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  • 1. Alriksson, Stina
    et al.
    Öberg, Tomas
    Conjoint analysis: a useful tool for assessing preferences for environmental issues.2008In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 15, no 2, p. 119-Article in journal (Other academic)
  • 2.
    Alriksson, Stina
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Conjoint analysis as a decision tool for evaluation of environmental performance2007Report (Other academic)
  • 3.
    Alriksson, Stina
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Conjoint analysis as a tool for risk communication2006In: Annual Meeting of the Society for Risk Analysis, Baltimore, Maryland, 3-6 december 2006, 2006Conference paper (Other academic)
  • 4.
    Alriksson, Stina
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Conjoint analysis for environmental evaluation: a review of methods and applications.2008In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 15, no 3, p. 244-257Article in journal (Refereed)
    Abstract [en]

    BACKGROUND, AIM AND SCOPE: Conjoint analysis and the related choice-modelling methods have been used for many years in marketing research to evaluate consumer behaviour and preferences for different kinds of product attributes. Recently, the number of applications in environmental science and management has started to grow. Conjoint analysis is found in many different forms, and the environmental studies evaluated in this review display the same range of methods as in other fields. The key characteristic of all these methods is that trade-offs are evaluated by jointly considering a number of important attributes. MAIN FEATURES: This paper is a review of the literature on environmental applications of conjoint analysis and assesses in which environmental area conjoint analysis has been most successful. The method and the design of the studies are reviewed as well. RESULTS: A total of 84 studies were found, dealing with environmental issues that were evaluated by conjoint analysis. The studies concern agriculture, ecosystem management, energy, environmental evaluation, forestry, land management, pollution, products, recreation, environmental risk analysis and waste management. DISCUSSION: Choice experiments seem to have a comparatively stronger position in environmental studies than elsewhere. Most of the environmental applications are related to natural resource management. This is somewhat surprising, but a number of reports have appeared also on product evaluation, which could be a key application area in the future. CONCLUSIONS: Compared to marketing and transportation, the number of environmental conjoint studies is rather small but increasing, and the method has proven to work effectively in eliciting preferences on environmental issues. In environmental issues, experimenters often use choice experiments, especially concerning ecosystem management and environmental evaluations. When it comes to evaluating preferences concerning agriculture, forestry, energy and products, a more traditional approach of conjoint analysis is favoured. RECOMMENDATIONS AND PERSPECTIVES: Two new areas of application are identified in this review--environmental communication and expert elicitation. Conjoint analysis can thus be developed into a useful instrument for environmental risk analysis and communication, both of which are necessary for an efficient approach to risk governance.

  • 5.
    Alriksson, Stina
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Towards a closed steel eco-cycle - cojoint analysis as a decision tool2005In: Proceedings Kalmar ECO-TECH´ 05: Conference on Waste to Energy Bioremediation and Leachate Treatment / [ed] William Hogland, Tonje Broby, Kalmar: Högskolan i Kalmar , 2005, p. 27-36Conference paper (Refereed)
    Abstract [en]

    The Swedish steel industry has over the past 20 years made substantial efforts to promote energy efficiency and environment protection. However, the dominant part of these investments has been directed to the individual production sites, most of which today have 'solved' their own acute environmental problems. The focus has therefore switched to the properties and performance of the steel products where the evaluation of environ­mental performance is a complex task that often requires simultaneous consideration of many different attributes.

     

    Conjoint analysis is commonly used in marketing research, to evaluate how consumers appreciate specific attributes in products. It has also been widely used in health care, traffic planning and quality management. Conjoint analysis has also been applied to environmental issues such as energy, recreation, environmental valuation, ecosystem management, consumer preferences to products, public preferences to industrial projects, waste management, and environmental policy development. This previous research has shown that the method is well suited for evaluating environmental issues.

     

    Here we briefly present the methodology and review some papers on environmental applications. It is our intention to use this approach as a tool to integrate environmental considerations into both process and product development within the steel industry.

     

  • 6.
    Alriksson, Stina
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Towards a closed steel eco-cycle. Conjoint analysis as a decision tool2005In: University of Kalmar, 2005Conference paper (Other academic)
  • 7.
    Augustsson, Anna
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Filipsson, Monika
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Bergbäck, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    The aspect of climate change in risk assessment of contaminated land2010Conference paper (Other academic)
  • 8.
    Augustsson, Anna
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Filipsson, Monika
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Bergbäck, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Climate change - an uncertainty factor in risk analysis of contaminated land2011In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 409, no 22, p. 4693-4700Article in journal (Refereed)
    Abstract [en]

    Metals frequently occur at contaminated sites, where their potential toxicity and persistence require risk assessments that consider possible long-term changes. Changes in climate are likely to affect the speciation, mobility, and risks associated with metals. This paper provides an example of how the climate effect can be inserted in a commonly used exposure model, and how the exposure then changes compared to present conditions. The comparison was made for cadmium (Cd) exposure to 4-year-old children at a highly contaminated iron and steel works site in southeastern Sweden. Both deterministic and probabilistic approaches (through probability bounds analysis, PBA) were used in the exposure assessment. Potential climate-sensitive variables were determined by a literature review. Although only six of the total 39 model variables were assumed to be sensitive to a change in climate (groundwater infiltration, hydraulic conductivity, soil moisture, soil:water distribution, and two bioconcentration factors), the total exposure was clearly affected. For example, by altering the climate-sensitive variables in the order of 15% to 20%, the deterministic estimate of exposure increased by 27%. Similarly, the PBA estimate of the reasonable maximum exposure (RME, defined as the upper bound of the 95th percentile) increased by almost 20%. This means that sites where the exposure in present conditions is determined to be slightly below guideline values may in the future exceed these guidelines, and risk management decisions could thus be affected. The PBA, however, showed that there is also a possibility of lower exposure levels, which means that the changes assumed for the climate-sensitive variables increase the total uncertainty in the probabilistic calculations. This highlights the importance of considering climate as a factor in the characterization of input data to exposure assessments at contaminated sites. The variable with the strongest influence on the result was the soil:water distribution coefficient (Kd).

