1999 CW8 is an Apollo asteroid and near-Earth object that is a B-type asteroid, relatively rare in the asteroid belt but common in the inner solar system. The asteroid never approaches Earth closer than 0.2 AU, but occasionally makes close approaches to Mars of 0.07 AU. It makes one such approach in 2073, at 0.067 AU, and another one in 2103, at 0.094 AU. Due to 1999 CW8's relatively high inclination, although it passes closer to the Sun than the Earth (0.9 AU), it never comes closer than 0.2 AU.
Based on absolute magnitude, and assuming an albedo between 0.05 and 0.3, typical of most asteroids, the asteroid is between 500 and 1100 meters across, and if it impacted the Earth would cause significant damage, but not as much as the Cretaceous–Paleogene extinction event progenitor, which brought about a mass extinction, as it is only 1/20 to 1/10 the size. However, it is unlikely to come close enough to Earth to impact it, or even become a risk of impact.