While the sweet smell of incense can induce a feeling of relaxation or is part of many cultures’ religious ceremonies, new research is calling into question the practice of burning it regularly in homes.

A study looked at more than 61,000 ethnic Chinese living in Singapore, where most people use long sticks or coils of incense that burn slowly over an extended period. The participants were followed for up to 12 years, and researchers found a link between heavy incense use and various respiratory cancers.

Incense is made from fragrant plant materials, like tree bark and resins, and past research has found that burning these materials can produce potentially cancer-causing substances. However, no previous studies had linked burning incense to an increased cancer risk over time, according to the researchers from the Statens Serum Institute in Copenhagen. The findings are published in The Cancer Journal.

The study found that incense use was associated with a higher risk of cancers of the upper respiratory tract, but not of lung cancer risk. Those who used incense heavily also had higher rates of squamous cell carcinoma, which are tumors that arise in the cells lining the body’s internal and external surfaces. Study participants who used incense heavily in their homes were 80 percent more likely than non-users to develop squamous cell carcinoma of the entire respiratory tract. The link between incense use and increased cancer risk held when other factors, including cigarette smoking, diet and drinking habits, were considered.

For me, incense is an occasional addition to a yoga class, or a pleasing smell that helps mask odours at home, but several people I know do use it regularly when meditating. Is burning incense part of your culture or something you use regularly to promote relaxation?

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