  • 9. Barlow, Sue
    et al.
    Schlatter, Josef
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Castoldi, Anna
    Court Marques, Danièle
    Cutting, Andrew
    Jacobs, Miriam
    Lahaniatis, Majlinda
    Liem, Djien
    Manini, Paola
    Mohimont, Luc
    Rortais, Agnes
    Smille, Laura
    Steinkellner, Hans
    Scientific report of the Endocrine Active Substances Task Force2010In: EFSA Journal, ISSN 1831-4732, Vol. 8, no 11, p. Article ID: 1932-Article in journal (Other academic)
    Abstract [en]

    Discussions within the Scientific Committee and the Advisory Forum have called for the development of a common approach within EFSA towards endocrine active substances. The aim of this report by an internal EFSA task force is to clarify the state-of-play, and provide recommendations for scientific and communication issues. Both specific issues and new regulations make it necessary to follow up on recent developments with the EU bodies, Member States, and internationally, in order to avoid diverging assessment approaches and the duplication of work. The proposed actions for EFSA are to contribute to the work in progress under the auspices of DG Environment and to continue its participation in the ongoing OECD activities in the area of testing of chemicals. The development of a generally accepted risk assessment methodology is an additional challenge due to the complexity of the issues involved. Here, the task force recommends that EFSA continues its activities aimed at developing harmonised methodologies for risk assessment of combined exposures to endocrine active substances in food. EFSA should continue to build a dialogue to develop a common strategy with the EC, other EU bodies, Member States’ Competent Authorities, international organisations and partners, as well as external experts and stakeholders on the before mentioned issues. In line with these recommendations, it is proposed that EFSA creates a working group of Panel experts and national experts to advise on prioritising the work on endocrine active substances. EFSA should also work with the experts in its Advisory Group on Risk Communications in conjunction with the communication experts from Member States, and continues to monitor and analyse media and stakeholder developments, in order to define a strategy for communications addressing both the collective group and specific endocrine active substances.

  • 10.
    Bergius, Kristine
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Initial screening of contaminated land: a comparison of US and Swedish methods.2007In: Environmental Management, ISSN 0364-152X, E-ISSN 1432-1009, Vol. 39, no 2, p. 226-34Article in journal (Refereed)
    Abstract [en]

    Preliminary surveys are used to prioritize between contaminated sites to select those to be investigated more thoroughly. The data-gathering steps are almost identical between countries; however, the assessment procedures differ significantly. In this study, we have investigated 21 contaminated sites assessed as belonging to the high-risk or the very high-risk class using the Swedish Methods for Inventories of Contaminated Sites (MICS). We then applied the US Preliminary Assessment (PA) method to the same sites and compared the results and conclusions from the two screening procedures. In both cases, all sites were recommended for further investigation and the two approaches seem to corroborate one another; however, the PA assessment scores and the preliminary MICS classifications did not correlate. The results obtained with the PA method were easier to explain than the final MICS classification. The PA method also seems more transparent and easier to standardize, although objections could be made regarding the weighting scheme, because the outcome in this study was entirely dependent on the surface exposure pathway. However, to examine this in greater detail, it is necessary to include sites with less contamination: The importance of preliminary surveys in the overall risk management process gives a strong motivation for such an evaluation. Generally, the lack of research and scientific support for the various assessment procedures in use suggests that there is a need for method development, standardization, and validation.

  • 11. Bergström, Jan
    et al.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Incineration of PCB and other hazardous wastes1987In: American Flame Research Committee, 1987Conference paper (Other academic)
  • 12. Bergström, Jan
    et al.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Organiska mikroföroreningar från avfallsförbränning1986Report (Other academic)
  • 13.
    Bhhatarai, Barun
    et al.
    University of Insubria, Italy.
    Teetz, Wolfram
    German Research Center for Environmental Health, Germany.
    Liu, Tao
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Jeliazkova, Nina
    Ideaconsult Ltd, Bulgaria.
    Kochev, Nikolay
    University of Plovdiv, Bulgaria.
    Pukalov, Ognyan
    University of Plovdiv, Bulgaria.
    Tetko, Igor
    German Research Center for Environmental Health, Germany.
    Kovarich, Simona
    University of Insubria, Italy.
    Papa, Ester
    University of Insubria, Italy.
    Gramatica, Paola
    University of Insubria, Italy.
    CADASTER QSPR Models for Predictions of Melting and Boiling Points of Perfluorinated Chemicals2011In: Molecular Informatics, ISSN 1868-1751, Vol. 30, no 2-3, p. 189-204Article in journal (Refereed)
    Abstract [en]

    Quantitative structure property relationship (QSPR) studies on per- and polyfluorinated chemicals (PFCs) on melting point (MP) and boiling point (BP) are presented. The training and prediction chemicals used for developing and validating the models were selected from Syracuse PhysProp database and literatures. The available experimental data sets were split in two different ways: a) random selection on response value, and b) structural similarity verified by self-organizing-map (SOM), in order to propose reliable predictive models, developed only on the training sets and externally verified on the prediction sets. Individual linear and non-linear approaches based models developed by different CADASTER partners on 0D-2D Dragon descriptors, E-state descriptors and fragment based descriptors as well as consensus model and their predictions are presented. In addition, the predictive performance of the developed models was verified on a blind external validation set (EV-set) prepared using PERFORCE database on 15 MP and 25 BP data respectively. This database contains only long chain perfluoro-alkylated chemicals, particularly monitored by regulatory agencies like US-EPA and EU-REACH. QSPR models with internal and external validation on two different external prediction/validation sets and study of applicability-domain highlighting the robustness and high accuracy of the models are discussed. Finally, MPs for additional 303 PFCs and BPs for 271 PFCs were predicted for which experimental measurements are unknown.

  • 14.
    Brandmaier, Stefan
    et al.
    German Research Center for Environmental Health, Germany.
    Peijnenburg, Willie
    National Institute for Public Health and the Environment - RIVM, The Netherlands ; Leiden University, The Netherlands.
    Durjava, Mojca K.
    National Institute of Health Environment and Food, Slovenia.
    Kolar, Boris
    National Institute of Health Environment and Food, Slovenia.
    Gramatica, Paola
    University of Insubria, Italy.
    Papa, Ester
    University of Insubria, Italy.
    Bhhatarai, Barun
    University of Insubria, Italy.
    Kovarich, Simona
    University of Insubria, Italy.
    Cassani, Stefano
    University of Insubria, Italy.
    Roy, Partha Pratim
    University of Insubria, Italy.
    Rahmberg, Magnus
    IVL Swedish Environmental Research Institute.
    Öberg, Tomas
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Jeliazkova, Nina
    Golsteijn, Laura
    Comber, Mike
    Charochkina, Larisa
    Novotarskyi, Sergii
    Sushko, Iurii
    Abdelaziz, Ahmed
    D’Onofrio, Elisa
    Kunwar, Prakash
    Ruggiu, Fiorella
    Tetko, Igor V.
    The QSPR-THESAURUS: The Online Platform of the CADASTER Project2014In: ATLA (Alternatives to Laboratory Animals), ISSN 0261-1929, Vol. 42, no 1, p. 13-24Article in journal (Refereed)
    Abstract [en]

    The aim of the CADASTER project (CAse Studies on the Development and Application of in Silico Techniques for Environmental Hazard and Risk Assessment) was to exemplify REACH-related hazard assessments for four classes of chemical compound, namely, polybrominated diphenylethers, per and polyfluorinated compounds, (benzo)triazoles, and musks and fragrances. The QSPR-THESAURUS website (http: / /qspr-thesaurus.eu) was established as the project's online platform to upload, store, apply, and also create, models within the project. We overview the main features of the website, such as model upload, experimental design and hazard assessment to support risk assessment, and integration with other web tools, all of which are essential parts of the QSPR-THESAURUS.

