Radiation Protection in Canada: Part VII. Setting Standards for Radiation Protection

The current recommendations of the International Commission on Radiological Protection have as a basic objective the limitation of the radiation dose to “that which involves a risk that is not unacceptable to the individual and to the population at large”. The problem is to decide what degree of risk is acceptable, in relation to the benefits of a practice that necessitates a radiation exposure. At the present time it is not possible to make more than very rough estimates of some of the risks of exposure to radiation, but such estimates can be usefully compared with some of the other risks that are tolerated by society. On the assumption that it would be possible to make quantitative assessments of both the benefits and the risks, the question is raised as to how and by whom an appropriate balance should be made.     

Quantitative Radiation Effects in Hemoproteins and their Constituents

In order to verify the “radiation protection” effect of prosthetic groups in irradiated conjugated proteins and the influence of their electronic structure on intramolecular excitation transfer, two series of substances were examined. The first was composed of ferrihemoglobin and its constituents and the second was composed of similar hemoproteins with heme groups with major differences in electronic structure. The results point to a strong radiation protection effect of the heme groups and a dependence of radical yield of hemoproteins on the electronic structure of the heme. A possible interpretation of this latter effect is discussed.     

Radiation Protection in Canada: Part II. * The Role of the Radiation Protection Division in Safeguarding the Health of Radiation Workers

The current status of radiation protection in Canada is discussed in the second of a three-part series and particular emphasis is placed on the role of the Radiation Protection Division of the Department of National Health and Welfare. Administrative and operational control procedures have been developed, involving prior approval of health safeguards in the radioisotope user''s facilities and techniques, and systematic monitoring and inspection. Where necessary, a medical follow-up of accidents and excessive radiation exposures is carried out. In 1963 more than 1600 radioisotope licences were issued. Filmmonitoring service was provided to about 15,500 isotope and x-ray workers. Semiautomatic handling procedures have been developed to meet the increasing demand for film-monitoring services.Monitoring and inspection services have been provided for x-ray workers, and a committee has been formed to develop administrative procedures for health and safety control in x-ray work. Committees have also been set up to review the health and safety aspects of the operation of nuclear reactors and particle accelerators.     

Reduction of Fallout Radiation Hazards in Health Installations

The purpose of this paper is to provide guidance for Canadian hospital medical directors in planning the provision of protection for their patients and staff against gamma radiation hazard from nuclear war. The implications of the distribution of fallout in Canada are that the probability of exposures in excess of 600 r in the period “96 hours after fallout” is high in Southern Ontario and Quebec but low in the western provinces and in the North. All hospitals should have a shielding capacity; for many, this will entail structural alterations. The aim would be to provide a protective factor of 100 or better, together with necessary standards of habitability. The engineering significance of the recommendations is discussed.     

Dengue Virus Neutralizing Antibody Levels Associated with Protection from Infection in Thai Cluster Studies

Background

Long-term homologous and temporary heterologous protection from dengue virus (DENV) infection may be mediated by neutralizing antibodies. However, neutralizing antibody titers (NTs) have not been clearly associated with protection from infection.

Methodology/Principal Findings

Data from two geographic cluster studies conducted in Kamphaeng Phet, Thailand were used for this analysis. In the first study (2004–2007), cluster investigations of 100-meter radius were triggered by DENV-infected index cases from a concurrent prospective cohort. Subjects between 6 months and 15 years old were evaluated for DENV infection at days 0 and 15 by DENV PCR and IgM ELISA. In the second study (2009–2012), clusters of 200-meter radius were triggered by DENV-infected index cases admitted to the provincial hospital. Subjects of any age ≥6 months were evaluated for DENV infection at days 0 and 14. In both studies, subjects who were DENV PCR positive at day 14/15 were considered to have been “susceptible” on day 0. Comparison subjects from houses in which someone had documented DENV infection, but the subject remained DENV negative at days 0 and 14/15, were considered “non-susceptible.” Day 0 samples were presumed to be from just before virus exposure, and underwent plaque reduction neutralization testing (PRNT). Seventeen “susceptible” (six DENV-1, five DENV-2, and six DENV-4), and 32 “non-susceptible” (13 exposed to DENV-1, 10 DENV-2, and 9 DENV-4) subjects were evaluated. Comparing subjects exposed to the same serotype, receiver operating characteristic (ROC) curves identified homotypic PRNT titers of 11, 323 and 16 for DENV-1, -2 and -4, respectively, to differentiate “susceptible” from “non-susceptible” subjects.

Conclusions/Significance

PRNT titers were associated with protection from infection by DENV-1, -2 and -4. Protective NTs appeared to be serotype-dependent and may be higher for DENV-2 than other serotypes. These findings are relevant for both dengue epidemiology studies and vaccine development efforts.     

