Life Years Lost at Hazardous Waste Sites: Remediation Worker Fatalities vs. Cancer Deaths to Nearby Residents

We present a hypothetical case study using the Years of Potential Life Lost (YPLL) metric to compare cancer risks incurred by residents living near a Superfund site to occupational fatality risks incurred by workers employed in that site's remediation. Since cancer occurs late in life, and because we assume its mortality rate is 60%, each case results in 8.8 YPLL. Each occupational fatality, which typically occurs earlier in life, results in 38.1 YPLL. In our case study, the residential population of 5000 incurred 1.3 YPLL, compared to 5.7 YPLL incurred by the 500 workers. Several uncertain assumptions may influence our calculations; moreover, occupational risks may be viewed as more "voluntary" than risks incurred by residents. However, because the magnitude of the YPLL incurred by workers and residents may be comparable, risk managers should consider occupational risks when evaluating remedial alternatives.     

Hazardous Waste Incineration at Sea: EPA Decision Making on Risk

This paper critiques the Environmental Protection Agency's assessment of risk for hazardous waste incineration at sea. It reviews operational and transportation risks and considers alternative approaches for managing chlorinated organic hazardous wastes. It concludes that depending on the scale of the program, ocean incineration will either contribute little to the overall management of this waste stream or else it will engender significant risks, especially in the coastal environment. Furthermore, past assessments on the part of EPA have tended to understate the risks of incineration at sea while simultaneously holding out the promise of the technology as a commercial-scale management option. Finally, this paper observes that the Western European countries that pioneered incineration in the North Sea are now finding practical alternatives. It is recommended that waste reuse, on-site treatment, and techniques of waste reduction provide viable alternatives and obviate the need for incineration at sea.     

Peak Exposures in Epidemiologic Studies and Cancer Risks: Considerations for Regulatory Risk Assessment

We review approaches for characterizing “peak” exposures in epidemiologic studies and methods for incorporating peak exposure metrics in dose–response assessments that contribute to risk assessment. The focus was on potential etiologic relations between environmental chemical exposures and cancer risks. We searched the epidemiologic literature on environmental chemicals classified as carcinogens in which cancer risks were described in relation to “peak” exposures. These articles were evaluated to identify some of the challenges associated with defining and describing cancer risks in relation to peak exposures. We found that definitions of peak exposure varied considerably across studies. Of nine chemical agents included in our review of peak exposure, six had epidemiologic data used by the U.S. Environmental Protection Agency (US EPA) in dose–response assessments to derive inhalation unit risk values. These were benzene, formaldehyde, styrene, trichloroethylene, acrylonitrile, and ethylene oxide. All derived unit risks relied on cumulative exposure for dose–response estimation and none, to our knowledge, considered peak exposure metrics. This is not surprising, given the historical linear no‐threshold default model (generally based on cumulative exposure) used in regulatory risk assessments. With newly proposed US EPA rule language, fuller consideration of alternative exposure and dose–response metrics will be supported. “Peak” exposure has not been consistently defined and rarely has been evaluated in epidemiologic studies of cancer risks. We recommend developing uniform definitions of “peak” exposure to facilitate fuller evaluation of dose response for environmental chemicals and cancer risks, especially where mechanistic understanding indicates that the dose response is unlikely linear and that short‐term high‐intensity exposures increase risk.     

Foundational Issues in Risk Assessment and Risk Management

This is a perspective article on foundational issues in risk assessment and management. The aim is to discuss the needs, obstacles, and challenges for the establishment of a renewed, strong scientific foundation for risk assessment and risk management suited for the current and future technological challenges. The focus is on (i) reviewing and discussing the present situation and (ii) identifying how to best proceed in the future, to develop the risk discipline in the directions needed. The article provides some reflections on the interpretation and understanding of the concept of “foundations of risk assessment and risk management” and the challenges therein. One main recommendation is that different arenas and moments for discussion are needed to specifically address foundational issues in a way that embraces the many disciplinary communities involved (from social scientists to engineers, from behavioral scientists to statisticians, from health physicists to lawyers, etc.). One such opportunity is sought in the constitution of a novel specialty group of the Society of Risk Analysis.     

