Sawing masonry pieces with portable masonry saws was identified as among the most hazardous tasks.

IRSST Finds Tunnel Drillers at Highest Silica Risk

The Montreal research agency's database identified a group of skilled workers that includes bricklayers and heavy equipment operators as the second group exposed.

A large database of Quebec construction workers' occupational exposures to silica has been completed by researchers at the Institut de recherche Robert-Sauvé en santé et en sécurité du travail and pinpoints the tasks and tools that expose workers to the highest risk, according to its June 8 announcement.

Underground workers and workers who operate heavy equipment for drilling tunnels are at the highest risk of all, the analysis indicated. As for tasks and tools, sawing masonry pieces with portable masonry saws, roughening (bushhammering), cracking masonry pieces (hammer drills and jackhammers, on concrete or ceramic), tunneling, and grinding joints of brick or stone are the most hazardous.

Cement finishers, bricklayers, drillers, semi-skilled workers, and skilled operators of heavy equipment used for milling roads are the group with the second-highest exposures on average at levels above or near to Quebec's prescribed limit, the database shows.

Discussing exposure controls, one of the lead researchers on the project said substitution has limited use as a strategy because silica is present in so many basic construction materials. "The technical means of controlling exposure, such as sprinkling and exhaust ventilation, are well known," said researcher Chantal Dion. "Although they promote a significant decrease in the concentration of silica in the air, they do not, according to data collected, comply with exposure limits. What is required, therefore, is to optimize these means, complemented by the use of respiratory protective equipment, improve the tuning and maintenance of tools and equipment, and adopt work methods that limit the emission of dust."

The research report is available in French at

Founded in 1980, IRSST is a private, nonprofit research agency whose board is divided equally between union and employer representatives. The Commission de la santé et de la sécurité du travail (CSST) provides most of the institute's funding from contributions it collects from employers.

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