Light-emitting diodes, or LEDs, cast a bluish glow in the sky and are about 20 percent more efficient than industry-standard streetlamps, which generate red-colored light pollution.

With LED efficiency expected to double to 40 percent in a few years, it's inevitable that governments worldwide will opt to save energy by switching to LEDs, which also last longer and require less maintenance, experts say.

(Related: "Tough Road to Getting LED Lights on the Streets.")

Yet it's uncertain how much the color of light pollution will change as LEDs take over, experts say. Also unknown are effects of blue light pollution on nocturnal wildlife, such as sea turtles, which can be confused by artificial lights when coming ashore to lay their eggs.

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