by April McCarthy

December 30, 2014

from PreventDisease Website




Even though incense is commonly used for religious and ritual purposes in some of the most populated nations in the world, few studies have ever examined incense burning as a potential health threat.


Investigators have found a link between long-term incense use and increased cardiovascular mortality.


Just about any smoke is harmful to our lungs if it's inhaled. Incense burns four times more particulate matter than cigarette smoke.

Incense is popular in Asian countries. It is common for the Buddhism and Taoism religions to burn incense daily. The air pollution in and around various temples has been documented to be harmful effects on health. But it's also popular in America.

The study used data from the Singapore Chinese Health Study, which enrolled a cohort of 63,257 Chinese adults aged 45-74 years between 1993 and 1998.


The authors identified cardiovascular deaths of cohort members via a nationwide death registry, checking the registry yearly through 31 December 2011. They stratified their analysis for factors such as smoking history, education level, baseline history of cardiovascular disease, and gender.


They also performed a sensitivity analysis to examine potential confounding by exposure to secondhand smoke.

More than three-quarters of the participants reported currently using incense, and another 13% were former users. Most had used incense daily for at least 20 years, typically keeping it burning intermittently throughout the day.


The authors estimated that current long-term incense users had a 12% increased risk of cardiovascular mortality compared with former and never users, including a 19% increased risk for stroke and a 10% increased risk for coronary heart disease.

Previous studies reported concentrations of volatile organic compounds and particulate matter in incense emissions similar to those in cigarette smoke.


Others showed that long-term exposure to incense smoke increased blood vessel inflammation and affected blood flow in rats. In vitro studies have indicated adverse impact to human coronary and lung cells.

Incense is dangerous to health according to researchers in the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill.

"Hazard assessment of United Arab Emirates (UAE) incense smoke" appears in an issue of Science of the Total Environment.



What's in Incense?

A typical composition of stick incense consists of,

  • 21% (by weight) of herbal and wood powder

  • 35% of fragrance material

  • 11% of adhesive powder

  • 33% of bamboo stick

Like any cigarette smoke and wood smoke, incense smoke contains particulate matter, gas products (carbon monoxide, cardiodioxide, and sulfur dioxide) and other organic compounds (benzene, toluene, xylenes, aldehydes and polycyclic aromatic hydrocarbons) shown to harm human health.

A study published in the September 2001 issue of the Bulletin of Environmental Contamination and Toxicology indicates that burning incense can expose people to dangerous levels of cancer-causing chemicals.

One PAH called benzopyrene, which is linked to lung cancer in smokers, was found to be 45 times more concentrated in the indoor zones using incense than in homes where people smoked cigarettes.

When researchers first studied the more than 61,000 ethnic Chinese living in Singapore, they were followed for up to 12 years and the investigators found a link between heavy incense use and various respiratory cancers.

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.


The researchers also looked at total suspended particles (TSPs), a measurement that reflects the total weight of small and potentially harmful airborne pollutants that all of us are exposed to on an ongoing basis.

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.


The Singapore data research claims to be the first study to provide epidemiological evidence of effects at the population level resulting from habitual day-to-day burning of incense at home, says senior author Woon-Puay Koh, an epidemiologist at Duke-National University of Singapore Graduate Medical School.

"This study is of particular significance given that cardiovascular disease is one of the most common chronic diseases in the population worldwide," says Karin Yeatts, an epidemiologist at the University of North Carolina at Chapel Hill, who has studied indoor air quality in the Middle East.

In contrast with outdoor air pollution, incense exposure may be easier for an individual to avoid, but Karin Yeatts says education will be needed to help people understand the risks of these exposures, similar to educational campaigns about cigarette smoking.

Koh published an earlier prospective study that found an association between incense use and upper respiratory cancer. Next she and her coauthors hope to look at cardiovascular risk biomarkers in relation to diseases such as diabetes mellitus and hypertension.


Itís also unclear why the estimated impact on stroke was greater than that on heart disease, says first author An Pan, an epidemiologist at the National University of Singapore.

"That could be very interesting to look at in terms of future research."


Part of an International Health Concern

Indoor air pollution is an international health concern.


The World Health Organization (WHO) estimates that more than 1 million people a year die from chronic obstructive respiratory disease (COPD), primarily a result of exposure to pollutants from cook stoves and open hearths. Burning incense releases similar pollutants, including carbon monoxide.

Two types of incense (Oudh and Bahkoor) are most often used. Both are made with agarwood, which is taken from trees that develop an aromatic smell in response to fungal infection.


Bahkoor has a number of additives, including sandalwood tree resin, essential oils and other substances.


Researchers found that both types of incense emitted significant amounts of particles, carbon monoxide, formaldehyde, and oxides of nitrogen, resulting in the cellular inflammatory response.

Future studies, they proposed, should measure additional compounds caused by incense burning and offer a more in-depth analysis of inflammatory markers.