Burning incense, a popular meditative and medicinal aid, can expose people to cancer-causing chemicals.
Incense burning also creates more local pollution than road traffic.
Levels of highly carcinogenic polycyclic aromatic hydrocarbons (PAHs) inside a poorly ventilated temple in Taiwan were 19 times higher inside the temple than outside, and also somewhat higher than at a nearby local intersection.
The PAH benzopyrene, which is thought to cause lung cancer in smokers, had a concentration in the temple that was up to 45 times higher than in homes where residents smoke, and as much as 118 times higher than in areas with no indoor source of combustion.
Total suspended particles (the range of particles that comprise most of the emissions from human activity) were three times higher inside the temple than at the traffic intersection, and 11 times higher than outside the temple.
The concentrations inside the temple exceed the standard "safe" levels for air set in Taiwan.