Regional Risk Assessment for Point Source Pollution Based on a Water Quality Model of the Taipu River,China

Point source pollution is one of the main threats to regional environmental health. Based on a water quality model, a methodology to assess the regional risk of point source pollution is proposed. The assessment procedure includes five parts: (1) identifying risk source units and estimating source emissions using Monte Carlo algorithms; (2) observing hydrological and water quality data of the assessed area, and evaluating the selected water quality model; (3) screening out the assessment endpoints and analyzing receptor vulnerability with the Choquet fuzzy integral algorithm; (4) using the water quality model introduced in the second step to predict pollutant concentrations for various source emission scenarios and analyzing hazards of risk sources; and finally, (5) using the source hazard values and receptor vulnerability scores to estimate overall regional risk. The proposed method, based on the Water Quality Analysis Simulation Program (WASP), was applied in the region of the Taipu River, which is in the Taihu Basin, China. Results of source hazard and receptor vulnerability analysis allowed us to describe aquatic ecological, human health, and socioeconomic risks individually, and also integrated risks in the Taipu region, from a series of risk curves. Risk contributions of sources to receptors were ranked, and the spatial distribution of risk levels was presented. By changing the input conditions, we were able to estimate risks for a range of scenarios. Thus, the proposed procedure may also be used by decisionmakers for long‐term dynamic risk prediction.     

Consideration of Background Exposures in the Management of Hazardous Waste Sites: A New Approach to Risk Assessment

The current approach to health risk assessment of toxic waste sites in the U.S. may lead to considerable expenditure of resources without any meaningful reduction in population exposure. Risk assessment methods used generally ignore background exposures and consider only incremental risk estimates for maximally exposed individuals. Such risk estimates do not address true public health risks to which background exposures also contribute. The purpose of this paper is to recommend a new approach to risk assessment and risk management concerning toxic waste sites. Under this new approach, which we have called public health risk assessment, chemical substances would be classified into a level of concern based on the potential health risks associated with typical national and regional background exposures. Site assessment would then be based on the level of concern for the particular pollutants involved and the potential contribution of site contaminants to typical background human exposures. While various problems can be foreseen with this approach, the key advantage is that resources would be allocated to reduce the most important sources of human exposure, and site remediation decisions could be simplified by focussing on exposure assessment rather than questionable risk extrapolations.     

Life cycle impact assessment: a challenge for risk analysts.

Modern technology, together with an advanced economy, can provide a good or service in myriad ways, giving us choices on what to produce and how to produce it. To make those choices more intelligently, society needs to know not only the market price of each alternative, but the associated health and environmental consequences. A fair comparison requires evaluating the consequences across the whole "life cycle"--from the extraction of raw materials and processing to manufacture/construction, use, and end-of-life--of each alternative. Focusing on only one stage (e.g., manufacture) of the life cycle is often misleading. Unfortunately, analysts and researchers still have only rudimentary tools to quantify the materials and energy inputs and the resulting damage to health and the environment. Life cycle assessment (LCA) provides an overall framework for identifying and evaluating these implications. Since the 1960s, considerable progress has been made in developing methods for LCA, especially in characterizing, qualitatively and quantitatively, environmental discharges. However, few of these analyses have attempted to assess the quantitative impact on the environment and health of material inputs and environmental discharges Risk analysis and LCA are connected closely. While risk analysis has characterized and quantified the health risks of exposure to a toxicant, the policy implications have not been clear. Inferring that an occupational or public health exposure carries a nontrivial risk is only the first step in formulating a policy response. A broader framework, including LCA, is needed to see which response is likely to lower the risk without creating high risks elsewhere. Even more important, LCA has floundered at the stage of translating an inventory of environmental discharges into estimates of impact on health and the environment. Without the impact analysis, policymakers must revert to some simple rule, such as that all discharges, regardless of which chemical, which medium, and where they are discharged, are equally toxic. Thus, risk analysts should seek LCA guidance in translating a risk analysis into policy conclusions or even advice to those at risk. LCA needs the help of RA to go beyond simplistic assumptions about the implications of a discharge inventory. We demonstrate the need and rationale for LCA, present a brief history of LCA, present examples of the application of this tool, note the limitations of LCA models, and present several methods for incorporating risk assessment into LCA. However, we warn the reader not to expect too much. A comprehensive comparison of the health and environmental implications of alternatives is beyond the state of the art. LCA is currently not able to provide risk analysts with detailed information on the chemical form and location of the environmental discharges that would allow detailed estimation of the risks to individuals due to toxicants. For example, a challenge for risk analysts is to estimate health and other risks where the location and chemical speciation are not characterized precisely. Providing valuable information to decisionmakers requires advances in both LCA and risk analysis. These two disciplines should be closely linked, since each has much to contribute to the other.     

