New research is suggesting that using incense for long periods could increase the risk of developing cancers of the respiratory tract.
According to a new study which examined the long term use of incense and cancer risk, a team of researchers from Denmark, Singapore and the U.S. say incense use was associated with a significantly increased risk of upper respiratory tract cancer.
The authors say this is the first prospective investigation of incense and cancer risk and given the widespread and sometimes involuntary exposure to the smoke of burning incense, the findings carry significant public health implications.
In many parts of Asia incense burning is an integral part of daily life, but incense is made of plant materials mixed with oils which the researchers say produces a mixture of possible carcinogens, including polyaromatic hydrocarbons, carbonyls and benzene.
Because incense smoke is inhaled, a number of studies have examined the possible link between incense burning and lung cancer, but with inconsistent results and the possible link between incense and other respiratory tract cancers has had little attention.
The study led by Dr. Jeppe Friborg of the Statens Serum Institut in Copenhagen, Denmark and colleagues in Singapore and the U.S., examined the associations between exposure to incense and the whole range of respiratory tract cancers.
The large study, initiated in the 5 years between 1993 and 1998, involved 61,320 Singapore Chinese aged 45-74, who were all free of cancer.
All completed a comprehensive interview on living conditions and dietary and lifestyle factors and were followed through to 2005; it was recorded which participants developed cancer during that time.
Dr. Friborg's team found a total of 325 upper respiratory tract cancers, including nasal/sinus, tongue, mouth, laryngeal and other cancers as well as 821 lung cancers.
The researchers say while there was no overall effect on lung cancer, incense use was associated with a significantly increased risk of upper respiratory tract cancer, other than nasopharyngeal.
The researchers also found that the duration and intensity of incense use was linked to an increased risk of squamous cell carcinomas in the entire respiratory tract - squamous cells cover the internal and external surfaces of the body.
According to the research, incense use seemed to add to the increased risk of upper respiratory tract squamous cell carcinoma in smokers and also considerably increased the risk in never smokers, which points to an independent effect of incense smoke.
The authors say that incense use extends beyond Chinese populations and is used on a daily basis in both temples and homes in many non-Chinese, Asian communities, including those in Southeast Asia and the Indian subcontinent.
They say regular use also occurs in the West and more research is needed to identify the least harmful types of incense.
The research appears in the October 1, 2008 issue of CANCER, a peer-reviewed journal of the American Cancer Society.