Incense, the aromatic material burned to release fragrant smoke, has grown from a traditional religious practice to become a common fixture for meditation, aromatherapy, or simply getting rid of unwanted odors. Though it’s often associated with spirituality and cleansing, incense may actually have a link to something more dangerous — harming cells and their genetic material.

A new study published in Environmental Chemistry Letters not only examined the health effects of burning incense inside, but compared the effects of incense and cigarette smoke. Two different types of incense were tested in the study, both containing agarwood and sandalwood, which are among the most common ingredients used to make incense. Various tests were run with the products, some of which gauged the effects of incense and cigarette smoke on ovary cells of hamsters and on Salmonella tester strains.

The researchers found that incense smoke was mutagenic, which means that its chemical properties could potentially change genetic material such as DNA, therefore causing mutations. Incense was also found to be more cytoxic and genotoxic than the cigarette used in the study, meaning that incense smoke is potentially more toxic to a cell, and genetic contents are especially vulnerable. All of these toxins have been linked to the development of cancers.

The sampled incense was found to have more unsavory properties — it consisted almost exclusively of ultrafine and fine particles, meaning it was more likely to cause adverse health effects, and the four samples contained 64 different compounds all together. Most of these irritants were only slightly harmful, but ingredients in two of the samples are known to be extremely toxic.

"Clearly, there needs to be greater awareness and management of the health risks associated with burning incense in indoor environments," said Rong Zhou, of the South China University of Technology and the China Tobacco Guangdong Industrial Company, and leader of the study.

Zhou also said he hopes the results of the study will lead to further evaluation of incense products, and contribute to measures that reduce smoke exposure. He does warn, however, that one study cannot conclude that incense smoke is more dangerous than cigarette smoke.

Source: Zhou R, et al. Higher cytotoxicity and genotoxicity of burning incense than cigarette. Environmental Chemistry Letters. 2015.