Ionizing Radiation and the Physician

The increasing awareness of the medical profession and the general public of the dangers associated with ionizing radiation necessitates a thorough understanding by the physician of the uses and dangers of this hazard. In addition to their application in the fields of diagnosis and therapeutic radiology, x-rays and radioisotopes are increasingly used in research laboratories and in various industries. The effects of low levels of ionizing radiation are still uncertain and it is possible that there is a “threshold” dose at which cellular damage is evident. With the increased number of atmospheric nuclear tests the concentrations of strontium-90, cesium-137, and the shorter lived isotopes such as iodine-131 in food will increase. The present levels of these isotopes do not merit concern and their early efficient removal will assure continued low fallout levels in our major food supplies.     

Erythropoietic Protoporphyria IV. Protection from Sunlight

Dihydroxyacetone and lawsone, in a vanishing cream base, applied to the skin was found to protect patients with erythropoietic protoporphyria against sunlight. The use of the same ingredients in a 50% isopropyl alcohol/water solution did not induce adequate light protection. The chemically induced ultraviolet light filter in the stratum corneum allowed these patients to change their lives from an “indoor” to an “outdoor” environment.     

Artificial and Solar UV Radiation Induces Strand Breaks and Cyclobutane Pyrimidine Dimers in Bacillus subtilis Spore DNA

The loss of stratospheric ozone and the accompanying increase in solar UV flux have led to concerns regarding decreases in global microbial productivity. Central to understanding this process is determining the types and amounts of DNA damage in microbes caused by solar UV irradiation. While UV irradiation of dormant Bacillus subtilis endospores results mainly in formation of the “spore photoproduct” 5-thyminyl-5,6-dihydrothymine, genetic evidence indicates that an additional DNA photoproduct(s) may be formed in spores exposed to solar UV-B and UV-A radiation (Y. Xue and W. L. Nicholson, Appl. Environ. Microbiol. 62:2221–2227, 1996). We examined the occurrence of double-strand breaks, single-strand breaks, cyclobutane pyrimidine dimers, and apurinic-apyrimidinic sites in spore DNA under several UV irradiation conditions by using enzymatic probes and neutral or alkaline agarose gel electrophoresis. DNA from spores irradiated with artificial 254-nm UV-C radiation accumulated single-strand breaks, double-strand breaks, and cyclobutane pyrimidine dimers, while DNA from spores exposed to artificial UV-B radiation (wavelengths, 290 to 310 nm) accumulated only cyclobutane pyrimidine dimers. DNA from spores exposed to full-spectrum sunlight (UV-B and UV-A radiation) accumulated single-strand breaks, double-strand breaks, and cyclobutane pyrimidine dimers, whereas DNA from spores exposed to sunlight from which the UV-B component had been removed with a filter (“UV-A sunlight”) accumulated only single-strand breaks and double-strand breaks. Apurinic-apyrimidinic sites were not detected in spore DNA under any of the irradiation conditions used. Our data indicate that there is a complex spectrum of UV photoproducts in DNA of bacterial spores exposed to solar UV irradiation in the environment.     

A Generalized Radiation Model for Human Mobility: Spatial Scale,Searching Direction and Trip Constraint

We generalized the recently introduced “radiation model”, as an analog to the generalization of the classic “gravity model”, to consolidate its nature of universality for modeling diverse mobility systems. By imposing the appropriate scaling exponent λ, normalization factor κ and system constraints including searching direction and trip OD constraint, the generalized radiation model accurately captures real human movements in various scenarios and spatial scales, including two different countries and four different cities. Our analytical results also indicated that the generalized radiation model outperformed alternative mobility models in various empirical analyses.     

Radiation Protection in Canada: Part III. * The Role of the Radiation Protection Division in Safeguarding the Health of the Public

The current status of radiation protection in Canada is discussed in the last of a three-part series. Particular emphasis has been placed on the role of the Radiation Protection Division of the Department of National Health and Welfare. A radioactive fallout study program has been established involving the systematic collection of air and precipitation samples from 24 locations, soil samples from 23 locations, fresh-milk samples from 16 locations, wheat samples from nine areas and human-bone specimens from various hospitals throughout Canada. A whole-body-counting facility and a special study of fallout in Northern areas have also been initiated. For any age group, the highest average strontium-90 concentration in human bone so far reported has been less than four picocuries per gram of calcium compared with the maximum permissible level of 67 derived from the International Committee on Radiation Protection (ICRP) recommendations. By the end of 1963 a general downward trend of levels of radioactivity detected in other parts of the program has been observed. Programs to assess the contribution to the radiation exposure of members of the population from medical x-rays, nuclear reactor operations and natural background-radiation sources have also been described. The annual genetically significant dose from diagnostic x-ray examinations in Canadian public hospitals has been estimated to be 25.8 mrem. Results from the reactor-environment monitoring programs have not suggested the presence of radioactivity beyond that contributed from fallout.     

