Breathing 'can cause heart attacks'

Breathing can cause heart attacks, scientists have warned, after increasing air pollution was linked to health problems.

Experts say evidence is mounting that a rise in pollution from traffic and industry could be linked to an increase in deaths from heart attacks. Heart disease is usually associated with genetic factors and lifestyles like smoking, poor diet and lack of exercise.

However, research has begun in the new field of environmental cardiology which is examining the link between air pollution and heart disease. Research in six US cities found that people died earlier - often from heart disease - when they lived in areas with high pollution levels.

Another study of 250 metropolitan areas round the world found an increase in air pollution led to a sudden rise in heart attacks. And research in Salt Lake City in the US found that when a nearby steel mill shut down for months there was a drop in death rates of up to six per cent. Mortality rose to previous levels when the steel mill re-opened.

People who seem to be most susceptible to environmental pollutants are those who are already vulnerable, including the elderly and people with coronary artery disease. There is also some evidence that diabetics, women and people who are obese may be at greater risk.

Researchers are now trying to find out which pollutants are harmful and how they damage the cardiovascular system. The study has identified the worst air pollutants as ozone, nitrates, sulfates and metals.

It has found the risk of a heart attack particularly increases when people spend a lot of time in heavy traffic.

Researcher Dr Aruni Bhatnagar, from Louisville University, found that pollution from smoke, including that from cigarettes or car exhausts, increased blood cholesterol levels and activated enzymes that cause plaque in blood vessels to rupture. When plaque ruptures, it can cause a blood clot, which may block an artery and lead to a heart attack.

The team found that within 15 minutes of inhaling pollutants, there is a very rapid increase in blood pressure. Blood vessels react to the pollutants by producing an inflammatory response to attack the foreign matter. However, the inflammatory response itself can set off a complex bodily reaction that is harmful to the blood vessels.

Co-researcher Dr Robert Brook said people who live in built-up areas should take steps to reduce the risk of air pollution. During times when air quality is poor, it is recommended to exercise indoors.

People who want to exercise outdoors should do it when pollution is at a lower level, such as outside peak commuting times.