosis
Asbestos mining 2394%* 244%*
*Statistically significant (α=0.05)

 

Building maintenance and repair

Ongoing exposure to asbestos can occur among workers during the removal of asbestos-containing products, maintenance, renovation, or demolition of older buildings. Asbestos was used in many different construction materials including insulation, drywall, flooring, and cement. Insulators have a particularly high risk due to the prevalence and high levels of asbestos in insulation materials installed prior to 1990 [11]. Any workers working close to or with asbestos-containing materials are at risk of inhaling asbestos fibres.

In the ODSS, workers employed in construction trades occupations had the greatest risk of both mesothelioma and asbestosis compared to other workers. Insulating workers, pipefitters and plumbers, electricians and carpenters were among the occupations with highest incidence rates, but many more were at increased risk [12].

Occupation Increased risk
Mesothelioma Asbestosis
Insulating 2482%* 3420%*
Pipefitting and plumbing 488%* 718%*
Construction trades 138%* 264%*
Electricians and repairers 113%* 228%*
Carpenters and related 73%* 96%*
*Statistically significant (α=0.05)

 

Education services

Substantial amounts of asbestos were used in schools and university buildings to protect them from fires. Upon further analysis, the elevated risks in the education sector was largely associated with occupations involved in the maintenance of school buildings as opposed to teaching activities. Approximately 25% of mesothelioma and asbestosis cases were among school cleaning and janitorial staff, and approximately 40% of the cases were among construction and maintenance workers. Approximately 20% of the mesothelioma cases were observed among teaching and related staff.

Excess risks of asbestos-related disease among teaching staff may be due to exposure in schools, but some of those in teaching also had previous compensation claims indicating previous employment in other industries, such as manufacturing. However, the ODSS does not have complete work histories for all workers. A large US study saw similar increased risks among teaching occupations and suggested a previous history of employment in other occupations with probable asbestos exposure, environmental, residential, or spousal exposure may have contributed to their risk of mesothelioma [13].

Occupation Increased risk
Mesothelioma Asbestosis
Education services 32% 57%*
*Statistically significant (α=0.05)

  

Metal-related work

Increased risks of mesothelioma and asbestosis were observed for workers in metal-related manufacturing in the ODSS.

Working with metal products can involve extreme heat in many processes such as forming, shaping, and welding. Asbestos was a common insulating material used in machinery, equipment, and protective clothing for hot metalworking processes. Gloves, jackets, masks, and aprons contained asbestos as it was able to effectively protect workers from the extreme heat. Some metal products would also be finished with an asbestos-containing coating for durability and fire-proofing. Increased risks of mesothelioma and asbestosis have been reported in previous studies in metal-related industries and occupations, attributing this risk to asbestos in the work environment [14-16].

Industry or Occupation Increased risk
Mesothelioma Asbestosis
Primary metal manufacturing industries  76%* 139%*
Boilermakers, platers, and structural metalworking occupations 236%* 845%*
Welding and flame cutting occupations 65%* 33%
*Statistically significant (α=0.05)

  

Non-metal manufacturing

Increased risk of mesothelioma and asbestosis was also observed in the ODSS among workers in non-metal manufacturing. Those working in non-metallic mineral manufacturing industries are at particularly high risk as this group includes those that create asbestos-containing products. Asbestos-insulated heating equipment was used in various non-metal manufacturing industries as it aids in processing or shaping different materials. Chemical manufacturing industries also used similar heating equipment to produce chemical reactions. Asbestos-coated workbenches and protective clothing were also used as it is resistant to chemicals and does not dissolve in water nor evaporate [17].

Asbestos was also used as a filler in plastic products which would make the final products resistant to moisture, heat, acid, and electricity and was commonly incorporated into tools and cookware products. Exposure may also have occurred through asbestos contaminated talc which is used in the production of many products including ceramics, plastics, and paper materials [18].

