HERE is a post on the Understanding Uncertainty blog that tries to define a suitable unit for communicating risk. They compare a micro-mort and a micro-life.
A Micro-Mort is; a 1-in-a-million chance of sudden death, for some defined activity.
A Micro-Life is; 30 minutes off your life expectancy.
Notwithstanding the assumptions that are of necessity involved in this kind of thing I reckon that this isn't a bad effort.