Inverse-pollution art.

An excellent find by the ever intriguing PlaceboKatz:

Alexandre Orion is cleaning São Paulo’s tunnels by scraping the deposited vehicle exhaust soot from the walls to make hundreds of sculls. Even so police turned up several times they couldn´t do much as cleaning is no crime. After some time the São Paulo municipal started their own cleaning mission, consequently only cleaning the parts already cleaned by Alexandre. Again the skulls appeared on the remaining soot canvas and this time the city decided to clean all tunnels.