MONDAY AUGUST 25, 2008 (foodconsumer.org) -- A new study in the October 1, 2008 issue of Cancer suggests that long term exposure to incense increases risk of developing cancers of the respiratory tract.

Buring incense made of plant materials and oils produces a mixture of possible carcinogens such as polyaromatic hydrocarbons, carbonyls and benzene. Early studies showed tried to link incense burning and lung cancer, but results were inconsistent.

The study led by Dr. Jeppe Friborg of the Statens Serum Institut in Copenhagen, Denmark and colleagues in Singapore and the U.S. was meant to examine the association between exposure to incense and the risk of respiratory tract cancers in a large population in Singapore.

The researchers followed 61,320 Singapore Chinese free of cancer age 45 to 74 starting in 1993 to 1998 through 2005 to see how many and who developed cancer during the follow-up. During the follow-up, 325 upper respiratory tract cancers and 821 lung cancers were recorded.

Dr. Friborg's team found that incense use was associated with a significantly increased risk of upper respiratory tract cancer, but not overall risk of lung cancer.

They noted that the duration and intensity of incense were linked with an increased risk of squamous cell carcinomas in the entire respiratory tract.

"Given the widespread and sometimes involuntary exposure to smoke of burning incense, these findings carry significant public health implications," the researchers wrote.

"Besides initiatives to reduce incense smoke exposure, future studies should be undertaken to identify the least harmful types of incense," they added.