MONTREAL — Aluminum giant Rio Tinto Alcan is studying its options, including whether to seek the reopening of collective agreements, at it moves to reduce costs over the next 12 to 18 months to offset the challenges of a tough global market for the metal.The Montreal-based aluminum division has provided cost reduction targets to each of its facilities around the world, but won’t release them publicly.Rio Tinto Alcan met Thursday with Canadian Auto Workers union representatives to discuss employee concerns about the weak global aluminum market, cost-reduction efforts and the planned closure this year of its cathode facility in Arvida. About 50 employees affected by the closure will be relocated to other facilities.The meeting followed a general meeting of union employees about 10 days ago.[np-related]Company spokeswoman Claudine Gagnon says Rio’s facilities in Quebec and elsewhere around the world have to reduce costs. The Arvida facility also faces an additional challenge because it will no longer meet Quebec’s environmental standards as of 2015.She said the company hasn’t made any decisions about seeking the reopening of some collective agreements, but it is one of the options being considered. Other options include achieving savings by changing work rules.CAW officials couldn’t be immediately reached for comment, but Marc Maltais of the United Steelworkers in Alma, Que., said the union has yet to meet with Rio about its demands.While the union recognizes the difficulties facing the global aluminum industry, he said cheap energy makes Quebec one of the lowest cost operations in the world.