Life-Cycle Assessment in Relation to Risk Assessment: An Evolving Perspective

A life-cycle approach takes a cradle-to-grave perspective of a product's numerous activities from the raw material extraction to final disposal. There have been recent efforts to develop life-cycle assessment (LCA) to assess both environmental and human health issues. The question then arises: what are the capabilities of LCA, especially in relation to risk assessment? To address this question, this paper first describes the LCA mass-based accounting system and then analyzes the use of this approach for environmental and human health assessment. The key LCA limitations in this respect are loss of spatial, temporal, dose-response, and threshold information. These limitations affect LCA's capability to assess several environmental issues, and human health in particular. This leads to the conclusion that LCA impact assessment does not predict or measure actual effects, quantitate risks, or address safety. Instead, LCA uses mass loadings with simplifying assumptions and subjective judgments to add independent effects and exposures into an overall score. As a result, LCA identifies possible human health issues on a systemwide basis from a worst case, hypothetical hazard perspective. Ideally, the identified issues would then be addressed by more detailed assessment methods, such as risk assessment.     

Safe and Sorry: Risk, Environmental Equity, and Hazardous Waste Management Facilities

Many empirical environmental equity analyses have attempted to determine if hazardous waste treatment, storage, or disposal facilities (TSDFs) are in disproportionately minority or low-income areas. These prior analyses did not explain the extent of the risks posed by TSDFs, nor did they weight the distribution of those risks by the individual characteristics of the TSDFs. This study evaluated the risks posed by TSDFs in general and then examined whether any such risks were distributed inequitably when each TSDF was weighted by the amount of hazardous waste that it managed. Based on an assessment of the nature of the hazardous wastes that TSDFs manage, the possible exposure paths to risk from TSDFs, the laws designed to minimize the risks that TSDFs pose, and TSDFs' safety records, the attention devoted to TSDFs by environmental equity researchers is greatly exaggerated. Furthermore, based on this study's analyses, there was no pattern of the TSDFs or the risks that they posed being inequitably concentrated in disproportionately minority or low-income areas. Most of the TSDFs and the hazardous waste that they manage are in areas that are either unpopulated or have fewer minority or low-income people than the national average. There are, however, some TSDFs that are in highly populated, heavily minority or low-income areas, which results in such people being more likely overall to be in close proximity to these facilities.     

A Process for Incorporating Comparative Risk into Environmental Policymaking in Louisiana

The goal of Louisiana's 1990–1991 comparative risk project, also called the Louisiana Environmental Action Plan (LEAP), was to incorporate risk assessment into state environmental planning and policymaking. Scientists, government officials, and citizens were brought together to estimate the relative risk to human health, natural resources, and quality of life posed by 33 selected environmental issues. The issues were then ranked according to their relative estimated risks. It was hoped that this ranking of "comparative risks" would enable state policymakers to target the most important environmental problems and allocate scarce public resources more rationally and efficiently. As a result of the project, the governor issued an Executive Order forming a permanent Public Advisory Committee to continue this type of comparative risk assessment in Louisiana.     

Risks of Municipal Solid Waste Incineration: An Environmental Perspective

The central focus of the debate over incineration of municipal solid waste (MSW) has shifted from its apparent management advantages to unresolved risk issues. This shift is a result of the lack of comprehensive consideration of risks associated with incineration. We discuss the need to expand incinerator risk assessment beyond the limited view of incinerators as stationary air pollution sources to encompass the following: other products of incineration, ash in particular, and pollutants other than dioxins, metals in particular; routes of exposure in addition to direct inhalation; health effects in addition to cancer; and the cumulative nature of exposure and health effects induced by many incinerator-associated pollutants. Rational MSW management planning requires that the limitations as well as advantages of incineration be recognized. Incineration is a waste-processing--not a waste disposal--technology, and its products pose substantial management and disposal problems of their own. Consideration of the nature of these products suggests that incineration is ill-suited to manage the municipal wastestream in its entirety. In particular, incineration greatly enhances the mobility and bioavailability of toxic metals present in MSW. These factors suggest that incineration must be viewed as only one component in an integrated MSW management system. The potential for source reduction, separation, and recycling to increase the safety and efficiency of incineration should be counted among their many benefits. Risk considerations dictate that alternatives to the use of toxic metals at the production stage also be examined in designing an effective, long-term MSW management strategy.     

