(Let me assure you further that the risk analysis of rare events is a tricky, indeed specialist, subject, to which I don't have the space here to do justice.)
PBL
What better risk analysis can you have than 50 years of records and millions of flights?
The undisputable facts are that NO ONE has been killed in the whole history of aviation by ASH.
You are trying to do a risk analysis on something which to date statistically has shown NOT to be a risk.
There were two incidents where aircraft entered dense ASH clouds at night.
I am not talking about flying into dense ash cloud but flying in VMC daylight through ash concentrations which are so low that they are invisible to the human eye.
You have to differentiate between a threat or risk to life on which statistics over 50+ years show there to be none and a financial risk where there is a vague possibility that flying in low levels of ash or indeed any pollution may reduce the engine life. That is an accountants job not a health and safety issue.
If you want to do a risk analysis then great but look at areas which do have a record of continuing threat to life which we accept such as bird migrations sea based airports, weather winds etc etc etc.
My concern as a pilot would be flying into something which would cause an immediate failure in flight and thus cause me a problem. I do not believe until someone shows me otherwise that low density ash is a threat to causing an inflight failure.
If the engineers start posting here that they are finding ash damage which could cause that failure then I will sit up and listen but it hasnt happened yet.
But this is going round and round in circles and it maybe better to agree to disagree.
Pace