The researchers collected air samples from three sites: a traffic intersection, inside a temple where incense is frequently burned, and outside the temple. They found that incense created more pollution than the automobiles idling at the intersection. They also found levels of one chemical believed to cause lung cancer was 40 times higher in the temple than in the homes of smokers, says the article.
"There is a potential cancer risk," says Dr. Ta Chang Lin of the National Cheng Kung University in Taiwan. "We just cannot say how serious it is." But steps should probably be taken to lower the amount of pollution in the air of temples by improving ventilation. "We are concerned for the health of the workers or keepers in the temples," Lin says.
The researchers were most concerned with levels of polycyclic aromatic hydrocarbons (PAHs) produced by the incense. PAHs are chemicals that are released when some substances are burned, and they are known to be cancer-causing.