With the warm weather upon us, it's time to visit the subject of sunscreens.

A recent study from the Environmental Working Group, a nonprofit research organization based in Washington, D.C., found that 4 out of 5 sunscreens offer inadequate protection against harmful rays or could contain harmful chemicals.

While most of these products do help against sunburn, the question of skin cancer is more troubling. Our increasing efforts to slather on the sunscreen have had little effect on the prevalence of melanoma, the deadliest form of skin cancer.

John Baily, chief scientist at the Personal Care Products Council, a trade association for the cosmetic and personal care products industry, defends the industry's testing methods:

These materials are tested in a number of ways in animal studies, but also in clinical studies, before being approved. I think that (the Environmental Working Group) is being very selective in the criteria they use to categorize these products. They are taking studies that may be conducted in the laboratory, not on humans, and extrapolate that to say that these products are unsafe and should be avoided.

But when pressed on the cancer question, Baily conceded:

Scientifically, I cannot say that sunscreens protect against melanoma.

If you would like to read more about the story, head over to the article written by Ann Fernholm, Chronicle Staff Writer at the San Francisco Chronicle.