These are a few of the environmental problems to be discussed by senior officials from 100 countries at the first UN Environmental Programmeconference ever held in Asia when it opens in South Korea next week.

Already one in six of the world's people live without access to fresh water, according to Klaus Toepfer, the head of the UN body organising the conference.

"The arithmetic is awesome and simple. One in six people, or one billion souls, are currently deprived of this most basic of human needs," he said in a report ahead of the three-day conference.

Unless action is taken, a third of the world's population is likely to suffer from chronic water shortages within a few decades, Toepfer explained. "The quantity and quality of fresh water remain the most serious and critical issues of the 21st century," he said.

Asia already has the lowest per capita freshwater availability in the world, its cities are among the world's most polluted and the region's natural habitats are severely endangered.

These environmental problems, and those of the air pollution cloaking Asian and other mega-cities of the world, will figure high up on the conference agenda.

Asia is now recognized as a driving force of the world economy, but environmentalists warn that the region could pay a heavy price if it repeats the pattern of environmental degradation seen elsewhere in the world.

"The historical pattern of development in the economies of Europe, North Africa and Japan, was to industrialize first and clean up later," said Toepfer. "Such outdated thinking is no longer possible in a world of six billion people and counting."

One critical emerging issue at the conference is so-called 'dead zones' in the world's seas and oceans. These areas of sea water completely deprived of oxygen can no longer sustain life.

The issue is "all due to pollution" and has "big implications for the fisheries and the conservation of marine wildlife, and of course for people," said Nick Nuttall, head of media at the UNEP.

A possible link with a two-mile-thick blanket of sooty pollution that has worried environmentalists for years and has been dubbed the Atmospheric Brown Cloud will be explored at the meeting, according to organisers.

More specific to North East Asia is the environmental threat from sand storms driven by high winds from the deserts of China over the Korean peninsula and Japan, reaching as far as the US West Coast.

The UNEP described the storms as a "significant health, economic and environmental threat to the region and beyond."

China is responding in consultation with neighbouring countries by taking steps to halt the eastwards spread of the Gobi desert, including returning developed farmland to forest grassland.

"Though progress has been slow, the measures have been effective in holding off desert encroachment," a UNEP report said.

During the conference, which will take place on South Korea's southern island of Jeju, the UNEP will unveil its Global Environment Outlook Year Book, a progress report on issues including the drive to reduce by half the proportion of people without sustainable access to safe drinking water by 2015.

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