Standing on the roof of Two World Financial Center, amid mounds of debris that still litter the streets and rooftops around the World Trade Center, New York police officers -- among them former Marines -- raised the flags of the United States, Marines, Navy, Army, Air Force and Coast Guard.

CNN: Marines honor fallen members of armed forces

That amounted to almost 5000 pieces of litter per kilometre of shoreline cleaned around Northern Ireland's coast.

BBC: High tide of rubbish on Northern Irish beaches

Litter is scattered over the streets around Issac Sheppard school in north Philadelphia.

BBC: Obesity rates fall in Philadelphia

What about clearing up the clutter of complexes, hang-ups, and memories that litter the mind and color our perception of those around us?

FORBES: What We Humans Value: The Indulgence of Being Loved

In recent months leading wildlife experts have called for people to be more careful with their litter after a basking shark was filmed with plastic around its nose and a grey seal was photographed with plastic around its throat near Kitterland.

BBC: Manx beach clean collects record amount of rubbish

You know how in most cities when you walk around there are garbage cans that you use to throw away litter?

FORBES: Hey Philadelphia: It's Time To Embrace The Most-Toxic Title