Examination of Particle Characteristics and Quantification of Emission Factors for Smoke Generated from a Popular Indian Incense Burnt in an Experimental Chamber

Smoke released from the burning of incenses, a quotidian practice in India, is found to contain many toxic chemicals on particles making it a prominent source of indoor air pollution. This study analyzes the smoke and ash particles emitted from a popular incense brand in India, inside an experimental chamber. Emission factor (EF) for PM_3.2 generated from burning the incense is found to be 12.5 ± 4.2 mg/g which is higher than the EF of biomass like sugarcane, rice straw and fuelwood (range: 1.69–10.9 mg/g). This EF value is either in the same range or higher than some of the incenses from Japan, Taiwan, and Thailand. From 60 to 70% of the PM_3.2 mass collected consists of particles less than 1 μm in size. The maximum particle number count emitted from the incense exceeds 10⁷ which is three orders of magnitude (i.e., 10³) higher than the number count reported in another study from Italy (10⁴). The composition of water-soluble ions and particle-bound metals in the smoke is similar to that reported for incense-based studies worldwide. This is the first study in India focusing on emission characteristics from burning incense in an experimental chamber, eliminating any external interference. Toxic elements like iron, zinc, and lead, affecting health substantially, on regular exposure are also detected. Studies have revealed that the toxicity associated with incense emissions can be higher than cigarette smoke. More comprehensive chemical analysis of the incense smoke and relevant health risk exposure is highly recommended.