Which one of the following is NOT true concerning Radon?

Radon Radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days. Often the single largest contributor to an individual's background radiation dose Radon continues to decay to emit alpha paicles. Rn-222 represents a long-term hazard despite its sho half life of 3.8 days.