WASHINGTON, Aug. 29-The reason people with red hair have higher rates of skin cancer than people with black hair likely lies in the different photochemical properties of their melanin pigments, researchers reported here.



Because of slight variations in its chemical structure, red pigment loses electrons relatively easily when hit by ultraviolet light (UV). Black pigment, on the other hand, requires a jolt of high-energy UV, which is usually screened out by the atmosphere, to knock off its electrons, reported John D. Simon, Ph.D., of Duke University in Durham, N.C.



Electron loss is the first step to generating oxygen free radicals, which in turn cause damage to DNA that can lead to skin cancer, Dr. Simon said Sunday at a presentation at the American Chemical Society Annual Meeting.

Action Points Advise redheaded patients that there is a scientific explanation for why they have a greater propensity for skin cancer.



No such photochemical analysis of red and black pigments has been done before, in part because of the extreme difficulty of removing melanin granules from human hair and tissue without altering their natural chemical properties, Dr. Simon said.



However, Dr. Simon and colleagues were able to isolate red and black pigment from hair samples using a new technique developed by Italian scientists. "We spent a year characterizing these pigments so that we could establish that we had optimized the isolation to yield as close to natural pigments as possible," Dr. Simon said.



The researchers then bombarded the pigments with varying frequencies of UV light and determined the resulting electron loss with a technique called photoelectron emission microscopy.



"The red pigment is more pro-oxidant under normal atmospheric UV exposure and more prone to cause oxidative stress in cells," Dr. Simon said.



"The work suggests that the photochemical properties of the pigments themselves may contribute to the different incidence of cancer between tissues containing the different pigments," he concluded.