The findings showed that when pollution hits the mark of 25 micrograms per cubic metre, it increases the risk for people with non-O blood types.
"Once you go above that, each additional 10 micrograms of pollution per cubic metre of air provided substantially higher risks," said lead investigator Benjamin Horne, clinical epidemiologist from the Intermountain Heart Institute in Utah, US.
"At levels higher than 25 micrograms per cubic metre of pollution, the increase in risk is linear, while below that level there's little, if any, difference in risk."
In the study, the researchers studied genetic differences between O blood types and non-O, which includes positive and negative A, B, and AB blood types.
"The one that's been found in genetic studies to be lower risk is O. The other three were higher risk," Horne said.
However, "this association between heart attacks and pollution in patients with non-O blood isn't something to panic over, but it is something to be aware of", he said.
Moreover, people with type O blood also have higher risk of heart attack or unstable chest pain in times of high air pollution.
But their level of risk is much smaller, at 10 per cent instead of the non-O blood type's 25 per cent per 10 additional micrograms per cubic metre, Horne said.
So at the 65 micrograms per cubic metre pollution level, a person with type O blood faces risk that is 40 per cent higher than if the air wasn't polluted.
The results were presented at the 2017 American Heart Association Scientific Sessions in California.
Staying indoors, exercising indoors, compliance with heart medication may help reduce risks, the researchers said.
