A copper smelter in northwest Quebec will be permitted to release 15 nanograms of arsenic per cubic metre of air -- five times the provincial norm -- Quebec's environment minister said Monday.

The factory in Rouyn-Noranda, Que., which has been in operation since 1927 and employs around 650 people, has been a cause for serious concern in the region after studies have shown that residents of the city have higher rates of lung cancer than the provincial average. Owned by Switzerland-based Glencore, the smelter is currently allowed to emit 100 nanograms of arsenic per cubic metre of air -- 33 times the provincewide standard.

Environment Minister Benoit Charette travelled to the town Monday and said the 15-nanogram cap recommended last week by public health would be the new goal the company must reach within five years.

"We are turning the page on a certain era today," Charette told reporters.

"It's impossible to be at three nanograms (per cubic metre of air) within five years in the most-affected sector," Charette said about the district closest to the copper factory. But he said it is possible for the air to be at three nanograms -- the provincial norm -- "on the majority" of Rouyn-Noranda's territory. "And that's good news."

The new limit, he said, will be included in the updated certification for the company.

"If Glencore fails to comply with government requirements, the Horne smelter will have to close its doors," Charette said.

Meanwhile, online and in-person consultations with Rouyn-Noranda residents will take place in the following weeks, he said. "We want to know if the population feels listened to with this proposition."

Glencore Canada welcomed the new cap on Monday, saying it "remains committed to achieving the most ambitious goals possible."

"Our teams and our partners are fully mobilized around a major transformation project, which will make the Horne smelter one of the most efficient in the world," Cindy Caouette, a spokesperson for the copper factory, said in a statement.

"We are continuing our efforts to meet the requirements that will appear in our next certification."

But Dr. Claudel Naud-Bellavance, a family doctor who grew up and works in Rouyn-Noranda, said Charette's decision to follow the public health recommendation is disappointing.

"Public health said that 15 nanograms or less were deemed safe … so everything above … isn't safe, and it's not reasonable to accept that the four next years, the five next years will be above 15 nanograms," Naud-Bellavance said in an interview Monday.

"Five years, it's long in the life of a child."

Studies by Quebec's public health institute estimated that if the concentration of arsenic in the smelter's emissions wasn't reduced, between one and 14 additional residents would develop lung cancer by 2040. The new arsenic emissions cap, according to the Institut national de sante publique du Quebec, will help to reduce the risk of developing lung cancer to a "level deemed acceptable in similar North American contexts."

According to a report from Radio-Canada, lung cancer rates in Rouyn-Noranda between 2013 and 2017 were 140.3 cases per 100,000 people, compared to the provincial average of 107.7 cases per 100,000 people.

Boileau has said that the new emissions cap would "strongly protect the health of unborn babies and young children."

Charette said the new agreement between Quebec and the factory will also include updated emissions limits on nickel, sulfur dioxide, lead and cadmium.

- This report by The Canadian Press was first published on Aug. 15, 2022. This story was produced with the financial assistance of the Meta and Canadian Press News Fellowship.