Industry or Occupation Increased risk
Mesothelioma Asbestosis
Miscellaneous non-metallic mineral manufacturing industries 547%* 737%*
Industrial chemical manufacturing industries 286%* 466%*
Pulp and paper mill industries 17% 131%*
Plastics fabricating industries 46% 87%*
Clay, glass, and stone processing, forming, and related occupations 33% 101%*
*Statistically significant (α=0.05)

 

Motor vehicle manufacturing and repair

Asbestos-containing materials have historically been widely used in brake pads and other friction products used in motor vehicles, such as clutch pads. Although the manufacturing and use of asbestos-containing parts in the auto industry ceased in Canada in the 1980s, replacement parts would continue to be imported until the 2018 federal ban on the sale and use of asbestos products [19]. Older vehicles on the road still have asbestos-containing parts and occupational exposures during vehicle handling and repairing processes may continue to affect workers. In the ODSS, motor vehicle mechanics and repairers had a 33% increased risk of mesothelioma compared to all other workers.

Occupation Increased risk
Mesothelioma Asbestosis
Industrial, farm, and construction machinery mechanics  76%* 46%*
Mechanics and repairers  33%* 8%
*Statistically significant (α=0.05)

 

Exposure Controls and Risk Recognition

Regulations under environmental protection and management statute govern asbestos management and disposal in Ontario. These regulations provide requirements for how asbestos waste is managed once it leaves the workplace, regarding transportation, storage, disposal, labelling of containers, protective clothing and equipment for workers, and permitting and reporting requirements [20]. Environmental regulations focused on the transportation and disposal of asbestos containing materials define asbestos waste as “solid or liquid waste that contains asbestos in more than a trivial amount”. Under Occupational Health & Safety regulations, materials containing a minimum of 0.5% asbestos are considered to be asbestos-containing [20]. It is required that asbestos waste only be transported by a driver trained in asbestos waste management. There is also legislation that provides training and education for specific workers, such as those employed in the construction sector in Ontario [20].

Assessment of asbestos risk varies by jurisdiction in Canada. In Ontario, risk categories are defined by Type 1 (low risk), Type 2 (moderate risk), and Type 3 (high risk). There are a number of operations that fall under each type and details can be found in the Asbestos Management in Canada: Assessing the Need for a National Standard report [20].

The technical guideline for asbestos exposure management programs by the Government of Canada also provides a detailed description of risk levels and control measures [21]. There are federal and provincial regulations that outline approaches to control asbestos exposure based on the level of risk for workers which include [22-25]:

    • Engineering controls (i.e. using a vacuum with a high efficiency particulate air (HEPA) filter)
    • Administrative controls (i.e. providing change rooms and laundering services at the worksite)
    • Training staff
    • Exposure monitoring
    • Wearing personal protective equipment

There is also the Ontario Asbestos Workers Registry which tracks exposure to asbestos-containing materials so that asbestos-exposed workers can be identified and advised to receive a medical examination after 2000 hours of exposure (equivalent to one full year’s employment) [26].

Recently, the Lung Cancer Screening Pilot for People at High Risk was introduced in Ontario to be able to diagnose high-risk individuals with lung cancer early on, when treatment is more effective. Eligibility is currently based on age and smoking status, but occupational exposures, such as asbestos, is being discussed and may be considered in the future [27].

Canadians who are diagnosed with asbestos-related diseases (i.e. mesothelioma or asbestosis) that were exposed to asbestos in the workplace may be eligible for the workers’ compensation through the Workplace Safety and Insurance Board (WSIB) [28-29].

The 2018 ban on asbestos was a positive step to reduce the burden of asbestos-related disease but exposure to asbestos in existing buildings and previously manufactured products remain an important concern for some workers. Asbestos-related disease will continue to be diagnosed today as a result of past exposure due to the long period between exposure to asbestos and disease onset. Continued awareness and monitoring of asbestos exposure and asbestos-related disease will continue to be important for decades to come to keep workers safe.

