ANNEX B
Note by the Chief Scientific Adviser
Summary of conclusions of Risk Assessment
- In broad terms the individual risk of a fatality
on an annual basis was moderate to high in areas 4 and 5, low
in area 3 and minimal in areas 1 and 2.
- The longer-term individual risk on an annual basis
from exposure to ash varied widely over the island, being at present
low to minimal in the north (areas 1 and 2 in particular) and
moderate to high in the west and the south (areas 3 and 4).
- In societal risk terms over the next six months
and given the current distribution of population, there was around
a one in 10 chance of one or more fatalities, a one in 100 chance
of 10 or more fatalities and a one in 10,000 chance of 200 or
more fatalities.
- These estimates of societal risk could be cut by
more than an order of magnitude by strict implementation of the
present Exclusion Zone boundary (southern edge of area 3) and
made lower still by complete evacuation of area 3.
- Some groups were receiving high exposure to ash
but perhaps not high enough to result in silicosis yet, though
there was concern that small children might be at particular risk.
Verbal descriptions of individual risk such as "high"
and "moderate" are used in the same sense as the terms
in the following individual risk scale defined and commonly used
by the Chief Medical Officer (England) in describing probabilities
of events.
| Verbal description | Risk magnitude
|
| |
| High | greater than 1 in 100
|
| Moderate | 1 in 100 to 1 in 1,000
|
| Low | 1 in 1,000 to 1 in 10,000
|
| Very low | 1 in 10,000 to 1 in 100,000
|
| Minimal | 1 in 100,000 to 1 in a million
|
| Negligible | less than 1 in a million
|
Issued by BGS 18 December 1997.
| 
