August 26, 2008

Burning Incense May Hike Cancer Risk

Researchers in Denmark report that people who regularly inhale incense might be increasing their risk of respiratory tract cancers.

The researchers followed thousands of Chinese men and women for up to 12 years, and found a clear link between the consistent use of incense and respiratory cancers.

Incense is usually derived from fragrant plant substances, like flowers, roots, tree bark, resins and essential oils.  Although previous studies have found that burning these materials can produce potentially cancer-causing substances, such as polyaromatic hydrocarbons and benzene, the current  study is the first to link the burning of incense to an increased risk of cancer over time, the researchers said.

In conducting their study, the research team, led by Dr. Jeppe T. Friborg of the Statens Serum Institute in Copenhagen, followed 61,320 Singapore Chinese men and women aged 45 to 74 from the Hokkien or Cantonese dialect group. All participants were free of cancer at the beginning of the study.

The subjects reported on their incense use, including how often they burned it in their homes and the duration of use.  Over the following 12 years, 325 men and women developed nasal, oral or throat cancer, and another 821 developed lung cancer.

While the study indicates that incense use is associated with a statistically significant increased risk of most upper respiratory tract cancers, the researchers found no overall effect on lung or nasopharyngeal cancer.

Heavy incense users who burned incense in their homes all day or throughout the day and night had an 80 percent increased risk of squamous cell carcinoma of the entire respiratory tract, regardless of smoking status, the researchers said.  Squamous cell carcinoma is a type of cancer that forms in the cells lining internal and external body surfaces.  

The cancer risk associated with incense use was present even after accounting for other factors, such as diet, cigarette smoking and drinking habits.

"This association is consistent with a large number of studies identifying carcinogens in incense smoke," Friborg's team wrote in a report about the study.

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

The scientists said additional research is needed to determine whether different types of incense are associated with different degrees of cancer risk.  In Singapore, for instance, people typically burn coils or long sticks of incense that burn slowly over an extended period, the researchers wrote.

Many cultures have used incense for centuries as part of various religious and spiritual ceremonies. Many Asians burn incense in the homes, a practice that is becoming more popular in Western countries as well.


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On The Net:

The Statens Serum Institute

Squamous Cell Carcinoma