Canadian Occupational Safety

14 www.cos-mag.com Canadian Occupational Safety n 1998, Bruce Ritchie, a dis- trict 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 arbitra- tion 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 fatali- ties — 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 work- ers. Fortunately, research is constantly extending the body of knowledge for carcinogenic agents. OHS profession- als have long been aware of some of the most harmful workplace carcino- gens, 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 understand- ing to reduce the exposures that cause work-related cancers. "We know reasonably well, from different studies done in other coun- tries, 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 Pre- vention, School of Population and Public Health, at the University of British Columbia in Vancouver. "If we know a lot about the types of expo- sures that cause cancer, we should be able to act on it." 4 LEADING HAZARDS Occupational cancer is cancer caused wholly or partly by exposure to a cancer-causing agent at work. Accord- ing 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. Accu- mulative 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 can- cers. 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-prin- cipal 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 con- struction, followed by farming and building care and maintenance. About 380,000 Canadian work- ers are exposed to silica, according to Carex Canada. The industry with the highest exposure is construc- tion (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 asbes- tos are mesothelioma (cancer of the protective lining of many internal organs) and lung, laryngeal and ovar- ian 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-contain- ing building materials," says Larry Stoffman, an independent occupa- tional health and safety consultant based in Vancouver. Diesel engine exhaust is a mixture of gases, vapours, aerosols and par- ticulate 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 classi- fied 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 trans- portation and in transit and ground passenger transportation. Workers are most at risk in areas where die- sel-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. Millions of Canadians are exposed to cancer-causing agents at work. More needs to be done to identify these risks and reduce workers' exposure. By Linda Johnson

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