Most people wouldn't know if anything bad was lurking in the water, air or soil unless it was the size of a large alligator and grabbed their leg.
All that crap is still there, it didn't magically dissipate into deep space. The DDT is still there, the mercury is still there. There's stuff in Colorado's water supply from mining a hundred years ago.
On July 14, 1991, a train derailed 45 miles north of Lake Shasta, CA, dumping a pesticide into the Sacramento River. It killed every living thing in the river.
New York Times article, 7-22-1991 If you have children, they were born with a couple of hundred foreign chemicals in their body.
Sue