Washington ? Redheads sunburn easily, but that may not be the only reason they are at high risk of skin cancer. New research suggests the pigment that colors their skin may set them up for cancer-spurring sun damage even if they do not burn.

More than 1 million Americans develop some form of skin cancer each year. Among those most at risk are people with light skin, hair and eyes, a combination frequent in redheads. They are particularly prone to sunburns, a risk factor for anyone, especially if the burns occur in childhood.

Scientists long have wondered if something else plays a role in redheads’ high risk. One theory focuses on melanin, the skin pigment that darkens with sun exposure to provide either a tan or freckles. People with red hair have a chemically different type of melanin than people with dark hair.

Duke University researchers on Sunday reported the first direct evidence that those melanin differences indeed may be a culprit. It turns out that redheads’ melanin is more vulnerable to a type of DNA-damaging stress from the sun’s ultraviolet rays.

His research, funded by the government and Duke, was presented at a meeting of the American Chemical Society.