Hazard Assessment Strategies Research Articles

Testing forecasts of a new Bayesian time-predictable model of eruption occurrence

In this paper we propose a model to forecast eruptions in a real forward perspective. Specifically, the model provides a forecast of the next eruption after the end of the last one, using only the data available up to that time. We focus our attention on volcanoes with open conduit regime and high eruption frequency. We assume a generalization of the classical time predictable model to describe the eruptive behavior of open conduit volcanoes and we use a Bayesian hierarchical model to make probabilistic forecasts. We apply the model to Kilauea volcano eruptive data and Mount Etna volcano flank eruption data. The aims of the proposed model are: (1) to test whether or not the Kilauea and Mount Etna volcanoes follow a time predictable behavior; (2) to discuss the volcanological implications of the time predictable model parameters inferred; (3) to compare the forecast capabilities of this model with other models present in literature. The results obtained using the MCMC sampling algorithm show that both volcanoes follow a time predictable behavior. The numerical values inferred for the parameters of the time predictable model suggest that the amount of the erupted volume could change the dynamics of the magma chamber refilling process during the repose period. The probability gain of this model compared with other models already present in literature is appreciably greater than zero. This means that our model provides better forecast than previous models and it could be used in a probabilistic volcanic hazard assessment scheme.

Large earth flows in Emilia-Romagna (Northern Apennines, Italy): origin, reactivation and possible hazard assessment strategies

Large earth flows in Emilia-Romagna (Northern Apennines, Italy): origin, reactivation and possible hazard assessment strategies

Rockfall hazard analysis using LiDAR and spatial modeling

Rockfalls have been significant geohazards along the Canadian Class 1 Railways (CN Rail and CP Rail) since their construction in the late 1800s. These rockfalls cause damage to infrastructure, interruption of business, and environmental impacts, and their occurrence varies both spatially and temporally. The proactive management of these rockfall hazards requires enabling technologies. This paper discusses a hazard assessment strategy for rockfalls along a section of a Canadian railway using LiDAR and spatial modeling. LiDAR provides accurate topographical information of the source area of rockfalls and along their paths. Spatial modeling was conducted using Rockfall Analyst, a three dimensional extension to GIS, to determine the characteristics of the rockfalls in terms of travel distance, velocity and energy. Historical rockfall records were used to calibrate the physical characteristics of the rockfall processes. The results based on a high-resolution digital elevation model from a LiDAR dataset were compared with those based on a coarse digital elevation model. A comprehensive methodology for rockfall hazard assessment is proposed which takes into account the characteristics of source areas, the physical processes of rockfalls and the spatial attribution of their frequency and energy.

Linking debris-flow hazard assessments with geomorphology

Debris-flow hazard assessment schemes are commonly based on empirical, physical, or numerical methods and techniques. Inherent in all methods is generally the assumption of unlimited sediment supply. This study compares model inputs of sediment requirements for debris flows with estimated sediment reproduction from both solifluction and rockwall retreat. The analysis is carried out in Bíldudalur, a community in the Westfjords of Iceland. Geomorphic techniques are applied to determine the set of natural processes acting in this landscape to estimate spatial distribution of relevant processes, to approximate level of processes activity, and to provide information for scenario modeling. Debris-flow volumes are determined by coupling rainfall magnitudes and catchment sizes with average sediment contents. Rockwall retreat and solifluction rates are based on literature reviews. For a rainstorm with a 10-year return period, debris-flow volumes are calculated for 12 different creeks. Rates are assumed for solifluction with a velocity of 0.25 m/yr at an average depth of 0.5 m and for rockwall retreat with 2 mm/yr. Comparing sediment requirements with estimated sediment reproduction leads to a factor of deficit ranging between 6.2 and 8.5. Thus, the sediment storage is not refilled as fast as the next potential triggering rainfall occurs. Consequently, if a debris flow has occurred in the past, all sediment is removed, and the following rainstorm event is ‘just’ causing a flood, which is by far less destructive than a debris-flow event. The challenge of future debris-flow hazard-assessment schemes is to include geomorphic analysis to be able to obtain more sustainable results.

