Cancer and incense

Burning incense may create a sweet scent, but regularly inhaling the smoke could put people at risk of cancers of the respiratory tract, researchers reported. In a study of more than 61,000 ethnic Chinese living in Singapore who were followed for up to 12 years, the investigators found a link between heavy incense use and various respiratory cancers. The findings are published in the medical journal Cancer on Monday. Incense has been used for millennia in many cultures' religious and spiritual ceremonies. In Asia, people commonly burn incense in their homes - a practice that is becoming more popular in western countries as well. 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. However, no studies until now had linked the practice of burning incense to an increased cancer risk over time, according to the researchers, led by Jeppe Friborg of the Statens Serum Institute in Copenhagen. For their study, the researchers followed 61,320 Singapore Chinese men and women between the ages of 45 and 74 from the Hokkien or Cantonese dialect group. All of the subjects were cancer-free at the outset. Participants reported on their typical incense use, including how often they burned it in their homes and for how long - only at night, for instance, or all day and night. Over the next 12 years, 325 men and women developed cancer of the upper respiratory tract, such as nasal, oral or throat cancer. Another 821 developed lung cancer. The researchers found that incense use was associated with a statistically significant higher risk of cancers of the upper respiratory tract, with the exception of nasopharyngeal cancer. However, they observed no overall effect on lung cancer risk. Those who used incense heavily also had higher rates of a type of cancer called squamous cell carcinoma, which refers to tumors that arise in the cells lining the internal and external surfaces of the body. The risk was seen in smokers and nonsmokers. Study participants who used incense in their homes all day or throughout the day and night were 80% more likely than non-users to develop squamous cell carcinoma of the entire respiratory tract.