  • 15.
    Brandmaier, Stefan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Sahlin, Ullrika
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Tetko, Igor
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    PLS-Optimal: A stepwise D-Optimal design based on latent variables2012In: Journal of Chemical Information and Modeling, ISSN 1549-9596, Vol. 52, no 4, p. 975-983Article in journal (Refereed)
    Abstract [en]

    Several applications, such as risk assessment within REACH or drug discovery, require reliable methods for the design of experiments and efficient testing strategies. Keeping the number of experiments as low as possible is important from both a financial and an ethical point of view, as exhaustive testing of compounds requires significant financial resources and animal lives. With a large initial set of compounds, experimental design techniques can be used to select a representative subset for testing. Once measured, these compounds can be used to develop quantitative structure–activity relationship models to predict properties of the remaining compounds. This reduces the required resources and time. D-Optimal design is frequently used to select an optimal set of compounds by analyzing data variance. We developed a new sequential approach to apply a D-Optimal design to latent variables derived from a partial least squares (PLS) model instead of principal components. The stepwise procedure selects a new set of molecules to be measured after each previous measurement cycle. We show that application of the D-Optimal selection generates models with a significantly improved performance on four different data sets with end points relevant for REACH. Compared to those derived from principal components, PLS models derived from the selection on latent variables had a lower root-mean-square error and a higher Q2 and R2. This improvement is statistically significant, especially for the small number of compounds selected.

  • 16. Brandmaier, Stefan
    et al.
    Sahlin, Ullrika
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Tetko, Igor
    Stepwise D-Optimal design based on latent variables2011In: Posterpresentation vid SETAC Europe 21st Annual Meeting i Milano, 17-19 maj, 2011., 2011Conference paper (Other academic)
  • 17.
    Brandmaier, Stefan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Tetko, Igor
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    An evaluation of experimental design in QSARmodelling utilizing the k-medoid clustering2012In: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, Vol. 26, no 10, p. 509-517Article in journal (Refereed)
    Abstract [en]

    A reliable selection of a representative subset of chemical compounds has been reported to be crucial for numeroustasks in computational chemistry and chemoinformatics. We investigated the usability of an approach on the basisof the k-medoid algorithm for this task and in particular for experimental design and the split between training andvalidation set. We therefore compared the performance of models derived from such a selection to that of modelsderived using several other approaches, such as space-filling design and D-optimal design. We validated the performance on four datasets with different endpoints, representing toxicity, physicochemical properties and others.Compared with the models derived from the compounds selected by the other examined approaches, those derivedwith the k-medoid selection show a high reliability for experimental design, as their performance was constantlyamong the best for all examined datasets. Of all the models derived with all examined approaches, those derivedwith the k-medoid approach were the only ones that showed a significantly improved performance compared witha random selection, for all datasets, the whole examined range of selected compounds and for each dimensionalityof the search space.

  • 18. Cederqvist, Lars
    et al.
    Sorensen, Carl D.
    Reynolds, Anthony P.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Improved process stability during friction stir welding of 5 cm thick copper canisters through shoulder geometry and parameter studies2009In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 14, no 2, p. 178-184Article in journal (Refereed)
    Abstract [en]

    The spent nuclear fuel from Swedish power plants will be placed in copper canisters that are sealed with friction stir welding and the stability and robustness of this process is now being optimised in three steps: first, the shoulder geometry was identified that produced the most stable weld cycle, then the welding parameters were optimised for that geometry with regards to stability, and finally, the chosen geometry and welding parameters were verified and evaluated during multiple weld cycles. The shoulder study showed that stable welds could be produced repeatedly with a convex scroll geometry which proved more stable than various concave and flat scroll geometries. In the subsequent parameter study, not only were the most stable values for the welding parameters derived, but a clear relationship was shown between power input and tool temperature. This relationship can be used to more accurately control the process within the parameter windows, not only for this application but for other applications where the welding temperature needs to be kept within a specified range. Similarly, the potential of the convex scroll shoulder geometry for use in applications with other metals and thicknesses is evident.

  • 19.
    Cederqvist, Lars
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Reliability study of friction stir welded copper canisters containing Sweden's nuclear waste2008In: Reliability Engineering & System Safety, ISSN 0951-8320, E-ISSN 1879-0836, Vol. 93, no 10, p. 1491-1499Article in journal (Refereed)
    Abstract [en]

    The plan for the final disposal of spent fuel from Swedish nuclear power plants is to place it in copper canisters that are sealed and stored in a deep repository. The canisters will be sealed by friction stir welding (FSW) and the reliability of this process has now been evaluated. The reliability study was performed in three steps: first an optimization experiment to identify optimal process settings and establish the process window; then a demonstration experiment with welding under production-like conditions; and finally a post-demonstration series to evaluate an adjustment in the welding equipment. A process window was defined around the optimal process setting, i.e., the limits within which the welding variables must lie in order for the process to produce the desired result. In the demonstration experiment, a series of 20 sealing welds was carried out under production-like conditions. The maximum discontinuity in each weld — detected by non-destructive testing — was fitted to a generalized extreme value distribution. The 95% confidence interval for the maximum discontinuity in a production series of 4500 canisters was estimated at 4.5–7.7 mm. The best estimate from the post-demonstration series suggests that the maximum size of a discontinuity will not exceed 2.3 mm. A main conclusion is that the FSW process produces reliable results, fulfilling the predetermined requirements for minimum copper thickness by a very good margin.

