On the eve of the International Day for the Preservation of the Ozone Layer, Sep 16, the people of Tierra del Fuego were the world's most exposed population to the sun's harmful ultraviolet (UV) rays, as the hole in this natural atmospheric shield was located this week over the far southern province.

The ozone layer is found 15 to 50 km above the Earth's surface and protects all living species from UV rays, which are harmful to human health, potentially causing burns, skin cancer and loss of sight. Excessive UV radiation can also damage crops.

"We in Tierra del Fuego have known for a long time that we have to be extremely cautious about exposure, but we live in an area where the sun is mostly absent. And when it does appear, it is sometimes hard to remember the danger and avoid going outside," Graciela Fuchs, a schoolteacher in the town of Rio Grande, told IPS.

The Southern Hemisphere winter in this province is very harsh, with an average temperature of one degree Celsius and only a few hours of daylight.

The Argentine air force's Global Atmospheric Monitoring Station reported that during the two days of extreme risk in Tierra del Fuego, the Dobson units measurement, which indicates the thickness of the ozone layer, descended from the normal level of 300 to less than 200.

Health officials have urged the residents of Tierra del Fuego, who are known in Spanish as 'fueginos', to remain inside from 11:00 am to 3:00 pm local time, and to wear caps with visors and to use sun-blocking creams on exposed skin when outside.

Since 1980, scientists have observed a dramatic cyclical thinning of the ozone layer over Antarctica, usually lasting from August to December each year. The thinning of this protective layer has become known as a "hole" that is thousands of kilometres in diameter.

The phenomenon is the result of human activities, particularly the manufacture and use of products that contain gases known as chlorofluorocarbons (CFCs) or halons.

In the past, CFCs were commonly used in refrigerators, aerosols, air-conditioning equipment and in solvent cleaning, while halons were used as flame retardants and in fire extinguishing materials.

Industrialised countries have almost completely halted production and use of these substances.

The Montreal Protocol, signed in 1987, establishes the deadline to eliminate the use of ozone-depleting gases worldwide by 2010.

The industrialised North worked quickly toward that objective, making great strides, but the countries of the developing South have made little progress, leading experts to doubt that they will meet the goal in eight years.

"The status of the ozone hole over Antarctica and the South American southern cone has been relatively constant over the last few years," said Argentine physicist Rub�n Piacentini, a member of a Latin American monitoring team.

"There were some significant fluctuations of the maximum extension of the hole and it made a prolonged stay over the Argentine Sea and the south of the country, reaching 29 million square km in October 2000, two million more than the previous year, but within a broader picture of no major fluctuations," Piacentini explained in a conversation with IPS.

The month, as the annual cycle began, the size of the ozone hole quickly stabilised, and "now is smaller than it was in 2001," and is following a similar pattern to last year's cycle, said the physicist.

Pablo Canziani, director of the Middle Atmosphere Group at the University of Buenos Aires, had a similar interpretation. "What has occurred in the last few days is a normal event that has happened for the last 10 or 12 years over Tierra del Fuego and the southern tip of the continent," he told IPS.

However, said Canziani, the phenomenon has grown more acute over that populated region, with extreme thinning to just 145 Dobson units, and forces the fueginos to take the same precautions in the middle of winter as they would if they were at a beach on summer vacation.

The problem no longer seems to be advancing at the pace recorded a few years back, and there are currently international legal instruments in place to reduce the activities that cause ozone depletion, but it is still too early to claim victory, agree experts.

Emiliano Ezcurra, environmental activist with the Argentine office of Greenpeace International, told IPS he thinks the problem now is that the public believes the ozone hole was cured with the signing of the Montreal Protocol.

"Our work is not yet done, and we run the risk that the Montreal Protocol could be weakened after having served as a valuable tool for achieving important successes," Ezcurra said.

People, flora and fauna will continue to be in grave danger for years to come, even if all use of CFCs and halons were eliminated today, because it would be a half-century before the ozone layer recovered its optimal level for protecting life on Earth, he explained.

Furthermore, "large developing nations like Brazil, China and India and the countries of Eastern Europe will increase emissions of these gases instead of reducing them if they do not receive adequate financial help to convert their industries," predicted the activist.

Schoolteacher Fuchs says she does what she can to educate her students about the importance of protecting themselves from the sun's rays, although they need some exposure to the sun for its health benefits, such as providing vitamin D for strong bones.

World Ozone Day 2002