Long-Term Incense Use Linked to Cancer

Regularly inhaling the smoke from incense may increase the risk of most respiratory tract cancers, a new study suggests. The increased risk was observed in both smokers and non-smokers.

Incense has been around for thousands of years and is derived from fragrant plant materials like flowers, essential oils, tree bark, roots and resins. It is commonly used in Asian and Indian cultures for spiritual and medicinal purposes. Many integrative therapies, such as aromatherapy, acupuncture and meditation, also involve the use of incense.

When incense is burned, it has been shown to produce benzene and polyaromatic hydrocarbons, which are some of the compounds in cigarette smoke that have been linked to lung cancer. For this reason, several studies have examined a possible link between incense and lung cancer. However, findings so far have not been conclusive.

In this latest study, more than 61,000 Chinese residents of Singapore who participated in a larger health study were followed from enrollment (between 1993 and 1998) to 2005. At the beginning of the study, none of the subjects had cancer. Participants answered questions about their dietary and lifestyle habits, including the frequency and duration of incense exposure.

By the end of the study, 325 men and women developed cancer of the upper respiratory tract, such as oral, nasal, or throat cancer. Another 821 developed lung cancer. The results, published in the journal Cancer, indicate that heavy exposure to incense was associated with a statistically significant higher risk of cancers of the upper respiratory tract, with the exception of nasopharyngeal cancer, in both smokers and non-smokers. However, incense did not increase the risk of lung cancer.

People who used incense all day or all day and night were 80 percent more likely to develop squamous cell carcinoma of the entire respiratory tract than non-users. This type of cancer causes tumors to develop in the cells that line the internal and external surfaces of the body.

Comments

[Kathleen B.]

Yikes! I wonder how many yoga studios end up erasing all the benefits of their practice (better mental health and mood, enhanced flexibility and core strength, a healthy spine, and more) by exposing their students to incense? Seems awful to think that while you were doing your back, body, and brain a major favor, you were inadvertently increasing the chance that you'd get some of cancer of the respiratory tract.

[Cecelia]

I think people assume that just because incense is made from herbs, it's safe. But if you think about it, cigarettes are derived from the tobacco plant. So, it's really not that surprising that inhaling incense smoke is linked to respiratory cancers. It's just unfortunate that it's used in many therapies aimed at healing the body.

I wonder if Ayurvedic practitioners or meditation instructors will be reluctant to incorporate incense in their therapies now.

I also wonder if researchers will test specific types of incense to determine which, if any, are safe to use.

[Ashley]

Cecelia brings up a good point. Too many people link natural with safe. I personally do not enjoy the smell of incense. In a study published in 2001, the air was tested inside a temple in Taiwan where incense was burned freely. One PAH (polycyclic aromatic hydrocarbons) - benzopyrene - was found to be 45 times more concentrated in the temple than in homes where smokers smoked cigarettes. (Benzopyrene has been linked to lung cancer in smokers.) Good airflow and circulation can cut down on the amount of harmful substances found in the air.

[Karina]

Cecelia, I think you bring up a good point about the fact that things derived from herbs do not guarantee that they are safe to use. People sometimes automatically assume that natural products are free from doing harm. I feel as though there probably is a greater risk of developing cancer if incense use is frequently and you are breathing it in similar to cigarette smoke. I can definitely see the connection between cancer and breathing in cigarette smoke or inhaling incense.

[Jenny W.]

This information makes me worry about all the Buddhist monks around the world. My parents are Buddhist, and I was taught the same traditions growing up. Monks are surrounded by incense every day. Incenses are used for prayer, meditation and many other aspects of daily life. I wonder if the constant exposure to incense is truly imposing a health hazard on monks whose intentions are good and pure. It would be such a shame to know that!

[Gail]

I don’t find this all that surprising. Concentrated and regular inhalation of any smoke just can’t be good for the lungs. Plus, while many incense products are made from natural compounds, such as herbs, there are also a number of man-made substances in there, whether an artificial fragrance or some chemical to make the product look or feel as consumers think it should.

[Jimmy]

A carcinogen is a carcinogen. If benzene and polyaromatic hydrocarbons are found in both cigarette smoke and incense smoke, and these two types of chemicals are known carcinogens, it is not a surprise that both types of smoke may cause cancers, especially if cigarette smoke is known to cause cancer. What surprises me is that the incense does not contribute to lung cancer, but other types of cancers associated with the respiratory tract.

