PORT LOUIS, Mauritius (Reuters) -- Sailing the world's remotest seas in search of the awesome sperm whale, the steel-hulled Odyssey has been dredging up some dark secrets about mankind's damaging impact on the oceans.

A scientific research vessel circumnavigating the globe, the 93-foot sailing boat has been tracking the giant whales in the hope that they may hide in their bulk important clues to the state of the world's seas.

The mission is not over, but the early indications are ominous. Pollutants, the debris of man's life on land, have poisoned the waters that dominate the planet.

Working for the U.S.-based Ocean Alliance, a whale conservation and research body, the Odyssey set out in March 2000 to quantify that toxicity, using tissue samples from sperm whales to indicate how polluted the waters really are.

"We chose to study the toxicity levels in sperm whales because they are one of the most abundant great whale species left on the planet and are found in all seas and oceans in the world," said Genevieve Johnson, Ocean Alliance's education director.

"We were surprised by the levels of pesticides like DDT found in our preliminary analysis of sperm whale tissue samples. "We have completed almost four years of our five-year study and have so far taken tissue samples from about 900 sperm whales in various parts of the world." BANNED BUT WIDELY USED

An adult male sperm whale can reach lengths of 60 feet and weigh more than 60 tons. It is believed to be the biggest toothed predator in the world.

There are about 350,000 sperm whales around the world, but Johnson said the pesticides found in their blubber could spell danger for the species.

DDT is banned in many countries because of its harmful effect on humans and animals. It is still used widely in developing countries, sold on the black market because of its low cost and effectiveness as an insecticide.

Other toxins like polychlorinated biphenyls (PCBs) have also been found in sperm whales. Made and used on land, these are released into the environment and eventually make their way into the oceans through rivers and rainfall.

Johnson said the toxins could prevent whale fetuses from developing properly, result in high levels of sexual abnormality, cancers, birth defects or sterility.

There could also be repercussions for humans.

"The toxicants that we are finding in these whales could have serious implications for humans as we are also feeding high on the oceanic food chain," Johnson said.

Toxic fish and oceanic plants have been found to contaminate land in some parts of the world and Canada's Inuit people have been warned to stop eating fish, the staple of their diet for generations.

Studies suggest poisons are showing up in the breast milk of nursing mothers who pass them on to their babies.