Fonderie Horne accounts for 87% of Quebec's arsenic emissions, rising trend alarms researchers

The Horne smelter in Rouyn-Noranda accounts for 87 per cent of all arsenic emissions released by industries in Quebec, according to data compiled by RevolvAir, an organization dedicated to raising public awareness about air quality issues.

Of the 16.3 metric tons of arsenic released by industries in 2024, 14 metric tons came from the Horne smelter—owned by multinational Glencore. The foundry reported discharging 20 metric tons of arsenic in 2025, a jump of 6 metric tons from 2024. While 2025 data remains incomplete, the upward trajectory has alarmed environmental researchers.

Guillaume Simard, founder of RevolvAir and a teacher at Cégep de Sainte-Foy, notes that emissions from the Horne smelter have been rising in recent years. "If we round to the nearest whole number, it's around 12 metric tons in 2023, 14 metric tons in 2024, and in 2025, the latest data indicates roughly 20 metric tons," Simard explained. However, he also emphasizes that emissions have decreased significantly over three decades—the smelter emitted 100 metric tons in 2001.

The Horne smelter is also the primary source of arsenic emissions in Canada. Of 33 metric tons emitted by industrial facilities in Canada in 2024, 14 came from the Rouyn-Noranda facility.

RevolvAir, founded in 2022, develops air quality monitoring stations and works to translate complex environmental data into accessible formats for schools, municipalities and citizens. According to a 2021 Health Canada report, air pollution in Quebec is linked to 4,000 premature deaths per year and costs the healthcare system more than $30 billion annually.