Shawn Smallwood makes his living looking at the ground. Currently he is working at a dump site of toxic sludge. This sludge was dumped in New York many years ago, but Smallwood thinks that animals like gophers are digging up the dirt and it is becoming airborne. This is common in many toxic dumps. The top layer hardens trapping the gases and liquids beneath it.
Animals come along and dig it up bringing it to our lungs.
It is easy to understand why it is brought back up, when a burrowing animal such as a gopher is digging it naturally prefers to dig in the soft man-made dirt than in the well packed natural dirt. For this reason there is some reason to be concerned about buried waste. Humans have thought to bury the waste in boxes or barrels thinking that this would keep the waste contained when it was buried. Unfortunately, a gophers sense of curiosity and strong teeth can penetrate these. Gophers aren't the only things that bring soil to the surface.