New York:"People exposed to fine-particulate air pollution caused primarily byvehicle exhausts, coal-fired power plants and other industrial sources couldface the risk of developing heart disease," says a study.

The study by Joel Kaufman of the University of Washingtonand other researchers found that air pollution is a much bigger factor indeaths from heart ailments or strokes than has previously been recognised,reported an online edition of health magazine WebMD.

Researchers followed 66,000 women-aged 50-79  living in36 cities. All the women were enrolled in an ongoing health study, the Women'sHealth Initiative.

After adjusting for other risk factors for heart disease andstroke, the researchers in their study said that each 10-unit increase in airlevels of fine particulate matter was associated with a 76 percent increase inthe risk of death from cardiovascular disease.

Particulate matter is the general term used for a mixture ofsolid particles and liquid droplets in the air. It includes aerosols, smoke,fumes, dust, ash and pollen.

The composition of particulate matter varies with place,season and weather conditions. Fine particulate matter is 2.5 microns indiameter and less.

It is also known as PM2.5 or 'respirable' particles becauseit penetrates the respiratory system further than larger particles.

Earlier scientific studies have linked particulate matter,especially fine particles, with a series of significant health problems,including premature death, respiratory disorder, chronic bronchitis anddecreased lung function.