The Development of Risk Analysis: A Personal Perspective March 19th 2012 2:30pm
Ragsdale, Sachiyo, Managing Editor has reference to this Academic Journal, PHwiki organized this Journal The Development of Risk Analysis: A Personal Perspective March 19th 2012 2:30pm Harvard School of Public Health Richard Wilson Mallinkrodt Professor of Physics (emeritus) 1800s Try out the technology, modify if any problems arise. In 1833, when the first passenger railway in the world Liverpool to Manchester opened, an engine ran down a Member of Parliament, who failed to get out of the way. Was the outcome good or bad Depends on his Party affiliation!
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What do we mean by Risk Measures of Risk How do we Calculate Risk History (b) Event Tree (c) Animal Analogy (d) Other
What about public perception
Yet data show unequivocally that life is getting better. We all know that! So what are the public saying What is Life Expectancy Both the specific death rate in addition to the life expectancy at birth have a dip at 1919 world wide influenza epidemic. BUT anyone born in 1919 will not actually see this dip. Peculiarity of definition of life expectancy. Uncertainties in addition to Perception Types of Uncertainties Role of Perception Kahnemans 2002 economics Nobel prize (Tversky in addition to Kahneman, 1981) People are inconsistent but the inconsistency has a pattern Major differences between Public in addition to Expert perceptions
Tverskys Analysis Assuming that the U.S. is preparing as long as an outbreak of a disease imported from Asia two alternative programs: Program A: 200 people would be saved. Program B: 1/3 chance that 600 will be saved in addition to 2/3 that no one will be saved. (72%) Alternatively Program C: 400 people will die. Program D: a 1/3 probability that no one will die in addition to a 2/3 probability that 600 will die. Tverskys Analysis (cont.) (78%) Simple arithmetic tells us that options C in addition to D have the same effect as options A in addition to B. When the question was posed as saving lives the students were risk averse. BUT When the question was posed as preventing deaths they favored risk! Stan as long as d in addition to Harvard students were the same
MEASURES of Risk Simple risk of Death (assuming no other causes) by age by cause Risk of Injury by cause by type by severity Per year lifetime unit operation event ton unit output RISK MEASURES (continued) Loss of Life Expectancy (LOLE) Years of Life Lost (YOLL) Man Days Lost (MDL) Working Days Lost (WDL) Public Days Lost (PDL) Quality Adjusted Life Years (QALY) Disability Adjusted Life Years (DALY) Different decisions may dem in addition to different measures LOLE from cigarette smoking In USA 600 billion cigarettes made (presumably smoked) 400,000 people have premature death (lung cancer, other cancers, heart) 1,500,000 cigarettes per death Each death – 17 years (8,935,200 minutes) off life or 6 minutes per cigarette ABOUT THE TIME IT TAKES TO SMOKE ONE
What questions are you asking IF YOU DONT KNOW THE CHANCE OF A SENSIBLE ANSWER IS REDUCED. The Importance of Models Every risk calculation involves a model. The simplest is: NEXT YEAR WILL BE LIKE LAST YEAR. NEXT YEAR WILL BE LIKE LAST YEAR WITH IMPROVEMENTS. EVERY MODEL HAS ASSUMPTION WHICH MUST BE CLEARLY STATED Wigner: whenever there is a lot of energy in one place in addition to a lot of people in the same place, there is a potential as long as disaster. 1848 no petroleum products brought up the Thames River closer than 30 miles east of London Bridge (Canvey Isl in addition to ) (VERY WISE) 1978 120 seventeen million gallon tanks in Canvey ( as long as LNG each is 20 Hiroshimas) Plus 500 vacation cottages With one access road EASY TO IMAGINE DISASTER
Even ignored historical data includes big risks 65 million years ago – large meteor impact may have destroyed the dinosaur Risk per year 1/65 million as long as everyone Lifetime risk 1 in a million including smaller impacts we get lifetime risk 1/100,000 Yet EPA pretended to regulate at 1 in a million! Beware of risk assessments that make assumptions that an important parameter is precise. (US EPA) Large Accidents in New Technologies After World War II, the old paradigm was inadequate: try it in addition to if it gives trouble, fix it Society now dem in addition to s evidence, in advance, that the technology is safe. The first major example was nuclear energy. WHY WAS THAT THE FIRST EXAMPLE
A number of reasons have been suggested: The new technology was in h in addition to s of fundamental scientists from start: 1946 The US Atomic Energy Commission (AEC) The new technology used new physical principles. The new technology arose simultaneously with a new deadly as long as m of war. The new technology posed unprecedented hazards. Atomic Energy Commission Established an Advisory Committee on Reactor Safeguards (ACRS) to advise on safety. Outst in addition to ing Scientists: Glenn Seaborg, John Von Neuman, Robert Bacher, Edward Teller, Eugene Wigner in addition to Richard Feynman Defense in Depth (a name borrowed from the military) Imagine the worst thing that can reasonably go wrong in the reactor, the Maximum Credible Accident devise an engineered safeguard to prevent it Large reactors, particularly first in a series, in unpopulated areas, following Wigners principle. The Reactor Safety Study (Rasmussen et al. 1975) calculated beyond the maximum credible accident
ASSUMPTIONS We have drawn all possible trees with consequences The probabilities are independent (design to make them so; look very carefully at correlation Consider carefully – with some confidentiality – actions that can artificially correlate the separate probabilities INDEPENDENCE IS CRUCIAL DO NOT break down detail in event tree beyond what independence allows Fukushima: Earthquake in addition to Tsunami are NOT independent But effect of radiation in addition to accident calculation are independent
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