The Journal identified exposure to particulate matter (PM-10) and nitrogen dioxide – both found to be at elevated levels of concentration in urban centers – as possible triggers of heart attacks. The Journal lists the risk as minute – up to 1.3 percent increased risk of a heart attack up to six hours after exposure to those two substances – but claim the two pollutants can speed the occurrence of a looming heart attack.
Krishnan Bhaskaran and six colleagues at the London School of Hygiene and Tropical Medicine examined 79,288 heart attacks that occurred in 15 urban areas throughout the UK from 2003 to 2006. The team then evaluated the level of pollution in those 15 areas at the time patients suffered heart attacks. The group concluded that, "Higher ambient levels of the traffic-associated pollutants, PM10 and NO2, were followed by a transiently increased risk of myocardial infarction up to six hours later." Playing in traffic isn't going to cause a heart attack, but it also isn't going to make your heart better, so be careful out there.