Burning incense is a source of indoor air pollutants that may cause inflammation in human lung cells, a study led by researchers at University of North Carolina found.

In the past, research linked incense smoke with numerous health issues, including respiratory symptoms, headaches, exacerbation of cardiovascular disease and changes in lung-cell structure.

In the current study, the authors identified and measured the particles and gases emitted over the course of three hours from two kinds of incense typically used in homes in the United Arab Emirates where an estimated 94 percent of households engage in the practice weekly. Furthermore, the experiment was carried out in a specially designed indoor environmental chamber constructed to reflect a typical living room from that region of the world.

The researchers then analyzed both particulate concentrations and levels of gases, such as carbon monoxide, sulfur dioxide, oxides of nitrogen and formaldehyde.

By placing human lung cells in the smokey chamber, then incubating them for 24 hours so as to allow particulates to settle and the cells to respond, the scientists discovered a resulting inflammatory response similar to that of lung cells exposed to cigarette smoke.

All told, the World Health Organization estimates that more than 1 million people die every year from chronic obstructive respiratory disease (COPD), the primary cause of which, it says, has to do with pollutants from cook stoves and open hearths. However, burning incense releases similar pollutants, including carbon monoxide, and is used widely in the Eastern world to perfume clothing and air and remove cooking odors. 

Compounding this issue is that charcoal briquettes are frequently used to ignite and burn the incense, adding significantly to potentially harmful levels of carbon monoxide and other pollutants, the study's authors noted.

In order to combat the potential health risks of this pervasive practice, the team recommends implementing better ventilation in UAE homes where incense is burned, such as opening a door or window to improve air flow, and using alternatives to charcoal, including electric combustion devices.

Going forward, they propose that studies should measure additional compounds caused by incense burning and offer a more in-depth analysis of inflammatory markers.