[Juan]

This is very interesting, especially since incense it is a huge part of spiritual and healing rituals in some cultures. It is difficult to tell a group of people that something is not good for them when it’s a strong element in their culture. It would be a hard battle to convince certain cultures to stop using incense. Personally, I would die if someone told me salsa was bad for my health and that I had to stop eating it. Fortunately, salsa is full of antioxidants, and I have not used incense since I was 16.

[Sean]

You have to consider any product that’s combusted (anything burned) is going to contain some level of benzopyrene as a byproduct. Even things such as barbecued meats or burned toast can have some levels of the carcinogen. There was a barbecue feature on the Today Show two years ago that suggested that if you get any charring on your meat, it should be removed. However, the remaining non-blackened portion of the meat should be safe for consumption. Frequent consumption of grilled foods has even been shown to change the metabolism of certain drugs.

[Shawn]

I agree with Juan. Even with the results of this study, it is going to be hard to convince the groups of people who have been using incense for centuries, with no obvious adverse effects. If anything, perhaps people and religious centers will start using incense in moderation. Some people cannot tolerate incense due to health reasons, as conditions like asthma, allergies, and chronic cough can be aggravated by smoke. Opening windows and using exhaust fans can decrease the amount of smoke in the air.

[selva p]

Here’s some background information on benzopyrene (the PAH found in the temple in Taiwan). Benzo[a]pyrene, C20H12, is a five-ring polycyclic aromatic hydrocarbon that is mutagenic and highly carcinogenic. It is a crystalline yellow solid. Benzo[a]pyrene is a product of incomplete combustion at between 300 and 600 °C. Benzo[a]pyrene was determined in 1933 to be the component of coal tar responsible for the first recognized occupation-associated cancers, the sooty warts (cancers of the scrotum) suffered by chimney sweeps in 18th-Century England. In the 19th Century, high incidences of skin cancers were noted among fuel industry workers. By the early 20th Century, the toxicity of benzo[a]pyrene was demonstrated when malignant skin tumors were produced in laboratory animals by repeatedly painting them with coal tar.

[Bob S.]

Just to go into benzo[a]pyrene a bit more, it was the first identified carcinogen. However, benzo[a]pyrene needs to be metabolized into its carcinogenic form, so it may be considered a “pro”-carcinogen, since it is not active as a carcinogen until metabolized. Once metabolized to benzo[a]pyrene diol epozide, it can intercalate into DNA, disrupting the gene sequence, subsequently resulting in cancer.

[ohmi]

It is interesting that this study did not find an increased risk of lung cancer, but only an increased risk in upper respiratory tract cancers. One would think that inhaling the smoke into your lungs would cause an increase in cancers of the lung. The study was not in a controlled environment, and while the users of incense were asked about their frequency and duration of incense exposure, it could vary among subjects.

[Dennis N.]

Here’s some background information on benzene (a product produced when incense is burned): Benzene, or benzol, is an organic chemical compound and a known carcinogen with the molecular formula C6H6. It is sometimes abbreviated Ph–H. Benzene is a colorless and highly flammable liquid with a sweet smell and a relatively high melting point. Because it is a known carcinogen, its use as an additive in gasoline is now limited, but it is an important industrial solvent and precursor in the production of drugs, plastics, synthetic rubber and dyes. Benzene is a natural constituent of crude oil, and may be synthesized from other compounds present in petroleum. Benzene is an aromatic hydrocarbon and the second [n]-annulene ([6]-annulene), a cyclic hydrocarbon with a continuous pi bond.

[B. Layne]

Since incense is suggested to cause upper respiratory tract cancers, use should be limited and only in well-ventilated areas. If there are no religious ties to incense, maybe switching over to scented candles is an option. However, older and certain imported candles may have lead cores in their wicks, which can vaporize when burned, releasing lead into the air.

