Ecological risk assessment framework for low-altitude aircraft overflights: I. Planning the analysis and estimating exposure.

An ecological risk assessment framework for low-altitude aircraft overflights was developed, with special emphasis on military applications. The problem formulation and exposure analysis phases are presented in this article; an analysis of effects and risk characterization is presented in a companion article. The intent of this article is threefold: (1) to illustrate the development of a generic framework for the ecological risk assessment of an activity, (2) to show how the U.S. Environmental Protection Agency's ecological risk assessment paradigm can be applied to an activity other than the release of a chemical, and (3) to provide guidance for the assessment of ecological risks from low-altitude aircraft overflights. The key stressor for low-altitude aircraft overflights is usually sound, although visual and physical (collision) stressors may also be significant. Susceptible and regulated wildlife populations are the major assessment endpoint entities, although plant communities may be impacted by takeoffs and landings. The exposure analysis utilizes measurements of wildlife locations, measurements of sound levels at the wildlife locations, measurements of slant distances from aircraft to wildlife, models that extrapolate sound from the source aircraft to the ground, and bird-strike probability models. Some of the challenges to conducting a risk assessment for aircraft overflights include prioritizing potential stressors and endpoints, choosing exposure metrics that relate to wildlife responses, obtaining good estimates of sound or distance, and estimating wildlife locations.

Ecological risk assessment framework for low-altitude aircraft overflights: II. Estimating effects on wildlife.

An ecological risk assessment framework for aircraft overflights has been developed, with special emphasis on military applications. This article presents the analysis of effects and risk characterization phases; the problem formulation and exposure analysis phases are presented in a companion article. The framework addresses the effects of sound, visual stressors, and collision on the abundance and production of wildlife populations. Profiles of effects, including thresholds, are highlighted for two groups of endpoint species: ungulates (hoofed mammals) and pinnipeds (seals, sea lions, walruses). Several factors complicate the analysis of effects for aircraft overflights. Studies of the effects of aircraft overflights previously have not been associated with a quantitative assessment framework; therefore no consistent relations between exposure and population-level response have been developed. Information on behavioral effects of overflights by military aircraft (or component stressors) on most wildlife species is sparse. Moreover, models that relate behavioral changes to abundance or reproduction, and those that relate behavioral or hearing effects thresholds from one population to another are generally not available. The aggregation of sound frequencies, durations, and the view of the aircraft into the single exposure metric of slant distance is not always the best predictor of effects, but effects associated with more specific exposure metrics (e.g., narrow sound spectra) may not be easily determined or added. The weight of evidence and uncertainty analyses of the risk characterization for overflights are also discussed in this article.

Generic assessment endpoints are needed for ecological risk assessment.

This article presents arguments for the development of generic assessment endpoints for ecological risk assessment. Generic assessment endpoints would be ecological entities and attributes that are assumed to be worthy of protection in most contexts. The existence of generic assessment endpoints would neither create a requirement that they be used in every assessment nor preclude the use of other assessment endpoints. They would simply be a starting point in the process of identifying the assessment endpoints for a particular assessment. They are needed to meet legal mandates, to provide a floor for environmental degradation, to provide some consistency in environmental regulation, as exemplars for site- or project-specific assessment endpoints, to allow development of methods and models, to give risk managers the courage to act, for screening and site-independent assessments, to support environmental monitoring, to facilitate communication, and to avoid paralysis by analysis. Generic assessment endpoints should include not only a list of entities and attributes, but also explanations of each endpoint, guidance on their use and interpretation, and measures and models that could be used to estimate them.

An approach for balancing health and ecological risks at hazardous waste sites.

