Everyone knows that smoking is bad for the health, and many know that secondhand smoke is just as dangerous--if not more so. But most probably won't be able to tell you what happens when you let yourself be exposed too often. According to a study published in the Journal of the American College of Cardiology, breathing in secondhand smoke for even just 30 minutes may cause damage to the lining of your blood vessels.

Using a smoking machine, researchers were able to create three low-level secondhand smoke scenarios—clean air, lingering smoke in a smoker’s home or in a restaurant, and a smoky bar or casino—for their 33 healthy non-smoking volunteers.

Results showed that those who were exposed to lingering smoke for even half an hour developed problems in a blood vessel found in the upper arm. Researchers discovered that the brachial artery did not dilate properly because of the exposure to secondhand smoke. While this may seem insignificant, the study authors say that repeated exposure may lead to something worse, like a heart attack or a stroke.

The study presents very real health threats associated with secondhand smoke. If you’re living with a smoker, consider talking to him or her about smoking somewhere else. If you’re a smoker yourself, perhaps it’s time to reevaluate. Your seemingly harmless habit may already be causing significant health damage to your friends and family.

(Photo by Conan via Flickr Creative Commons)