We know that ozone pollutes the air, seeps into the lungs and prompts health alerts that keep people indoors. Now add this to your ozone worry list - your body creates ozone, and it may cause heart disease.
California researchers say the same ozone formed by the body's immune system to fight off infections in the bloodstream - a function discovered a year ago - may contribute to atherosclerois, a major killer.
Although breathing ozone may hurt your respiratory system, it isn't damaging your arteries, according to researchers from the Scripps Research Institute in LaJolla.
"The penetration of ozone into the body from external inhalation is so small that it will not enter the bloodstream," Dr. Paul Wentworth Jr., the lead researcher, wrote in response to e-mailed questions.
But a yearlong study using human tissue samples found that ozone naturally occurring in the blood may contribute to clogging of the arteries, which is a major factor in many heart attacks and strokes.
The findings were published in today's issue of Science.
Atherosclerosis is a progressive disease in which fat, cholesterol, calcium and cellular wastes form unwanted tissue in the arteries. The buildup damages artery walls, creating tears and inflammation, which makes it more difficult for blood to carry oxygen and nutrients throughout the body.
Smoking, high blood pressure and high-fat diets are believed to be contributing factors.
There is a process for repairing artery wall damage that involves progenitor cells, which migrate from the bone marrow. But with aging, the process breaks down, making people more susceptible to artherosclorsis.
"It becomes harder for the repair cells to do their job, and the inflammation presents more of a threat," said Dr. Pascal J. Goldschmidt, chairman of medicine at Duke University School of Medicine and an expert on artherosclerosis.
Last year, the Scripps team published findings showing that when the immune system kicks in to fight inflammation in the arteries, it creates ozone - an unstable and potentially hazardous form of oxygen.
In the study released yesterday, the researchers used those findings to go a step further and show that ozone contributes to development of atherosclerosis.
They took 15 samples of atherosclerotic tissue from patients and exposed them to a chemical that stimulates the immune system. When they examined the chemical signatures of the oxidants created in the process, they found ozone.
Experts say the results could lead to new drug therapies and help unravel many mysteries remaining about artherosclorosis.
"It supports the concept that arthersclerois is a dynamic process and a lot more complicated than a simple buildup of fat and cholesterol in the arteries," said Dr. Roger Blumenthal, director of preventive cardiology at the Johns Hopkins School of Medicine.
Physicians continue to recommend that people minimize the risk of stroke and heart attack by not smoking, exercising regularly, reducing cholesterol with a low-fat diet and monitoring blood pressure with checkups.
Goldschmidt said atherosclerosis begins with damage to arterial walls created by "free radicals," highly reactive molecules that can modify the structure of proteins in the blood. The more of these proteins, or reactive oxidants, that are in the bloodstream, the worse it is for the arteries, he said.