New Study Challenges Arsenic Risks from Quebec's Horne Smelter

A new study funded by the Horne Smelter in Rouyn-Noranda, Quebec, has found that local residents face no greater arsenic exposure risk than other Canadians. The findings challenge earlier concerns about health dangers linked to the facility’s emissions. Researchers analysed urine and nail samples from 245 participants, including 81 children and 164 adults. The study concluded that diet—not proximity to the smelter—was the primary source of arsenic exposure. Foods like rice and seafood contributed more to arsenic levels than living near the Horne Smelter. According to the chief toxicologist, arsenic concentrations among Rouyn-Noranda residents matched or fell below the national average.

This contradicts a 2019 biomonitoring report, which found arsenic levels in fingernails of Notre-Dame neighbourhood residents four times higher than those in Amos, a control group. That earlier study also noted higher concentrations in children and a link between exposure and distance from the smelter.

Despite a drop in emissions—from 73 ng/m³ in 2022 to 40.9 ng/m³ in 2025—the smelter still exceeded Quebec’s provincial standard by 13.6 times. Public health authorities had previously flagged elevated cancer risks tied to the facility’s arsenic output.

Glencore Canada, which operates the smelter, called the new findings reassuring. The company stated that the results confirm the Horne smelter poses no additional risk to public health. The study shifts focus away from the smelter as the main source of arsenic exposure in Rouyn-Noranda. Instead, dietary habits appear to play a larger role in arsenic intake. However, the facility’s emissions remain significantly above provincial limits, leaving questions about long-term monitoring.