UV alert Seven summer safety tips.(CR Health)

'We are expecting near-record levels of ultraviolet radiation over North America this summer," warns Betsy Weatherhead, Ph.D., a senior research scientist at the University of Colorado at Boulder. Although the rate of decline in the ozone layer is leveling off, it is still close to its lowest point in history, according to a report by Weatherhead and a Danish colleague in the May 4, 2006, journal Nature.

Overexposure to UV radiation is a preventable cause of skin aging and skin cancer, so it's more important than ever to take precautions when spending time in the sun. Here's how:

1 Use sunscreen, but know its limits. Check the label for products that help protect against UVA and UVB rays, since both types can cause potentially cancerous changes in cells. Choose a sun protection factor (SPF) of at least 15, or higher for more protection. Apply an ounce of sunscreen on all exposed skin a half-hour before sun exposure. Reapply every two hours and after swimming or heavy sweating. Remember that repeat applications do not mean you can prolong the time you can stay in the sun. Even when scrupulously applied, sunscreen lets some radiation slip through, so limit sun exposure between 10 a.m. and 3 p.m. Wear sunscreen on overcast days, too, since a substantial amount of the sun's radiation penetrates clouds.

2 Wear the right clothing. Wear clothes of tightly woven fabric, and boost their sun-shielding ability by washing them with detergent that contains "brighteners," which absorb some ultraviolet rays.

3 Shield your eyes. Wear a broad-brimmed hat and choose large-frame, wraparound sunglasses for maximum protection. Sunglasses that block UVA and UVB rays may reduce the cumulative effect of UV damage linked to cataracts and age-related macular degeneration.

4 Don't rely on shade. Just because you're sitting under a leafy tree doesn't mean you're shielded from the damage of the sun's UV rays.

5 Stay hydrated. Thirst can lag behind dehydration, so in warm weather drink before you become thirsty. When exercising on humid or hot, overcast days, sweat won't evaporate quickly or cool you efficiently, so you're at greater risk of dehydration.