Evaluation of approaches for terrestrial hazard classification

Hazard assessment is an essential element in the evaluation of the potential effects of chemical substances on the environment. To date, most work has focused on hazard assessment schemes for the aquatic environment, but in recent years, a number of proposals have been developed for other environmental compartments. Due to limited datasets, the suitability of the toxicity cut-off values in these schemes has not been fully determined and the practicalities associated with using these approaches have not been fully established. This study, which focused on the soil compartment, was performed to examine cut-off values proposed by two terrestrial hazard assessment schemes and establish the availability of data. Data on earthworms indicated that current proposals for toxicity cut-off values are appropriate. However, analysis of IUCLID (International Uniform ChemicaL Information Database) indicates that even for commonly used high production volume chemicals, insufficient data are available to enable classification. Whilst the necessary data may already be available for selected groups of substances (e.g. pesticides and veterinary medicines), a significant experimental testing programme would therefore be required before a terrestrial classification system could be applied widely. Such data may become available in the future as a result of initiatives such as REACH.

Regulatory use of (Q)SARs in toxicological hazard assessment strategies

In 2001, the European Commission published a policy statement ("White Paper") on future chemicals regulation and risk reduction that proposed the use of non-animal test systems and tailor-made testing approaches, including (Q)SARs, to reduce financial costs and the number of test animals employed. The authors have compiled a database containing data submitted within the EU chemicals notification procedure. From these data, (Q)SARs for the prediction of local irritation/corrosion and/or sensitisation potential were developed and published. These (Q)SARs, together with an expert system supporting their use, will be submitted for official validation and application within regulatory hazard assessment strategies. The main features are: • two sets of structural alerts for the prediction of skin sensitisation hazard classification as defined by the European risk phrase R43, comprising 15 rules for chemical substructures deemed to be sensitising by direct action with cells or proteins, and three rules for substructures acting indirectly, i.e., requiring biochemical transformation; • a decision support system (DSS) for the prediction of skin and/or eye lesion potential built from information extracted from our database. This DSS combines SARs defining reactive chemical substructures relevant for local lesions to be classified, and QSARs for the prediction of the absence of such a potential. The role of the BfR database, and (Q)SARs derived from it, in the use of current and future (EU) testing strategies for irritation and sensitisation is discussed.

Waste site hazard assessment: a taxonomy of current methods and criteria

Dozens of schemes have been developed for assessing the hazards and implicit risks posed by waste disposal sites in the United States. Effective hazard-assessment processes guide decision makers, policy makers, and the public toward more appropriate risk management solutions. Just as in quantitative risk assessment, however, the utility of a hazard assessment scheme depends upon the applicability and totality of the parameters, as well as upon the validity of the assumptions and logic underlying that process. Examination of the range of hazard assessment methods that have been employed reveals some common limitations and a universe of applicable parameters. Understanding the scope of United States efforts is vital to the effective transfer of hazard assessment technology to waste site stakeholders in other industrialized countries. A useful set of modeling criteria is provided as a foundation for future application of the hazard assessment concept at the thousands of waste sites worldwide where hazards are yet to be investigated.

Estimation of consumer exposure to chemicals: application of simple models

Occupational and consumer exposure only recently has become an issue meriting a more systematic approach. This paper offers a method for the estimation of consumer exposure on the basis of limited data sets. Following a selection of exposure route(s) of concern, acute, subchronic and chronic exposure scenarios are identified based on the expected exposure frequency and duration. Algorithms for the estimation of the external exposure are presented and illustrated by example calculations. The external and internal exposure assessment is further integrated into a hazard assessment scheme for consumer products including the determination of no-effect levels for man and the calculation of hazard quotients.

Microbiotests in aquatic ecotoxicology: Characteristics, utility, and prospects

AbstractSmall‐scale biological tests (microbiotests) have steadily increased in development and application over the last 30 years in the field of aquatic ecotoxicology. Multitrophic level assessment requirements, attractive features of microbiotests, and the constant search for simplicity and cost efficiency of testing are reasons explaining the expanding use of microbiotests. In this article, the major characteristics that advantageously confer popularity on microbiotests are presented and 25 currently applied aquatic toxicity microbiotests are listed. Conducted with bacteria, protozoans, microalgae, small invertebrates, and fish cell lines, these microbiotests represent a realistic cross section of those that are now becoming an essential part of ecotoxicological assessment. Microbiotests can be profitably employed for ranking and screening chemicals, for novel applications enabling rapid detection of ecotoxic effects in complex liquid samples, and for increasing the cost efficiency and diagnostic potential of hazard assessment schemes. Microbiotesting research, development, and applications will continue to surge in the 1990s, driven, among other factors, by the imperative need for cost effectiveness in environmental programs. Research in the fields of ecotoxicology, biotechnology, and immunochemistry should provide interesting breakthroughs to further enhance the specificity and diagnostic value of microbiotests.

