I would say, that with our current atmosphere and magnetic field there's not a "direct" threat to life as they shield the Earth.
The atmosphere is opaque to X-ray radiation that can come from outside. It seems that much of that opacity comes from water vapor, and the amount of that in the atmosphere changes depending on different factors. X-ray radiation has also effects on the ionosphere and can change its size, which affects communications but I don't know whether life is affected for that.
Earth's magnetic field is disturbed by a CME and that has also various effects like inducing currents that, as you said, pose a risk to power grids and telecommunications. However there's another effect that's also associated with CMEs and solar flares: Solar Energetic Particles, these types of events are, I believe, the one that could have a more direct effect to life. If they are happening together with the disturbance of the magnetic field produced by a CME, then our shield is weakened. The maximum flux of the chain reaction they produced when they reach Earth happens at 18km above the sea level, and at the altitude of a commercial flight is ~300 times more than at sea level. However, only seems to pose a "risk" to frequent flyers (crew and passengers) as the cumulative effects could produce cancer. I've extracted these numbers from the Extreme Space Weather report by the Royal Academic of Engineering and references therein.