Setting Reference Levels Research Articles

Recent Recommendations on Emergency Exposure Situations and a Discussion on Setting Reference Levels with the NEA Perspective

Expert Group on Implementation of New International Recommendations for Emergency Exposure Situations (EGIRES) of the Working Party on Nuclear Emergency Matter (WPNEM) has been mandated by the Committee of Radiation Protection and Public Health (CRPPH) of the OECD Nuclear Energy Agency to investigate issues in, and approaches to, the implementation of the new ICRP recommendations and revised Basic Safety Standards of the IAEA for emergency exposure situations, specifically nuclear/radiological emergencies including accidents and consequence management for malicious acts. This also includes the application of optimisation of protection strategies, setting of reference levels and the inclusion of stakeholder input in this process. The expected output of the expert group is to prepare a report on issues covering mentioned topics. Emergency exposure situations, as defined by the ICRP, are unexpected situations that may require urgent protective actions, and perhaps longer-term protective actions to be implemented. The Commission continues to recommend optimisation and the use of reference levels to ensure an adequate degree of protection with respect to exposure to ionising radiation in emergency exposure situations. Setting reference levels is a responsibility of national authorities and reference levels represent the level of dose or risk, above which it is judged to be inappropriate to plan to allow exposures to occur and for which therefore protective actions should be planned and optimized. EGIRES decided to analyze the established processes for optimization of the protection strategy for emergency exposure situations and practical implementation of reference levels concept in several member states of the NEA by performing a survey. It is planned to collect information on the definition of optimization strategy in different countries, optimization of protection for different protective actions and also optimization of urgent protective actions. In addition, national criteria in setting reference levels, its use, relevant processes including specific triggers and dosimetric quantities in setting reference levels are focus points that will be evaluated. Benefits expected from the work of the expert group will be useful to find a path and even common understanding of surrounding issues in emergency exposure situations with the inclusion of national perspectives and also to discuss stakeholder involvement.

Inferring Adult Status and Trends from Juvenile Density Data for Atlantic Salmon

AbstractTypically, juvenile survey data are not used explicitly to determine status, trends, or abundance designations for Atlantic salmon Salmo salar, even though they can be the only source of information for many populations. To determine whether juvenile data can be informative about adult abundance and status in Atlantic salmon, we evaluated the similarities in trends among age‐classes for two data‐rich populations using a nested log‐linear model. We found relatively consistent and significant trends for the age‐0, adult and egg time series, but the trends in juvenile density data for older age‐classes were less consistent with adult abundance trends. A threshold‐based analysis demonstrated that relatively low misclassification rates for adult status relative to a set reference level could be obtained from juvenile density estimates. Together, these results suggest that juvenile density data can be an informative proxy for adult abundance and may be useful as an indicator for large changes in population status relative to reference points. This would make data collection via electrofishing an appropriate monitoring method for fisheries management or conservation programs. However, the validity of the idea that dramatic changes in adult abundance will be mirrored in juvenile data partially depends on the specific age‐classes monitored, the survey design, and the timing of density dependence in the population. Using juvenile data as an index would necessitate some prior knowledge of the underlying population dynamics before the method could be applied more generally.Received May 9, 2012; accepted August 8, 2012

An Integrated Laser Radar Receiver Channel Utilizing a Time-Domain Walk Error Compensation Scheme

An integrated receiver channel for a pulsed time-of-flight (TOF) laser rangefinder has been designed and fabricated in a 0.35-μm SiGe BiCMOS process. The receiver channel generates a timing mark for the TDC by means of a leading-edge timing discriminator that detects the crossover of the received pulse with respect to a set reference level. The walk error generated by the amplitude variation is compensated in the time domain on the basis of the measured dependence of the walk on the length of the received pulse. The measurement accuracy is ±15 ps with compensation within a dynamic range of 1:100000, and the single-shot precision and power consumption are 120 ps for a minimum detectable signal of ~1 μA and 115 mW, respectively.

Population reference intakes and micronutrient bioavailability: a European perspective

The processes of setting population reference intakes in the European Union and elsewhere have highlighted the paucity of data for informing the assessments and the need to take the opportunity to establish transparent, physiologically based approaches to setting reference values for safe and adequate intakes, including considerations of excess exposures. The confusion arising from the European exercise contributed to a number of initiatives to rationalize approaches to setting reference levels and safe upper levels of intake. A biologically based approach to nutrient risk assessment, which has many features that could be extended advantageously to the creation of a similar approach to setting nutrient reference values, has been proposed. This approach has yet to be explored, but an additional product of the earlier confusion has been the development of proposals for the international harmonization of approaches to setting nutrient-based dietary standards that could lead to internationally agreed-upon standards for nutrient risk assessment and for setting key intake values.

Patient radiation doses in the most common interventional cardiology procedures in Croatia: first results

