Quebec study identifies tools, jobs with high risk of silica exposure

Study suggests underground workers, tunnel drillers at higer risk

Researchers at Montreal-based L'Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST) have developed a database on occupational exposure for construction workers, which identifies tasks and tools that most expose workers to silica, as well as job designations that create high risk of exposure.

The IRSST analysis identifies the tasks and tools that may expose workers to silica at levels above the allowed exposure limit by regulations. These tasks and tools include sawing masonry pieces with portable masonry saws, roughening (bushhammering), cracking masonry pieces (hammer drills and jackhammers, on concrete or ceramic), tunnelling and grinding joints of brick or stone.

The study also suggests employees working underground as well as operators of heavy equipment used for drilling tunnels have a higher risk of exposure to silica concentrations exceeding the level prescribed by Quebec regulations, according to a report from the IRSST. Cement finishers, bricklayers, drillers, semi-skilled workers and skilled operators of heavy equipment used for milling roads are another group at risk of exposure to levels above or near to the prescribed level.

Crystalline silica is a basic component of soil, sand, granite and many other minerals. Prolonged inhalation of this substance at high concentrations can cause a lung disease called silicosis. This substance is also known to be carcinogenic when inhaled in the workplace, and deaths have been associated with exposure to silica, the IRSST said in its report.

The presence of silica in several of the basic materials used in the construction sector makes it difficult to use substitution as an approach to eliminating hazards at source, the IRSST said.

Technical means of controlling exposure, such as sprinkling and exhaust ventilation promote a significant decrease in the concentration of silica in the air, but they do not comply with exposure limits, according to data collected by the IRSST. Researchers recommend optimizing these means, complemented by the use of respiratory protective equipment, improving the tuning and maintenance of tools and equipment, and adopting work methods that limit the emission of dust.

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