This is in my home town and my first job out of high school was giving tours of the various mining sites for tourists. I can tell you the official story was at

This is in my home town and my first job out of high school was giving tours of the various mining sites for tourists. I can tell you the official story was at the time it was believed that if you send the pollution high enough, it wouldn’t lead to so much damage. For context, prior to the super stack, ore was refined by burning huge fields (the size of football fields) of crushed ore to separate the metals. The result is why Sudbury is known for barren black rock. We later won international awards for our regreening efforts. Does that mean I think the stack was a good idea or fair to the world? No. But I do think it was understandable. Today, something like 99% of the “smoke” is actually steam, because they’ve done such a good job of filtering the smoke that they needed to pump steam in to get it to reach the top of the stack. They’ve also been talking about decommissioning and tearing it down for years, but it’s somewhat beloved as a major landmark.