The Contrast Between Risk Assessment and Rules of Evidence in the Context of International Trade Disputes: Can the U.S. Experience Inform the Process?

Risk assessment provides a formalized process to evaluate human, animal, and ecological responses associated with exposure to environmental agents. The purpose of risk assessment is to answer two related questions.

• ? How likely is an (adverse) event to occur?
• ? If it does, how severe will the impact be?

In the United States, the science of risk assessment has evolved out of the necessity to make public health decisions in the face of scientific uncertainty. Its basic propositions have been established over the past three decades and its applications have impacted virtually every aspect of public health and environmental protection in many countries, including the United States. More recently, the World Trade Organization's (WTO) dispute‐settlement process has provided additional incentive for the reliance on risk assessments internationally through the requirement that member countries be able to provide scientific justification, based on a risk assessment, for public health and environmental regulatory measures that are challenged. The purpose of this article is to review the history of risk assessment in the United States, emphasizing the development of both its scientific and policy aspects, as one example of the development of institutional capacity for risk assessment. This article discusses the importance of the social, political, and economic contexts of risk assessment and risk management in shaping the approaches taken while highlighting the reality that the analytic or risk assessment part of the decision‐making process, in the absence of scientific data, can be completed only by inserting inferences, or policy judgments, which may differ among countries. This article recognizes these differences, and the consequent difference between risk assessment that incorporates public health protective assumptions and the rules of evidence that seek to answer questions of causality, and discusses implications for the WTO dispute‐settlement process. It further explores the value of country‐specific risk assessment guidelines to facilitate consistency within a country along with the appropriateness and feasibility of international risk assessment guidelines.     

Evaluating Efficiency-Equality Tradeoffs for Mobile Source Control Strategies in an Urban Area

In environmental risk management, there are often interests in maximizing public health benefits (efficiency) and addressing inequality in the distribution of health outcomes. However, both dimensions are not generally considered within a single analytical framework. In this study, we estimate both total population health benefits and changes in quantitative indicators of health inequality for a number of alternative spatial distributions of diesel particulate filter retrofits across half of an urban bus fleet in Boston, Massachusetts. We focus on the impact of emissions controls on primary fine particulate matter (PM_2.5) emissions, modeling the effect on PM_2.5 concentrations and premature mortality. Given spatial heterogeneity in baseline mortality rates, we apply the Atkinson index and other inequality indicators to quantify changes in the distribution of mortality risk. Across the different spatial distributions of control strategies, the public health benefits varied by more than a factor of two, related to factors such as mileage driven per day, population density near roadways, and baseline mortality rates in exposed populations. Changes in health inequality indicators varied across control strategies, with the subset of optimal strategies considering both efficiency and equality generally robust across different parametric assumptions and inequality indicators. Our analysis demonstrates the viability of formal analytical approaches to jointly address both efficiency and equality in risk assessment, providing a tool for decisionmakers who wish to consider both issues.     

Life cycle environmental impacts of consumer packaging products in Japan

Several Japanese companies and the government are recently promoting a plastic ban and imposing a tax levy to curb litter and reduce greenhouse gas emissions. This has led to a rapid rise of nonplastic packaging alternatives. While plastics and litter are pressing concerns, it is paramount to examine environmental risks of other alternatives before wide application and legislative action, to not further the risk of environmental damage. This study aims to quantify and compare plastic products such as polyethylene-terephthalate (PET) bottles and high-density polyethylene (HDPE) bags with widely available alternatives in Japan like glass bottles, aluminum bottles, paper bags, and textile bags, to find a product with the least environmental impact. A life cycle assessment is conducted from a cradle-to-grave environmental impact approach that includes raw material extraction, production, transportation, end-of-life treatment, and disposal. Sixteen impact categories including climate change, acidification, aquatic-toxicity, so forth, and weighing is assessed using the MiLCA software. The functional unit is one piece of each packaging product, and impacts of product-filling, storage, recycling, and reuse are excluded for a consistent comparison. HDPE bags performed better than paper and textile bags in 15 of the 16 analyzed impact categories. Similarly, PET bottles outperformed aluminum and glass bottles in 12 out of the 16 impact categories analyzed. Weighted results also highlight the heightened negative environmental impacts of replacing plastic packaging with widely available alternatives.     

