The US had just two 500-foot smokestacks in 1970 and more than 180 by 1985 to dilute pollution

In an effort to mitigate local air pollution, American power companies constructed towering smokestacks, effectively releasing sulfur dioxide and nitrogen oxides into higher winds. Unfortunately, this practice contributed to acid rain, harming ecosystems throughout North America. In response, Congress revised the Clean Air Act to restrict the use of tall stacks and improve emission control by emphasizing source capture instead.