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A boatman sleeps in his boat anchored in the polluted waters of the River Buriganga in Dhaka, Bangladesh, Sunday, April 22, 2012. April 22 is observed as Earth Day every year as a tool to raise ecological awareness. (AP Photo/Pavel Rahman)

World celebrates Earth Day

On Sunday April 22, the world celebrates the 42nd annual Earth Day, a global event meant to celebrate the Earth and raise awareness for environmental causes. Even though it's nice to see how far we've come, images from around the planet remind us how much work is still to be done.