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Tolerability today vs Whitman


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Tolerability and acceptability criteria require updating as changes in the world, risk perception and demographic change.
This paper explores how a acceptability curve can be built from a G8 perspective, by analyzing recent events (last decade) such as Fukushima, 9/11 Twin Towers, quakes in Italy, traffic accidents etc.

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Tolerability today vs Whitman

  1. 1. Oboni Riskope Associates Inc. 500-1045 Howe Street Vancouver, B.C., V6Z 2A9What Fukushima (2010) nuclear accident, the Twin Towers (9/11) terrorattack, deadly traffic accidents and Aquila earthquake (Italy) have incommon?An update of Whitmans and ANCOLD tolerability/acceptability curves (casualtiesfrom man-made or natural catastrophes, large dams failures) shows evidence for aG8-wide societal acceptability threshold.By Franco & Cesar Oboni, Oboni Riskope Associates Inc. Vancouver, www.riskope.comAs already repeatedly stressed, balanced, sensible decisions related to mitigation and variousaspects of planning can be taken only if risks are compared with a tolerability/acceptabilitycriterion. The term tolerability generally refers to physical losses, business interruption losses etc.,whereas acceptability refers to life losses, casualties.Whitman and ANCOLD tolerability/acceptability thresholdsAcceptability criteria were first explicitly established in the mid-eighties by researchers such asWhitman and Morgan. Their original curves (which used a “double scale”, as they simultaneouslydisplayed physical losses and casualties -a concept that is quite impopular and therefore rarely usedtoday) are reproduced in Figure 1, together with another set established by the Australian NationalCommittee on Large Dams Incorporated (ANCOLD Inc). In general, authors present a "low" curve,i.e. a conservative one, and a “high”curve, or an aggressive one.Operational risks tolerability curves can be established, generally for physical losses, businessinterruption, etc. Figure 2 shows a real example (names have been replaced with achronims toprotect clients confidentiality, where major risk scenarios are compared to clients tolerability.Why to update?For a recent study, it became necessary to check if an update of Whitman curves was due,specifically in terms of human losses (casualties). The “feeling” was indeed that since our world haschanged, demographics have changed, airplanes are larger, media coverage has changed and, aboveall, our social sensitivity has changed, the curves have to be updated.(c)Oboni Riskope Associates In. Page 1 of 5
  2. 2. It also seems that if on one hand we are very sensitive to the single loss, or personal tragedy, on theother, we are becoming numbed to large numbers.Fig. 1 TolerabilityAcceptability thresholds defined by Whitman (1984) and Ancold (for each one the"conservative" and the "aggressive" thresholds are displayed). The bubbles display common eventsfor various industries. In the original papers the horizontal axis showed casualties as well asmonetary losses -a concept that is considered quite unpopular nowadays.Fig. 2 Real life Risk Assessment results, with an operational tolerability curve superimposed to the"risk landscape" of a major operation (fourteen risk scenarios are displayed).(c)Oboni Riskope Associates In. Page 2 of 5
  3. 3. Defining an updated societal, large scale, G8 acceptability thresholdInstead of using Riskopes ( proprietary algorithm to define thetolerability/acceptability threshold, for the sake of this exercise, we proceeded empirically, usingfacts emerging from the G8 countries, including Japan, United States, Italy as follows: • Several dozens casualties per week-end, several times per year, lead the Italian government to invest a large capital in a continuous real time speed checking and enforcing system (Traffic Tutor), as the situation was intolerable. • A quake causing 308 casualties (Aquila), thirty years after another catastrophic one (Irpinia) lead to the conviction of a large number of public officers for mass man-slaughter and various other charges (no such reaction for the Irpinia one, thirty years before). • A terrorist act (9/11, New York) caused approx. 