Unlike the nose, which harbors many types of bacteria, the sinuses--the air-filled cavities in the skull surrounding the nose--remain curiously free of intruders. The sinuses, like the rest of the body, are a warm, bacteria-friendly environment. It should be perfect for bacteria to live there, says Jon Lundberg, a physician at the Karolinska Institute in Stockholm. Lundberg and his colleagues have discovered one way that the sinuses stay sterile: they produce nitric oxide, a gas considered a pollutant in the atmosphere and one that is lethal even in small doses to bacteria and viruses.
Lundberg and his colleagues used a syringe and a catheter to remove air from the sinuses of dozens of healthy, nonsmoking subjects. When they analyzed the air samples, they found nitric oxide levels that were close to the highest permissible atmospheric pollution levels. They later removed small pieces of the membrane lining the sinuses, which consist ...