The Interplay of Science, Values, and Experiences Among Scientists Asked to Evaluate the Hazards of Dioxin, Radon, and Environmental Tobacco Smoke

To investigate the extent to which personal values and experiences among scientists might affect their assessment of risks from dioxin, radon, and environmental tobacco smoke (ETS), we conducted an experiment through a telephone survey of 1461 epidemiologists, toxicologists, physicians, and general scientists. Each participant was read a vignette designed to reflect the mainstream scientific thinking on one of the three substances. For half of the participants (group A) the substance was named. For the other half (group B), the substance was not named but was identified only as Substance X, Y, or Z. Knowing the name of the substance had little effect on the scientists' evaluation of dioxin, although those who knew the substance to be dioxin were more likely to rate the substance as a serious environmental health hazard (51% vs. 42%, p = 0.062). For radon, those who knew the substance by name were significantly more likely to consider it an environmental health hazard than were those who knew it as substance Z (91% vs. 78%, p less than 0.001). Participants who knew they were being asked about ETS rather than substance X were significantly more likely to consider the substance an environmental health hazard (88% vs. 66%, p less than 0.001), to consider the substance a serious environmental health hazard (70% vs. 33%, p less than 0.001), to believe that background exposure required public health intervention (85% vs. 41%, p less than 0.001), and to believe that above-background exposure required public health intervention (90% vs. 74%, p less than 0.001). These findings suggest that values and experiences may be influencing health risk assessments for these substances, and indicate the need for more study of this phenomenon.     

An integrated environmental risk assessment framework for coal-fired power plants: A fuzzy logic approach

This study quantifies the environmental risk of a coal-fired thermal power plant during operation by using environmental monitoring data, site surveys, and documented evidence. The following criteria are assessed: emissions (CO, SO₂, NO_x, PM₁₀), impact on aquatic ecosystem (fish protection at cooling water intake and cooling water discharge temperature), and waste management (fly ash and bottom ash). Fuzzy sets were defined for each criterion, taking environmental regulatory context as an expert judgment. A survey was conducted with multiple stakeholders to determine the relative importance of risk factors. The survey results showed that the most concerned risks are SO₂ and NO_x emissions. The proposed method estimates the risk of each environmental criterion separately and then accumulates them into an environmental risk index (ERI). Accordingly, we assessed the Catalagzi coal-fired power plant, which has been in operation on the Black Sea coast in northwestern Turkey. For this case study, the ERI resulted in a value of 0.78 (on a scale of 0–1), showing high environmental risk to the facility. Moreover, the applicability of the proposed framework was tested in several existing coal-fired power plants using simultaneous measurements. All studied coal-fired power plants in Turkey have unacceptable pollutants (PM₁₀, SO₂, and NO_x) concentration levels indicating high health risk potential. The application of the integrated environmental risk assessment framework showed that new environmental regulations are needed in Turkey to specify more strict emission limits and to monitor CO₂, fine particulate matter emissions, cooling water discharge, and fish protection at cooling water intake.     

Nuclear Plant PRA: How Far Has It Come?

Nearly ten years have passed since the publication in August 1974 of the draft Reactor Safety Study (WASH 1400), the first detailed attempt to apply probabilistic risk assessment (PRA) techniques to estimate the public risks posed by commercial nuclear power plants. Now is an opportune time to look back and see how PRA has fared over these ten years. We will not attempt to pass judgement on how the Reactor Safety Study report itself has withstood the test of time, as that task is best left to others less directly involved in preparing the report. Instead, we will examine advances in the understanding, acceptance, and utilization of PRA techniques, as well as technical advances in PRA methods. Some of the significant insights gained from PRAs will be discussed. Finally, some observations on the future of PRA will be offered.     

