David Rosner, professor of public health and history at Columbia University and the author of "Lead Wars," a history of the battle over lead in the environment, explained the special significance of Flint in the history of American industry's embrace of lead when I spoke with him by phone  Tuesday.

"Lead was introduced into gasoline as tetraethyl lead by General Motors," Rosner said, "the people that brought you Flint, Michigan." Meaning the city: Flint was home to GM at its inception. When the company created a new type of fuel that burned lead, it had a new advantage over its competitors at Ford. It was only the newest way in which the industry relied on lead in manufacturing its product.

"In the 1930s, 1940s, 1950s, the industry basically quenched concerns about low-level exposures by saying that lead was a 'gift of God,' essential to modern industry, essential to modern production. It had to go into everything and we couldn't live without it," Rosner said. "Gift of God" is not Rosner's phrasing; it was an expression used by a representative of GM. Lead, Rosner says, "became the basis for the new car industry" -- even as concerns about it were increasing.

General Motors' success "led to the creation of a whole set of ancillary industries all along the Flint River, going up to Saginaw," Rosner said. "Battery plants, paint manufacturers, the soldering materials. The modern car is a giant industrial product that contains large amounts of all sorts of toxins. Not only oils and lubricants, but lead. Basically, the Flint River was the outlet for all this stuff." (In October  2014, General Motors stopped using Flint River water at its facility because it was worried about corrosion.)

Flint, in other words, was an epicenter of America's lead problem. But the problem predates Flint.