New York City Mayor Michael Bloomberg said Wednesday that the United States’ coal industry’s days are numbered.

“Even though the coal industry doesn’t totally know it yet or is ready to admit it, its day is done. … Here in the U.S., I’m happy to say, the king is dead. Coal is a dead man walking,” Bloomberg said at the Advanced Research Projects Agency — Energy (ARPA-E) Energy Innovation Summit near Washington, D.C.

Bloomberg has been a vocal advocate for killing coal-fired power. He said health problems from pollution and climate change-exacerbated events like Hurricane Sandy have fomented growing recognition that coal “doesn’t deserve” its reputation as a cheap energy source.

For now, coal is still the leading supplier of electricity. It accounted for 37.4 percent of the nation’s electricity mix last year, according to U.S. Energy Information Administration statistics released Tuesday.

But that figure also represented a 12.5 percent drop from the previous year. Natural gas, on the other hand, spiked 21.4 percent to provide 30.4 percent of the nation’s power.

Bloomberg attributed coal’s struggles to the Environmental Protection Agency’s regulations to curb emissions in the name of public health, grassroots environmental efforts and low natural-gas prices.