Constituent bioconcentration in rainbow trout exposed to a complex chemical mixture.

Classically, aquatic contaminant fate models predicting a chemical's bioconcentration factor (BCF) are based upon single-compound derived models, yet such BCF predictions may deviate from observed BCFs when physicochemical interactions or biological responses to complex chemical mixture exposures are not adequately considered in the predictive model. Rainbow trout were exposed to oil-shale retort waters. Such a study was designed to model the potential biological effects precluded by exposure to complex chemical mixtures such as solid waste leachates, agricultural runoff, and industrial process waste waters. Chromatographic analysis of aqueous and nonaqueous liquid-liquid reservoir components yielded differences in mixed extraction solvent HPLC profiles of whole fish exposed for 1 and 3 weeks to the highest dilution of the complex chemical mixture when compared to their corresponding control, yet subsequent whole fish extractions at 6, 9, 12, and 15 weeks into exposure demonstrated no qualitative differences between control and exposed fish. Liver extractions and deproteinized bile samples from exposed fish were qualitatively different than their corresponding controls. These findings support the projected NOEC of 0.0045% dilution, even though the differences in bioconcentration profiles suggest hazard assessment strategies may be useful in evaluating environmental fate processes associated with complex chemical mixtures. 12 references, 4 figures,more » 2 tables.« less

Hazard assessment — A summary of analysis and integrated evaluation of exposure and potential effects from toxic environmental chemicals

The increasing uses of commercial chemicals have forced governments and international organisations, such as OECD, EEC etc. in the years following World War II to address the problem of toxic chemicals in the environment. The scientific basis for any chemical regulation is the knowledge of potential fate and effects of chemicals. Practically every chemical law which has been developed in recent years requests manufacturers and/or importers to register (notify) their production of their marketing of new chemicals to national authorities. The notifications comprise series of data on physico-chemical properties and biological (i.e. toxicological and ecotoxicological) characteristics of the chemicals. From such data it is attempted to establish a hazard ranking (or preliminary hazard assessment) of chemicals. This involves evaluation, or possibly calculation, of the expected exposure from the chemicals and of the potential effects resulting from such exposure. Some basic knowledge on the target, i.e. the ecosystem need to be included in the evaluation process. The possible use of mathematical modelling in hazard ranking and hazard assessment is presently confined to the exposure analyses, which are based on calculations from physico-chemical data of the chemicals and from parameters describing over-all properties of a so-called Unit World. In contrast, the potential effects of a chemical is assessed from a limited number of toxicological and ecotoxicological laboratory tests. The main criteriae used in hazard ranking are established from laboratory data on degradability, mobility and potential for bioaccumulation of the individual chemicals. Such data are selected as the fate (exposure) characteristics of primary importance, while information on acute toxicity to rat, fish, and daphnia are the measures used for evaluation of potential effects. In various ranking schemes these characteristics are expressed in simple numerical scales, and classification codes are assigned to each. These can be scoring systems, or - even more simple - descriptive codes as for instance colour codes, such as Black for ‘Damaging to the environment’, Grey for ‘Dangerous to the environment’, and White for ‘Potentially dangerous to the environment’. The limitations of presently known hazard rankings schemes are discussed, and it is suggested that basic chemical properties (such as the OECD/EEC base-set data or similar) should not realistically be utilised beyond the stage of simple classification rules, e.g. for labelling purposes. More elaborate hazard assessment schemes are still to be expected, and they should be based on more individually developed case-by-case studies.

Applicability of microbial toxicity assays to assessment problems

Microbial assays of dissolved oxygen (DO) uptake and resazurin reduction (RR) assays were compared with regard to applicability for hazard assessment schemes and determination of bioactive residues in soil and biota. The DO method is simpler and less expensive, but is less sensitive and more variable than the RR method. Both gave highly comparable results with pure or mixed cultures of microbes.

APPLICABILITY OF MICROBIAL TOXICITY ASSAYS TO ASSESSMENT PROBLEMS

Microbial assays of dissolved oxygen (DO) uptake and resazurin reduction (RR) assays were compared with regard to applicability for hazard assessment schemes and determination of bioactive residues in soil and biota. The DO method is simpler and less expensive, but is less sensitive and more variable than the RR method. Both gave highly comparable results with pure or mixed cultures of microbes.