It might be the summer of '09 before beachgoers can count on finding sunscreens to protect against the deeper, penetrating rays linked to wrinkles and cancer.

It might be the summer of '09 before beachgoers can count on finding sunscreens to protect against the deeper, penetrating rays linked to wrinkles and cancer.

The Food and Drug Administration on Thursday proposed long-delayed rules covering the ingredients, labeling and testing of sunscreens that boast of protecting against both the sun's ultraviolet B rays, which cause sunburn, and the ultraviolet A rays associated with more serious and longer-term damage.

The proposed rules keep in place the so-called SPF, or sun protection factor, rating system for UVB protection, while tweaking the testing requirements. The FDA proposes capping the SPF claims companies can make for their products at 50-plus, unless supported by further testing.

The proposal would add a requirement that sunscreen makers assess UVA protection as well if they want to make any claim that their products protect against those rays, whose damage is rarely immediately apparent.

Until recently, most sunscreens sold in the United States have filtered out mostly UVB but not UVA rays — even if they promised broad protection.

The proposed rules would institute a four-star system to rate the UVA protection provided by sunscreens and spell out the protection level as "low," "medium," "high," or "highest."

A product's UVB protection would also be described, alongside its SPF rating.

Companies that choose not to do the UVA testing would have to label their products "No UVA protection," according to the proposed rules. The FDA assumes three-quarters of the estimated 3,000 sunscreens on the market would undergo such testing.

The proposed rules probably remain at least several years from taking effect.

The agency will collect public comments for 90 days, make revisions as necessary and then publish a final rule. That rule, once it appears, would take effect only 18 months later — which puts it sometime in 2009, at earliest.

Under the rules, sunscreen labels also would be updated to further encourage sunbathers to reapply sunscreen as needed. And those sunscreens making any claim for water resistance would have to list, in minutes, how long the products block the sun's rays before they have to be reapplied following swimming, or simply sweating.