Which is a colorless, odorless gas that can cause lung cancer?

• A. Lead-Based Paint
• B. Toxic Mold
• C. UFFI
• D. Radon Gas

Answer: (D)

This question tests recognizing a colorless, odorless gas that can cause lung cancer. That gas is radon, a radioactive gas formed by the natural decay of uranium in soil and rocks. It can seep into homes through foundation cracks and accumulate to high levels, and long-term exposure increases the risk of lung cancer, even for non-smokers. Because you can’t see or smell radon, testing is essential; homeowners use short-term or long-term radon tests, and mitigation involves sealing entry points, improving ventilation, or installing a radon mitigation system that vents to the outside. Lead-based paint isn’t a gas—it's a solid coating whose hazards come from dust or ingestion; toxic mold is a living growth, not a gas; and UFFI relates to formaldehyde exposure, which is irritant and not the classic colorless, odorless lung cancer-causing gas.