Under the Hole in the Sky.(ozone layer over Punta Arenas, Chile)(Brief Article)

Maria Alvarado can tell whether it's a green-light day or an orange- light day or, as happens more frequently these days in the Chilean town of Punta Arenas, the world's most southerly city, a red-light day. Alvarado, 35, works 12-hour shifts in the streets of Punta Arenas keeping track of parked cars. She knows what it means when the sky turns eerily white and the sun's reflection off the surface of cars, windows and the sea becomes downright blinding. It means that the hole in the Earth's ozone layer is right smack overhead: it's a red-light day.

To the rest of the world, the ominously expanding Antarctic ozone hole was dispatched with the worldwide ban on the use of ozone-depleting substances in 1987-- one of the 20th century's biggest environmental victories. To the 120,000 residents of Punta Arenas, the ozone hole is a local nightmare. Each spring it still swells to about the size of North America, just nipping the southern coast of Chile. As variable as the weather, the hole makes sudden visits to the city. For days at a time, the sun's harsh ultraviolet rays, with no ozone shield to stop them, beat directly down on residents.

A few decades ago sunburns and skin cancer were virtually nonexistent in this cloudy, windy region. The expanding ozone hole changed all that. Since 1986 Punta Arenas has had more than 150 days in which 25 percent or more of the ozone layer was absent and a handful in which the loss exceeded 50 percent. Scientists report an even higher intensity of so-called UV-B rays, a particularly carcinogenic frequency of UV radiation. Skin cancer has soared 66 percent in the past seven years. Since UV-related disorders take decades to surface, the true impact may not be known for years. "It's like being placed on top of a high mountain without any time to acclimatize," says Jaime Abarca, the city's only dermatologist. "People living here just don't have time to adapt."

For years the city was reluctant to take action, in part from fear of scaring away tourists headed to nearby penguin colonies and other attractions. In 1998 health department officials devised the "solar stoplight" to give residents warning of intense periods of UV radiation. From September through December (the spring months), they activate actual stoplights in schools and businesses, and issue updates to local newspapers, television stations and ...