Researchers suggest acute heart problems including heart attacks should be added to the list of health risks that wide-ranging smoke from wildfires can present.

It has long been known that such smoke can result in respiratory problems such as bronchitis and asthma attacks, but now researchers at Australia's Monash University say they've found a link between exposure to fine particulate matter air pollution -- in other words, wildfire smoke -- and the risk of heart-related incidents.

The university is located in the Australian state of Victoria, which is particularly susceptible to large wildfires because of the climate and the effect on vegetation of recurring and protracted drought.

In December 2006 and January 2007 - the heart of the Australian summer - wildfires burned almost 250 million acres in the state.

Smoke from those fires reached cities far from the locale of the fires, the researchers point out, pushing air pollution levels above recommended healthy limits.

Analyzing data from the Victorian Ambulance Cardiac Arrest Registry and the Department of Health and Human Services, they found that an increase in particulate concentration from the 25th to the 75th percentile resulted in a 6.98 percent increase in out-of-hospital cardiac arrests.

The link between particulate pollution and cardiac arrests was particularly noticeable in men and in people 65 and older, the researchers report in the Journal of the American Heart Association.

Particulate matter in wildfire smoke is less than 2.5 thousandths of a millimeter in diameter - invisible to the naked eye - and can cause health issues if breathed in.

PM2.5 levels from wildfires can easily exceed air quality guidelines set by the World Health Organization, the researchers said.

Wildfire smoke may be particularly toxic because the small size of the particles allows it to penetrate deep into the lungs.

"Given the increased incidence and frequency of wildfires recently and the increased number of people at risk of smoke exposure, future research is required to investigate the role of fine particulate matter exposure from wildfire smoke in triggering acute coronary events," the researchers wrote.

An increase in the numbers and severity of wildfires in recent years emphasizes the importance of understanding the consequences of wildfire smoke exposure on health, says study lead author Dr. Anjali Haikerwal of Monash's Department of Epidemiology and Preventive Medicine.

"These particles may act as a trigger factor for acute cardiovascular events, therefore its important to not delay seeking medical help if you experience symptoms of heart problems during smoke episodes from wildfires," she says.

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