3,000 casualties and the USA “declared war on terrorism”. • A quake and a tsunami (Fukushima) with a wave considered to be larger than the Maximum Credible Event (MCE) have caused an evacuation zone of 20km, then 30km radius, with very large number of afflicted people (which may become ill in the future); Germany and other countries have decided to stop their nuclear energy programs, showing that the event was considered intolerable.In Figure 3 we show the empirical curve derived from these facts in blue colour, and we display inblack colour (for purposes of comparison with Whitman original acceptability) a least-squaresapproximation of the blue curve data. For the sake of this exercise we have extended Whitmanscurves to the right, to cover larger casualties events.Figure 3 displays in green colour the extended Whitman lower bound (lower limit of societaltolerability1) roughly passing through 10-6/year (1/1,000,000) and 1M death, i.e. a scenario with aprobability at the lower limit of credibility and losses comparable to a city destroyed to the ground(a scenario one could imagine, for example, in Naples, with a quake and a catastrophic eruption ofMount Vesuvius, for which Italian Authorities perform Civil Protection drills, but do not enforceseismic upgrade of buildings, as opposed to the high levels of capital investments allotted in thesame country to flood protection).The orange couloured threshold (Fig.3) corresponds to a theoretical constant-risk tolerability(meaning that the product between the number of casulaties and the probability is constant, in thiscase equal to one). This threshold is remarkably parallel, although slightly converging for highercasualties events, to the updated acceptability threshold (in black), showing that G8 societalperception leads to lower acceptability than constant risk for larger events.1 The upper limit of Whitman seems today difficult to defend because it is excessively "permissive", or in other words, shocking to the public.(c)Oboni Riskope Associates In. Page 3 of 5
  4. 4. Fig 3. Comparison of the various curves, i.e.: Whitman (upper and lower), Ancold (upper and lower),2011 Riskopes update, constant risk.Once the acceptability threshold is defined, it becomes possible, for each risk scenario, to determineif the risk is acceptable or not, then calculate how unacceptable it is (surface colored in orange) asdisplayed in Figure 4.Fig. 4. When probability and consequences of a scenario are evaluated, the total risk is equal (p*C)to the surface of the rectangle (sum of orange and blue areas). The blue area is the tolerable part ofthat scenario, the orange part is the intolerable portion. NB: the log-log scale requires some attentionwhen interpreting the relative size of surfaces, as shown in the bar diagram at the right, in decimalscale.(c)Oboni Riskope Associates In. Page 4 of 5
  5. 5. Appropriate responses based on a clear plan pave the road to long-term survival and development ofthe system and its owner, as we have noted and discussed in detail in our book2.ConclusionsThe following remarks can be made on the updated curve we generated: • Between 1984 Whitman lower bound and 2011 we note a clock-wise (to the right) “rotation” of the curve. This indicates that: • In the G8 countries, when looking at large scale catastrophes (1M casualties and more, country wide scale), societies are less tolerant than in the 80s • as opposite to the prior point, when looking at events potentially generating less than 1M casualties, societies are more tolerant than in the 80s • as a side note we remind that scale effects are very significant: for example, when shifting from a country wide scale to a “facility scale”, the acceptability (we are not showing that case today) is significantly lower than in 1984 • The Whitman aggressive (upper bound) curve is nowadays in the intolerable region starting at 1,000 casualties, as opposite to being in the tolerable region below 1,000 casualties • When comparing the 2011 curve with a “theoretical constant risk” curve, we note they are almost parallel, meaning that one-casualty-high-probability event is as acceptable as high- casualties-low-probabilities events. Instead, Withman lower and upper bound were “flatter” than the “theoretical constant risk”, characterising societies getting more tolerant as casualties increase and probabilities decrease.As we saw in detail in another paper, we have written several times 3 and anyone can understand byintuition, the part of intolerable risk is the key to the rational prioritization of risks and rationaldecision making when planning mitigations.Sound mitigation decisions will invest funds and resources appropriately, where risks are indeed themost critical, i.e. the most intolerable, allowing sustainable, reasonable and transparent riskmanagement. This will become of paramount importance with new challenges coming from climatechanges, shear demographic and population density, larger cities etc.Once the right approach has been developed and provided appropriate preparedness measures on asystem have been taken, time required for appropriate responses in case of occurrence of hazards(sources of risk) will definitely shortened.Lack of proper preparation can lead the system (and its owner, whether a company, governmententity, an NGO) to collapse.2) ) Riskope Associates In. Page 5 of 5