Air pollution is just as bad for your vascular system as it is for your lungs. Researchers determined that breathing in diesel exhaust fumes reduces blood flow and interferes with the body's natural ability to break up blood clots. A 2007 Clean Air Task Force study found that the pollution levels inside cars, buses, and trains are four to eight times higher than in the outdoor air in many urban areas. So if you live in a large metropolis, do your blood vessels a favor and walk to work. When exercising, choose a hike, ride, or trail run away from traffic.