Protecting scientific facts from partisan politics was one aim of the March for Science on April 22. What happens when the two merge? "Poisoned Water," premiering at 9 p.m. Wednesday on the PBS series "Nova," offers a cautionary tale.

The one-hour documentary is probably the most concise, compelling retelling yet of what happened in Flint when, as part of a money-saving effort, the city's water source was switched in 2014 from Lake Huron (supplied by Detroit) to the Flint River.

For those not fluent in chemical reactions and corrosion control, the "Nova" episode explains, step by step, how water should be cleaned properly and why the mistakes made in Flint resulted in the breakdown of the coating that develops inside pipes (a lining that can be mostly lead, but is protective; one expert compares it to "drinking water through lead-painted straws").

It also painstakingly, yet clearly, explores the awful impact of lead on the developmental growth of children. It's chilling to learn that lead essentially fools the body into thinking it's calcium, an insidious trick that ends up blocking communication between brain synapses.

Beyond making the technical side possible to grasp, "Poisoned Water" also tackles the larger questions of social justice. Why did it take a year and a half for a state of emergency to be declared? Why weren't officials at all levels of government more worried about the rashes, hair loss and brown water coming out of faucets? It took the efforts of people like crusading Flint mom LeeAnne Walters, EPA regional staffer Miguel Del Toral, Virginia Techchemical engineer Marc Edwards and pediatrican Dr. Mona Hanna-Attisha – all interviewed here – to expose the truth and make Michigan and the rest of the country face the extent of the problem.

As "Poisoned Water" reveals, there could be many other Flints across the country waiting to happen. What stands between us and more of these catastrophes, according to "Nova"? Ultimately, it is science, and those who believe in it.

A previous version of this story incorrectly used the quote about lead-painted straws to describe pipes that had lost their protective lining.