Assessments of Direct Human Exposure—The Approach of EU Risk Assessments Compared to Scenario-Based Risk Assessment

The awareness of potential risks emerging from the use of chemicals in all parts of daily life has increased the need for risk assessments that are able to cover a high number of exposure situations and thereby ensure the safety of workers and consumers. In the European Union (EU), the practice of risk assessments for chemicals is laid down in a Technical Guidance Document; it is designed to consider environmental and human occupational and residential exposure. Almost 70 EU risk assessment reports (RARs) have been finalized for high-production-volume chemicals during the last decade. In the present study, we analyze the assessment of occupational and consumer exposure to trichloroethylene and phthalates presented in six EU RARs. Exposure scenarios in these six RARs were compared to scenarios used in applications of the scenario-based risk assessment approach to the same set of chemicals. We find that scenarios used in the selected EU RARs to represent typical exposure situations in occupational or private use of chemicals and products do not necessarily represent worst-case conditions. This can be due to the use of outdated information on technical equipment and conditions in workplaces or omission of pathways that can cause consumer exposure. Considering the need for exposure and risk assessments under the new chemicals legislation of the EU, we suggest that a transparent process of collecting data on exposure situations and of generating representative exposure scenarios is implemented to improve the accuracy of risk assessments. Also, the data sets used to assess human exposure should be harmonized, summarized in a transparent fashion, and made accessible for all risk assessors and the public.     

Risk Management for Hazardous Materials Transportation: A Local Study in Lyons

A probabilistic risk assessment study has been undertaken in the French city of Lyons. The issue was to know whether it was justified to forbid hazardous material lorries in the city center and to divert them through the suburbs. Therefore, two routes, the City Center route and the Suburban route were compared. This paper describes the analysis and shows how the results were used in the decision-making process. It also lists the difficulties that are encountered when trying to incorporate formal risk analysis into actual decision-making processes. The risk analysis showed that rerouting is an effective option with respect to all criteria. The mathematical expectation of the number of deaths is divided by three, the reduction on the annual frequency of catastrophic accidents is even more important (about one order of magnitude for accidents involving more than 50 deaths). The spatial analysis proved that the risk was more evenly distributed along the Suburban route. However, the annual expected number of death is low: 0.5 in the worst case. So traditional decision-making approaches do not indicate the necessity of rerouting. Such a situation is believed to be typical for risk management of major hazards. In Lyons, the use of a very small risk aversion factor is sufficient to justify the rerouting option on a formal decision-aiding basis. This is rather unusual, but it is thought that the recognition of the importance of risk aversion by the decision-makers themselves is a very positive outcome from this study.     

Characterizing Environmental Harm: Developments in an Approach to Strategic Risk Assessment and Risk Management

Environmental policymakers and regulators are often in the position of having to prioritize their actions across a diverse range of environmental pressures to secure environmental protection and improvements. Information on environmental issues to inform this type of strategic analysis can be disparate; it may be too voluminous or even absent. Data on a range of issues are rarely presented in a common format that allows easy analysis and comparison. Nevertheless, judgments are required on the significance of various environmental pressures and on the inherent uncertainties to inform strategic assessments such as “state of the environment” reports. How can decisionmakers go about this type of strategic and comparative risk analysis? In an attempt to provide practical tools for the analysis of environmental risks at a strategic level, the Environment Agency of England and Wales has conducted a program of developmental research on strategic risk assessment since 1996. The tools developed under this program use the concept of “environmental harm” as a common metric, viewed from technical, social, and economic perspectives, to analyze impacts from a range of environmental pressures. Critical to an informed debate on the relative importance of these perspectives is an understanding and analysis of the various characteristics of harm (spatial and temporal extent, reversibility, latency, etc.) and of the social response to actual or potential environmental harm from a range of hazards. Recent developments in our approach, described herein, allow a presentation of the analysis in a structured fashion so as to better inform risk‐management decisions.     

Incorporating Risk Assessment and Benefit-Cost Analysis in Environmental Management1

Using data from interviews with a key set of individuals at the U.S. Environmental Protection Agency, this study examines intraagency views about the incorporation of risk assessment and benefit-cost analysis in environment management.     

