CONSIDER that the human head weighs about 10 pounds.

Now consider that last year, every man, woman and child tossed away an average of twice that weight in litter. And we're not just talking about 20 pounds of cups, cigarette butts, lottery tickets, trash bags, hamburger wrappings, and potato-chip bags. We're also talking about refrigerators, ovens, tires, scrap metal and construction waste, which is "short-dumped" in lots and on sidewalks throughout the city.

All told, we dumped nearly 17,000 TONS of crap in litter and debris . . . just last year. Welcome to the Cradle of Littery.

Last week, the Daily News launched an effort to work with the city clean up this mess. We've been monitoring cleanup efforts in the city, and noticed that often, after a block is cleaned up, it reverts to its original slovenly state within days.

We're not the only ones frustrated by this; the city's Streets Department is even more frustrated - since it has to clean up this mess. It has introduced more programs, such as an "unlitter us" campaign, and put out more trash bins, and the litter tonnage has moved downward (last year's 17,000 tons is down from 23,000 tons in 2008).

Rina Cutler, deputy mayor for transportation and utilities, would like to find a way to shame people into keeping their neighborhoods and streets cleaner. We would, too. Like Cutler, we wonder what can possibly be going through the head of someone who finishes a fast-food meal and casually tosses the paper and cup on the sidewalk, as we have seen more than once just in the past month.

We'll speculate that part of what's in their mind is the fact that they're only adding to what's already on the ground: litter begets litter. Litter is a sign that no one much cares.

But litter is also a sign that we are squandering money. In 2008, it cost the city nearly $2 million to pick up the litter and debris we left behind. (That doesn't include trash pickup.)

Last fiscal year, it cost $1.5 million. Considering the fact that this is a problem we could control, since 2008 we might as well have lit a match to $6.8 million.

Then there's the cost of the city's reputation as visitors take in the mess and go home to talk about "Filthadelphia" and think twice about ever coming back.

There are also costs that can't be measured in dollars or data: the psychic cost of living in a trash-filled dump.

And we all pay for that.

Join in the discussion as we look at solutions: Email, or sound off on Facebook: itup.