Summer's rays too risky for toasting

As summer approaches, it is tempting to indulge in some primitive solar worship, but GEOFF CUMMING advises sun sense instead.

Not getting enough is bad for your health. Toto much can be very bad for you.

Yet we worship the sun as the ancients did thousands of years ago.

If the sun shines through this holiday weekend, we will flock outdoors like lemmings, spirits raised by the warming rays, deep blue skies and the promise of a long, hot summer.

After 13 years of ominous warnings, most of us have heeded the slip, slop, slap message. We head out in the noonday sun under protective clothing, sunglasses and sunscreen. Even hats are back in vogue.

Rates of melanoma, the most dangerous skin cancer, have fallen from their early-1990s peak.

The generation, now in their 40s and 50s, who basted themselves in coconut oil and grilled both sides for 12 hours a day under a blazing sun will surely have been the last to do so.

Surveys show one in three New Zealanders still like to offer their bodies to the sun. But now, most at least use sunscreen.

Ultraviolet (UV) rays from the sun stimulate the skin's pigment, producing cells which give us a tan. More than half of us feel healthier with a tan, and both men and women find a bronzed body more alluring than lily-white skin.

Our relationship with the sun is more than skin-deep. We may take its daily appearance for granted, but the nuclear fusion taking place 150 million kilometres away unleashes the energy that drives our planet.

Astronomer Dr Ian Griffin says the sun is just an average star, halfway through its life.

"In 4 1/2 billion years it will swell up and gobble up the earth."

At its core, the temperature is 15.6 million degrees. There, nuclear fusion turns hydrogen into helium, releasing about 5 million tonnes of energy a second.

A fraction of this energy, corresponding to the power of 178,000 billion atomic power plants, is crucial to life on earth.

The ancient Greeks and Romans could see that the sun brought life to earth, and worshipped it as a god.

The Egyptians positioned pyramids to reveal the changing geometry of the sun and earth and establish the Egyptian calendar.

The pillars of Stonehenge were positioned so that the course of the sun could be tracked with the seasons and used to guide planting. It also served as a site for sun-worship.

The sun is good for us. It is the source of about 90 per cent of vitamin D in our bodies, vital to maintaining strong bones and useful in lowering the risk of heart disease and diabetes. A 1999 survey of 400 Auckland women found most were not getting enough vitamin D.

But this summer there is searing new evidence of the need to moderate our exposure.

In the southern Chilean port of Punta Arenas, the citizens have been told not to go out in the sun between 11 am and 3 pm. Health authorities last week called an orange alert - the second most dangerous level on a scale of four - in which UV exposure can cause skin burns in seven minutes. A red alert means burn-time is five minutes.

The advice is not far removed from our own Cancer Society's mantra to cover up and seek shade between 11 am and 4 pm.

Alarm in Punta Arenas has been raised by unprecedented UV radiation levels, due to record depletion of the ozone layer over Antarctica.

For 15 years, the ozone hole has appeared in late August or early September, a clear sign that greenhouse gases are eating away the protective layer of ozone which filters out the sun's UV rays.

Richard McKenzie, of the National Institute of Water and Atmospheric Research, says ozone levels here will be significantly reduced over the next couple of months as depleted air from Antarctica is redistributed.

Since 1985, ozone over New Zealand at the height of summer has decreased by 10 to 12 per cent, with UV intensity increasing by about 15 per cent. Even slight changes in UV intensity can increase the incidence of skin damage.

New Zealand has the world's highest rates of skin cancer on a population basis, with 20,000 new cases reported each year.

Three-quarters are basal cell carcinomas, which usually appear on the head, neck and upper body as small lumps, coloured red or a pale pearl. They can often be removed by a GP.

Melanoma, the least common, is the most serious. The first signs are a change in the colour and size of a freckle or mole, or a new spot on the skin. It may be brown, black, blue or red in colour. Its shape and size may change in weeks.

Melanomas spread rapidly through the body, forming secondary tumours in vital organs.

The risk is greatest in the northern North Island, where UV intensity can be twice as high as in the South Island.

Auckland is known as the melanoma capital of the world, with an estimated one in 10 suffering a cancerous growth at some time.

Nationally, about 1600 melanoma cases are notified each year and 190 will be fatal. In the early 90s there were 250-odd such deaths.

Coordinated publicity campaigns by the Cancer Society and general practitioners have driven the turnaround in the face of worsening ozone depletion.

Over the years, the Cancer Society has developed a broad spectrum armoury to repel UV radiation. In the mid-1990s it launched its own sunscreen and pressured the Ministry of Health into listing sunscreens which met New Zealand and Australian standards. Products with a protection factor of SPF15 are now recommended as the minimum level on exposed skin. SPF30+ is suggested on your face.

Norwegian research suggesting that a chemical used as a UV filter in sunscreens may itself be toxic rocked the society when it was published this month. Scientists at the Norwegian Radiation Protection Authority found the filtering substance, octyl methoxycinnamate, killed mice cells in an ethyl alcohol solution. The society was quick to counter that what happened to mice cells in a laboratory experiment was of little relevance to humans.

Its advice extends beyond sunscreens to covering up, as much as is practical, with a hat, sunglasses and UV-resistant clothing. The society has struck a deal with The Warehouse to market its own clothing range this summer, and the chain is promoting the label this weekend. Other brands, including the Ozone Clothing Company, also use fabrics tested for UV protection.

Society marketing manager Cath Chittenden says the fabrics contain no magic ingredient.

"It's all to do with the quality, the thickness and how tightly woven the fabric is. A lot of lightweight fabrics that come down from Asia may be cheaper, but they may not be very effective at screening UV rays."

The society knows it faces an uphill struggle persuading New Zealanders to practise what it preaches. Children and teenagers are our most avid sunseekers. Yet exposure in childhood is far more damaging than during adulthood, although the melanomas may not show up for 25 years.

As the society's medical director, Peter Dady, has lamented, teens think they are invincible.

Happily, sunglasses are an essential accessory with modern teenagers. But more important than brand name is that label states they are 100 per cent UV resistant.

In another fashion coup, children have embraced all-in-one lycra swimsuits which cover the torso - and reduce the need to slop on sunscreen every time they emerge from the water.

The society has also found schools receptive to its Sunsmart campaign. Many now make hats a mandatory part of summer uniforms and have adopted a "no hat, no [outdoor] play" policy.

But Cath Chittenden does not foresee the society following in the footsteps of the Punta Arenas authorities by telling citizens to stay indoors.

"We haven't said 'don't go outside' and we can't - nobody can tell you what to do. Given our lifestyle and love of the sun, that would be rather an extreme attitude for a Kiwi.

"But our message remains one of moderating your exposure to the sun as much as possible."