Study: Brief Secondhand Smoke Exposure Can Be Hazardous
A 30-minute exposure to the level of secondhand smoke that one might normally inhale in an average bar setting was enough to result in blood vessel injury in young and otherwise healthy lifelong nonsmokers, according to researchers at the University of California, San Francisco. Compounding the injury to the blood vessels themselves, the exposure to smoke impedes the function of the body's natural repair mechanisms that are activated in the face of the blood vessels' injury, the researchers report. Many of these effects persisted 24 hours later.
Study findings are reported in the online edition of the Journal of the American College of Cardiology, appear in the journal's May 6 print issue.
The researchers said their results showed that brief exposure to real-world levels of passive smoke have strong and persistent consequences on the body's vascular system, the researchers conclude.
For the study, subjects were exposed to carefully controlled levels of secondhand smoke in a research setting. The smoke was equivalent to being in a bar where smoking is allowed -- as it still is for 51 percent of the U.S. population and in other countries, such as Germany -- for 30 minutes. As a control, the same subjects were exposed to clean air on a different day.
In both settings, the researchers evaluated the subjects' blood vessel health through ultrasound to measure blood flow and analysis of blood samples. In the exposure environment, this was done before exposure to establish baseline measures, immediately after exposure, and then 1 hour, 2.5 hours, and 24 hours after exposure. The study involved 10 young adult subjects between the ages of 29 and 31.
The study is the first of its kind to link injury to blood vessels with the decreased efficacy of the body's own repair mechanism, namely the endothelial progenitor cells (EPCs), the researchers said. EPCs are circulating stem cells in the blood that play a key role in the repair mechanism of injured blood vessels.