  • 20.
    Farnelid, Hanna
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Riemann, Lasse
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Identity and dynamics of putative N-2-fixing picoplankton in the Baltic Sea proper suggest complex patterns of regulation2009In: Environmental Microbiology Reports, ISSN 1758-2229, E-ISSN 1758-2229, Vol. 1, p. 145-154Article in journal (Refereed)
    Abstract [en]

    Heterocystous filamentous cyanobacteria are regarded as the main N-2-fixing organisms (diazotrophs) in the Baltic Sea. However, some studies indicate that picoplankton may also be important. The aim of this study was to examine the composition of putative diazotrophs in the picoplankton (< 3 mu m) and to identify links to environmental factors. Nitrogenase (nifH) genes were amplified from community DNA by nested PCR, followed by cloning and sequencing. Clone libraries from nine environmental samples collected from the central Baltic Sea (April-October 2003, 3 m depth) and a negative control yielded a total of 433 sequences with an average clone library coverage of 92%. The sequences fell within nifH Clusters I, II and III and formed 15 distinct groups (> 96% amino acid similarity). Most of the sequences (77%) fell into nifH Cluster I (cyanobacteria and alpha-, beta- and gamma-Proteobacteria). However, only 26 sequences were related to cyanobacteria (e. g. Pseudanabaena) and among these no unicellular phylotypes were found. Sequences clustering with alternative nitrogenases (anfH) and Archaea were found in one sample while sequences related to anaerobic phylotypes were found in six samples distributed throughout the season. The identified phylogenetic groups showed covariance with several environmental factors but no strong links could be established. This suggests a variable and complex regulation of diazotrophic groups within Baltic Sea picoplankton.

  • 21.
    Filipsson, Monika
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Bergbäck, Bo
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Exponeringsfaktorer vid riskbedömning2008Report (Other academic)
  • 22.
    Filipsson, Monika
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Bergbäck, Bo
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Exponeringsfaktorer vid riskbedömning: Inventering av dataunderlag2008Report (Other academic)
    Abstract [en]

    Exposure is defined as the contact between a chemical, physical or biological agent and the outer boundary of an organism. Human exposure to chemicals in the environment is controlled not only by the occurrence of the pollutant, but also by behavior, physiological characteristics and different external factors. The quantifiable statistics used to describe this information are called The U.S. of such data, but similar attempts have also been made in Europe. However, human behavior, physiological characteristics and environmental factors differ between countries. It is therefore of value to also compile country-specific data for Sweden. A compilation could contribute towards the standardization of risk assessments.

    The exposure factors presented here cover the above mentioned areas and a substantial portion of them are similar to those covered by the international compilations. The selection and presentation is, however, to a large extent determined by the availability of data. In practice this means that for some factors we lack data on variability (natural variation) and uncertainty. These limitations in the available data are particularly pronounced with regard to the consumption of tap water and homegrown vegetables, and time-use patterns.

     However, there is a substantial amount of data available for physiological characteristics like body weight and skin surface area as well as for the general food consumption. These exposure factors have been characterized by statistical parameters like the mean, standard deviation, kurtosis, and skewness. Estimated uncertainty intervals are also given for these parameters. Percentiles are useful alternatives to present variability and these estimates are also presented together with the accompanying uncertainty intervals.

    Other exposure factors that are included in this report are; the age distribution of the population, moving patterns, residential building characteristics, contact with soil and dust, and soil properties. Apart from the tabulated values, references are also given to the primary data sources to facilitate for anyone interested to make more in-depth evaluations.

    The data collected is compared to the parameter settings suggested in the draft version of the Swedish exposure model for estimating guideline values. This comparison shows that the values selected sometimes correspond to a central or best estimate, often a conservative estimate, and sometimes a very conservative estimate. It is not possible from this comparison to draw firm conclusions regarding the impact on the final risk assessment or risk management decisions.

    The authors hope that this compilation of data on exposure factors will facilitate and accelerate the transition to risk assessment methods that permit evaluation and quantitative estimates of variability and uncertainty.

  • 23.
    Filipsson, Monika
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Henningsson, Marianne
    University of Kalmar, School of Human Sciences.
    Peltola, Pasi
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Exposure to contaminated sediments during recreational activities at a public bathing place2009In: Presentation vid SRA Europe annual meeting i Karlstad, 28 juni-1 juli 2009., 2009Conference paper (Other academic)
  • 24.
    Filipsson, Monika
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Henningsson, Marianne
    University of Kalmar, School of Human Sciences.
    Peltola, Pasi
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Exposure to contaminated sediments during recreational activities at a public bathing place2009In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 171, no 1-3, p. 200-207Article in journal (Refereed)
    Abstract [en]

    More and more time is spent on recreational activities, but few risk assessments focus specifically on these situations and exposure factor data are often scarce. To assess exposure to contaminants at a public bathing place in an urban environment, we have compiled literature data, conducted observation studies, and analyzed water and sediment samples. The levels of anthropogenic contaminants are high in urban environments and traffic frequently plays an important role. In this study, to characterize variability and uncertainty, the deterministic exposure calculations for metal pollutants were supplemented by a probability bounds analysis for the polycyclic aromatic hydrocarbons (PAH). The results from these calculations show that oral intake is the major exposure route for metals, while skin absorption, with present assumptions, is more important for the PAH. The presently measured levels of contaminants, at this public bathing place, cannot be anticipated to cause any significant adverse influence on public health.

  • 25.
    Filipsson, Monika
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Ljunggren, Lill
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Öberg, Tomas
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Gender differences in risk management of contaminated land at a Swedish authority2014In: Journal of Risk Research, ISSN 1366-9877, E-ISSN 1466-4461, Vol. 17, no 3, p. 353-365Article in journal (Refereed)
    Abstract [en]

    Any risk analysis process leading to the remediation of contaminated land will be affected by individual judgements. Many contaminated land risk assessments in Sweden are reviewed by the County Administrative Board (CAB), a regional government authority. The cost for risk assessments and eventually remediation is funded by whichever operator is legally responsible; however, when the responsible party is unknown, the cost can be met by government grants. A questionnaire was sent to all employees working with contaminated land at each of Sweden’s CABs to investigate whether gender, age and work experience, as well as funding source, affect the reviewing of risk assessments, and the employees’ perception of knowledge gained from the Sustainable Remediation (Hållbar Sanering) research programme. It was found that gender was the most significant factor, but also age and experience of the employees influenced the respondent’s answers. The reviews of risk assessments also varied depending on funding source.

  • 26.
    Filipsson, Monika
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Samuelsson, Lill
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Variability between individuals when reviewing environmental risk assessments at a public authority2010Conference paper (Other academic)
  • 27.
    Filipsson, Monika
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Undersökning och riskbedömning av Trekantens badplats - Riskkarakterisering2008Report (Other academic)
  • 28.
    Filipsson, Monika
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Undersökning och riskbedömning av Trekantens badplats: Riskkarakterisering2008Report (Other academic)
    Abstract [sv]

    Trekanten är en av Stockholms mer förorenade sjöar. Sedimenten i sjöns djupare delar innehåller höga halter tungmetaller och polycykliska aromatiska kolväten (PAH). Frågan om det kan vara hälsofarligt att komma i kontakt med sedimenten har uppkommit och oron har främst gällt bad vid badplatsen. Det har därför funnits skäl för att närmare utreda föroreningshalterna i anslutning till badplatsen och fastställa om någon hälsofara kan förekomma vid bad.

