Clouds hovering far from the land over the world's oceans are a sign that the smoke creating the pollution is now "overloading the atmosphere" according to Professor Mario Molina, and the United Nations Environment Programme (UNEP) is to launch an urgent investigation.
An enormous cloud of brown haze, the size of the United States, has been found over the Indian Ocean, 100 miles from the nearest shore, by an international scientific group. No one knows what has caused the smoke - it could come from forest fires, car exhausts on the Indian sub-continent, or perhaps from industrialised countries thousands of miles away.
Professor Molina, who was speaking after being given UNEP's $200,000 (pounds 128,000) Saskasawa Prize - the world's top environmental award - said the cloud over the Indian Ocean had only been found because scientists from the International Global Atmospheric Chemistry Group were specifically examining the area. He said there were signs of similar clouds over the Pacific and that he feared they could become a "global" phenomenon. Normally such pollution would be washed out of the air by rain, but the fact they were persisting suggested that an alarming change may be taking place.
He said he feared that pollution was "overloading the atmosphere beyond its capacity to clean itself".
Professor Klaus Topfer, UNEP's executive director, added that the cloud was a cause for "huge concern" and said he was planning to launch "co- ordinated scientific research" into the phenomenon.
However, Professor Molina, who is a scientific adviser to President Clinton added that, in the meantime, the level of ozone damaging chemicals in the atmosphere were gradually beginning to decrease as a result of international agreement to phase them out, marking the beginning of what is expected to be the first major victory over global atmospheric pollution.
But he added that the chemicals last so long in the atmosphere that the ozone layer is not expected to recover fully until the year 2050 even if all nations in the world succeed in banning them.