HALKIDIKI, Greece, May 15 (Reuter) - Around 300 scientists met in Greece on Monday to grapple with the ever-increasing destruction of the ozone layer -- blamed for causing skin cancer and eye cataracts.

Speakers on the first day of the week-long meeting, whose sponsors include the European Union, World Meteorological Organisation (WMO) and NASA space agency, warned the loss of life-protecting ozone is increasing in densely populated areas.

"In coming years we should expect further extreme ozone deficiency similar to that observed during the northern winter-spring season that has just passed," Rumen Bojkov, a United Nations advisor on ozone, said in a welcome address.

The scientists will pool their findings on depletion in the lower stratosphere, a zone located roughly 11-23 km above the earth where about 70 percent of life-protecting ozone is found.

"The WMO network observed in January-April the absolute record low over Siberia and near the record low over the entire middle latitudes of the northern hemisphere," said Bojkov, who advises WMO and will deliver a paper at the conference.

"These latitudes are where most people on the planet are living, including Japan, Russia, Europe and North America," Bojkov told Reuters.

The EU has outlined health hazards including skin cancer, cataracts and immuno-suppression that may result from exposure to the sun's UV-B radiation arriving unhampered when too little ozone is present to act as a barrier.

Paul Gray, an EU Commission research director, said a paper by a Dutch scientist estimated this winter's ozone drop meant about 19,000 extra cases of skin cancer in Germany. "My guess is it's something like 80,000 in the EU," he said.

"This sounds like a startling figure but it doesn't worry me too much because people can cover their skin. What is more worrying is that nature can't cover up," Gray said.

But if government complied with the 1987 Montreal protocol and its amendments, they could achieve a return to the ozone levels existant before the 1970s when industry began pumping destructive chemicals into the air.

"It took nature about one to two billion years to build the ozone layer. We could have it back again in 60-70 years through adherence to the protocols," Christos Zerefos, who runs the WMO's Northern Hemisphere Ozone Mapping Centre, told Reuters.

The main culprits in depleting ozone are chemicals known as chlorofluorocarbons (CFCs) and halons that contain chlorine and bromine, which react with oxygen and break up the ozone.

Their use in industrial production of foam rubber, refrigerators, fire extinguishers and aerosol sprays is being phased out or cut down under the protocols. "In this way we hope that the increase in chlorine loading in the atmosphere will reach its maximum around the year 2000 and then start to decline," Bojkov said.

Ozone destruction has also been blamed for injuries to animals and plant life and imbalances in aquatic and land eco-systems.

"When ozone goes down UV-B (radiation) goes up which is harmful to people, the eco-system and agriculture," said Zerefos, who also heads Thessaloniki University's Laboratory of Atmospheric Physics.

The conference marks the 10th anniversary of identification of the ozone hole over the Antarctic by Briton John Farman.