Millions of Canadians exposed to cancer-causing agents at work

More needs to be done to identify risks, reduce workers’ exposure

Millions of Canadians exposed to cancer-causing agents at work

In 1998, Bruce Ritchie, a district fire chief with the Toronto Fire Services, died of renal cell cancer at 53. He had worked for the fire service for more than 25 years. Initially, an arbitration board had determined his death was the result of natural causes, but that decision was overturned by the Ontario Superior Court, which said that the firefighter’s cancer could not be considered a normal disease and had resulted from “multiple exposures to toxic substances” while performing his job.

A study released in March 2018 by the University of the Fraser Valley in Abbotsford, B.C., found that cancer was the leading cause of death among firefighters. The study, based on 10 years of health and injury data, showed cancer had caused more than 86 per cent of firefighter fatalities — more than traumatic injuries. Researchers noted firefighters are regularly exposed to concentrated carcinogens in the air, soot and tar at fire sites. 

Cancer is a leading cause of illness and death among many types of workers. Fortunately, research is constantly extending the body of knowledge for carcinogenic agents. OHS professionals have long been aware of some of the most harmful workplace carcinogens, such as asbestos, and researchers are learning more all the time about what types of materials, and types of work, cause cancer. It is essential that employers use this new understanding to reduce the exposures that cause work-related cancers.

“We know reasonably well, from different studies done in other countries, as well as smaller studies in Canada, that between two and 10 per cent of cancers are caused by occupational exposure,” says Trevor Dummer, associate professor at the Centre of Excellence in Cancer Prevention, School of Population and Public Health, at the University of British Columbia in Vancouver. “If we know a lot about the types of exposures that cause cancer, we should be able to act on it.” 

Occupational cancer is cancer caused wholly or partly by exposure to a cancer-causing agent at work. According to a recent study done by Cancer Care Ontario and the Occupational Cancer Research Centre (OCRC) titled Burden of Occupational Cancer in Ontario, most occupational cancer cases in the province are caused by four materials: solar ultraviolet (UV) radiation, crystalline silica, asbestos and diesel engine exhaust.

Depending on exposure levels, sun exposure can cause melanoma and non-melanoma skin cancers. Accumulative exposure, which outdoor workers are likely to have, causes non-melanoma skin cancer. Sun exposure has also been associated with cancers of the lip and those in and around the eye.

“Many times, there are a number of different causes for certain cancers. But with skin cancer, there’s mostly just the one, which is sun exposure, so that makes it a bit of a unique carcinogen in the workplace. And though in Canada, we remain covered up most of the year, in the summertime we generally aren’t, and people get a lot of exposure in the summer,” says Cheryl Peters, co-principal investigator at Vancouver-based Carex Canada and research scientist at Alberta Health Services in Calgary.

According to the OCRC, about 1.5 million Canadians are exposed to solar ultraviolet radiation at work. The highest exposure occurs in construction, followed by farming and building care and maintenance.

About 380,000 Canadian workers are exposed to silica, according to Carex Canada. The industry with the highest exposure is construction (trade contractors and building construction). Silica is a component of soil, sand and rocks and is a very common mineral. Crystalline silica becomes a dust as a result of many industrial processes.  

“When it’s ground up really fine and is a very small size fraction, as can happen if you’re cutting up concrete or doing sandblasting, for example, it can get deep within the lungs and cause lung cancer,” Peters says. 

The term asbestos refers to six naturally occurring, fibrous silicate minerals. While the Canadian government has banned its use, asbestos is still present in building and other products. Negative health effects result from inhaling fibres released from asbestos-containing products. The worker’s family members are also at risk from “take-home” exposure to asbestos, through exposure to the worker’s clothing. The International Agency for Research on Cancer (IARC) classifies asbestos as a known carcinogen.

The main health effects of asbestos are mesothelioma (cancer of the protective lining of many internal organs) and lung, laryngeal and ovarian cancer. About 152,000 Canadians are currently exposed to asbestos in their workplaces. Exposures affect workers mostly in manufacturing and construction.

“In construction, you’re looking at people working in renovations and demolition of older buildings, where there’s a legacy of asbestos-containing building materials,” says Larry Stoffman, an independent occupational health and safety consultant based in Vancouver. 

Diesel engine exhaust is a mixture of gases, vapours, aerosols and particulate substances produced from burning diesel fuel. Diesel engines are used in such vehicles as trains and ships, and in industrial equipment, such as those used in mining and construction. Diesel exhaust is classified as a known carcinogen: long-term exposure increases the risk of lung cancer and possibly bladder cancer.

About 897,000 workers in Canada are exposed to diesel engine exhaust, according to Carex Canada. The greatest exposures are in truck transportation and in transit and ground passenger transportation. Workers are most at risk in areas where diesel-powered vehicles (such as trucks, trains and construction vehicles) are used and where diesel exhaust can accumulate (such as in warehouses, bus depots and mines). The highest exposure is in transportation and warehousing.

These four substances have long been known to cause cancer. Other established causes of cancer that can affect workers are tobacco smoke, radon, arsenic, benzene and welding fumes, chromium (VI) compounds and nickel compounds.