Characterizing the Risk of Infection from Mycobacterium tuberculosis in Commercial Passenger Aircraft Using Quantitative Microbial Risk Assessment

Quantitative microbial risk assessment was used to predict the likelihood and spatial organization of Mycobacterium tuberculosis ( Mtb ) transmission in a commercial aircraft. Passenger exposure was predicted via a multizone Markov model in four scenarios: seated or moving infectious passengers and with or without filtration of recirculated cabin air. The traditional exponential ( k  = 1) and a new exponential ( k  = 0.0218) dose-response function were used to compute infection risk. Emission variability was included by Monte Carlo simulation. Infection risks were higher nearer and aft of the source; steady state airborne concentration levels were not attained. Expected incidence was low to moderate, with the central 95% ranging from 10⁻⁶ to 10⁻¹ per 169 passengers in the four scenarios. Emission rates used were low compared to measurements from active TB patients in wards, thus a "superspreader" emitting 44 quanta/h could produce 6.2 cases or more under these scenarios. Use of respiratory protection by the infectious source and/or susceptible passengers reduced infection incidence up to one order of magnitude.     

Hazardous Materials Releases in the Northridge Earthquake: Implications for Seismic Risk Assessment

In recent years, increasing attention has been given to the problem of earthquake-initiated hazardous materials releases (EIHRs). While the evidence indicates that EHIRs are an important part of the earthquake hazard profile, little attention has been given to documenting them in a way that could form the basis for more systematic estimates of their probability and consequences. Data from the January 17, 1994 Northridge earthquake document the range and nature of hazardous materials events in the impact area, including those at fixed-site facilities and in transportation systems. Proportional estimates of hazmat incidence are provided, and the implications of these data for developing risk assessments and earthquake hazard management are discussed.     

Using GIS in Risk Analysis: A Case Study of Hazardous Waste Transport

This paper provides an illustration of how a geographic information system (GIS) can be used in risk analysis. It focuses on liquid hazardous waste transport and utilizes records archived by the London Waste Regulatory Authority. This data source provides information on the origin and destination of each waste stream, but not the route followed during transport. A GIS was therefore employed to predict the paths used, taking into account different routing criteria and characteristics of the available road network. Details were also assembled on population distribution and ground-water vulnerability, thus providing a basis for evaluating the potential consequences of a waste spillage during transport. Four routing scenarios were implemented to identify sections of road which consistently saw heavy traffic. These simulations also highlighted that some interventions could lead to risk tradeoffs rather than hazard mitigation. Many parts of the research would not have been possible without a GIS, and the study demonstrates the considerable potential of such software in environmental risk assessment and management.     

Risks of Hazardous Waste Sites versus Asteroid and Comet Impacts: Accounting for the Discrepancies in U.S. Resource Allocation

Approximately $6 billion is spent annually in the United States on the cleanup of sites regulated under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA, or Superfund). The current health risks posed by such sites are thought to be quite small; the expenditures are justified primarily as protecting hypothetical future residents of these sites. Approximately 0.05% of this amount, or $3 million, is spent annually by the U.S. government on the detection of asteroids or comets that could strike the earth. Such damaging impacts do occur from time to time--most recently in 1908 in an unpopulated region of Siberia--but no person is confirmed ever to have died as a result. Anticipated impacts over the course of 1 million years would yield deaths that, when annualized, total approximately 4,000 per year. The risk reduction goal for CERCLA is 15 orders of magnitude greater than that for asteroid/comet detection. A modest increase in resources devoted to asteroid detection would greatly increase the chances of early detection of a threatening object, allowing an effective defense to be attempted. This article argues that the much lower risk-to-resources ratio for CERCLA cleanups than for asteroid and comet detection can be explained by four primary factors: (1) the regard for future generations, since CERCLA benefits mainly the unborn; (2) concrete fears, since toxics are much more feared than asteroids or comets; (3) the source of the threat, since toxic contamination is caused by human beings, unlike impacts from space objects; and (4) the greater political constituencies for hazardous waste cleanup than for space object detection.     

