求!帮我大致翻译一下这篇文章吧~~（英译中—）
A new study has found no evidence that sunscreen, commonly used to reduce the risk of skin cancer, actually increase the risk.
Researchers from the University of Iowa based their findings on a review of 18 earlier studies that looked at the association between sunscreen use and melanoma (黑素瘤). They said that they found flaws in studies that had reported associations between sunscreen use and higher risk of melanoma.
Most health experts believe that by protecting the skin from the harmful effects of the sun, sunscreen helps prevent skin cancer, which is increasing in incidence (发生率) faster than any other cancer in the United States.
But questions has been raised about sunscreen and whether it may has opposite effect, perhaps by allowing people to remain exposed to the sun longer without burning.
The researchers said that among the problems with some earlier studies is that they often failed to take into account that those people most at risk for skin cancer--- people with fair skin and freckles (雀斑), for example--- are more likely to use sunscreen. As a result, it may appear that sunscreen users get cancer more often.
The studies, which generally relied on volunteers to recall their sunscreen use, were also unable to prove how well the products had been applied, said the new study.