I came across these blog entries from David Spiegelhalter at the weekend from a statistician. In his posts he talks about quantifiying the risk from various activities (even just living) using the terminology of the ‘microlife‘ and the ‘micromort‘.

The microlife is defined as 30 minutes – very approximately a millionth of the remaining life expectancy of a young adult. I’m only a couple of sentences into this blog post and I’ve already spent a tenth of a microlife writing them! So just living for 30 minutes will take a microlife from you, but there are ways of rattling through them more quickly – e.g. smoking (half a microlife a cigarette) and eating unhealthily. However, it’s not all bad news; Spiegelhalter explains that we actually gain bonus microlifes each day simply due to ongoing improvements in medical science. Once you’ve spent about a million microlives, you die. On average, of course. Isn’t it nice to be reminded that you’re hurtling forward in time towards your death?

The micromort is a bit easier to define – being a one-in-a-million chance of death due to some prescribed activity. So a parachute jump, according to the blog, is a 10 micromort activity (each jump gives a one in one-hundred thousand chance of death), which is quite low. Similar to driving 4000 km in a car in the UK. Climbing Mt Everest is an eye-watering 40,000 micromort activity (or 40 millimorts, I suppose).

I have previously talked about the risks from exposure to radiation. What matters in terms of risk is the effective dose equivalent, that you receive. The information I have available quickly to hand, gives a rough risk factor of 1 in 60 chance (i.e. about 17000 micromorts) of something really nasty happening to you per sievert of effective dose equivalent. The dose equivalent you get from background radiation (and this varies hugely depending on where exactly you live) is typically of order 2 millisieverts per year, i.e. giving about 30 micromorts per year. That’s three parachute jumps, or 12000 km driving. Not something to worry much about from day to day,

Anyway, have a read of the articles, they are quite amusing and rather frightening. In this time taken to write this post a microlife has vanished from my account, so it is time I did something rather more productive.