Incense stick smoke may cause health hazard

Priyanka Choudhury

According to British newspaper The Telegraph, Incense may need a health warning over ‘toxic’ smoke, claims research. Analysis of incense smoke, used in both western and Asian religious ceremonies for possibly thousands of years, found it contains many chemicals, some of which may be harmful.

The researchers – two of whom worked for a tobacco company – tested the residue of tobacco and incense smoke directly on animal and bacteria cells in a laboratory. They did this to see whether they could induce mutations in the DNA and if the smoke was toxic to the cells. They found the effect of some of the incense smoke tested on the cells was greater than that of the tobacco smoke. However, only four incense sticks and one cigarette were tested, so we have to be cautious about these results.

But incense isn’t smoked and so is not drawn directly into the lungs in the way tobacco smoke is, so the effects on lung cells may be very different. It is also unclear how exposure to incense smoke compares to the health risks associated with passive smoking.

Still, the study is a reminder that burning anything – whether it’s incense, coal or tobacco – produces smoke that can irritate and damage the lungs. If you want to make your home smell nicer, we would recommend sticking to air freshener.

Where did the report come from?

In fact, a group of researchers from the South China University of Technology (SCUT) and the China Tobacco Guangdong Industrial Company jointly carried out the research on the possible health hazard caused by incense stick smoke. Although it is not clear about the initiator or funder of this research, it was learnt that the lead researcher of this team had worked for the tobacco company. That is why, some critics are raising question about the impartiality of this research.

The study was published in the peer-reviewed science journal Environmental Chemistry Letters, and is available on an open access basis to read online or download as a PDF file.

The pattern of the research:

According to newspaper reports, this laboratory research used instruments to measure and identify the types of particles and chemicals given off by burning incense. After measuring the chemicals, the researchers did in vitro studies of the effects of the smoke on bacteria and animal cells.

The researchers burned four incense sticks and one cigarette in a machine that collected particles of smoke through a series of filters. They graded the size of the particles collected, and performed chemical analysis by gas chromatography and mass spectrometry on the contents of the filters. They then tested the smoke residues on cells in petri dishes.

The first test, on salmonella cells, was to see whether the samples prompted mutations in the DNA of the cells. Mutations in DNA can sometimes lead to cancer. The second test used cells from the ovaries of Chinese hamsters to see whether the samples had toxic effects on the cells.

The basic results:

Smoke from burning incense created a mixture of fine and ultrafine particles, which are known to be bad for lung health. The chemical analysis found 64 compounds, taking into account all the components of all four incense sticks.

These included chemical components of essential oils and lignin wood, which is commonly used in incense. The compounds were mostly “irritants”, although some toxic compounds were found. The paper did not give the equivalent results on particle size and chemical compounds found in the cigarette tested.

The four incense smoke samples and one cigarette smoke sample caused varying degrees of mutation in the salmonella cells. The incense and cigarette smoke was toxic for the hamster ovary cells. Toxicity was maintained at all different levels for the different samples. The incense smoke was toxic at lower concentrations than the cigarette smoke.

Interpretation of the results:

The researchers showed smoke from some incense samples was “higher than for the reference cigarette sample with the same dose”, and said their findings suggest that, “incense smoke was more cytotoxic against Chinese hamster ovary cells” than cigarette smoke.

However, they added: “We cannot simply conclude that cigarette smoke is less cytotoxic than incense smoke, firstly because of the small sample size analysed in this study, and secondly because of huge variability in the consumption of incense sticks and cigarettes.”

According to the laboratory study, smoke from burning incense can produce fine particles and chemical compounds of a type that may irritate the lungs and damage health. This is not surprising, as most types of smoke indoors produces fine particles that are likely to have this effect, whether from cooking, smoking tobacco, or burning incense.

The suggestion that incense smoke might be more harmful than cigarette smoke needs to be treated with caution. The four incense stick samples had different effects when tested for the ability to mutate cell DNA and toxicity to cells. These were compared with just one cigarette.

The way we use incense and tobacco is different. Cigarette smoke is drawn directly into the lungs and held there before being exhaled. Incense smoke is burned into the environment and inhaled from the surrounding air. The amount of smoke that gets into the lungs will depend on how much incense is burned, for how long, and on the size and ventilation of the room.

It seems sensible that people who have lung conditions should avoid using incense, and the rest of us should limit its use for personal reasons, such as improving the smell of your home.

At the same time, we really need to be cautious while burning incense stick. We need to make sure, incense stick smoke isn’t inhaled by anyone or incense stick is being burnt inside a closed room. Authorities in every country now need to instruct the incense stick manufacturers to add a label on their products describing the health warning.

Priyanka Choudhury is the assistant editor of Blitz

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