    I föreliggande rapport redovisas de exponeringsberäkningar och den riskbedömning som har gjorts utifrån de undersökningar som genomfördes under sommaren 2006 och 2007. Undersökningarna har omfattat dels en studie av badvanor, dels provtagning och analys av föroreningar i sediment och ytvatten. Exponeringsberäkningarna baseras även på sammanställningar av modeller och exponeringsfaktorer från den vetenskapliga litteraturen liksom svenska undersökningar. Ett informationsutbyte har även skett med tjänstemän vid det amerikanska naturvårdsverket (U.S. EPA).

    Undersökningarna har visat att föroreningshalterna i sand vid badplatsen och i ytvatten är låga. Halterna av PAH och metaller i sanden var lägre än de generella riktvärdena för förorenad mark som avser känslig markanvändning. Halterna av PAH och metaller (med undantag för krom) i ytvatten var lägre än normerna för dricksvatten.

     Exponeringsberäkningarna har genomförts separat för barn och vuxna. Huvudsakligen avser beräkningarna punktskattningar, dels en bästa skattning, dels en skattning av rimlig maximal exponering. För PAH-föreningar har utvärderingen även kompletterats med en sannolikhetsberäkning för att beskriva variabilitet och osäkerheter i dataunderlaget. Den beräknade exponeringen är i de flesta fall under de toxikologiska referensvärden som har använts.

    Slutsatsen från de genomförda undersökningarna är att exponeringen för PAH och metaller vid bad i sjön Trekanten, vid nu uppmätta halter, inte kan förutses medföra någon ogynnsam påverkan av betydelse för befolkningens hälsa.

  • 29.
    Filipsson, Monika
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Bergbäck, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Variability and uncertainty in Swedish exposure factors for use in quantitative exposure assessments2011In: Risk Analysis, ISSN 0272-4332, E-ISSN 1539-6924, Vol. 31, no 1, p. 108-119Article in journal (Refereed)
    Abstract [en]

    Information of exposure factors used in quantitative risk assessments has previously been compiled and reported for U.S. and European populations. However, due to the advancement of science and knowledge, these reports are in continuous need of updating with new data. Equally important is the change over time of many exposure factors related to both physiological characteristics and human behavior. Body weight, skin surface, time use, and dietary habits are some of the most obvious examples covered here. A wealth of data is available from literature not primarily gathered for the purpose of risk assessment. Here we review a number of key exposure factors and compare these factors between northern Europe—here represented by Sweden—and the United States. Many previous compilations of exposure factor data focus on interindividual variability and variability between sexes and age groups, while uncertainty is mainly dealt with in a qualitative way. In this article variability is assessed along with uncertainty. As estimates of central tendency and interindividual variability, mean, standard deviation, skewness, kurtosis, and multiple percentiles were calculated, while uncertainty was characterized using 95% confidence intervals for these parameters. The presented statistics are appropriate for use in deterministic analyses using point estimates for each input parameter as well as in probabilistic assessments.

  • 30.
    Iqbal, Muhammad Sarfraz
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Golsteijn, Laura
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Sahlin, Ullrika
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Papa, Ester
    Kovarich, Simona
    Huijbregts, Mark A. J.
    The influence of uncertainty in quantitative structure-property relationships on persistence and long-range transport potential: the case of polybrominated diphenyl ethers (PBDEs)2012Conference paper (Other academic)
  • 31.
    Iqbal, Muhammad Sarfraz
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Golsteijn, Laura
    Radboud University.
    Öberg, Tomas
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Sahlin, Ullrika
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Papa, Ester
    Insubria University.
    Kovarich, Simona
    Insubria University.
    Huijbregts, Mark A. J.
    Radboud University.
    Understanding quantitative structure-property relationships uncertainty in environmental fate modeling2013In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 32, no 5, p. 1069-1076Article in journal (Refereed)
    Abstract [en]

    In cases in which experimental data on chemical-specific input parameters are lacking, chemical regulations allow the use of alternatives to testing, such as in silico predictions based on quantitative structure–property relationships (QSPRs). Such predictions are often given as point estimates; however, little is known about the extent to which uncertainties associated with QSPR predictions contribute to uncertainty in fate assessments. In the present study, QSPR-induced uncertainty in overall persistence (POV) and long-range transport potential (LRTP) was studied by integrating QSPRs into probabilistic assessments of five polybrominated diphenyl ethers (PBDEs), using the multimedia fate model Simplebox. The uncertainty analysis considered QSPR predictions of the fate input parameters' melting point, water solubility, vapor pressure, organic carbon–water partition coefficient, hydroxyl radical degradation, biodegradation, and photolytic degradation. Uncertainty in POV and LRTP was dominated by the uncertainty in direct photolysis and the biodegradation half-life in water. However, the QSPRs developed specifically for PBDEs had a relatively low contribution to uncertainty. These findings suggest that the reliability of the ranking of PBDEs on the basis of POV and LRTP can be substantially improved by developing better QSPRs to estimate degradation properties. The present study demonstrates the use of uncertainty and sensitivity analyses in nontesting strategies and highlights the need for guidance when compounds fall outside the applicability domain of a QSPR.

  • 32.
    Iqbal, Muhammad Sarfraz
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Öberg, Tomas
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Description and Propagation of Uncertainty in Input Parameters in Environmental Fate Models2013In: Risk Analysis, ISSN 0272-4332, E-ISSN 1539-6924, Vol. 33, no 7, p. 1353-66Article in journal (Refereed)
    Abstract [en]

    Today, chemical risk and safety assessments rely heavily on the estimation of environmental fate by models. The key compound-related properties in such models describe partitioning and reactivity. Uncertainty in determining these properties can be separated into random and systematic (incompleteness) components, requiring different types of representation. Here, we evaluate two approaches that are suitable to treat also systematic errors, fuzzy arithmetic, and probability bounds analysis. When a best estimate (mode) and a range can be computed for an input parameter, then it is possible to characterize the uncertainty with a triangular fuzzy number (possibility distribution) or a corresponding probability box bound by two uniform distributions. We use a five-compartment Level I fugacity model and reported empirical data from the literature for three well-known environmental pollutants (benzene, pyrene, and DDT) as illustrative cases for this evaluation. Propagation of uncertainty by discrete probability calculus or interval arithmetic can be done at a low computational cost and gives maximum flexibility in applying different approaches. Our evaluation suggests that the difference between fuzzy arithmetic and probability bounds analysis is small, at least for this specific case. The fuzzy arithmetic approach can, however, be regarded as less conservative than probability bounds analysis if the assumption of independence is removed. Both approaches are sensitive to repeated parameters that may inflate the uncertainty estimate. Uncertainty described by probability boxes was therefore also propagated through the model by Monte Carlo simulation to show how this problem can be avoided.