Human health and ecological risks must be balanced at hazardous waste sites in order to ensure that remedial actions prevent unacceptable risks of either type. Actions that are designed to protect humans may fail to protect nonhuman populations and ecosystems or may damage ecosystems. However, there is no common scale of health and ecological risk that would allow comparisons to be performed. This paper presents an approach to addressing this problem based on classifying all risks (i.e., health and ecological risks due contaminants and remediation) as insignificant (de minimis), highly significant (de manifestis), or intermediate. For health risks the classification is based on standard criteria. However, in the absence of national guidance concerning the acceptability of ecological risks, new ecological criteria are proposed based on an analysis of regulatory precedents. Matrices and flow charts are presented to guide the use of these risk categories in remedial decision making. The assessment of mercury contamination of the East Fork Poplar Creek is presented as an example of the implementation of the approach.

[Intravenous anesthesia with propofol versus thiopental-/enflurane anesthesia. A consumption and cost analysis]. / Intravenöse Anästhesie mit Propofol versus Thiopental-/Enflurananästhesie. Eine Verbrauchs- und Kostenanalyse.

It may be possible to reduce costs in anaesthesia when there is a choice of drugs and methods. Two of the most widespread techniques are inhalation anaesthesia with enflurane following induction with thiopentone, and intravenous anaesthesia (IVA) with propofol. The aims of our study were to compare the costs, effectiveness and side effects of the anaesthetics involved in these two techniques, and to measure significant clinical parameters. METHODS. After approval by the hospital ethics committee, 40 adult patients of ASA physical status 1 and 2 who had been scheduled for elective septorhinoplasty and had given informed consent were entered in our prospective, single-blind randomized study. In 20 patients anaesthesia was induced with thiopentone (4-5 mg/kg) and suxamethonium (1-1.5 mg/kg) and maintained with enflurane. The other 20 patients received an initial i.v. bolus of propofol (2-2.5 mg/kg) followed by a propofol infusion adjusted to their individual clinical needs. Ventilation was performed in both groups with 70% nitrous oxide in oxygen, using a nonrebreathing system. Muscle relaxation was maintained with atracurium. The amounts of anaesthetics, oxygen, nitrous oxide, and muscle relaxants used were measured and a record of the costs was kept. In addition, circulatory and respiratory parameters and quantitative and qualitative aspects of recovery from anaesthesia were recorded. RESULTS. The biometric and clinical data did not differ significantly between the two groups. For induction, 382 (+/- 55.9) mg thiopentone costing 1.24 Swiss francs (SFr), or 172 (+/- 25.1) mg propofol costing 11.87 (SFr) was used. For maintenance, 28.3 (+/- 6.4) ml enflurane costing 21.96 SFr/h, or 450.7 (+/- 247) mg propofol costing 29.75 SFr/h was required. The need for muscle relaxants, oxygen, and nitrous oxide was also not significantly different in the two groups. Additional expenses were due to relaxation antagonists (1.91 SFr per patient in both groups) and to the perfusion pump system (8.60 SFr per patient in the IVA group only). Circulatory and respiratory parameters remained normal in both groups. In the propofol group, the heart rate tended to increase more at the beginning of anaesthesia, whereas later on it showed a tendency to lower values than in the thiopentone/enflurane group. Patients receiving IVA generally had a shorter awakening period, a higher degree of wellbeing during recovery, and needed less systemic analgesics (P < 0.05). CONCLUSIONS. Costs of anaesthetic drugs in the IV group totalled 54.50 SFr during the first hour, i.e. 1.65 times the costs in the thiopentone/enflurane group for the same time. However, with continuing duration of anaesthesia this ratio declines to 1.43 in anaesthesia lasting 2 h. In addition, IVA patients had a noticeably faster and far more pleasant recovery. Minute ventilation, oxygen consumption, heart rate and CO2 production indicated a less pronounced stress response and sympathetic activity during and after propofol. Quicker recovery of cognitive and psychomotor abilities, less postoperative pain and less impairment of respiratory function after IVA may lead to an earlier release from the postoperative recovery unit. This might be a cost-reducing factor that should be taken into account when these two anaesthetic regimens are concerned.