[Rachel]

From what I understand from the previous comments, benzene is produced in some amounts whenever anything is burned. Would substituting candles cut down significantly on the amount of benzene? I know many people who keep candles burning pretty much all the time. I do wish the article had said more about what type of incense was used in the study. Did it contain, for instance, saltpeter, a component of many commercial incenses? I had an idea that some of the toxins in cigarette smoke had to do with compounds added by the tobacco manufacturer; I could be wrong there, and I'm certainly not saying cigarette smoke is good for anyone. But there are many different kinds of incense. Certain types of Japanese incense, for example, are specially formulated to produce very little smoke. Is it the smoke or is the benzene a byproduct unrelated to the smoke? There are so many warnings issued these days. It would be helpful to have more specifics.

[Angelina]

Without a doubt candles are safer than burning incense. The byproducts of burning candles are water and carbon dioxide. No benzene or benzo[a]pyrene here! The soot or smoke coming from a candle is usually the result of incomplete combustion, but is different chemically from the soot created during the combustion of fossil fuels, and are safe.

[Jenni G.]

This article is going to make me think twice about burning incense. While I use it sparingly, I don’t want to subject my body to smoke and possibly cancer just to smell the odor. Some might think that because incense comes from plant-derived materials — like cedar, sandalwood, juniper, vanilla, and sage, just to name a few — that it is safe to use. Just because there are herbs and plants contained in incense does not mean it good for the body.

[Sean]

Like the title of the article suggests, the true risk is in long-term use. That’s true with most harmful things we breathe…cigarette smoke, asbestos, smoke from coal mining. The harmful effects come from decades of continued inhalation. Moderation is probably the key for most people who light incense in their homes. Perhaps people who burn them continuously for spiritual and medicinal purposes are at the greatest risk and should consider some type of moderation.

[Matthieu]

B.Layne brings up a good point. Perhaps the use of scented candles may be an option. However, according to the National Candle Association, scented candle usage indoors may cause high levels of respirable soot, with risks to occupants for both acute and chronic health effects, including an increased risk of cancer. Similarities between candle and diesel soot suggest the potential for similar toxicological effects on exposed occupants. I feel as though this concern is applicable to almost anything we burn. I wonder if fire crackers will be the next topic of interest?

[Christine]

Incense is available in various forms and degrees of processing. However, incense can generally be separated into direct burning and indirect burning types depending on how it is used. Preference for one form or another varies with culture, tradition and personal taste. Indirect burning incense, also called non-combustible incense, is simply a combination of aromatic ingredients not prepared in any particular way or encouraged into any particular form. The use of these requires a separate heat source since it does not generally kindle a fire capable of burning itself and may not ignite at all under normal conditions. This incense can vary in the duration of its burning with the texture of the material. Direct burning incense also called combustible incense, generally requires little preparation prior to its use. When lit directly by a flame and then fanned out, the glowing ember on the incense will continue to smolder and burn away the rest of the incense without continued application of heat or flame from an outside source. This class of incense is made from a moldable substrate of fragrant finely ground (or liquid) incense materials and odorless binder.

[Bee Lover]

Beeswax candles burn much cleaner than paraffin candles. Paraffin is described as the grayish sludge produced as a leftover byproduct from petroleum plants. Certain paraffin candles can even emit toxic chemicals like acetone, lead and benzene. So if one were to switch over from incense to candles, make sure they are made from beeswax and not paraffin.

[liz]

I agree with Rachael. Could the difference in findings be attributed to different kinds of incense being studied? I think, in addition to the duration, the type and composition of incense would be a determining factor in the association and risk of cancer.

[jennifer]

Aside from the duration of incense use and the composition of the incense, I wonder if the placement of the incense in the home was studied at all. Inhaling incense smoke all day is clearly not healthy for the respiratory system, but preventative measures when burning it in your home could significantly decrease its impact. Opening the windows in the room that it is burning in would provide more ventilation and air movement, so the smoke is not hanging in the air you are breathing in. Also, simply keeping it away from your face (on the other side of the room, for example) and consciously trying to avoid breathing in the smoke could make all the difference.

[K.K.]

Burning incense has long been a concern of mine regarding its long-term effects on health. Burning consumes oxygen, reducing the available oxygen for healthy breathing, especially among those with impaired lungs. The fumes produced contain carbon in some form, and some of these forms, as pointed out in the article, can be harmful to the lungs. Incense smoke is the same as second-hand smoke from cigarettes - only it contains fragrances! Some consideration should be given to the potential confounding impact of poorer air quality in the Singapore area that could have impacted the results of this study.