For firemen, it's the flames; for secretaries, it's carpal tunnel; and for priests and yogis, the occupational hazard seems to be incense. According to a recently completed study published in the medical journal, Cancer, people who use incense have an increased risk of getting cancers of the upper respiratory tract--including mouth, sinus, throat, and laryngeal cancers--as well as squamous cell carcinoma. Note: the elevated risk seems to be associated only with very heavy use over a period of years.
The study followed 61,320 Chinese men and women between the ages of 45 and 74 for 12 years. Subjects reported how often they burned incense--daily, weekly, or less regularly--where in the house they burned it and over how long a period of years. Seventy-eight percent of the subjects used incense regularly, and of those, 84 percent had been using it for over 40 years, with 93 percent reporting that they used it every day.
Although the risk of contracting upper respiratory cancers remains slight, heavy incense users had double the incidence, according to the findings. Also, women seemed more prone to incense-related cancers--which the researchers attributed to the fact that Chinese women spend more hours during the day in smoke-filled homes.
Study director Dr. Jeppe Friborg, of Statens Serum Institute in Copenhagen, commented, "Given that our results are backed by numerous experimental studies showing that incense is a powerful producer of particulate matter and that incense smoke contains carcinogenic substances, I believe incense should be used with caution."
When burned, incense releases carcinogens such as polyaromatic hyodrcarbons (PAHs), a class of toxins that includes formaldehyde and that has been linked to lung cancer in smokers. An earlier study found PAH content in temples that burn incense up to 45 times higher than in homes where people smoke. Incense typically contains other carcinogens such as carbonyls and benzene, which can trigger DNA mutations in human cells. Although the components of incense typically include benign plant and flower matter along with essential oils, most formulations also incorporate not-so-benign artificial fragrances and binders. The smoke produced as incense burns releases particulate matter, and because it slowly smolders, it releases even higher concentrations.
Is all incense equally toxic? Certainly if you're going to burn it, you're better off using incense made wholly from organic materials, but even so you might not be protected as the chemistry in the burning process creates the toxic byproducts. An occasional whiff is not going to set off any disease process, but being constantly enveloped in the smoke might.
As Dr. Len Horvitz, a pulmonary specialist at Lenox Hill Hospital in New York City, said, "Anything that affects air quality negatively is not a good thing. Burning in general and the release of smoke, these things are certainly to be avoided. At the very least, chemical irritants will set off asthma, and that's reversible. Cancer is not reversible."
Whereas in Eastern cultures incense overload is omnipresent, in the West, most of us only have occasional exposure. But those who spend lots of time in certain religious settings, in meditation halls, and in dorm rooms may be at risk.
"This is not unlike the type of risk that one experiences from secondhand tobacco smoke," said Dr. Len Lichtenfeld of the American Cancer Society. His colleague, Dr. Norman Edelman of the American Lung Association added, "It's not nearly the danger of smoking a pack a day for 20 years, but it's a danger." On the other hand, burning incense produces particulates greater than 45 mg/g burned as compared to only 10 mg/g burned for cigarettes--more than four times the load. So if you're sitting right on top of burning incense and breathing it in, you're getting a heavier whack of particulates than you would from smoking a Marlboro. The saving grace is that most people use incense to permeate a room rather than inhaling a focused current of toxic smoke directly into the body.
Incense has been implicated before in numerous studies (along with its cousin, scented candles). One such study found that exposure to burning incense at least once a week during pregnancy increases the risk that the child will develop leukemia by 2.7 times. Another measured air quality in several Dutch churches that burned candles and incense and found the particulate levels 20 times higher than they were next to a typical busy road. Other studies have determined links between incense allergic contact dermatitis, various respiratory conditions including asthma, and cancers of the nervous system.
The bottom line is that there is a price to pay if you use incense. The point of incense in religious ritual usually is one of purification, but as these studies show, purification (at least physically) is not what happens--although if incense is an important part of your religious or meditative practice, the risk is small. Then again, maybe some fresh flowers on your alter may do the trick. Also note that if you're using incense to cover the aroma of pot-smoke filled rooms, you might want to reconsider - the pot, that is. A New Zealand study earlier this year found that smoking just one joint a day had the same effect as smoking 20 cigarettes; heavy pot-smokers increased their risk of getting lung cancer by more than 600 percent--and burning incense simply compounds that risk.
Oh, I almost forgot to mention. Yet another recent study found that burning frankincense (Boswellia resin) relieves depression and anxiety. Ah! What to do? What to do? What to do?