Risk Criteria in EU
Risk Criteria in EU
Risk Criteria in EU
V.M. Trbojevic
ABSTRACT: This paper focuses on risk criteria used in the EU for population living in vicinity of hazardous
facilities. The criteria vary from fully risk-based and goal setting to the prescriptive consequence based criteria. In spite of the philosophical differences in the formulation of risk criteria, there is a single EU Directive
(Seveso 2) on the control of major accident hazards involving chemicals which applies to every member state
and clearly the level of safety across the EU should be very similar if not the same. Therefore the first aim of
the paper was to minimise the differences between the variety of safety approaches across the EU in order to
develop risk acceptance criteria with the potential to converge to a unified set. The second aim was to develop
societal risk criteria completely consistent with the legally applied individual risk criteria.
1 INTRODUCTION
Approach to safety differs considerably across the
EU. While on one side there is a basic recognition
that zero risk is not attainable and that the real aim
must always be to identify, control and reduce risk,
on the other side, as a sharp contrast, there is still a
belief that application of good practice embodied in
design and other standards removes risk. Between
the two extremes there are several variations, the
simplest one being that as long as risk is lower that a
prescribed threshold, it is acceptable, and even that
the regulator can accept developments up to that
prescribed limit. This situation is obviously reflected in the risk acceptance criteria and the safety
legislation. This paper focuses risk criteria used in
the EU for population living in vicinity of hazardous
facilities, for which the following classification is
proposed:
1 Risk based, goal setting criteria where safety goal
is specified and not the means of achieving it
(UK).
2 Prescriptive, risk based criteria where a prescribed maximum level of risk is used for risk
control (The Netherlands, Hungary, Czech Republic) and some form of risk reduction may be
specified but not necessarily implemented.
3 Prescriptive, consequence based criteria where
the prescribed level of impact is used for control
(France) or no risk is allowed outside the boundary of the facility (Germany).
-4
UK
10-5
3 x 10-6
LUP limit of
acceptability (converted
from risk of dangerous
dose of 3 x 10-7)
10-6
10-7
10-8
The Netherlands
Hungary
Czech Republic
Upper limit
Impact Thresholds
France
Lower limit
Effects
Thermal
radiation
Overpressure
140 mbar
50 mbar
Toxic dose
Based on irreversible
effects (first inuries) and
exposure time (passage
of the cloud)
Germany
No risk to be
imposed on
people or the
environment
the frequency of 1 in 5,000 per annum can be considered as intolerable. The broadly acceptable level
of risk is suggested as a line three decades lower
than the upper tolerable line. This evolution of the
upper tolerable level of risk over 20 years is presented in Figure 1, and clearly demonstrates the
value of ALARP dynamics and the goal setting approach in reducing the upper level of tolerability of
risk.
The quoted criteria are not systematically used in the
UK, however HSE is using ARICOMAH risk integral,
HSE 2003, for evaluation of societal risk. This approach is based on the accident with the highest
number of fatalities Nmax and its frequency f(Nmax),
which are used to evaluate an approximate level of
the Potential Loss of Life (PLL) or the fatal accident
rate, using the risk aversion exponent of 1.4 (slope
of 1.4). The explanation for the choice of this exponent seems to be that it matches the historical
data.
Table 3
Category of development
Sensitivity Level - 2003
> 10-5
Inner Zone
Middle Zone
Outer Zone
Assessment required.
Assessment required
Housing developments
providing for more than 25 Against development if > Against development if >
75 people
25 people
people (Category A)
Level 1
Small workplaces, parking
areas, etc. (Category B)
Level 2
Canvey, 1981
Allow development
DAA
DAA
DAA
Allow development
Allow development
Allow development
AA
DAA
DAA
Assessment required.
Assessment required.
Retail, community, leisure
facilities, some workplaces, Against development if > Against development if >
300 people
100 people
(Category C)
1.E-1
Annual Frequency of N or More Fatalities
Allow development
ACMH, 1991
1.E-2
Level 3
R2P2, 2001
1.E-3
1.E-4
Level 4
DAA
AA
1.E-5
1.E-6
1
Figure 1
the UK
10
100
Number of Fatalities [N]
1000
10000
AA
AA
DAA
Against development
Assessment required.
Against development if >
25 people
Specific assessment
required
AA
AA
AA
1.E-2
1.E-3
1.E-4
1.E-5
UK (R2P2)
1.E-6
UK (Old LUP)
UK (COMAH)
1.E-7
Dutch (Old)
Dutch (New)
1.E-8
CZ (New)
FRANCE
1.E-9
1
10
100
1000
Number of Fatalities N
Figure 2
Comparison of FN Criteria
Criterion
F(1)
Aversion
Factor
IR
UK (R2P2)
1.E-2
1.00E-5
9,763
UK (Old LUP)
1.E-3
1.00E-5
163
UK (New LUP)
1.E-3
1.5
3.00E-6
847
Dutch (Old)
1.E-3
1.00E-5
163
Dutch (New)
1.E-3
1.00E-6
1,644
CZ (New)
1.E-4
1.00E-6
163
Nmax
10-5
10-6
Target level
10-7
10-8
Negligible risk
Figure 3
1 Goal-setting version - The intolerable limit of individual risk is defined and is the same for all
zones. In addition, the population density, or the
maximum number of people is defied for each
zone. This can be achieved by specifying or limiting the potential loss of life for each zone. As
the result there will be an upper tolerable boundary for each zone, as shown in Figure 4 for the
maximum individual risk of 3 x 10-6 per annum
and Nmax equal to 10, 100 and 1,000 corresponding to the inner, middle and outer zones, respectively. Consequently, the FN curves will have to
be calculated for each zone and compared against
the corresponding criterion. The ALARP dynamics applies below the upper tolerable level of
risk.
2 Prescriptive version The target limit (lower than
the upper tolerable) is defined along the same
lines described in the previous point. The requirements for the FN curve is to be below the
target boundary.
1.E-2
1.E-3
1.E-4
1.E-5
REFERENCES
1.E-6
1.E-7
1.E-8
1.E-9
1.E-10
1
10
100
1000
Number of Fatalities N
Figure 4