New research suggests air pollution can increase and individuals risk of developing heart disease.

Researchers from the Johns Hopkins Bloomberg School of Public Health have found a link between higher levels of a specific kind of air pollution in major urban areas and an increase in cardiovascular-related hospitalizations such as for heart attacks in people 65 and older.

"We suspected that there was an association between coarse particles and health outcomes, but we didn't have the research to back that up before," Roger D. Peng, who led the study, said in a statement. "This work provides the evidence, at least for cardiovascular disease outcomes. I don't feel like we need another study to convince us. Now it's time for action."

For the study, researchers collected and analyzed data from an air monitoring network set up by the U.S. Environmental Protection Agency (EPA) in 110 large urban counties in the United States and linked it to Medicare data on hospitalizations in those same areas from 1999 to 2010. The hospitalizations covered people ages 65 and older.

The investigators found that on days when coarse particle levels were higher, cardiovascular hospitalizations were also higher that same day. They did not find a correlation in the following days.

Researchers said their findings varied by geographic region. While there were higher concentrations of coarse particles found in the western United States, there were more cardiovascular events requiring hospitalization in the eastern United States.

"Just because the particles are the same size doesn't mean they are made of the same material," Peng said. "It's possible that the chemical composition of the particles in the east could make them more toxic."

The findings are detailed in the journal Environmental Health Perspectives.