Radiation protection in space

The challenge for planning radiation protection in space is to estimate the risk of events of low probability after low levels of irradiation. This work has revealed many gaps in our knowledge that require further study. Despite investigations of several irradiated populations, the atomic-bomb survivors remain the primary basis for estimating the risk of ionizing radiation. Compared with previous estimates, two new independent evaluations of available information indicate a significantly greater risk of stochastic effects of radiation (cancer and genetic effects) by about a factor of three for radiation workers, including space travelers. This paper presents a brief historical perspective of the international effort to assure radiation protection in space.Invited paper presented at the International Symposium on Heavy Ion Research: Space, Radiation Protection and Therapy, Sophia-Antipolis, France, 21–24 March 1994     

A Radiation Hybrid Map of the BRCA1 Region

A locus on chromosome 17q, designated “BRCA1,” has been identified as a predisposition gene for breast cancer. A panel of chromosome 17–specific radiation-reduced somatic cell hybrid clones has been assembled for high-resolution mapping of chromosome 17. A series of 35 markers, known to span the BRCA1 locus, were tested against this hybrid panel by PCR assays. Statistical analysis of these data yields a BRCA1 radiation hybrid map at a density sufficient to initiate YAC cloning and pulsed-field gel electrophoretic mapping of the candidate region. In addition, many of the markers reveal genetic polymorphisms and may be tested in breast cancer families and in loss-of-heterozygosity studies of sporadic breast cancers to better define the BRCA1 gene candidate region.     

Radiation Protection in Canada: Part I *

The current status of radiation protection in Canada has been summarized in the present paper, the first of a three-part series. Particular emphasis has been placed on the role of the Radiation Protection Division of the Department of National Health and Welfare. Somatic and hereditary effects of radiation exposure are briefly discussed as a basis for an understanding of the radiation protection standards which have been developed at national and international levels. The rapid increase in use of radioactive materials and x-ray apparatus in medicine, industry and research, and the extensive atmosphere testing of nuclear weapons have led to the development of comprehensive radiation protection activities in Canada, especially in the Department of National Health and Welfare. Well-established lines of communication and liaison exist among the various agencies responsible for these activities.     

Coastal Wetlands Planning, Protection, and Restoration Act: A programmatic application of adaptive management

The Coastal Wetlands Planning, Protection, and Restoration Act (CWPPRA), commonly referred to as ‘The Breaux Act’, has provided some of the resources necessary to begin implementing a comprehensive, large-scale, long-term coastal wetland restoration program for Louisiana USA. Due to the dynamic nature of this ecosystem and the uncertainty associated with large-scale restoration, adaptive management principles were embedded throughout CWPPRA’s organizational structure, planning process, project implementation, and monitoring program to facilitate achieving the mandates associated with the Breaux Act. Feedback loops were established within and between each of the programmatic components to encourage continuous learning, which is central to adaptive management. The knowledge gained has led to institutionalized change in projects as well as the program. This paper describes how the formation of the CWPPRA Task Force and associated committees and groups resulted in an integrated coast-wide process for planning, selection, construction, operation, maintenance, monitoring, and scientific evaluation of 84 restoration projects implemented or scheduled for implementation throughout coastal Louisiana.     

Protection of Photosynthesis against Ultraviolet-B Radiation by Carotenoids in Transformants of the Cyanobacterium Synechococcus PCC7942

The cyanobacterium Synechococcus PCC7942 was transformed with various carotenogenic genes, and the resulting transformants either accumulated higher amounts of β-carotene and zeaxanthin or showed a shift in the carotenoid pattern toward the formation of zeaxanthin. These transformants were exposed to ultraviolet-B (UV-B) radiation, and the degradation of phycobilins, the inactivation of photosynthetic oxygen evolution, and the activity of photosystem II were determined. In the genetically modified cells, the influence on destruction of phycobilins was negligible. However, protection of photosynthetic reactions against UV-B damage was observed and was dependent on the carotenoid concentrations in the different transformants. Furthermore, it was shown that endogenous zeaxanthin is more effective than β-carotene. Our results suggest that carotenoids exert their protective function as antioxidants to inactivate UV-B-induced radicals in the photosynthetic membrane.     

Beyond UHC: Monitoring Health and Social Protection Coverage in the Context of Tuberculosis Care and Prevention

Tuberculosis (TB) remains a major global public health problem. In all societies, the disease affects the poorest individuals the worst. A new post-2015 global TB strategy has been developed by WHO, which explicitly highlights the key role of universal health coverage (UHC) and social protection. One of the proposed targets is that “No TB affected families experience catastrophic costs due to TB.” High direct and indirect costs of care hamper access, increase the risk of poor TB treatment outcomes, exacerbate poverty, and contribute to sustaining TB transmission. UHC, conventionally defined as access to health care without risk of financial hardship due to out-of-pocket health care expenditures, is essential but not sufficient for effective and equitable TB care and prevention. Social protection interventions that prevent or mitigate other financial risks associated with TB, including income losses and non-medical expenditures such as on transport and food, are also important. We propose a framework for monitoring both health and social protection coverage, and their impact on TB epidemiology. We describe key indicators and review methodological considerations. We show that while monitoring of general health care access will be important to track the health system environment within which TB services are delivered, specific indicators on TB access, quality, and financial risk protection can also serve as equity-sensitive tracers for progress towards and achievement of overall access and social protection.

