Despite being large (390 ft, or ~130 meters for us using the metric system), its composition (mostly solid ice) makes it so that in the case of the wrong trajectory and an impact on Earth, most of it is supposed to evaporate and burn; it would quickly be fragmented in thousands of pieces, and have huge impacts in a small area, and almost no impact to the Earth's ecosystem. This is AFAIK, and I am not an astronomer or an expert. Please correct me if I am wrong. Unfortunately there's no Palermo Hazard scale for this particular asteroid [0].

There's some very relevant Wikipedia pages about the subject [1], [2].

[0]: https://en.wikipedia.org/wiki/Palermo_Technical_Impact_Hazar...

[1]: https://en.wikipedia.org/wiki/Impact_event#Geological_signif...

[2]: https://en.wikipedia.org/wiki/Asteroid_impact_avoidance