  • 33.
    Iqbal, Muhammad Sarfraz
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Uncertainty in fugacity-based multimedia modeling: probabilistic and non-probabilistic methods2011In: Posterpresentation vid SETAC Europe 21st Annual Meeting i Milano, 17-19 maj, 2011, 2011Conference paper (Other academic)
  • 34.
    Lindell, Lina
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Åström, Mats E.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Effects of land use change vs natural control on stream water chemistry in the subandean Amazon, Peru.2009In: Proceedings of XII Brazilian Congress on Geochemistry and VIII International Symposium on Environmental Geochemistry. Oct 18-22, Ouro Preto, Brazil., 2009Conference paper (Refereed)
  • 35.
    Lindell, Lina
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Åström, Mats E.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Land-use change versus natural controls on stream water chemistry in the Subandean Amazon, Peru2010In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 25, no 3, p. 485-495Article in journal (Refereed)
    Abstract [en]

    This study evaluates the effects of deforestation and land-use change, as compared to natural controls, on stream water chemistry in the Subandean Amazon Dissolved major and trace elements were determined near the stream outlet of 48 independent watersheds with varying morphology. bed rock composition and intactness of forest cover (pristine to highly exploited) Geomorphological characteristics were derived from a digital elevation model, geological formations from digitalized maps and forest cover from digital classification of SPOT satellite images Partial least square regression and multiple linear regression showed that watershed average elevation, which ranged between 396 and 1649 m, was the strongest control on stream water chemistry, explaining >70% of the variation in K and a considerable part also for Mn, U, Mg and HCO3 with near exponential concentration increases down the altitude gradient Forest cover, which ranged between 7% and 99%, correlated strongly with average elevation (Spearman correlation coefficient, r(s) = 0.8), but had no statistically significant impact on stream solute concentrations Thus, in the studied Subandean region, watershed scale deforestation has not resulted in measurable impacts oil stream water chemistry which is dominated by the spatial variation in natural controls.

  • 36.
    Lindell, Lina
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Åström, Mats E.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Land-use versus natural controls on soil fertility in the Subandean Amazon, Peru.2010In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 408, no 4, p. 965-975Article in journal (Refereed)
    Abstract [en]

    Deforestation to amplify the agricultural frontier is a serious threat to the Amazon forest. Strategies to attain and maintain satisfactory soil fertility, which requires knowledge of spatial and temporal changes caused by land-use, are important for reaching sustainable development. This study highlights these issues by evaluating the relative effects of agricultural land-use and natural factors on chemical fertility of inceptisols on redbed lithologies in the Subandean Amazon. Macro and micronutrients were determined in topsoil and subsoil in the vicinity of two villages at a total of 80 sites including pastures, coffee plantations, swidden fields, secondary forest and, as a reference, adjacent primary forest. Differences in soil fertility between the land cover classes were investigated by principal component analysis (PCA) and partial least squares regression (PLSR). Primary forest soil was found to be chemically similar to that of coffee plantations, pastures and secondary forests. There were no significant differences between soils of these land cover types in terms of plant nutrients (e.g. N, P, K, Ca, Mg, Mo, Mn, Zn, Cu and Co) or other fertility indicators (OM pH,, BS, EC, CECe and exchangeable acidity). The parent material (as indicated by texture and sample geographical origin) and the slope of the sampled sites were stronger controls on soil fertility than land cover type. Elevated concentrations of a few nutrients (NO3 and K) were, however detected in soils of swidden fields. Despite being fertile (higher CECe, Ca and P) compared to Oxisols and Ultisols in the Amazon lowland, the Subandean soils frequently showed deficiencies in several nutrients (e.g. P, K, NO3, Cu and Zn), and high levels of free Al at acidic sites. This paper concludes that deforestation and agricultural land-use has not introduced lasting chemical changes in the studied Subandean soils that are significant in comparison to the natural variability.

  • 37.
    Liu, Tao
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Nicholls, Ian A.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Comparison of theoretical and experimental models for characterizing solvent properties using reversed phase liquid chromatography (RPLC)2011In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 702, no 1, p. 37-44Article in journal (Refereed)
    Abstract [en]

    Theoretical and experimental quantitative structure–retention relationships (QSRR) models are useful for characterizing solvent properties and column selectivity in reversed phase liquid chromatography (RPLC). The chromatographic behavior of a model analyte, the herbicide atrazine, in a system derived from nine organic solvents and three chromatographic columns was used for developing QSRR models. Multiple linear regression (MLR) and partial least squares regression (PLSR) were used as statistical approaches. The similarities and differences between linear solvation energy relationships (LSER), and semi-empirical and theoretical molecular models were demonstrated. QSRR models show high predictive power, and can successfully predict retention factor (log k) for new solvents. The models are useful for solvent optimization and reducing time for method development in RPLC. The herbicide atrazine can be readily analyzed at a low level, and all three columns provided good resolution, high-performance and symmetrical peaks. The method is suitable for analysis of atrazine in water samples.

  • 38.
    Liu, Tao
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Modelling of partition constants: Linear solvation energy relationships or PLS regression?2009In: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, Vol. 23, no 5, p. 254-262Article in journal (Refereed)
    Abstract [en]

    Estimation methods for partition constants are needed in many fields of engineering and science. The partitioning between phases is determined by the free energy of the transfer and all estimation methods must therefore describe the same entity. Linear solvation energy relationships (LSERs) try to split the contributions to van der Waals and polar interactions into directly interpretable solute descriptors, while projection-based regression methods can accomplish a similar dimensionality reduction from a set of theoretical descriptors. Here, we use the partitioning between octanol and water (Kow) and water solubility (Sw) to investigate similarities and differences between LSER and partial least squares regression (PLSR) models. The similarities in model structure are described, and shown to transform into a comparable prediction performance. We also demonstrate the opportunity to accomplish an analogous chemical interpretation of a PLSR model - either directly or through a linear transformation of the PLS factors - as with an LSER model. Much of the alleged difference between the mechanistic or semi-empirical LSER and the statistical PLSR models will then disappear. The choice of a modelling approach should therefore primarily be driven by the availability of data and predictive performance.