This paper is part of the PLOS Universal Health Coverage Collection.

Summary Points

1. The WHO has developed a post-2015 Global TB Strategy emphasizing that significant improvement to TB care and prevention will be impossible without the progressive realization of both universal health coverage and social protection. This paper discusses indicators and measurement approaches for both.
2. While access to high-quality TB diagnosis and treatment has improved dramatically in recent decades, there is still insufficient coverage, especially for correct diagnosis and treatment of multi-drug resistant TB.
3. Continued and expanded monitoring of effective coverage of TB diagnosis and treatment is needed, for which further improvements to existing surveillance systems are required.
4. Many households face severe financial hardship due to TB. Out-of-pocket costs for medical care, transport, and food are often high. However, income loss is the largest financial threat for TB-affected households.
5. Consequently, the financial risk protection target in the post-2015 Global TB Strategy—“No TB affected families experience catastrophic costs due to TB”—concerns all direct costs as well as income loss. This definition is more inclusive than the one conventionally used for “catastrophic health expenditure,” which concerns only direct medical costs.

     

Microbial Contamination on Disposable Hypodermic Syringes Prior to Sterilization by Ionizing Radiation

A large number of syringes were taken from the production lines of three independent manufacturers; the numbers and types of microorganisms contaminating these randomly sampled syringes were assessed in the laboratories maintained by each of these manufacturers for routine sterility testing, according to a standard protocol devised by the Research Committee of the UK Panel on Gamma and Electron Irradiation, which coordinated the investigation and analyzed the results. Items produced by a manufacturer were assessed for microbiological contamination both in their own laboratories and in the laboratories of the other manufacturers. The level of “false-positive” results was determined independently for each laboratory by the testing of “known sterile” items which had been subjected to the radiation-sterilization process. Both the percentage of syringes initially sterile and the average number of organisms per contaminated syringe differed among the three manufacturers. When corrected for interlaboratory differences, the number of syringes initially sterile ranged from 16 to 48%, and the mean number of organisms per contaminated syringe was 20 to 70. Of 964 syringes tested by all three laboratories, only one contained over 1,000 aerobic organisms (1,133). The most common organisms found were coagulase-negative, gram-positive cocci. Two manufacturers assessed contamination by anaerobic organisms; of 610 syringes, 1 contained 4,275 organisms and 3 more had 100 to 1,000 organisms, but 488 (80%) were uncontaminated by anaerobes. The results are discussed in the context of the choice of radiation dose necessary for the sterilization of medical products manufactured under controlled hygienic conditions.     

Equal Sensitivity of the Two Strands of øX174 Replicative DNA to Breakage by Ionizing Radiation

The supertwisted, double-stranded, replicative intermediate of øX174 DNA (RFI) has been used to determine whether one of the two strands of the double helix is uniquely sensitive to induction of single-strand breaks by ionizing radiation. This could result from a particularly sensitive base sequence or a transfer of energy to a specific location of the DNA molecule. The results indicate that both strands of the double helix are equally broken, even though their base compositions are significantly different. If there are “hot spots” in the strands, then they are present in equal amounts in each strand.     

Rabies-Specific Antibodies: Measuring Surrogates of Protection against a Fatal Disease

Antibodies play a central role in prophylaxis against many infectious agents. While neutralization is a primary function of antibodies, the Fc- and complement-dependent activities of these multifunctional proteins may also be critical in their ability to provide protection against most viruses. Protection against viral pathogens in vivo is complex, and while virus neutralization—the ability of antibody to inactivate virus infectivity, often measured in vitro—is important, it is often only a partial contributor in protection. The rapid fluorescent focus inhibition test (RFFIT) remains the “gold standard” assay to measure rabies virus–neutralizing antibodies. In addition to neutralization, the rabies-specific antigen-binding activity of antibodies may be measured through enzyme-linked immunosorbent assays (ELISAs), as well as other available methods. For any disease, in selecting the appropriate assay(s) to use to assess antibody titers, assay validation and how they are interpreted are important considerations—but for a fatal disease like rabies, they are of paramount importance. The innate limitations of a one-dimensional laboratory test for rabies antibody measurement, as well as the validation of the method of choice, must be carefully considered in the selection of an assay method and for the interpretation of results that might be construed as a surrogate of protection.