Americans will spend more than $1.1 billion on sun protection products this year, a market that's grown by an annual rate of 10 percent since 2004.

But is it worth it?

A recent study from the Environmental Working Group, an eco-advocacy 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.

If anything, the rate of contracting skin cancer is holding steady. Among

young white American women, in fact, it's actually trending up, according to the National Cancer Institute.

Many medical experts are starting to question the efficacy of sunscreen in fighting cancer, despite protests from the cosmetics industry.

"There is no evidence that sunscreens work against melanoma," said Dr. Marianne Berwick, a melanoma specialist who heads the division of epidemiology at the University of New Mexico.

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," Baily said. "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 said: "Scientifically, I cannot say that sunscreens protect against melanoma."

Several scientists actually warn that wearing sunscreen can give users a false sense of security, leading consumers to stay out in the sun longer. "It is a natural experiment that has been going on for 40 years," said Edward Gorham, an assistant professor at Moores Cancer Center at the University of California, San Diego.

Why doesn't a sunscreen that keeps you from getting burned possibly keep you from getting cancer?

One hypothesis is that sunscreens traditionally have been designed to protect only against ultraviolet B (UVB) rays, which cause sunburn.

Scientific studies have found that if a person burns often, there is an increased risk for melanoma later in life. Therefore, sunscreen developers and doctors have assumed, reducing the number of sunburns must protect against melanoma. But it might not be that simple.

In the ultraviolet spectrum, there are two different UV-rays, UVB and UVA.

"For a long time, UVB was thought to be the primary carcinogen in the sunlight, but what is happening now is that UVA is being viewed as a melanoma carcinogen," Gorman said.

While wearing sunscreen with a high SPF factor, sun worshippers have been able to stay in the sun for much longer without getting the natural warning sign of a red skin. But they have still been exposed to dangerous UVA rays and, in the end, people have obtained a much higher dose of UVA rays.

Margaret Tucker, director of the Human Genetics Program and chief of the Genetic Epidemiology Branch at the National Cancer Institute, said she believes the newer generation of sunscreens protects against melanoma.

"The last three to four years, sunscreens have gotten much better," she said.

Tucker is critical of the view that sunscreens might increase the risk of skin cancer because people stay longer in the sun.

"The sales of sunscreen have nothing to do with the appropriate use of it," Tucker said. "Many put too little on and never reapply it during the day. If you are sweating, you need to reapply it every 20 minutes, and you should reapply at least after two hours."

Distributed by Scripps Howard News Service