I used to work as a contractor for an environmental remediation firm. All the waterways that you joke about not swimming in are actually full of some awful carcinogen. Old industrial plants dumped awful chemicals for years and years. Some of these issues are being slowly addressed, but regulation is always well behind the science. But often, if the liability is significant enough, companies will spend millions of dollars a year to kick the can down the road doing studies and monitoring so that they can avoid what would be hundreds of millions to actually remediate the problem.