The Brief Northern Iron, a longtime foundry in St. Paul, will close in December after more than 100 years in business. The closure follows state action over air pollution concerns, including soot and lead emissions. A century-old foundry in St. Paul is shutting down, leaving neighbors relieved after years of concerns about air pollution. The decision comes after state regulators moved to pull the company’s air permit due to concerns about air pollution, including elevated levels of lead. State regulators also pointed out that Northern Iron refused to turn over information about its air emissions, something they called "extremely rare."