In many cultures across the world, burning incense is ceremonial or a widespread pastime. A new study, however, has shown that the smoke produced by burning incense could be causing lung problems.

The study, published in the August issue of Science of the Total Environment, showed that the types of incense most often used in the United Arab Emirates (UAE) emit a “significant” amount of carbon monoxide, formaldehyde, and nitrogen oxide particles. These particles were found to create an inflammatory response in lung cells. The study’s authors stated that these chemicals are the same ones known to cause chronic obstructive respiratory disease, from which more than 1 million people die every year.

Researchers at the University of North Carolina simulated a “typical” UAE living room using an enclosed environmental chamber. They measured particles emitted from incense during three-hour tests, which they say is normal for the amount of time incense is burned. Human lung cells were then placed inside the chamber for 24 hours to expose them to the particles. The inflammatory responses seen in the cells, say the study’s authors, were similar to those associated with asthma, or seen when such cells are exposed to cigarette smoke.

This study adds to others that have linked incense smoke to other health troubles, including asthma; headaches; changes in lung-cell structure; and eye, nose, throat, and skin irritation. The researchers concluded that better ventilation is needed when burning incense in the UAE, where people are estimated to spend 90% of their time indoors.