A Heuristic Risk Assessment Technique for Birdstrike Management at Airports

Collisions between birds and aircraft (birdstrikes) have caused the loss of at least 88 aircraft and 243 lives in world civil aviation. Conservative estimates suggest that more routine damage and delays following birdstrikes cost the industry and its insurers US$1.2-1.5 billion per year. The majority of strikes happen close to airports and most countries have regulations that require airport managers to control the birdstrike risk on their property. Birdstrike prevention has, however, lagged behind other aspects of flight safety in the development and implementation of risk assessment protocols, possibly because of the inherent difficulty in quantifying the variability in the populations and behavior of the various bird species involved. This article presents a technique that uses both national and airport-specific data to evaluate risk by creating a simple probability-times-severity matrix. It uses the frequency of strikes reported for different bird species at a given airport over the preceding five years as a measure of strike probability, and the proportion of strikes with each species that result in damage to aircraft, in the national birdstrike database, as a measure of likely severity. Action thresholds for risk levels for particular bird species are then defined, above which the airport should take action to reduce the risk further. The assessment is designed for airports where the reporting and collation of birdstrike events is reasonably consistent over time and where a bird hazard management program of some sort is already in place. This risk assessment is designed to measure risk to the airport as a business rather than risk to the traveling passenger individually. It therefore takes no account of aircraft movement rate in the calculations and is aimed at minimizing the number of damaging incidents rather than concentrating on catastrophic events. Once set up at an airport, the technique is simple to implement for nonexperts, and it allows managers to focus bird control resources on the species causing the greatest risk, hence maximizing the return on investment. This protocol is now being successfully used at major airports in the United Kingdom and elsewhere in the world.     

Assessment of Inhalation Exposures and Potential Health Risks to the General Population that Resulted from the Collapse of the World Trade Center Towers

In the days following the collapse of the World Trade Center (WTC) towers on September 11, 2001 (9/11), the U.S. Environmental Protection Agency (EPA) initiated numerous air monitoring activities to better understand the ongoing impact of emissions from that disaster. Using these data, EPA conducted an inhalation exposure and human health risk assessment to the general population. This assessment does not address exposures and potential impacts that could have occurred to rescue workers, firefighters, and other site workers, nor does it address exposures that could have occurred in the indoor environment. Contaminants evaluated include particulate matter (PM), metals, polychlorinated biphenyls, dioxins, asbestos, volatile organic compounds, particle-bound polycyclic aromatic hydrocarbons, silica, and synthetic vitreous fibers (SVFs). This evaluation yielded three principal findings. (1) Persons exposed to extremely high levels of ambient PM and its components, SVFs, and other contaminants during the collapse of the WTC towers, and for several hours afterward, were likely to be at risk for acute and potentially chronic respiratory effects. (2) Available data suggest that contaminant concentrations within and near ground zero (GZ) remained significantly elevated above background levels for a few days after 9/11. Because only limited data on these critical few days were available, exposures and potential health impacts could not be evaluated with certainty for this time period. (3) Except for inhalation exposures that may have occurred on 9/11 and a few days afterward, the ambient air concentration data suggest that persons in the general population were unlikely to suffer short-term or long-term adverse health effects caused by inhalation exposures. While this analysis by EPA evaluated the potential for health impacts based on measured air concentrations, epidemiological studies conducted by organizations other than EPA have attempted to identify actual impacts. Such studies have identified respiratory effects in worker and general populations, and developmental effects in newborns whose mothers were near GZ on 9/11 or shortly thereafter. While researchers are not able to identify specific times and even exactly which contaminants are the cause of these effects, they have nonetheless concluded that exposure to WTC contaminants (and/or maternal stress, in the case of developmental effects) resulted in these effects, and have identified the time period including 9/11 itself and the days and few weeks afterward as a period of most concern based on high concentrations of key pollutants in the air and dust.     

Issues in Ecological Risk Assessment: The CRAM Perspective

In 1989, a Committee on Risk Assessment Methodology (CRAM) was convened by the National Research Council (NRC) to identify and investigate important scientific issues in risk assessment. One of the first issues considered by the committee was the development of a conceptual framework for ecological risk assessment, defined as "the characterization of the adverse ecological effects of environmental exposures to hazards imposed by human activities." Adverse ecological effects include all biological and nonbiological environmental changes that society perceives as undesirable. The committee's opinion was that a general framework is needed to define the relationship of ecological risk assessment to environmental management and to facilitate the development of uniform technical guidelines. The framework for human health risk assessment proposed by the NRC in 1983 was adopted as a starting point for discussion. CRAM concluded that, although ecological risk assessment and human health risk assessment differ substantially in terms of scientific disciplines and technical problems, the underlying decision process is the same for both. Therefore, CRAM recommended that the 1983 risk assessment framework be modified to accommodate both human health and ecological risk assessment. CRAM defined an integrated health/ ecological risk assessment framework consisting of the four components: Hazard Identification, Exposure Assessment, Exposure-Response Assessment, and Risk Characterization. CRAM further provided recommendations on the scope of issues to be addressed in ecological risk assessment, critical research needs, and mechanisms for providing more detailed guidance on the scientific content of ecological risk assessments.     