Workers are exposed to carcinogenic substances in many industries. One industry that presents this hazard on a major scale is construction. There are a number of different exposures, depending on the job. Workers are exposed to diesel engine exhaust, silica, asbestos, paint and solvents and, because they often work outside, the sun. 

Agricultural workers are also among those most exposed to cancer-causing substances. The most important factor here is the amount of time spent outdoors, which increases the risk of skin cancer. Agricultural workers also use chemicals, such as pesticides, that are either known or suspected carcinogens.

Other industries that have high rates of cancer-causing exposures are manufacturing (chemicals, metals, solvents, dusts and radiation), mining, forestry, custodial care (cleaning materials) and potentially certain service industries, where workers are exposed to hazards such as second-hand cigarette smoke and traffic fumes. 

In recent years, studies have also led researchers to recognize night shift work as a significant carcinogen. In fact, IARC has ranked it as “probably carcinogenic to humans.”
“It doesn’t definitely cause cancer in humans, but there is accumulating evidence that it could increase the risk of breast cancer if you work night shifts or rotating shifts for long periods of time,” says Peters.

Working night shifts interferes with the body’s circadian rhythm, the body’s biological clock, disrupting genes that regulate the production of a protein known to promote cancer growth. Studies have shown an increased risk of breast cancer among long-term night shift workers, in contrast with people who do not work at night. Working night shifts has also been associated with ovarian cancer and melanoma skin cancer.

Industries with the highest number of people working night shifts include trades, health care and social assistance, accommodation and food services and manufacturing. According to Carex Canada, about 1.8 million workers in Canada worked a regular night or rotating shift schedule in 2011.

Employers can do a lot to protect workers from carcinogenic hazards by making sure they do their due diligence and follow regulations, Peters says. They should check with their provincial OHS regulator to discover the exposure limits for any possible carcinogens they use in their workplace and the exposure control plans they are required to have in place.
It’s also important, she adds, for employers to establish a safety culture so workers feel able to speak up about a substance or practice they think may be hazardous.

“Workers have to feel safe that they can go to their employers and say, ‘I think we have a problem.’ And they need to know there’s a safety culture there and their employer will take them seriously and will look into it. There are a lot of resources available to employers to help them protect their workforce,” Peters says.

Reducing worker exposure to carcinogens must be seen as a multi-level responsibility, Dummer says. At the top, politicians and industry leaders need to create health and safety guidelines that deal with each individual cancer-causing agent in an appropriate way. Employers need to manage their workplaces to control exposures properly, according to the hierarchy of controls. They must also educate their workers to make sure they are aware of the risks of the carcinogenic materials they are using, and they must provide workers with appropriate guidelines on how to avoid those risks. 

To reduce exposures effectively, Stoffman says, employers need to act on the information we have now. They should have a good management system in place, which starts with conducting a rigorous, thorough audit, one aimed at listing all relevant exposures that may occur in the work environment.

“As an employer, you need to do an inventory of cancer-causing materials that you may be using. If you use any, then you need to look for the feasibility of eliminating the use of that material,” he says. “Where you cannot eliminate something, you still need to have an active procurement policy and supply chain management. Then, as best practices evolve or people in some other part of the world come up with an alternative, you implement that alternative. In the meantime, you use the best kind of engineering controls to make sure people aren’t exposed to the hazard.”

One big obstacle to reducing worker exposure to carcinogens, Peters says, is that new exposures are always appearing on the scene — a result of new technologies, such as 3D printers, and new workplace procedures. It can be difficult for researchers to keep up with the changes and be able to specify safe exposure levels.

“We have new chemicals and new nanotechnologies becoming available all the time, and we don’t necessarily have the research to know what a reasonably safe level is for workers to be exposed to,” she says.

Another challenge to reducing exposures, Stoffman says, is that implementation of prevention strategies is sporadic and inconsistent, and regulatory requirements are not always vigorously enforced. According to legislation across Canada, employers have a general duty to ensure workers are not exposed to hazardous substances. But in fact, the requirement on employers to minimize or eliminate workers’ exposure to a very serious hazard is not being fulfilled except by those who have the very best practices.

“There isn’t really a lot of work being done to eliminate an exposure unless there’s a significant action taken at the government level to actually ban the substance and its use, as was recently done with asbestos,” Stoffman says. “So, we should have much more robust prevention programs that would look at eliminating hazards where you can, including exposure to cancer-causing material.”

One major obstacle to reducing workplace cancers, Dummer says, is the large number of different exposures that are known to, or that may, cause cancer, as identified by the IARC.

“So the challenge is making sure we have policies and legislation appropriate to the carcinogenic hazard.”

The good news, Dummer says, is that research done in recent years has led to a better understanding of the problem. He points to the Burden of Occupational Cancer in Ontario study, which produced a lot of data that will prove useful for researchers and organizations across Canada trying to reduce on-the-job exposures to carcinogenic hazards.

“As we’ve gone forward, we’ve become better at understanding what all these different exposures are. And we’ve started to understand more about the magnitude of the problem,” he says. “And by quantifying it better, we’ve made it quite clear that occupational cancer should be avoidable. It should be preventable.”  

Linda Johnson is a Toronto-based freelance journalist who has been writing for COS for eight years.

This article originally appeared in the February/March 2019 issue of COS.