Which of the following is a significant source of indoor air pollution?

Tobacco smoke is a significant source of indoor air pollution due to the toxic substances it releases into the air when tobacco products are burned. These substances include harmful chemicals like nicotine, tar, carbon monoxide, and various carcinogens, which pose serious health risks to both the smoker and others who may be exposed to secondhand smoke. The pollutants from tobacco smoke can linger in the indoor environment for extended periods, affecting air quality and contributing to respiratory problems, cardiovascular issues, and other health concerns.

While pollen, household dust, and outdoor air particles can affect indoor air quality, they are generally not as severe or harmful as tobacco smoke. Pollen primarily causes allergic reactions rather than long-term health effects, household dust can carry allergens but is less harmful in terms of toxic exposure, and outdoor air particles typically dilute when mixed with indoor air, making their direct impact less significant compared to the concentrated pollutants from tobacco smoke.