Risk Assessment for Invasive Species

Although estimates vary, there is a broad agreement that invasive species impose major costs on the U.S. economy, as well as posing risks to nonmarket environmental goods and services and to public health. The domestic effort to manage risks associated with invasive species is coordinated by the National Invasive Species Council (NISC), which is charged with developing a science-based process to evaluate risks associated with the introduction and spread of invasive species. Various international agreements have also elevated invasive species issues onto the international policy agenda. The World Trade Organization (WTO) Sanitary and Phytosanitary (SPS) Agreement establishes rights and obligations to adhere to the discipline of scientific risk assessment to ensure that SPS measures are applied only to the extent required to protect human, animal, and plant health, and do not constitute arbitrary or unjustifiable technical barriers to trade. Currently, however, the field of risk assessment for invasive species is in its infancy. Therefore, there is a pressing need to formulate scientifically sound methods and approaches in this emerging field, while acknowledging that the demand for situation-specific empirical evidence is likely to persistently outstrip supply. To begin addressing this need, the Society for Risk Analysis Ecological Risk Assessment Specialty Group and the Ecological Society of America Theoretical Ecology Section convened a joint workshop to provide independent scientific input into the formulation of methods and processes for risk assessment of invasive species to ensure that the analytic processes used domestically and internationally will be firmly rooted in sound scientific principles.     

A Framework for Assessing Uncertainty Associated with Human Health Risks from MSW Landfill Leachate Contamination

Landfilling is a cost‐effective method, which makes it a widely used practice around the world, especially in developing countries. However, because of the improper management of landfills, high leachate leakage can have adverse impacts on soils, plants, groundwater, aquatic organisms, and, subsequently, human health. A comprehensive survey of the literature finds that the probabilistic quantification of uncertainty based on estimations of the human health risks due to landfill leachate contamination has rarely been reported. Hence, in the present study, the uncertainty about the human health risks from municipal solid waste landfill leachate contamination to children and adults was quantified to investigate its long‐term risks by using a Monte Carlo simulation framework for selected heavy metals. The Turbhe sanitary landfill of Navi Mumbai, India, which was commissioned in the recent past, was selected to understand the fate and transport of heavy metals in leachate. A large residential area is located near the site, which makes the risk assessment problem both crucial and challenging. In this article, an integral approach in the form of a framework has been proposed to quantify the uncertainty that is intrinsic to human health risk estimation. A set of nonparametric cubic splines was fitted to identify the nonlinear seasonal trend in leachate quality parameters. LandSim 2.5, a landfill simulator, was used to simulate the landfill activities for various time slices, and further uncertainty in noncarcinogenic human health risk was estimated using a Monte Carlo simulation followed by univariate and multivariate sensitivity analyses.     

Data Available for Evaluating the Risks and Benefits of MTBE and Ethanol as Alternative Fuel Oxygenates

The wide-scale use of methyl tertiary butyl ether (MTBE) in gasoline has resulted in substantial public controversy and action to ban or control its use due to perceived impacts on water quality. Because oxygenates are still required under federal law, considerable research has focused on ethanol as a substitute for MTBE. In this article, we summarize the currently available literature on the air and water quality risks and benefits of MTBE versus ethanol as alternative fuel oxygenates. We find that MTBE-fuel blends are likely to have substantial air quality benefits; ethanol-fuel blends appear to offer similar benefits, but these may be at least partially negated because of ethanol's propensity to increase emissions and ambient concentrations of some air contaminants. Releases of gasoline containing either MTBE or ethanol could have an impact on some drinking water sources, although the impacts associated with MTBE tend to relate to aesthetics (i.e., taste and odor), whereas the impacts associated with ethanol generally relate to health risk (i.e., greater exposure to gasoline constituents such as benzene). It is likely that these water quality impacts will be outweighed by the air quality benefits associated with MTBE and perhaps ethanol use, which affect a much larger population. A lack of data on environmental exposures and associated health impacts hinders the completion of a comprehensive quantitative risk-benefit analysis, and the available air and water quality data should be evaluated in a broader risk-management context, which considers the potential life-cycle impacts, costs, and feasibility associated with alternative fuel oxygenates.     

Risk Perception in Context: The Savannah River Site Stakeholder Study

Environmental managers are increasingly charged with involving the public in the development and modification of policies regarding risks to human health and the environment. Involving the public in environmental decision making first requires a broad understanding of how and why the public perceives various risks. The Savannah River Stakeholder Study was conducted with the purpose of investigating individual, economic, and social characteristics of risk perceptions among those living near the Savannah River Nuclear Weapons Site. A number of factors were found to impact risk perceptions among those living near the site. One's estimated proximity to the site and relative river location surfaced as strong determinants of risk perceptions among SRS residents. Additionally, living in a quality neighborhood and demonstrating a willingness to accept health risks for economic gain strongly abated heightened risk perceptions.The Consortium for Risk Evaluation with Stakeholder Participation (CRESP)The Consortium for Risk Evaluation with Stakeholder Participation (CRESP)The Consortium for Risk Evaluation with Stakeholder Participation (CRESP)     

Assessing human health response in life cycle assessment using ED10s and DALYs: part 2--Noncancer effects.

