As the crisis over the water in Flint, Michigan, rolls on, we’re learning more and more about the irresponsibility and callousness of officials and politicians in charge.

The mix of austerity politics, environmental racism and sheer ineptitude makes for a shocking brew, yet the physical conditions that have made it literally toxic for Flint residents are neither as exceptional nor as recent as much of the media coverage suggests.

Long before that fateful decision two years ago to turn to the Flint River for the city’s drinking water, pipes made of lead had threaded throughout the city’s underbelly. Flint shares this historical legacy with thousands of other cities, suburbs, and towns across our country, and most likely this is not the first time, even in Flint, that these pipes have conveyed tiny amounts of the toxin into homes and children.

Over the past few decades, our environmental laws and agencies have met with much success in curbing some of Americans’ exposure to lead, a damaging neurotoxin. Yet they have struggled to contain this continuing danger precisely because it is literally built into our water systems.

Given that lead has been known as a poison for centuries, why did our forebears in the 19th and early 20th centuries rely on it to carry so vital a fare as drinking water? The answer to this question explains why there are many more Flints waiting to happen.