ISSN:0272-4332    

DOI:10.1111/j.1539-6924.1996.tb01430.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0272-4332    

DOI:10.1111/j.1539-6924.1996.tb01431.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

One of the main steps in an uncertainty analysis is the selection of appropriate probability distribution functions for all stochastic variables. In this paper, criteria for such selections are reviewed, the most important among them being any a priori knowledge about the nature of a stochastic variable, and theCentral Limit Theoremof probability theory applied to sums and products of stochastic variables. In applications of these criteria, it is shown that many of the popular selections, such as the uniform distribution for a poorly known variable, require far more knowledge than is actually available. However, the knowledge available is usually sufficient to make use of other, more appropriate distributions. Next, functions of stochastic variables and the selection of probability distributions for their arguments as well as the use of different methods of error propagation through these functions are discussed. From these evaluations, priorities can be assigned to determine which of the stochastic variables in a function need the most care in selecting the type of distribution and its parameters. Finally, a method is proposed to assist in the assignment of an appropriate distribution which is commensurate with the total information on a particular stochastic variable, and is based on the scientific method. Two examples are given to elucidate the method for cases of little or almost no information.

ISSN:0272-4332    

DOI:10.1111/j.1539-6924.1996.tb01432.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Accidents in the chemical industry, such as those that took place in Seveso (1976) and Bhopal (1984), may kill or injure thousands of people, cause serious health hazards and irreversible environmental damage. The aim of this paper is to examine the ever‐increasing risk of similar accidents becoming a frequent ocurrence in the so‐called industrializing countries. Using figures from some of the worst chemical accidents in the last decades, data on the Bhopal disaster, and Brazil's social and institutional characteristics, we put forward the hypothesis that present social, political and economic structures in industrializing countries make these countries much more vulnerable to such accidents and create the type of setting where–if and when these accidents occur–they will have even more catastrophic consequences. The authors argue that only the transformation of local structures, and stronger technical cooperation between international organizations, industrialized and industrializing countries could reduce this vulner

ISSN:0272-4332    

DOI:10.1111/j.1539-6924.1996.tb01433.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Despite the widespread conviction that the mass media tend to “blow risks out of proportion,” the question has received little systematic attention. The mass‐media literature also presents the opposite argument, namely that the media minimize the kinds of reporting that might upset large‐scale capitalistic industries. Still other perspectives hold, on the one hand, that media reports tend to have more subtle anti‐technology effects, created by “even‐handed” coverage and on the other hand, that reporters give “establishment” figures the opportunity to “keynote” or “put the facts in perspective” in ways that exert a subtly pro‐technology effect. Drawing on a systematic sample of 128 hazard events developed by researchers at another university and factually summarized by Lexis‐Nexis, we analyze the effects of emotionalism on actual levels of coverage; a variety of analyses show that the only variables to exert significant effects are those that involve objective information, such as the number of casualties or the level of damage created. Given the argument that the effects of emotionalism can be conveyed in ways that are largely independent of the facts, e.g., by headlines, photographs, and “loaded” words, we next compare the emotionalism conveyed by factual summaries vs. the original stories and headlines. Even for incidents involving nuclear and/or toxic hazards, we find the net effect of the full stories is tolessenthe emotionalism. Overall, the hypothesis receiving strongest support is that the “keynoting” helps create an overall impression that the “responsible authorities” are actingmoreresponsibly than might be assumed on the basis of factual summaries alone. The widespread impression within the technical community, while understandable, may well have as much to do with the selective perceptions of scientists and engineers as

ISSN:0272-4332    

DOI:10.1111/j.1539-6924.1996.tb01434.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A Monte Carlo procedure for the construction of complementary cumulative distribution functions (CCDFs) for comparison with the U.S. Environmental Protection Agency (EPA) release limits for radioactive waste disposal (40 CFR 191, Subpart B) is described and illustrated with results from a recent performance assessment (PA) for the Waste Isolation Pilot Plant (WIPP). The Monte Carlo procedure produces CCDF estimates similar to those obtained with importance sampling in several recent PAs for the WIPP. The advantages of the Monte Carlo procedure over importance sampling include increased resolution in the calculation of probabilities for complex scenarios involving drilling intrusions and better use of the necessarily limited number of mechanistic calculations that underlie CCDF construction.

