The study showed that the risk of heart attack was three times higher within the first hour after exposure to traffic and a statistically high rate within three hours of exposure. This study looked at 1454 patients and supported another study conducted with 691 patients in 2004.
Most of the heart attack victims were drivers, but others were exposed to traffic in public transportation or while riding a bicycle. Those most at risk were women, elderly men, those who were unemployed and patients who had previously been diagnosed with angina.
While this study examined heart attack victims, it follows other studies that looked at the effect of diesel fumes on drivers. These studies, which looked at both previous heart attack victims and healthy participants, exposed the participants to diesel fumes in a chamber. Heart activity was monitored and blood was drawn one and six hours after the exposure. The results showed changes in the heart's electrical activity and decreased production of a naturally occurring protein which prevents blood clots from forming within the blood vessels. These studies showed an increased risk of heart attack and stroke after prolonged exposure to diesel fumes. Diesel fumes were studied because they carry more particulate matter than gasoline fumes.
While not specifically mentioned, the effect of stress combined with the environmental factors in driving could also contribute. It has long been known that stress can lead to a heart attack and, for commuters stuck in traffic, stress is an integral part of driving. The stress of delays or from trying to avoid potential collisions with other drivers puts a strain on the body. When faced with stress the body automatically responds with the "fight or flight response". The fight or flight response, shared by all animals, prepares the body to deal with a dangerous situation by shifting blood flow to the large muscles and releasing a dose of adrenaline that prepares the body to either stand and face the danger (fight) or to run away (flight). Either way, the body goes through a very real physical change. Unfortunately, a driver stuck in traffic can neither fight nor flee so the response designed to save your life adds to the break-down of the body’s defenses.
Drivers in high risk groups (women, elderly men, the unemployed, angina sufferers, and those with previously diagnosed heart problems) should be aware of this danger and take steps to avoid problems.