Researchers reported that burning incense, apart from giving a sweet fragrance, could increase the risk of respiratory tract cancers. Researchers from Statens Serum Institute in Copenhagen, Denmark studied more than 61,000 Chinese living in Singapore for a 12 year period to try to discover a link between heavy incense use and respiratory cancers.

Incense derived from fragrant plant products such as bark, resins, roots, flowers and essential oils have been used for centuries as a part of religious and spiritual ceremonies. In Asia, incense is not only burned at temples and religious ceremonies but is commonly used in homes as well. This practice is now catching on in many homes in the West as well.

Earlier research has found that the burning of these incense sticks can produce substances that have cancer causing potential including benzene and polyaromatic hydrocarbons. The study led by Dr. Jeppe T. Friborg found that regular exposure to burning incense almost doubled the risk of developing squamous cell upper respiratory tract carcinomas including nasal/sinus, tongue, mouth and laryngeal.

The team studied Singapore Chinese men and women between the ages of 45 and 74 from the Hokkien or Cantonese dialect group who were all cancer-free at the beginning. The subjects were asked how often they burned incense in their homes and for how long. Over the next 12 years 821 people developed lung cancer, while 325 developed cancer of the upper respiratory tract such as the nasal, oral or throat.

The researchers reported that though there was a statistically higher risk of upper respiratory tract cancers with the exception of nasopharyngeal cancer, overall there was no real increase in lung cancer risk seen. Incense users did see an 80 % increased risk of squamous cell carcinoma of the lung, which has tumors in the epithelial cells, which line the body as compared to non incense users. This risk was seen in both smokers and non smokers and increased cancer risk held for incense users when other factors such as diet, drinking habits and cigarette smoking were taken into consideration.

Dr. Jeppe Friborg, of the department of epidemiology research at Statens Serum Institute, told HealthDay, “Given that our results are backed by numerous experimental studies showing that incense is a powerful producer of particulate matter and that incense smoke contains carcinogenic substances, I believe incense should be used with caution.”

The team further elaborates, “This association is consistent with a large number of studies identifying carcinogens in incense smoke, and given the widespread and sometimes involuntary exposure to smoke from burning incense, these findings carry significant public health implications.”

The study is to be published in the medical journal Cancer, and says further studies are needed to establish if the degree of cancer risk changes with the type of incense that is used. In Singapore the most commonly used incense sticks are either long or coiled sticks that are slow burning and last for an extended period of time.