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Biomedical subjects

Sven Ove Hansson

Publications and source records attributed to Sven Ove Hansson.

11 recordsLinked to original sources
PubMed2006

Principles of protection: a formal approach for evaluating dose distributions.

One of the central issues in radiation protection consists in determining what weight should be given to individual doses in relation to collective or aggregated doses. A mathematical framework is introduced in which such assessments can be made precisely in terms of comparisons between alternative distributions of individual doses. In addition to evaluation principles that are well known from radiation protection, a series of principles that are derived from parallel discussions in moral philosophy and welfare economics is investigated. A battery of formal properties is then used to investigate the evaluative principles. The results indicate that one of the new principles, bilinear prioritarianism, may be preferable to current practices, since it satisfies efficiency-related properties better without sacrificing other desirable properties.

Humans↗
PubMed2006

Uncertainty and the ethics of clinical trials.

A probabilistic explication is offered of equipoise and uncertainty in clinical trials. In order to be useful in the justification of clinical trials, equipoise has to be interpreted in terms of overlapping probability distributions of possible treatment outcomes, rather than point estimates representing expectation values. Uncertainty about treatment outcomes is shown to be a necessary but insufficient condition for the ethical defensibility of clinical trials. Additional requirements are proposed for the nature of that uncertainty. The indecisiveness of our criteria for cautious decision-making under uncertainty creates the leeway that makes clinical trials defensible.

Clinical Trials as Topic↗
PubMed2006

Ten challenges for improved ecotoxicological testing in environmental risk assessment.

New regulations, in particular the new European chemicals legislation (REACH), will increase the demands on environmental risk assessment (ERA). The requirements on efficient ecotoxicological testing systems are summarized, and 10 major issues for the improvement of ERA practices are discussed, namely: (1) the choice of representative test species, (2) the development of test systems that are relevant for ecosystems in different parts of the world, (3) the inclusion of sensitive life stages in test systems, (4) the inclusion of endpoints on genetic variation in populations, (5) using mechanistic understanding of toxic effects to develop more informative and efficient test systems, (6) studying disruption in invertebrate endocrine mechanisms, that may differ radically from those we know from vertebrates, (7) developing standardized methodologies for testing of poorly water-soluble substances, (8) taking ethical considerations into account, in particular by reducing the use of vertebrates in ecotoxicological tests, (9) using a systematic (statistical) approach in combination with mechanistic knowledge to combine tests efficiently into testing systems, and (10) developing ERA so that it provides the information needed for precautionary decision-making.

Animals↗
PubMed2005

Priority setting in the REACH system.

Due to the large number of chemicals for which toxicological and ecotoxicological information is lacking, priority setting for data acquisition is a major concern in chemicals regulation. In the current European system, two administrative priority-setting criteria are used, namely novelty (i.e., time of market introduction) and production volume. In the proposed Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) system, the novelty criterion is no longer used, and production volume will be the main priority-setting criterion for testing requirements, supplemented in some cases with hazard indications obtained from QSAR modelling. This system for priority setting has severe weaknesses. In this paper we propose that a multicriteria system should be developed that includes at least three additional criteria: chemical properties, results from initial testing in a tiered system, and voluntary testing for which efficient incentives can be created. Toxicological and decision-theoretical research is needed to design testing systems with validated priority-setting mechanisms.

Chemical Industry↗
PubMed2005

Evaluating the risk decision process.

In order to ensure that risk assessment and risk management serve their purposes efficiently, it is essential to systematically evaluate actual practices. In this overview, it is proposed that such evaluation studies constitute an important field of study that should be recognized as a sub-discipline of regulatory toxicology with its own research issues and its own methodologies. Previous such evaluation studies are summarized. Methods are described that can be used for comparing different risk assessments of one of the same substance, for checking the consistency of harmonized classifications with the available data, for assessing the actual margin of safety (i.e. size of uncertainty factors) in exposure limits, and for comparing different lists of exposure limits. In conclusion, some important problem areas for future evaluation studies are pointed out.

Animals↗
PubMed2005

Improving REACH.

The European Commission has proposed a new system for chemicals control, the REACH system. The objectives of REACH with respect to risk assessment can be summarized in the form of two overarching goals. First, REACH aims at improved knowledge about the properties and the uses of individual chemical substances. Secondly, REACH is intended to increase the speed and efficiency of the risk assessment process and to make producers and importers of chemicals responsible for this process. The implementation of the REACH proposal will lead to increased availability of toxicological information but not to the extent that would be needed to achieve a sound scientific basis for risk assessment of individual substances. In this paper, we propose certain amendments of the current REACH proposal. The purpose of these proposals is to improve priority-setting and testing strategies and to simplify the risk assessment procedures.

Animals↗
PubMed2004

Indicators of uncertainty in chemical risk assessments.

For most of the chemical substances that are subject to regulatory and industrial decision making, important toxicological data are missing. The available dataset is often difficult to interpret, and the differences between alternative, scientifically reasonable interpretations may have major impact on decision making. Since such uncertainties are an important factor in decision making it is essential that they be reported in a transparent and understandable way. In order to clarify how toxicologists report uncertainties, 30 risk assessments for one and the same substance (trichloroethylene) from the years 1973-2001 were searched for phrases indicating uncertainty. These phrases can be divided between four categories: contentual, epistemic, conditionalising, and inferential uncertainty indicators. A typology of uncertainty indicators, based on these categories, is proposed. It is concluded that the use of uncertainty indicators in these texts is not transparent and that the development of standardised uncertainty indicators should significantly improve communications both within the scientific community and between scientists and policymakers.

Animals↗
PubMed2003

How accurate are the European Union's classifications of chemical substances.

The European Commission has decided on harmonized classifications for a large number of individual chemicals according to its own directive for classification and labeling of dangerous substances. We have compared the harmonized classifications for acute oral toxicity to the acute oral toxicity data available in the RTECS database. Of the 992 substances eligible for this comparison, 15% were assigned a too low danger class and 8% a too high danger class according to the RTECS data. Due to insufficient transparency-scientific documentations of the classification decisions are not available-the causes of this discrepancy can only be hypothesized. We propose that the scientific motivations of future classifications be published and that the apparent over- and underclassifications in the present system be either explained or rectified, according to what are the facts in the matter.

Animals↗
PubMed2002

Replacing the no-effect level (NOEL) with bounded effect levels (OBEL and LEBEL).

From experiments or epidemiological studies designed to search for a particular toxic effect, it is in general possible to determine an upper bound for that effect. This observed bounded effect level (OBEL) is defined for both positive and negative experiments. It is non-zero even for negative experiments, and it is inversely related to the size of the exposed group. The OBEL can be used to determine the linearly extrapolated bounded effect level (LEBEL) for various effect doses. Contrary to no-observed-effect' levels (NOELs), LEBEL values are designed to protect against type II (false negative) errors. It is proposed that LEBEL values replace NOELs as a tool for decision-making.

Animals↗