References
  1. Canadian Centre for Occupational Health and Safety. Asbestos – control strategies for workplaces. (2021).
  2. International Agency for Research on Cancer. IARC monographs on the evaluation of carcinogenic risks to humans. Volume 100C. A review of human carcinogens. Part C: Arsenic, Metals, Fibres and Dusts. Lyon: International Agency for Research on Cancer, 2012.
  3. Carex Canada. Asbestos profile. (2021).
  4. Occupational Cancer Research Centre. Burden of occupational cancer in Ontario. (2017).
  5. Occupational Cancer Research Centre. Mesothelioma. (2020).
  6. Cancer Care Ontario (Ontario Health). Mesothelioma cases in Ontario continue to rise. Ontario Cancer Facts.(2015).
  7. Garcia-Gomez M, Menendez-Navarro A & Castaneda L. Asbestos-related occupational cancers compensated under the Spanish national insurance system, 1978-2011.Int J Occup Environ Health.2015 Jan-Mar; 21(1): 31–39.
  8. Nielsen LS, Baelum J, Rasmussen J, Dahl S, Ege Olsen K, Albin M, Hansen NC & Sheron D. Occupational asbestos exposure and lung cancer—a systematic review of the literature. Arch Environ Occup Health, 2014;69(4):191-206. doi: 10.1080/19338244.2013.863752.
  9. Dupré JS, Mustard J, Uffen RJ. Report of the Royal Commission on matters of health and safety arising from the use of asbestos in Ontario – Vol 2. Toronto, ON: Ontario Ministry of the Attorney General 1984.
  10. Natural Resources Canada. Canadian Minerals Yearbook. Ottawa, Ontario: Natural Resources Canada (NRCan). 1950-1978.
  11. Government of Canada. Asbestos in the home (infographic). (2018).
  12. DeBono NL, Warden H, Logar-Henderson C, Shakik S, Dakouo M, MacLeod J & Demers PA. Incidence of mesothelioma and asbestosis by occupation in a diverse workforce. Am J of Ind Med, 2021, 64(6): 476-487.
  13. Cocco P, Dosemeci M. Peritoneal cancer and occupational exposure to asbestos: Results from the application of a job‐exposure matrix. Am J of Ind Med. 1999 Jan;35(1):9-14.
  14. Macleod JS, Harris MA, Tjepkema M, Peters PA, & Demers PA. Cancer risks among welders and occasional welders in a national population-based cohort study: Canadian Census Health and Environment Cohort (CanCHEC). Saf Health Work, 2017, 8(3).
  15. Goldberg M, Imbernon E, Rolland P, et al. The French National Mesothelioma Surveillance Program. Occup Environ Med. 2006;63(6):390-395.
  16. Rolland P, Gramond C, Lacourt A, et al. Occupations and industries in France at high risk for pleural mesothelioma: A population-based case-control study (1998-2002). Am J Ind Med. 2010;53(12):1207-1219.
  17. Canadian Centre for Occupational Health and Safety.  Asbestos – What is… (2021).
  18. International Agency for Cancer on Research. Carbon Black, Titanium Dioxide, and Talc. IARC Monographs on the Evaluation of Carcinogenic Risk to Humans Volume 93.
  19. Workplace Safety & Prevention Services. Canada’s new asbestos ban; a call to action for workplaces. (2017).
  20. CSA Group. Asbestos management in Canada: assessing the need for a national standard. (2021)
  21. Government of Canada. Technical guideline to asbestos exposure management programs. (2021)
  22. Infrastructure Health & Safety Association. Asbestos Controls for Construction, Renovation, and Demolition. (2006).
  23. Ontario Asbestos Regulation.  Asbestos: FAQs. (2011).
  24. Ministry of Labour, Training, and Skills Development. History of Asbestos Regulation. (2011)
  25. Minister of Justice. Canada Occupational Health and Safety Regulations.(2021).
  26. Ministry of Labour, Training and Skills Development (2011).
  27. Cancer Care Ontario (Ontario Health). Lung cancer screening information for healthcare providers. (2021).
  28. Cancer Care Ontario (Ontario Health). People with mesothelioma: getting workers’ compensation. (2021)
  29. Workplace Safety and Insurance Board. Asbestosis. (2021).

Surveillance Bulletins

The Occupational Disease Surveillance System (ODSS) Surveillance Bulletins provide summaries of occupational exposures and disease risks across different industries and occupational groups. The aim of these bulletins is to report on high risk occupations and industries and specific exposures detected through occupational disease surveillance. At this time the ODSS includes workers from 1983-2014 and follows their health outcomes until 2016. This bulletin reflects only the diseases currently tracked within the ODSS. The system is updated and expanded on an ongoing basis.

More information about the ODSS including data sources, methods and detailed results can be found at ODSP-OCRC.ca and OccDiseaseStats.ca.