  • 39. Mansouri, Kamel
    et al.
    Consonni, Viviana
    Kos Durjava, Mojca
    Kolar, Boris
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Todeschini, Roberto
    Assessing bioaccumulation of polybrominated diphenyl ethers for aquatic species by QSAR modeling2012In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 89, no 4, p. 433-444Article in journal (Refereed)
    Abstract [en]

    Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in textiles, foams and plastics. Highly bioaccumulative with toxic effects including developmental neurotoxicity estrogen and thyroid hormones disruption, they are considered as persistent organic pollutants (POPs) and have been found in human tissues, wildlife and biota worldwide. But only some of them are banned from EU market.

    For the environmental fate studies of these compounds the bioconcentration factor (BCF) is one of the most important endpoints to start with. We applied quantitative structure–activity relationships techniques to overcome the limited experimental data and avoid more animal testing.

    The aim of this work was to assess the bioaccumulation of PBDEs by means of QSAR. First, a BCF dataset of specifically conducted experiments was modeled. Then the study was extended by predicting the bioaccumulation and biomagnification factors using some experimental values from the literature. Molecular descriptors were calculated using DRAGON 6. The most relevant ones were selected and resulting models were compared paying attention to the applicability domain.

  • 40. Müller, Christina
    et al.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Strategy for verification and demonstration of the sealing process for canisters for spent fuel2004Report (Other academic)
    Abstract [en]

    Electron beam welding and friction stir welding are the two processes now being considered for sealing copper canisters with Sweden’s radioactive waste. This report outlines a strategy for verification and demonstration of the encapsulation process which here is considered to consist of the sealing of the canister by welding followed by quality control of the weld by non-destructive testing.

    Statistical methodology provides a firm basis for modern quality technology and design of experiments has been successful part of it. Factorial and fractional factorial designs can be used to evaluate main process factors and their interactions. Response surface methodology with multilevel designs enables further optimisation. Empirical polynomial models can through Taylor series expansions approximate the true underlying relationships sufficiently well. The fitting of response measurements is based on ordinary least squares regression or generalised linear methods.

    Unusual events, like failures in the lid welds, are best described with extreme value statistics and the extreme value paradigm give a rationale for extrapolation. Models based on block maxima (the generalised extreme value distribution) and peaks over threshold (the generalised Pareto distribution) are considered. Experiences from other fields of the materials sciences suggest that both of these approaches are useful.

    The initial verification experiments of the two welding technologies considered are suggested to proceed by experimental plans that can be accomplished with only four complete lid welds each. Similar experimental arrangements can be used to evaluate process "robustness" and optimisation of the process window.

    Two series of twenty demonstration trials each, mimicking assembly-line production, are suggested as a final evaluation before the selection of welding technology. This demonstration is also expected to provide a data base suitable for a baseline estimate of future performance. This estimate can then be used for the safety assessment.

    In order to provide data for the analysis of welds it is required to use well defined methods for the investigation of the weld integrity. As the total length of the welds produced during the verification and demonstration exceeds 140 m and these needs to be examined with a reasonable resolution non destructive methods (NDT) with high data acquisition rates are required. Destructive methods like metallographic sectioning and examination or tensile testing can be used only to provide complementary information as the acquisition of these data are labour-intensive and time consuming. As the analysis is relying on the reliability of the NDT it is required to have a strategy for the determination of this. Three different ways to investigate the reliability of NDT signals are described. The performance demonstration, the parameter approach and the Integral Approach: ROC – Receiver Operating Characteristic and its relation to POD (probability of detection). The first step of a performance demonstration is to define the essential technical parameters of the system. The ROC and POD methods are appropriate tools to provide a clear measure of integral performance of the system though it has to be paid by high effort in test series with realistic test samples. With POD the user can learn about the detection capability whereas the ROC gives more information about the system’s capability to distinguish between signal and noise. The modular approaches open the door to a promising technique – more efficient and with the capability also to optimize the system.

    The data evaluation methods chosen to be applied for this assessment is the quantitative POD (Probability of Detection) method according to MIL-STD 1823 /section B4/.

    The (1-POD) curve will provide the probability of missing a defect as function of defect size which can be used as input for probabilistic risk assessment.

    Finally, a hypothetical calculation example Appendix 2 is provided to illustrate the fitting of data and extrapolation using the extreme value models.

  • 41. Peijnenburg, Willie
    et al.
    Durjava, Mojca
    Gramatica, Paola
    Furusjö, Erik
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Jeliazkova, Nina
    Huijbregts, Mark
    Comber, Mike
    Tetko, Igor
    CAse studies on the Development and Application of in-Silico Techniques for Environmental hazard (CADASTER)2008In: Presentation at the 17th European Symposium on QSAR in 'omics' and Systems Biology, Uppsala, September 21-26., 2008Conference paper (Other academic)
  • 42.
    Peltola, Pasi
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Virtasalo, Joonas
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Åström, Mats E.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Geochemistry of surface sediments in the Archipelago Sea, SW Finland: a multiparameter and multivariate study2011In: Environmental Earth Sciences, ISSN 1866-6280, Vol. 62, no 4, p. 725-734Article in journal (Refereed)
    Abstract [en]

    This study investigates the geochemistry of soft, organic-rich brackish-water surface sediments in the Archipelago Sea (SW Finland). The area is one of the world’s largest archipelagos, and, although it is scarcely populated, frequent ship and boat traffic along with fish farming occurs. From 76 sites, 47 chemical elements were determined after aqua regia digestion. Other parameters determined were grain size, water, organic and nitrogen contents. At sampling, the sediments were visually classified into groups representing oxic, anoxic and fluctuating (intermediate) oxic seafloor conditions. The results show that the element concentrations are quite similar to other studies in the region but with clear signs of lower anthropogenic loading. Point source pollution was identified in one sample taken nearby a fish farm and a cable ferry. This site was strongly enriched in Cu, Zn and Sn derived from chemicals used in either, or both, activities at the site. Overall, the sediments can be divided into two groups that separate chemically and geographically. One group contains more fine-grained sediments that occur near shore, while the other group contains more anoxic, organic and sulfur-rich sediments occurring more offshore. The second group is interpreted to reflect material reworked from previous deposits as a result of shoaling of the area due to glacio-isostatic land uplift. The visual classes were included in both partial least squares regression (PLSR) and PLS discriminant analysis. These analyses showed that the oxic and anoxic seafloor sediments can be predicted from the chemical variables and grain-size distribution.