Apart from its benefits, the interventional cardiology (IC) is known to generate high radiation doses to patients and medical staff involved. The European Union Medical Exposures Directive 97/43/Euroatom strongly recommend patient dosimetry in interventional radiology, including IC. IC patient radiation doses in four representative IC rooms in Croatia were investigated. Setting reference levels for these procedures have difficulties due to the large difference in procedure complexity. Nevertheless, it is important that some guideline values are available as a benchmark to guide the operators during these potentially high-dose procedures. Local and national diagnostic reference levels (DRLs) were proposed as a guidance. A total of 138 diagnostic (coronary angiography, CA) and 151 therapeutic (PTCA, stenting) procedures were included. Patient irradiation was measured in terms of kerma-area product (KAP), fluoroscopy time (FT) and number of cine-frames (F). KAP was recorded using calibrated KAP-meters. DRLs of KAP, FT and F were calculated as third quartile values rounded up to the integer. Skin doses were assessed on a selected sample of high skin dose procedures, using radiochromic films, and peak skin doses (PSD) were presented. A relative large range of doses in IC was detected. National DRLs were proposed as follows: 32 Gy cm(2), 6.6 min and 610 frames for CA and 72 Gy cm(2), 19 min and 1270 frames for PTCA. PSD <1 Gy were measured in 72 % and PSD >2 Gy in 8 % of selected patients. Measuring the patient doses in radiological procedures is required by law, but rarely implemented in Croatia. The doses recorded in the study are acceptable when compared with the literature, but optimisation is possible. The preliminary DRL values proposed may be used as a guideline for local departments, and should be a basis for radiation reduction measures and quality assurance programmes in IC in Croatia.

Towards a coherent conceptual framework for emergency preparedness/response and rehabilitation – the application of the new ICRP recommendations given in ICRP 103

In the past, most emphasis in planning for and response to an emergency situation has been placed on selected protective measures in the early phase of an emergency to keep the doses received below levels where severe deterministic health effects can be excluded and/or where the risk of stochastic effects in the population is considered “acceptable”. Less emphasis has been placed on the development of comprehensive protection strategies which include considerations of the consequences of all exposure pathways and all phases, e.g. long-term rehabilitation. In its new publication 103, ICRP proposed a coherent conceptual framework for protection in all types of exposure situations including “emergency exposure situations” and “existing exposure situations”. In the context of developing protection strategies for these exposure situations, the Commission recommends that national authorities set reference levels between, typically, 20 mSv and 100 mSv annual effective dose (emergency exposure situation) and 1 mSv and 20 mSv (existing exposure situation). In order to optimise protection strategies, it is necessary to identify the dominant exposure pathways, the timescales over which the dose will be received, and the effectiveness of available protection options. The characteristics of the development and implementation of such protection strategies is described.

Proposed preliminary diagnostic reference levels for three common interventional cardiology procedures in Ireland

This study has gathered data across Ireland to determine the range of radiation doses received during interventional cardiology (IC) investigations. Radiation doses for three common types of IC examinations where investigated: coronary angiography (CA), percutaneous coronary intervention (PCI) and pacemaker insertions (PPI). A total of 22 cardiac imaging suites participated in the study. Radiation dose was monitored for 1804 adult patients using dose area product (DAP) meters. Individual patient DAP values ranged from 136-23,101 cGy cm2, 475-41,038 cGy cm2 and 45-17,192 cGy cm2 for CA, PCI and PPI respectively, with third quartile values of 4654 cGy cm2, 10,650 cGy cm2 and 1686 cGy cm2. The importance of optimising radiation dose, while not compromising diagnostic efficacy is clear. Although setting reference levels for these complex procedures has some difficulties, it is important that some guideline values are available as a benchmark to guide the operators during these potentially high dose procedures. The third quartile values as described by this paper may offer such guidance.

The Use of National and Locally Set Reference Dose Levels in a Regional Programme for Dose Reduction in Diagnostic Radiology

A programme of patient dose measurements in radiography and fluoroscopy has been ongoing for the past 5 years in accordance with the National Protocol for Patient Dosimetry. Dose measurements for radiography are carried out at approximately 3-yearly intervals with thermoluminescence dosemeters (TLDs) used to measure skin entrance dose for up to 10 common examinations. Dose-area product meters (DAPMs) are used for the assessment of dose in complex examinations including barium enemas and meals. Data have been collected from a number of hospitals across the region. The data from the initial round of measurements over 1992-1995 has been used in the setting of local reference dose levels against which, in addition to National Reference levels, all subsequent survey results can be compared. The results are presented, identifying the local reference levels set for the various examinations. The local figures act as a tighter constraint than the original national figures. The use of locally set reference levels has been a success with more relevance for participating hospitals, consequently having a greater impact on the optimisation programme.

Estimation of a Chromium Inhalation Reference Concentration Using the Benchmark Dose Method: A Case Study

The benchmark dose (BD) method has been proposed as an alternative to the NOAEL/UF method for setting reference levels. The BD is the 95% lower confidence limit on a dose corresponding to a 10% increase (or relative change) in an adverse effect. A case study exploring the suitability of the current Cr(III) and Cr(VI) inhalation toxicity data bases to the BD approach is presented. Because chromic acid mists, typical of many occupational Cr(VI) exposures, present a toxicological profile different from that of Cr(VI) particulates, representative of environmental exposures, Cr(VI) particulate data were evaluated separately from Cr(VI) acidic mist data. The current Cr(III) and Cr(VI) acidic mist data bases proved inadequate for BD analysis due to data and/or study quality limitations. Benchmark reference concentrations (RfCs) for particulate Cr(VI) ranging from 0.34 μg/m3 (for lactate dehydrogenase (LDH) in bronchoalveolar lavage fluid (BALF)) to 1.4 μg/m3 (for increased lung weights) are derived from data taken from U. Glaser et al. (Arch. Toxicol.57, 250-256, 1985) and U. Glaser et al. (Environmental Hygiene II, Springer-Verlag, Berlin/New York, 1990). A Cr(VI) particulate RfC of 0.34 μg/m3 based upon LDH in BALF as the critical effect is proposed. This value may be viewed as conservative since it represents the 95% lower confidence limit on the dose associated with a 10% increase in response for a sensitive endpoint and has appropriate dosimetric adjustments and uncertainty factors incorporated.