pollution, chemical contamination, ozone (and it does not take a lot), and many other man made problems/things can trigger heart attacks and cause DNA mutations and metabolic issues that lead to plaque build up... among a host of other diseases.
it is important that you understand it is not just one thing and that man has caused, both directly and indirectly, the bulk of the problems humans have in terms of health throughout history.
good people, doing mostly the right things do fall victim and die from man made causes...
both China and India have admitted over the last decade that millions die every year from air pollution alone - some via cancers and others due to cardiac arrest, among other things like COPD... this will only get worse as time goes on.