Another cost of energy

(CNN) -- Estimates for the amount of thick sludge that gushed from a Tennessee coal plant this week have tripled to more than a billion gallons, as cleanup crews try to remove the goop from homes and railroads and halt its oozing into an adjacent river....

Environmental advocates say the ash contains concentrated levels of mercury and arsenic.

[From Tennessee sludge spill estimate grows to 1 billion gallons - CNN.com]