Which problem was particular to smelting operations in sudbury ontario

The problem particular to smelting operations in Sudbury, Ontario is Acid Rain.

Sudbury or officially named as Greater Sudbury is the largest city in Northern Ontario, Canada. In mid of 20th century, the city suffered a near-total loss of native vegetation. They suffer air pollution and then acid rain. Acid rain was caused by the construction of the Inco Superstack in 1972.