Which is an example of a natural indoor air pollutant source?

Which is an example of a natural indoor air pollutant source?

• A. Insulation
• B. VOCs from furniture
• C. Radon from soil
• D. Lead paint

Answer: (C)

Natural indoor air pollutant sources come from substances that occur in nature or arise from natural processes. Radon fits this because it’s a gas produced by the natural radioactive decay of uranium in soil and rocks. It can seep into buildings through cracks and openings in foundations and accumulate indoors, especially where ventilation is limited, delivering a health risk with long-term exposure. The other options involve materials or products created by people—insulation is manufactured, VOCs come from off-gassing of furniture and other goods, and lead paint comes from historical coatings—so they’re not natural sources in the same sense.

Natural indoor air pollutant sources come from substances that occur in nature or arise from natural processes. Radon fits this because it’s a gas produced by the natural radioactive decay of uranium in soil and rocks. It can seep into buildings through cracks and openings in foundations and accumulate indoors, especially where ventilation is limited, delivering a health risk with long-term exposure. The other options involve materials or products created by people—insulation is manufactured, VOCs come from off-gassing of furniture and other goods, and lead paint comes from historical coatings—so they’re not natural sources in the same sense.