Regular inhalation of incense smoke could increase the risk of
a variety of respiratory cancers, according to a study conducted
by researchers from the Statens Serum Institute in Copenhagen,
Denmark, and published in the journal Cancer
"This association is consistent with a large number of studies
identifying carcinogens in incense smoke," the researchers wrote,
"and given the widespread and sometimes involuntary exposure to
smoke from burning incense, these findings carry significant public
Researchers interviewed 61,320 ethnically Chinese adults from
the Hokkien or Cantonese dialect group living in Singapore on
their patterns of incense use. The participants reported on how
often they burned incense at home and for how long. All participants
were between the ages of 45 and 74 and were free of cancer
when the study began. After 12 years, 325 participants had developed
upper respiratory cancers, while 821 had developed lung cancer.
The researchers found that people with heavier incense use were
significantly more likely to develop an upper respiratory cancer,
such as of the nose, mouth or throat. They were also significantly
more likely to develop squamous cell carcinoma of the respiratory
lining. In particular, people who burned incense all day or all
day and night had an 80 percent higher risk of squamous cell carcinoma
of the whole respiratory tract.
No correlation was found between incense use and the risk of lung
(lower respiratory) cancer. The correlations between upper respiratory
cancers or squamous cell carcinoma and incense use held strong,
however, even after the researchers adjusted for other risk factors
such as smoking, diet and alcohol consumption.
Prior studies have indicated that when burned, incense gives off
some substances that are known to be carcinogenic, including benzene
and polyaromatic hydrocarbons. The researchers said that further
investigations might determine whether certain types of incense
are more likely than others to increase the risk of cancer.