Acid rain was an environmental hyperbole covering the effect of sulfur dioxide and nitrogen dioxide gasses being washed out of the atmosphere by rainfall. Downstream from coal-fired power generation and metal reduction processes, these gasses were part of the gas stack chemistry; sourced as minor constituents of the process coal. The pollutants were only measured in ppm quantities in major smoke stacks … famously I measured 200 ppm in the air from the Inco Superstack, measured over Toronto air space. Ontario has no coal plants or stacks left after environmentally forced decommissioning.
