The devastation of Hurricane Katrina has created a vast toxic soup that stretches across south-eastern Louisiana and Mississippi, and portends the arrival of an environmental disaster to rival the awe-inspiring destruction of property and human life over the past week.

Toxicologists and public health experts warned yesterday that pumping billions of gallons of contaminated water from the streets of New Orleans back into the Gulf of Mexico - the only viable option if the city is ever to return to even a semblance of its former self -would have a crippling effect on marine and animal life, compromise the wetlands that form the first line of resistance to future hurricanes, and carry deleterious consequences for human health throughout the region.

The full extent of the danger is unknown and unknowable, but the polluted waters are known to contain human and animal waste, the bodies of people and animals, household effluence, and chemical and petrochemical toxins from the refineries that dot the Gulf coast in and around New Orleans.

"We're talking about a mass of decomposing dead bodies and animals. This is going to produce a horrible festering of unknown consequences," said Harold Zeliger, a chemical toxicologist and independent consultant based in New York State.