High Smog Levels Tied to Serious Heart Problems

High levels of particulate air pollution - commonly known as smog - raise the risk of heart attack and other serious heart problems, according to a new study.

Particulate air pollution refers to tiny particles in the air known as PM10. The European Union's PM10 safety threshold is 50 micrograms per cubic meter (mcg/m3), but this study suggests that the harmful effects of PM10 may occur below that level.

The researchers compared data on average daily concentrations of PM10 in Brescia, Italy, between 2004 and 2007 and daily hospitalizations for cardiac events during that period. They found a significant association between PM10 levels and the number of admissions for heart attack and other acute coronary syndromes (an umbrella term for conditions where blood supply to the heart muscle is suddenly blocked), heart failure, worsening heart failure and heart rhythm disorders. For every 10-microgram increase in PM10 levels, there was a 3 percent increase in hospital admissions for serious heart problems, according to the study.

The researchers also found that men and people older than 65 were especially vulnerable to having acute coronary syndromes or heart rhythm disorders with increasing PM10 levels. In addition, people who had previously been hospitalized for heart problems were more likely to be admitted to the hospital with heart problems when PM10 levels were higher. "We need to pay particular attention to protecting patients who are older and who have had a previous heart attack or other heart problem, as they are more vulnerable to having another cardiac event," study author Dr. Savina Nodari said.

"Previous studies support the hypothesis that air pollution may increase cardiovascular-event rates because PM10 can induce processes that are bad for the heart, including inflammation and coagulation," she added.

Nodari said the current PM10 threshold is too high, and the cutoff should be reduced to 20 to 30 mcg/m3 or less, "because, like cholesterol, the risk is continuous -- the higher the levels the greater the risk. If we can obtain a lower level of PM10 probably we will lower the risk of heart disease."