  • 43. Ronneteg, Ulf
    et al.
    Cederqvist, Lars
    Rydén, Håkan
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Müller, Christina
    Reliability in sealing of canisters for spent nuclear fuel: Final report, Swedish Energy Agency Project 31634-12006Report (Other academic)
    Abstract [en]

    The reliability of the system for sealing and inspection that has been developed for the future Encapsulation plant was investigated. In the investigation the occurrence of discontinuities that can be formed in the welds was determined both qualitatively and quantitatively. The probability that these discontinuities can be detected by nondestructive testing (NDT) was also studied.

    The friction stir welding (FSW) process was verified in several steps. The variables in the welding process that determine weld quality were identified during the development work. In order to establish the limits within which they can be allowed to vary, a screening experiment was performed where the different process settings were tested according to a given design. In the next step the optimal process setting was determined by means of a response surface experiment, whereby the sensitivity of the process to different variable changes was studied. Based on the optimal process setting, the process window was defined, i.e. the limits within which the welding variables must lie in order for the process to produce the desired result. Finally, the process was evaluated during a demonstration series of 20 sealing welds which were carried out under production-like conditions.

    Conditions for the formation of discontinuities in welding were investigated. The investigations show that the occurrence of discontinuities is dependent on the welding variables. Discontinuities that can arise were classified and described with respect to characteristics, occurrence, cause and preventive measures.

    To ensure that testing of the welds has been done with sufficient reliability, the probability of detection (POD) of discontinuities by NDT and the accuracy of size determination by NDT were determined.

    In the evaluation of the demonstration series, which comprised 20 welds, a statistical method based on the generalized extreme value distribution was fitted to the size estimate of the indications obtained with NDT. The predicted maximum discontinuity size in connection with the welding of 4500 canisters at the present stage of development of the process was conservatively determined to be less than one centimetre. All factors considered, the predicted minimum copper coverage for a 5 cm thick canister is 4 cm.

    Acceptance criteria for permitted process settings in the welding process in a future sealing system are proposed, as is the use of statistical process control based on nondestructive testing as an independent inspection system. Furthermore, principles for handling of process nonconformances are presented.

  • 44.
    Sahlin, Ullrika
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Aldenberg, Tom
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Towards guidance on how to characterize predictive uncertainty in QSAR regression models within the CADASTER project2011In: Presentation vid SETAC Europe 21st Annual Meeting i Milano, 17-19 maj, 2011, 2011Conference paper (Other academic)
  • 45.
    Sahlin, Ullrika
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Bhhatarai, Barun
    Papa, Ester
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Gramatica, Paola
    QSAR-based compound prioritization for lab-testing for chemical safety assessment2011In: Posterpresentation vid SETAC Europe 21st Annual Meeting i Milano, 17-19 maj, 2011, 2011Conference paper (Other academic)
  • 46.
    Sahlin, Ullrika
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Filipsson, Monika
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    A risk assessment perspective of current practice in characterizing uncertainties in QSAR regression predictions2011In: Molecular Informatics, ISSN 1868-1751, Vol. 30, no 6-7, p. 551-564Article in journal (Refereed)
    Abstract [en]

    The European REACH legislation accepts the use of non-testing methods, such as QSARs, to inform chemical risk assessment. In this paper, we aim to initiate a discussion on the characterization of predictive uncertainty from QSAR regressions. For the purpose of decision making, we discuss applications from the perspective of applying QSARs to support probabilistic risk assessment. Predictive uncertainty is characterized by a wide variety of methods, ranging from pure expert judgement based on variability in experimental data, through data-driven statistical inference, to the use of probabilistic QSAR models. Model uncertainty is dealt with by assessing confidence in predictions and by building consensus models. The characterization of predictive uncertainty would benefit from a probabilistic formulation of QSAR models (e.g. generalized linear models, conditional density estimators or Bayesian models). This would allow predictive uncertainty to be quantified as probability distributions, such as Bayesian predictive posteriors, and likelihood-based methods to address model uncertainty. QSAR regression models with point estimates as output may be turned into a probabilistic framework without any loss of validity from a chemical point of view. A QSAR model for use in probabilistic risk assessment needs to be validated for its ability to make reliable predictions and to quantify associated uncertainty.

  • 47.
    Sahlin, Ullrika
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Filipsson, Monika
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Öberg, Tomas
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Characterization of variability and uncertainty from QSARs for probabilistic risk assessments within REACH2010Conference paper (Other academic)
  • 48.
    Sahlin, Ullrika
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science. Centre of Environmental and Climate Research, Lund University, Lund.
    Jeliazkova, Nina
    Ideaconsult Ltd, Sofia, Bulgaria.
    Öberg, Tomas
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Applicability domain dependent predictive uncertainty in QSAR regressions2014In: Molecular Informatics, ISSN 1868-1751, Vol. 33, no 1, p. 26-35Article in journal (Refereed)
    Abstract [en]

    Predictive models used in decision making, such as QSARs in chemical regulation or drug discovery, call for evaluated approaches to quantitatively assess associated uncertainty in predictions. Uncertainty in less reliable predictions may be captured by locally varying predictive errors. In the current study, model-based bootstrapping was combined with analogy reasoning to generate predictive distributions varying in magnitude over a model’s domain of applicability. A resampling experiment based on PLS regressions on four QSAR data sets demonstrated that predictive errors assessed by k nearest neighbour or weighted PRedicted Error Sum of Squares (PRESS) on samples of external test data or by internal cross-validation improved the performance of the uncertainty assessment. Analogy using similarity defined by Euclidean distances, or differences in standard deviation in perturbed predictions, resulted in better performances than similarity defined by distance to, or density of, the training data. Locally assessed predictive distributions had on average at least as good coverage as Gaussian distribution with variance assessed from the PRESS. An R-code is provided that evaluates performances of the suggested algorithms to assess predictive error based on log likelihood scores and empirical coverage graphs, and which applies these to derive confidence intervals or samples from the predictive distributions of query compounds.

  • 49. Sander, Per
    et al.
    Bergbäck, Bo
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    An evaluation of software for probabilistic risk assessment2005In: Society for Risk Analysis Annual Meeting, Orlando, Florida, 4-7 December, 2005, 2005Conference paper (Other academic)
  • 50. Sander, Per
    et al.
    Bergbäck, Bo
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Öberg, Tomas
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Probabilistisk riskbedömning2009In: Posterpresentation vid Nätverket Renare Marks vårmöte i Stockholm, 24-25 mars, 2009Conference paper (Other academic)
1234 1 - 50 of 156
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