In the study of more than 61,000 subjects living in Singapore who were followed for up to 12 years, investigators found that being regularly exposed to burning incense almost doubled the risk of developing squamous cell upper respiratory tract carcinomas including nasal/sinus, tongue, mouth and laryngeal.
Squamous cell carcinoma refers to tumors that arise in the cells lining the internal and external surfaces of the body.
The study found no increased risk of lung cancer, but that incense did increase the risk of squamous cell carcinoma of the lung.
Incense is usually derived from fragrant plant materials, like tree bark, resins, roots, flowers and essential oils.
Past research has found that burning these materials can produce potentially cancer-causing substances, including benzene and polyaromatic hydrocarbons.