Leave it to “science” to pick and choose what history is important in these findings.

Prior to 1948 there was no wastewater treatment funding so Nationwide the water and its filtration methods varied.

The Federal Water Pollution Control Act of 1984 provided for comprehensive planning, technical services, research, and financial assistance by the federal government to state and local governments for sanitary infrastructure. The Act was amended in 1965, establishing a uniform set of water quality standards and creating a Federal Water Pollution Control Administration authorized to set standards where states failed to do so

EPA wasn’t established until the ‘70’s

Paris Green & DDT were heavily used

Housing, hospitals, the streets, all still had very poor and unsanitary living conditions.

... just to name a few.

Perhaps those, too, have contributed to poor health outcomes.