Scenario-Based Risk Assessment of Multi-Use Chemicals: Application to Solvents

The risk through chemical exposure is commonly characterized by ratios of exposure concentrations and effect levels (risk quotients). For chemicals with many different applications such as solvents, however, in addition to the risk quotients of different exposure situations it is useful to determine the corresponding numbers of exposed individuals, that is, not only the magnitude but also the extent of the risk. To this end, the Scenario-Based Risk Assessment (SceBRA) method has been developed that makes use of a large set of scenarios, each of which describes a typical situation regarding handling a solvent or solvent-containing product. The scenarios cover the life-cycle steps of production, distribution, and use of solvents. For each scenario, SceBRA provides the risk quotient, r, and the number of exposed individuals, N. This study investigated seven solvents that are used in large amounts in Switzerland. For each solvent, characteristic distributions of r and N values were calculated, making it possible to compare different solvents with respect to their risk profile. Graphical representations of the r, N data provide an informative way for analyzing and communicating the results of SceBRA.     

Whither Risk Assessment: New Challenges and Opportunities a Third of a Century After the Red Book

Six multi‐decade‐long members of SRA reflect on the 1983 Red Book in order to examine the evolving relationship between risk assessment and risk management; the diffusion of risk assessment practice to risk areas such as homeland security and transportation; the quality of chemical risk databases; challenges from other groups to elements at the core of risk assessment practice; and our collective efforts to communicate risk assessment to a diverse set of critical groups that do not understand risk, risk assessment, or many other risk‐related issues. The authors reflect on the 10 recommendations in the Red Book and present several pressing challenges for risk assessment practitioners.     

A New Approach to Hazardous Materials Transportation Risk Analysis: Decision Modeling to Identify Critical Variables

We take a novel approach to analyzing hazardous materials transportation risk in this research. Previous studies analyzed this risk from an operations research (OR) or quantitative risk assessment (QRA) perspective by minimizing or calculating risk along a transport route. Further, even though the majority of incidents occur when containers are unloaded, the research has not focused on transportation-related activities, including container loading and unloading. In this work, we developed a decision model of a hazardous materials release during unloading using actual data and an exploratory data modeling approach. Previous studies have had a theoretical perspective in terms of identifying and advancing the key variables related to this risk, and there has not been a focus on probability and statistics-based approaches for doing this. Our decision model empirically identifies the critical variables using an exploratory methodology for a large, highly categorical database involving latent class analysis (LCA), loglinear modeling, and Bayesian networking. Our model identified the most influential variables and countermeasures for two consequences of a hazmat incident, dollar loss and release quantity , and is one of the first models to do this. The most influential variables were found to be related to the failure of the container. In addition to analyzing hazmat risk, our methodology can be used to develop data-driven models for strategic decision making in other domains involving risk.     

Multicriteria Decision Framework for Cybersecurity Risk Assessment and Management

Risk assessors and managers face many difficult challenges related to novel cyber systems. Among these challenges are the constantly changing nature of cyber systems caused by technical advances, their distribution across the physical, information, and sociocognitive domains, and the complex network structures often including thousands of nodes. Here, we review probabilistic and risk-based decision-making techniques applied to cyber systems and conclude that existing approaches typically do not address all components of the risk assessment triplet (threat, vulnerability, consequence) and lack the ability to integrate across multiple domains of cyber systems to provide guidance for enhancing cybersecurity. We present a decision-analysis-based approach that quantifies threat, vulnerability, and consequences through a set of criteria designed to assess the overall utility of cybersecurity management alternatives. The proposed framework bridges the gap between risk assessment and risk management, allowing an analyst to ensure a structured and transparent process of selecting risk management alternatives. The use of this technique is illustrated for a hypothetical, but realistic, case study exemplifying the process of evaluating and ranking five cybersecurity enhancement strategies. The approach presented does not necessarily eliminate biases and subjectivity necessary for selecting countermeasures, but provides justifiable methods for selecting risk management actions consistent with stakeholder and decisionmaker values and technical data.