The Risk of Incense Burning

A cooperative study between researchers from Denmark and Singapore has resulted in a publication in the journal Cancer that evaluates a major risk from burning incense. It is believed to be the first to document an increased risk for certain cancers in people exposed to burning incense.

Singapore was chosen as the study site as incense use is an integral part of daily life in many parts of Asia. Over 60,000 Singapore Chinese who were free of cancer and aged 45 - 74 were enrolled between 1993 and 1998. At baseline they completed an interview on their living conditions, lifestyle, and diet. From enrollment up to 2005 cancer occurrence was determined from public records.

During follow-up there were 821 cases of lung cancer and 325 cancers of the upper respiratory tract (nasal and throat passages, tongue, mouth, larynx, and so on). The numbers of lung cancers were not influenced by exposure to incense. On the other hand, the upper respiratory tract tumors revealed a different story. These tumors could be classified into 2 types, nasopharyngeal and non-nasopharyngeal. Incense use was linked with a significantly increased risk of cancers of the non-nasopharyngeal type. And the use of incense was associated with an increased risk of squamous cell carcinoma – a type of cancer of surface cells seen with chronic irritation – throughout the respiratory tract. This effect was ‘dose-dependent’; the duration and intensity of incense use were associated with this increased risk of squamous cell cancer. When used on a daily basis, the risk for cancer more than doubled.

The results of this epidemiological study are consistent with the finding of numerous carcinogens in incense smoke. As incense burning is growing in popularity in the USA , family physicians and otorhinologists should be alert for such occurrences in their practices, especially in people likely to be using incense.