It hasn’t made big news yet outside of specialty publications such as Bond Buyer.

But a call this week by New York City Comptroller William C. Thompson could cast a new cloud over a half-dozen or more planned new coal-fired electric power plants.

Thompson called on the U.S. Treasury Department to investigate the practice of using tax-free bonds to finance new coal plants.

In the letter, online at www.comptroller.nyc.gov, Thompson pointed to recent research which found that coal plants were poor candidates for federal financing and problematic for investors.

There are at least a half-dozen planned new power plants that would rely on tax-exempt bonds.

The Treasury Department has announced it would take a hard look at use of such bonds for sports arenas. You’d think they ought to take an even harder look at old-fashioned coal plants.