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Incense: a dangerous guest that affects indoor air quality

14 April 2022
Article by Gabriela Ventura and Anabela Martins, researchers in the field of air quality.

Whether to aromatize the environment or help with relaxation, incense is still a popular product. It has, however, «hidden» dangers, unknown to most people, as it pollutes the air around it.

Exposure to indoor air pollutants is recognized as the cause of the increase in several health problems observed, namely at the respiratory level. In the indoor environment – ​​at home, at work, or on transport – the concentration of some pollutants can be 10 times higher than their levels outdoors. It is therefore very important to control the sources of pollutants within closed spaces.

INEGI, within the scope of its activity to support the industrial development of «clean» materials, prioritizes the control of emissions from a series of products, including consumer products, so it carried out a study of the emissions of various types of incense available. on the market1.

Incense, an aromatic material that gives off a smell when burned, is used at home, but is also often used in wellness and spa centers, gyms or yoga centers. In these spaces, respiratory intensity is higher, inhalation is more frequent, and the health consequences can therefore be more serious.

Incense emits harmful substances

To find out if there are actually health consequences resulting from the inhalation of these chemicals, a group of researchers from INEGI studied the gaseous component of the emissions resulting from the burning of incense.

Twelve products were selected, analyzed by scanning for VOCs (volatile organic compounds). This analysis resulted in the identification of compounds from different families: aromatic hydrocarbons, alkanes, alkenes, ketones and aldehydes.

The search for specific VOCs with serious chronic health effects (carcinogenic, mutagenic and reprotoxic) resulted in the detection of benzene, toluene, styrene, naphthalene, furfural, furan, isoprene, phenol, 2-furylmethylketone, formaldehyde, acetaldehyde and acrolein.

Assuming a scenario of using incense for 1 hour a day, 4 days a week, it is concluded that these products are indeed highly polluting and impact health. Concentrations of benzene - a carcinogenic element typically associated with tobacco - were observed between 100 and 3600 times higher than the values ​​recommended by the World Health Organization2. Formaldehyde, an irritating agent and also a carcinogen, also showed values ​​higher than recommended, between about 1.2 to 2.7 times. The other regulated compounds showed concentrations below the threshold values.

There are also substances that - despite not being subject to control and not having tabulated recommended values ​​- deserve attention. Acetaldehyde, acrolein, furfural and furan emerged as compounds with relevant concentration levels.

Researchers warn consumers

Some people believe that incense emits pleasant fragrances, which relieve stress and facilitate the achievement of physical, mental and spiritual balance, but, as the results obtained prove, these fragrances can pose a health risk.

To reduce the risk, there are essentially two strategies: source control, where its presence indoors is removed, replaced or moderated, and exposure control, essentially through adequate ventilation.

The first strategy is preferable because prevention is better than mitigation. Another way to control exposure is to restrict the time spent in a certain contaminated space and, as a last resort, dilution with increased ventilation, which can be implemented by the consumer. Special attention should be given to vulnerable people, such as children and people with health problems (asthma, COPD, etc.), who should not remain in spaces where incense is burned.

In the case of extreme conditions such as high temperatures, high levels of ozone and high levels of particulate matter, the use of incense should be avoided. These extreme conditions can potentiate higher levels of exposure, for example, to secondary pollutants resulting from chemical reactions that would not normally occur.


[1] Silva, G.V.; Martins, A.O.; Martins, S.D.S. Indoor Air Quality: Assessment of Dangerous Substances in Incense Products. Int. J. Environ. Res. Public Health 2021, 18, 8086.

[2] World Health Organization. WHO Guidelines for Indoor Air Quality: Selected Pollutants; WHO Press, WHO Regional Office for Europe: Copenhagen, Denmark, 2010. Available online: air-quality/publications/2010/who-guidelines-for-indoor-air-quality-selected-pollutants.

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