If you are feeling Zen, chances are you burn incense on a somewhat regular basis. Burning incense indoors is no longer just a hippie custom. It’s gone mainstream, though its origins and prevalence is central to many Asian cultures and religions. If you travel to Japan, you’ll observe it burning outdoors and indoors at most shrines and religious temples. Incense renders a pleasant smell and, unlike its close counterpart, tobacco, you would doubt there’s an associated health hazard. However, according to a new study, and past research, the hazard is real and serious.
A recent study out of South China University of Technology looked at incense exposure and revealed some surprising results. The study examined the effects of exposure to incense, compared to those from cigarette smoke. Two types of incense were tested, and both contained agarwood and sandalwood. The subjects, Chinese hamsters, were exposed to smoke from both types of incense. After the exposures, their ovary cells were examined. The researchers found that the hamsters exposed to both types of the incense smoke showed more mutations in the DNA of their cells, indicating that incense may be potentially toxic to the cells.
Also noted was the fact that the smoke from incense results in production of finer particles than cigarette smoke. This means that the particles from incense smoke can more easily penetrate deeper into lung airways.
The particles from nine different types of incense were investigated in another study done at National Cheng Kung University in China. The particles observed from these samples were primarily what are called polycyclic aromatic hydrocarbons (PAH’s) and their average size was 0.3 microns. The average size of cigarette smoke by-product particles is 4 microns (considerably bigger). So again, the smaller particles derived from incense have a much easier time getting into the lungs of individuals in the room, who are breathing in the smoke produced. An even bigger area of concern is the chemicals associated with incense. Aromatic hydrocarbons are based on “benzene rings,” which have been identified as carcinogenic (cancer-producing) in nature.
Another study done in the United Arab Emirates, where it’s estimated that over 90 percent of households use incense regularly, measured the particles and gases emitted over the course of three hours while exposed to human lung cells in an isolated chamber. The researchers found that by-products in the smoke including carbon monoxide, sulfur dioxide, and formaldehyde, resulted in inflammatory response similar to lung cells when they were exposed to cigarette smoke.
Compounding this issue is that charcoal briquettes are frequently used to ignite and burn the incense, and that in itself results in the production of carbon monoxide and other pollutants.
Incense aren’t a quick fix like cigarettes
It is also important to assess the time of exposure to incense smoke. When someone smokes a cigarette, smoke exposure is on average three to five minutes per cigarette, and it’s more often restricted to adults. If you consider a pack-a-day smoke, this would mean between one to two hours of total exposure to smoke and its particulate matter. Incense is usually burned continuously and exposes the whole family to these tiny particles for many hours. Because it’s also indoors, as opposed to smoking which now mostly occurs in open spaces due to new laws, there is constant exposure to the incense smoke.
If you use incense and enjoy the aroma, a safer alternative would be aromatherapy, which emits a mist of water to diffuse the oils and impart the aroma. At the very least, avoid using charcoal briquettes to burn the incense resin. Adequate indoor ventilation and circulation of air is crucial to safety when allowing any smoke or scents to permeate indoor spaces.
These studies tested animals and in vitro cells, so we are not clear on whether the implications and dangers apply to humans. The studies also involved small sample sizes of subjects, so clearly more research is needed. However, given how widely used and popular incense is, more awareness and safety precautions are advisable.
Chi-Ru Yang, Ta Chang Lin, Environmental Pollution 145: 606-615, 2007
Eli Hendel, M.D., is a board-certified internist/pulmonary specialist with board certification in Sleep Medicine. An Assistant Clinical Professor of Medicine at Keck-University of Southern California School of Medicine, and Qualified Medical Examiner for the State of California Department of Industrial Relations, his areas include asthma, COPD, sleep disorders, obstructive sleep apnea, and occupational lung diseases. Favorite hobby? Playing jazz music. Find him on Twitter @Lung_doctor.