Banksy: cop and pink balloon

It's been over a year since Banksy blew into town, a mysterious artist hiding his identity, letting his art speak for him (well, some art and a movie). While some of his graffiti works remain, I don't think anything survived untouched. The Lake Shore Boulevard painting of the police officer holding back a floating, pink balloon dog is still there with only the modifications that were done soon after the art went up - namely the dog's Grrr!, the white highlight with the vulture on top of the cop's head and the yellow "Robbin' BANKSY". You can see the original here on BlogTO and one of my post of the paintings here.
What I find fascinating is that the painting is still pretty pristine, other than the above noted additions, yet the barrels that were beside the graffiti still remain, rusting. I mean who leaves barrels outside like that? I think that it's something out of the Simpsons - they are full of spent nuclear fuel or toxic waste. I think Banksy realized the danger of these barrels - his dog was trying to get to the bad waste.