ISSN:0272-4332    

DOI:10.1111/j.1539-6924.1996.tb01435.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

This paper reports results from a survey designed to: (1) evaluate changes in industrial pollution prevention practices since the passage of the landmark environmental legislation, the Emergency Planning and Community Right‐to‐Know Act of 1986, also known as SARA Title III, and (2) identify those factors that may contribute to an industrial facility engaging in pollution prevention and risk communication activities. The survey was conducted under a Cooperative Agreement between the U.S. Environmental Protection Agency and the Columbia University Center for Risk Communication. Evidence from the survey indicates that a wide variety of waste and pollution reduction activities have been undertaken since passage of the Act. Virtually all facilities surveyed in the pulp and paper, chemical, and petroleum and refining industries reported that they had reduced pollutants or wastes on at least one often measures, including reducing toxic air emissions. Most facilities indicated paying more attention to pollution prevention activities as a result of SARA Title III and half reported that their communication activities have also increa

ISSN:0272-4332    

DOI:10.1111/j.1539-6924.1996.tb01436.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A methodology that simulates outcomes from future data collection programs, utilizes Bayesian Monte Carlo analysis to predict the resulting reduction in uncertainty in an environmental fate‐and‐transport model, and estimates the expected value of this reduction in uncertainty to a risk‐based environmental remediation decision is illustrated considering polychlorinated biphenyl (PCB) sediment contamination and uptake by winter flounder in New Bedford Harbor, MA. The expected value of sample information (EVSI), the difference between the expected loss of the optimal decision based on the prior uncertainty analysis and the expected loss of the optimal decision from an updated information state, is calculated for several sampling plan. For the illustrative application we have posed, the EVSI for a sampling plan of two data points is $9.4 million, for five data points is $10.4 million, and for ten data points is $11.5 million. The EVSI for sampling plans involving larger numbers of data points is bounded by the expected value of perfect information, $15.6 million. A sensitivity analysis is conducted to examine the effect of selected model structure and parametric assumptions on the optimal decision and the EVSI. The optimal decision (total area to be dredged) is sensitive to the assumption of linearity between PCB sediment concentration and flounder PCB body burden and to the assumed relationship between area dredged and the harbor‐wide average sediment PCB concentration; these assumptions also have a moderate impact on the computed EVSI. The EVSI is most sensitive to the unit cost of remediation and rather insensitive to the penalty cost associated with under‐re

ISSN:0272-4332    

DOI:10.1111/j.1539-6924.1996.tb01437.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A Bayesian compound Poisson benefit‐risk model is described in this paper, and used to evaluate recent revisions to the South Florida Building Code (SFBC). The model accounts for natural variability in hurricane frequency and severity, and uncertainty in the effectiveness of the revised code. Ranges of residential growth rate, code effectiveness, construction cost increase, and planning period length are assumed, to show the ranges of cost‐to‐performance ratio within which the code will make sense economically. The expected cost of residential hurricane damage over 50 years for ten South Florida counties assuming continuation of previous building practices was $93 billion, equivalent to the residential damage of 5.2 Andrews. Assuming a reduction in the growth of damageable housing in South Florida from 5.5% to 2% as a result of code revision, estimated damages under the new code were $45 billion. At a per‐house construction cost increase of 5%, the probability of at least recovering the estimated $40 billion cost of the specified wind‐resistant construction was estimated to be 47%. Expected return on investment was estimated at $7 billion over 50 years. The expected return lies between a $44 billion loss and a $47 billion gain, when growth in damageable housing is allowed to range from 1% to 4% and construction cost increases are assumed to lie between 3% and 8%. Actual monetary return for a 5% cost increase and 2% growth in damageable housing ranges from a $20 billion loss to a $100 billion gain with 95% probability, as a result of weather variability alone. Results support SFBC revisions on solely economic grounds, a conclusion strengthened considerably in light of potentially avoided deaths and hurricane traumas. The model represents one approach to evaluating economic aspects of the sustainability of new technological measures on the basis of available in

ISSN:0272-4332    

DOI:10.1111/j.1539-6924.1996.tb01438.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Monte Carlo simulation requires a pseudo‐random number generator with good statistical properties. Linear congruential generators (LCGs) are the most popular and well‐studied computer method for generating pseudo‐random numbers used in Monte Carlo studies. High quality LCGs are available with sufficient statistical quality to satisfy all but the most demanding needs of risk assessors. However, because of the discrete, deterministic nature of LCGs, it is important to evaluate the randomness and uniformity of the specific pseudo‐random number subsequences used in important risk assessments. Recommended statistical tests for uniformity and randomness include the Kolmogorov‐Smirnov test, extreme values test, and the runs test, including runs above and runs below the mean tests. Risk assessors should evaluate the stability of their risk model's output statistics, paying particular attention to instabilities in the mean and variance. When instabilities in the mean and variance are observed, more stable statistics, e.g., percentiles, should be reported. Analyses should be repeated using several non‐overlapping pseudo‐random number subsequences. More simulations than those traditionally used are also recommended for

ISSN:0272-4332    

DOI:10.1111/j.1539-6924.1996.tb01439.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY