IN the 90s the pursuit of safe-sun has become a numbers racket. Dave Cosgrove, according to his wife Wynnie, is a definite No. 45. The New Zealander, an avid outdoors-man, has the type of fair skin that makes him juicy bait for the wicked rays. ''Dave doesn't go outside without anything less than a 45,'' says Wynnie, referring to his favourite number of sun-block protection. But his wife, a ranked ultra-marathonner, never touches his stash. She prepares her feet and mind better, for the gruelling five or 24-hour runs, than her skin. ''I never put anything on. I've never been burned, even as a child. Maybe as a Chinese my skin is tougher. '' When Steen Andersen works-out on his rooftop gym, he grabs the portable telephone, not a tube of sun block. Since moving to Shek-O, the Danish businessman works from his home cum office and pumps iron on his roof. ''I'm only out there one or two hours,'' he explained. ''Since I sweat so much, the suntan lotion just runs off.'' An all-day hike or sailing race changes the habit. ''Then I use No. 15.'' When Brooks McMaster tags along with his father on Apollo, their 33-foot sloop, preparation begins before they leave home. ''I grease him up like a little pig,'' says Jim McMaster, of his 15-month old son. What he rubs into the baby's skin is a product designed for babies, ranging in sun factor protection from No.45 (the highest) to 25 and 15. ''By the time he's ready for lunch or a nap, we're into sun hats and cover-ups,'' adds Mr McMaster. As for Brooks' father? A No. 15 for his back; a No. 6 for the rest. In the quest for protection from the sun the Chinese, with a greater number of pigment-producing cells may have the edge, according to medical authority. The avalanche of research linking over-exposure in the sun to skin cancer has aroused the entrepreneurial spirit of the cosmetics industry. Their labour has jammed supermarket shelves with a dizzying array of sun blocks, screens and lotions that offer protection from the bad guy - the most harmful type of ultra-violet ray found in the sun (called UVB). Now, outdoors-men and bikini goddesses can, with some common sense and an outlay of cash, worship the golden orb greased with a degree of safety. But understanding the dangers is one thing. Doing something about it is another. Hongkong-born Dr Ronald Leung believes Chinese have two factors in their favour. ''Their pigment is a type of natural sun block, and culturally, getting a suntan is not popular as it is with Westerns,'' he explains. This secretary of the Asian Dermatological Association is emphatic about everyone, regardless of race, needing some protection from the sun. ''Among Chinese there is a slight chance of skin cancer. It is far more predominate among non-Chinese.'' Dr Leung advises people to avoid direct sunlight during noon to 2pm, when the intensity is greatest. Use No. 15 or higher. And wear hats and long sleeves. Most importantly, he adds, ''indoctrinate the children.'' A professional colleague of his agrees. ''Use No. 15 or higher,'' points out Dr K.K. Lo, chairman of the Hongkong Society of Dermatology & Venereology Ltd. He cautions everyone: ''The real harm is the UVB type of ultra-violet ray. Of the three (UVA, UVB, UVC), it is the most carcinogenic.'' ''Sun has an accumulative effect. If you sunbathe as children, then by the time you are 30 or 40, depending on race, you will have wrinkles and dryness. The pigment changes.'' Dr Lo stresses the importance of using sun block products correctly. ''Read the label. And re-apply it according to directions. Use a product with a high degree of sun protection factor (that's the number). No. 15, according to research, provides adequate protection for most people as long as it is used correctly and re-applied.''