Bad air isn't just rough on your lungs, it's also bad news for your heart. A new study out of Italy has shown that as daily air pollution levels go up, so too does the risk for severe cardiac events such as heart attacks.

The findings jibe with the growing recognition that air pollution, especially of the particulate matter variety belched out by vehicles and industry, is hazardous – in the short and the long term – to those with heart disease. "There is good evidence out there that air pollution is bad for the heart both chronically and when you're acutely exposed to it," said Robert A. Kloner, professor of cardiovascular medicine at the University of Southern California and the research director of the Heart Institute at Good Samaritan Hospital in Los Angeles, who was not involved in the study.

The research, conducted by Savina Nodari of the University of Brescia and presented recently at the Acute Cardiac Care Congress 2013, tracked daily hospitalizations for cardiac events in Brescia against an index of air quality known as PM10. That stands for particulate matter measuring 10 micrometers or less in diameter, or about one-seventh of the width of a human hair. The European Union's daily safety threshold for PM10 is 50 micrograms per cubic meter, though the air in industrialized Brescia often exceeds this level. (Here in the United States, the Environmental Protection Agency's daily PM10 safety standard is actually three times higher at 150 micrograms per cubic meter.) The Italian scientists noted a 3% increase in hospital admissions for major cardiovascular problems for every 10 microgram increase in PM10 levels.

Kloner explained that acute exposure to particulate matter is thought to trigger inflammation in the body. Studies have shown that particulate matter can end up in the blood, traveling directly to the heart and causing it to swell and function improperly. Over the long term, people with chronic exposures to air pollution – living near a freeway, for example – develop risk factors for cardiovascular disease, including increased blood pressure as well as thicker and harder arteries.

A key takeaway from the new study is that the established safety limits for PM10 exposure appear too high. Individuals with heart disease should thus do their best to take air pollution warnings seriously, given that the risk for harm probably kicks in at pollution levels well below those that prompt official alerts. "Especially on bad pollution days, we suggest that a patient stay indoors," said Kloner. "Don't go exercise where you're breathing in and out vigorously because that's going to increase your exposure."