The EPA library example photos on Cleveland from the 1970s goes hard, though with decades of improvement I can report there is no thick orange haze, and the auto body retaining wall on the river is gone,

the Cuyahoga national Park is an example of what collection action can be done to regenerate an ecology.

The Cuyahoga river has otters again. That would have been impossible throughout the 20th century due to pollution.

But through political organizing grass roots to the top, it got cleaned.