The cancer belt that stretches along the Gulf from Texas to Alabama is due to these industries already.  These substances will be entering an already saturated water table.

In addition to being carcinogenic, petrochemicals and other toxins released are mutagenic--that is, they cause birth defects.

The traumatic effect of this devastated environment will be long-term, thanks to the poor response of the US government.  A similar response to Chernobyl by the USSR--focused as it was on lying, cover-ups, incompetent leaders at the scene, and public relations--contributed to the collapse of the Soviet Union.  

It's hard to overstate the ecological, biological, and psychological magnitude of the Katrina disaster.