In Part 1 of this article we developed an approach for the calculation of cancer effect measures for life cycle assessment (LCA). In this article, we propose and evaluate the method for the screening of noncancer toxicological health effects. This approach draws on the noncancer health risk assessment concept of benchmark dose, while noting important differences with regulatory applications in the objectives of an LCA study. We adopt the centraltendency estimate of the toxicological effect dose inducing a 10% response over background, ED10, to provide a consistent point of departure for default linear low-dose response estimates (betaED10). This explicit estimation of low-dose risks, while necessary in LCA, is in marked contrast to many traditional procedures for noncancer assessments. For pragmatic reasons, mechanistic thresholds and nonlinear low-dose response curves were not implemented in the presented framework. In essence, for the comparative needs of LCA, we propose that one initially screens alternative activities or products on the degree to which the associated chemical emissions erode their margins of exposure, which may or may not be manifested as increases in disease incidence. We illustrate the method here by deriving the betaED10 slope factors from bioassay data for 12 chemicals and outline some of the possibilities for extrapolation from other more readily available measures, such as the no observable adverse effect levels (NOAEL), avoiding uncertainty factors that lead to inconsistent degrees of conservatism from chemical to chemical. These extrapolations facilitated the initial calculation of slope factors for an additional 403 compounds; ranging from 10(-6) to 10(3) (risk per mg/kg-day dose). The potential consequences of the effects are taken into account in a preliminary approach by combining the betaED10 with the severity measure disability adjusted life years (DALY), providing a screening-level estimate of the potential consequences associated with exposures, integrated over time and space, to a given mass of chemical released into the environment for use in LCA.     

Evaluating the Potential for a Helicobacter pylori Drinking Water Guideline

Helicobacter pylori is a microaerophilic, gram‐negative bacterium that is linked to adverse health effects including ulcers and gastrointestinal cancers. The goal of this analysis is to develop the necessary inputs for a quantitative microbial risk assessment (QMRA) needed to develop a potential guideline for drinking water at the point of ingestion (e.g., a maximum contaminant level, or MCL) that would be protective of human health to an acceptable level of risk while considering sources of uncertainty. Using infection and gastric cancer as two discrete endpoints, and calculating dose‐response relationships from experimental data on humans and monkeys, we perform both a forward and reverse risk assessment to determine the risk from current reported surface water concentrations of H. pylori and an acceptable concentration of H. pylori at the point of ingestion. This approach represents a synthesis of available information on human exposure to H. pylori via drinking water. A lifetime risk of cancer model suggests that a MCL be set at <1 organism/L given a 5‐log removal treatment because we cannot exclude the possibility that current levels of H. pylori in environmental source waters pose a potential public health risk. Research gaps include pathogen occurrence in source and finished water, treatment removal rates, and determination of H. pylori risks from other water sources such as groundwater and recreational water.     

Some Limitations of Qualitative Risk Rating Systems

Qualitative systems for rating animal antimicrobial risks using ordered categorical labels such as “high,”“medium,” and “low” can potentially simplify risk assessment input requirements used to inform risk management decisions. But do they improve decisions? This article compares the results of qualitative and quantitative risk assessment systems and establishes some theoretical limitations on the extent to which they are compatible. In general, qualitative risk rating systems satisfying conditions found in real‐world rating systems and guidance documents and proposed as reasonable make two types of errors: (1) Reversed rankings, i.e., assigning higher qualitative risk ratings to situations that have lower quantitative risks; and (2) Uninformative ratings, e.g., frequently assigning the most severe qualitative risk label (such as “high”) to situations with arbitrarily small quantitative risks and assigning the same ratings to risks that differ by many orders of magnitude. Therefore, despite their appealing consensus‐building properties, flexibility, and appearance of thoughtful process in input requirements, qualitative rating systems as currently proposed often do not provide sufficient information to discriminate accurately between quantitatively small and quantitatively large risks. The value of information (VOI) that they provide for improving risk management decisions can be zero if most risks are small but a few are large, since qualitative ratings may then be unable to confidently distinguish the large risks from the small. These limitations suggest that it is important to continue to develop and apply practical quantitative risk assessment methods, since qualitative ones are often unreliable.