Jan. 16 (Bloomberg) -- New Zealand's clean air and the thin southern hemisphere ozone layer are contributing to one of the world's worst rates of skin cancer, according to a study by government scientists and the University of Colorado.

Cancer-causing ultraviolet rays are 40 percent stronger in New Zealand than at similar latitudes in North America, research by the National Institute of Water & Atmospheric Research and the university shows. The study will be published in the next issue of the Cambridge, U.K.-based journal of Photochemical and Photobiological Sciences.

``The lack of pollution is the main factor,'' study co- author Richard McKenzie said in a telephone interview from the institute's Lauder facility in the South Island's central Otago region. ``I was surprised that the difference between New Zealand and the U.S. was so high.''

Skin cancer kills about 300 people annually in New Zealand, a nation of 4.1 million people, and costs about NZ$33 million ($23 million) a year, according to a University of Otago study in 2000. About 75 percent of the deaths are from melanoma, the most-deadly type, which occurs in the population at three times the rate in the U.S.

Melanoma is the fifth-most common cancer in New Zealand and the most common tumor in those aged 20 to 39 years, according to the country's Cancer Society.

New Zealanders, along with the European populations of former British colonies of South Africa and Australia, die from skin cancer at high rates because their lighter skin pigment provides less protection from the sun's ultraviolet radiation that causes the cancer.

Radiation

UV radiation typically gets stronger nearer the equator. In the southern hemisphere, though, UV levels are elevated by the thinner ozone layer over Antarctica. The ozone layer 24 kilometers (15 miles) above the earth's surface acts as a shield against UV radiation.

``We're not designed to be down here,'' said Wendy Billingsley, spokeswoman for Sunsmart New Zealand, a government- funded skin cancer awareness project. ``On top of that, the ozone is thinner, we have less pollution and we have a very outdoors-ey lifestyle.''

New Zealand and Australia lead the world for skin cancer, ahead of the U.S., which has the next-highest rate, according to World Health Organization data.

In Queensland, on Australia's northeast coast, new cases were being reported in 2002 at a rate of almost 85 among every 100,000 men, according to state government data. A 1999 study showed a rate of 77.7 per 100,000 among Europeans in Auckland, New Zealand's most-populous city. Maori and Pacific islanders account for about 20 percent of New Zealand's population and have a lower rate of skin cancer.

Invisible Threat

New Zealand has an added risk over its nearest neighbor Australia, Sunsmart's Billingsley said. Being further south and an island climate, temperatures are lower. Many people erroneously equate UV risk with temperature, when in fact, UV radiation can't be felt, she said.

``It's a combination of the light skins and the cooler temperatures,'' Niwa's McKenzie said. ``We want to be out in the sun. If you were in Fiji you wouldn't be because it's just too hot.''

The NIWA-University of Colorado study compared UV levels at Lauder in New Zealand against those at fifteen test sites across the U.S. and Canada managed by the U.S. Department of Agriculture.

It showed the sky over Lauder was clearer than at any of the North American sites. Lauder was also the only site below an altitude of 1,000 meters where UV levels regularly exceeded 11 on the open-ended UV index. Levels above 6 are considered high and those above 10 are extreme, according to the World health Organization's INTERSUN project.

``This is the downside of the lack of pollution in New Zealand,'' McKenzie said. The rates at Lauder are what you would expect 5 degrees, or 555 kilometers (347 miles) further north and at an altitude of 2,000 meters, he said.

Awareness

New Zealand began public programs promoting skin cancer awareness during the 1980s, encouraging people to use sun screens, to wear hats and to avoid being out in the sun during the hottest parts of the day. Sunsmart started work in 1993.

While death rates from melanoma are stabilizing, the number of cases reported are rising and are likely to do so for some years yet, New Zealand's Ministry of Health said in a 2002 projection of all the nation's cancer cases.

While the key risk factor for melanoma is excessive sunburn during childhood and adolescence, most cases don't appear for 20 years, Billingsley said. Health Ministry data shows 87 percent of the 1,842 cases reported in 2003 were in people over the age of 40, who would have pre-dated programs such as Sunsmart.

The next phase in the country's campaign against skin cancer will be a greater focus on the provision of shade around public buildings, such as schools, or at parks or summer sports grounds, Billingsley said.

While individuals are more aware of the cancer risk from the sun, better planning of public spaces can also increase the protection available, she said.

``It's pretty amazing how at risk we are,'' she said. ``We are getting radiated, basically, just by going outside. And at really high levels.''

To contact the reporter on this story: Gavin Evans in Wellington at gavinevans@bloomberg.net

Last Updated: January 15, 2006 06:01 EST