Heart attack linked to pollution?

An interesting article suggests a possible link between pollution in the atmosphere and heart attack/disease.. http://www.medilexicon.com/medicalnews.php?newsid=143359 Examples are based on observations of spikes in pollution levels and medical records,and an example of a steel mill being closed for a period then re-opening months later,with a possible correlation of fewer heart condition deaths in the intervening time..Any thoughts on this? Thanks for responses!