As a bricklayer and someone who has been around concrete and cement for much of his working life in several Canadian provinces, John Ferreira has seen and dealt with a lot of dust.
Ferreira, now a health and safety co-ordinator for LIUNA Local 183 in Toronto, one of the largest construction locals in North America, remembers doing cement-finishing work at construction sites in Toronto decades ago, where dust was flying everywhere during the grinding, blasting or chipping of concrete.
“When you walk in the stairwells of buildings downtown, you see exposed concrete. It looks beautiful, but before that it was rough concrete that someone had to grind. Someone had to breathe that dust from the grinding and that was really bad for his lungs,” Ferreira says.
Now, in his role as safety co-ordinator with the union, Ferreira says procedures to mitigate dust have improved, but he’s still seeing a lot of it.
“The problem is going to persist in the future because Toronto is booming … you’re going to see a lot of dust,” Ferreira says.
A common mineral, crystalline silica is a basic component of sand, soil, mortar, bricks, tiles and rocks such as granite and quartz. But silica dust and particles are a potential hazard on jobsites, and experts are sounding alarm bells about it.
Breathing silica dust and particles into the lungs often enough and long enough can lead to a disease called silicosis, which is disabling, and can lead to lung disease and possibly lung cancer.
Dr. Paul Demers, a cancer specialist with expertise in hazardous workplace exposures, led a recent study looking into workplace carcinogens and how to prevent exposure to them.
Among the study’s key findings is that the workplace carcinogens with the highest number of Ontario workers exposed included crystalline silica.
“Long-term exposure can cause lung cancer, lung disease, scarring of the lungs. It’s a problem that’s been around a long time — but there is often a lack of precautions taken to prevent those exposures,” says Demers, who is director of the Occupational Cancer Research Centre in Toronto, which conducts research on the causes and prevention of occupation-related cancers and is jointly funded by Cancer Care Ontario, the Ontario Ministry of Labour, and the Canadian Cancer Society.
“It’s not rocket science to reduce levels of dust. But in the rush to get construction done we’re experiencing a lot of people getting exposed … It’s not an uncommon exposure,” Demers says, referring to silica.
Silica is used widely in industrial and construction activities. But health hazards arise when products containing it are subjected to activities such as grinding, sandblasting, crushing, chipping, jackhammering or drilling at construction sites.
These activities produce a dust that becomes airborne and is breathed in by workers close to the source.
According to Demers’ 2017 study, Burden of Occupational Cancer in Ontario: Major workplace carcinogens and prevention of exposure, it’s estimated that 142,000 workers in Ontario are exposed to crystalline silica, which leads to almost 200 lung cancer cases each year.
The sun, asbestos and diesel engine exhaust are the other occupational cancer-causing agents with the highest number of workers exposed and the largest impact on the cancer “burden,” according to Demers’ study.
The report uses estimates because across Canada there is no “reliable, routinely collected” data on the number of cancer cases linked to exposure to workplace carcinogens, Demers’ study notes.
The report chose workplace carcinogens where 5,000 or more workers in Ontario are exposed. “Definitive human carcinogens” — defined as such by the World Health Organization’s International Agency for Research on Cancer’ monographs program, a program that evaluates carcinogenic risks — were also prioritized for the report.
The prevalence of exposure to carcinogens in Canadian workplaces was determined based on estimates developed by CAREX Canada, a research project that generates a national surveillance program to monitor exposures to cancer-causing agents.
Demers’ report, funded with a $1-million grant from the Canadian Cancer Society’s research institute, looked at exposures to work-related carcinogens from 1961 to 2010 that could have contributed to newly diagnosed tumour cancers in 2011.
The report includes recommendations calling for the creation of registries to track worker exposure to carcinogens.
Demers says construction sites, particularly in Toronto where condominium and office tower projects are constantly on the go, can be challenging when it comes to mitigating silica exposure.
“With a factory or someplace stationary, you can establish good procedures because those areas are easier to regulate than construction sites,” says Demers.
“With construction sites, new sites are always being developed and the site itself is constantly evolving as construction goes through various stages of operations,” he says.
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Standard procedures to mitigate silica dust at construction sites include spraying water where a task — chipping or grinding concrete, for example — is taking place.
In B.C., employers have free access to a Silica Control Tool, a database that uses about 4,500 silica exposure measurements from all over the world, collected from scientific literature, government databases and private companies that donate data.
The database takes into account a wide range of construction scenarios and is a joint effort between the B.C. Construction Safety Alliance, an industry association, the University of British Columbia and Work Safe B.C., the local regulator and enforcer of occupational health and safety in the province.
“We have models to tell us what type of exposure to expect for different activities. Construction companies can enter details about what they are doing and come up with a (silica mitigation) plan,” says Melanie Gorman Ng, a senior research scientist with the B.C. Construction Safety Alliance, and someone who worked on putting the database together.
Launched in the spring of 2017, the database has been used by more than 2,000 employers, including municipalities, school boards and construction firms.
It’s not the total amount of silica that is key, but rather the “respirable” amount — the actual particles that get into the gas exchange region in the lungs when you breathe silica in, Gorman Ng explains.
In B.C., the limit is .025 milligrams of respirable crystalline silica per cubic metre of air. In Ontario, it’s 0.10 milligrams per cubic metre for quartz-related materials under the province’s Occupational Health and Safety Act.
In Ontario, the responsibility falls on those running construction sites to ensure the proper steps are being taken to reduce the potential hazard silica poses, says Michael Russo, manager of quality assurance and projects with the Infrastructure Health and Safety Association (IHSA), a not-for-profit organization.
He points out that over time, industries have built enough data and intelligence to know that certain tasks can generate excessive levels of silica dust.
“And so, in those particular circumstances our efforts are better spent focusing on the precaution. So, cutting concrete dry for example is probably not a good practice, so you want to focus on precautions to mitigate risk,” Russo adds.
At the end of the day, Ontario’s Occupational Health and Safety Act stipulates that everyone has a role in health and safety, including unions, workers and construction companies, Russo points out.
The IHSA is of the opinion that when it comes to health and safety, workplaces should adopt a “holistic approach” — which entails implementing a “health and safety management system” so that potential hazards such as silica are not addressed on a “piecemeal basis,” Russo says.
Procedures could include the use of local exhaust ventilation, putting up barriers to keep bystanders clear where dust might be generated or closing these areas off completely, only allowing access for workers involved in the task, Russo says.
Proper respiratory protection — masks — are also part of the safety management system, but as a last resort and not to be relied on as the only precaution, Russo says. The Ministry of Labour, which enforces guidelines for worker safety in the province, should also be viewed as a last resort when it comes to addressing silica mitigation, Russo adds.