Incense is commonly used in a number of different countries for religious, spiritual or cultural purposes, but a new study shows that certain types of incense smoke could contribute to indoor air pollution.

The study, "Hazard assessment of United Arab Emirates (UAE) incense smoke" is published in the August 2013 issue of Science and the Total Environment and was conducted by a team at Gillings School of Global Public Health at the University of North Carolina at Chapel Hill.

Incense comes from the Latin word incendere, "to burn." It is used in numerous countries during religious ceremonies, aromatherapy, meditation or other spiritual reasons — especially in China, India, Japan and Tibet.

In the United Arab Emirates, an Arab country that borders Saudi Arabia, 94 percent of households burn incense weekly, according to the study. It is used to add a "perfumed" scent to the indoor air and clothing.

Oudh and Bahkoor are the two most popular types of incense used in UAE homes. It is common for hosts to pass bahkoor among guests in Arab households as a hospitable gesture, or to remove the odor of fish and other cooking smells after eating. Bahkoor is also used in Christian church services and blessings.

Indoor air pollution has become more of an issue in recent years — 1 million people die from chronic obstructive respiratory disease (COPD) annually, according to the World Health Organization (WHO). COPD is often caused by indoor pollutants that originate from cook stoves, open hearths, or incense. It is a disease that causes progressive difficulty in breathing and is most often caused by cigarette smoke.

The UNC researchers measured the gases emitted by Oudh and Bahkoor — carbon monoxide, sulfur dioxide, as well as nitrogen and formaldehyde — in a special room that provided a concentration of smoke similar to that of a typical UAE living room. They exposed human lung cells to the smoke in this room, allowed them to incubate, and discovered an inflammatory response that likens the response of lung cells exposed to cigarette smoke.

In the past, incense smoke has been linked to health problems like eye and skin irritation, asthma, headaches and changes in lung-cell structure. The study suggests that when using incense, people open doors or windows to improve ventilation. UNC researchers plan to conduct more in-depth studies to determine what other compounds in incense can cause inflammatory lung cell reactions.

Source: Rebecca Cohen, Kenneth G. Sexton, Karin B. Yeatts. Hazard assessment of United Arab Emirates (UAE) incense smoke. Science of The Total Environment, 2013