Blue eyes, big earplugs: Bad hearing?

For 30 years, evidence has mounted that black people, on average, hear better than whites, and that within both races, women surpass men. A partial explanation of the differences may lie in the abundance in the inner ear of melanin pigments, which are also found in skin and irises. Lending credence to that notion, numerous studies have found that people with light eye colors, such as blue, green, and hazel, are more vulnerable to hearing damage than are people with brown or black eyes.

Taking a new look at old data, Julia D. Royster of Environmental Noise Consultants in Raleigh, N.C., finds further reason to believe that eye color matters. She reanalyzed records collected some 20 years ago by her husband, Larry H. Royster, at a large, noisy textile plant in North Carolina. She reports that the 21 light-eyed, black workers showed significantly poorer hearing than the 327 dark-eyed, black workers. No comparable difference in hearing loss emerged between light-eyed and dark-eyed whites.

Reasons for the greater susceptibility among light-eyed blacks remain obscure, but "melanin may have something to do with it," she says. Researchers have determined that the inner ear produces extra melanin when stressed by noise. Melanin, however, may both protect and harm hearing. It sometimes mops up harmful molecules called free radicals, but at other times, it contributes to their creation.

Larry Royster, who is at North Carolina State University in Raleigh, also reanalyzed the data he collected in the late 1970s. He offers a new, anatomical explanation for the hierarchy of hearing detected among blacks and whites.

From the distributions of earplug sizes used by plant workers, he extrapolates that black women had the narrowest ear canals, black men and white women occupied a middle range, and white males had the widest canals. Since hearing ability follows the opposite pattern--black women having the best hearing and white men the worst--ear-canal size might correlate with "big differences in [potentially damaging] sound levels at the eardrums" and, consequently, in hearing loss, Royster says.