Can breathing polluted air increase stress on heart's regulation capacity?

Low oxygen. A lot of pollution can lower the oxygen content of the air you breath, which can cause heart irregularities ...

Yes. Several recent studies have shown that air pollution seems to contribute to an increased risk of coronary artery disease. In observational studies that correlated the degree of air pollution in various cities, there was a clear relationship between higher levels of air pollution and a higher incidence of heart disease. Very provocative recent work, but not surprising given the risk of cigarettes.