Calculations of background beta-gamma radiation dose through geologic time

Life on earth is exposed to a background level of ionizing radiation from a number of sources, including beta and gamma radiation from geologic and biologic materials. Radiation dose from geologic emitters has changed because of the chemical evolution of the continental crust, changes in the relative abundances of 235U and 238U, and the radioactive decay of uranium, thorium, and 40K with time. The radiation dose from internal 40K has decreased by a factor of about eight because of changes in the activity concentration of 40K in potassium over the past 4 billion years. Radiation exposure from geologic materials has decreased from about 1.6 mGy y(-1) to 0.66 mGy y(-1) over the past 4 billion years, and radiation exposure to an organism with a potassium concentration of 250 mmol L(-1) has decreased from about 5.5 to about 0.70 mGy y(-1). Accordingly, background radiation exposure from these two sources has dropped from about 7.0 to 1.35 mGy y(-1) during the time life has existed on Earth. The conservative nature of mutation repair mechanisms in modern organisms suggest that these mechanisms may have evolved in the distant past and that organisms may retain some of the capability of efficiently repairing damage from higher radiation levels than exist at present.     

Quantifying population recovery rates for ecological risk assessment

Ecological effects of modern agrochemicals are typically limited to brief episodes of increased mortality or reduced growth that are qualitatively similar to natural disturbance regimes. The long-term ecological consequences of agrochemical exposures depend on the intensity and frequency of the exposures relative to the rates of recovery of the exposed populations. This paper explores the feasibility of using readily available life history information to quantify recovery rates of aquatic populations. A simple modeling framework based on the logistic population growth model is used to compare population recovery rates for different types of organisms and to evaluate the influence of life history, initial percent reduction, disturbance frequency, and immigration on the time required for populations to recover from simulated agrochemical exposures. Recovery models are developed for aquatic biota ranging in size and longevity from unicellular algae to fish and turtles. Population growth rates and recovery times derived from life history data are consistent with measured recovery times reported in mesocosm and enclosure experiments, thus supporting the use of the models for quantifying population recovery rates for ecological risk assessment.     

Review of trends in the UK population dose.

The Radiation Protection Division of the Health Protection Agency (HPA-RPD), formerly the National Radiological Protection Board, has periodically reported the doses to members of the public and workers in the UK from all sources of radiation. This paper is a review of the doses reported in these publications from the 1970s to 2000 or later. The paper aims to present how the estimated doses received by the UK population have changed over this time period, and where possible from earlier years as well, from all sources of radiation. It was not possible to directly compare the doses reported in the earlier reports. There have been changes in the type of doses estimated, the dosimetry (in particular the definition of effective dose) and improvements made in the measurement of natural background doses. In these cases the earlier reported doses have been recalculated using modern dosimetry so that the doses can be compared. The occupational doses reported in this paper are for those workers involved in the civil nuclear power production industry, industrial radiography or from the medical use of radiation sources. For workers it was found that the individual and collective dose has decreased significantly over this time through the introduction of legislation, the improvement in technology and better working practices. Members of the public are exposed to radiation following the atmospheric testing of nuclear weapons, discharges from UK civil nuclear sites and from diagnostic radiology as well as from natural sources. Exposure to anthropogenic sources has decreased over the period considered in this paper. However, the dose to the UK population as a whole, presented as a per caput dose to a population of 55 million, has not changed significantly as it is dominated by the constant level of exposure to natural sources of radiation.     

Inconstant sun: how solar evolution has affected cosmic and ultraviolet radiation exposure over the history of life on Earth

Four billion years ago, sea-level UV exposure was more than 400 times as intense as today, the dose from solar cosmic rays was five times present levels, and galactic cosmic rays accounted for only about 10% their current contribution to sea-level radiation doses. Exposure to cosmic radiation accounts for about 10% of natural background radiation exposure today and includes dose from galactic cosmic rays and solar charged particles. There is little exposure to ionizing wavelengths of UV due to absorption by ozone. The sun has evolved significantly over its life; in the past there were higher levels of particulate radiation and lower UV emissions from the sun, and a stronger solar wind reduced radiation dose in the inner solar system from galactic cosmic rays. Finally, since the early atmosphere contained little to no oxygen, surface levels of UV radiation were far higher in the past.     

Gamma and neutrino radiation dose from gamma ray bursts and nearby supernovae

Supernovae and gamma ray bursts are exceptionally powerful cosmic events that occur randomly in space and time in our galaxy. Their potential to produce very high radiation levels has been discussed, along with speculation that they may have caused mass extinctions noted from the fossil record. It is far more likely that they have produced radiation levels that, while not lethal, are genetically significant, and these events may have influenced the course of evolution and the manner in which organisms respond to radiation insult. Finally, intense gamma radiation exposure from these events may influence the ability of living organisms to travel through space. Calculations presented in this paper suggest that supernovae and gamma ray bursts are likely to produce sea-level radiation exposures of about I Gy with a mean interval of about five million years and sea-level radiation exposures of about 0.2 Gy every million years. Comets and meteors traveling through space would receive doses in excess of 10 Gy at a depth of 0.02 m at mean intervals of 4 and 156 million years, respectively. This may place some constraints on the ability of life to travel through space either between planets or between planetary systems. Calculations of radiation dose from neutrino radiation are presented and indicate that this is not a significant source of radiation exposure for even extremely close events for the expected neutrino spectrum from these events.     

浅析职业性放射性肿瘤

本文从辐射致癌的人类证据,人类认识放射性肿瘤的历史,放射性肿瘤的发病机制、判定,我国相关诊断标准的变迁,我国职业性放射性肿瘤的诊断现状以及诊断程序等方面对放射性肿瘤进行解析。通过计算病因概率判定职业性放射性肿瘤,为个体受照后所患肿瘤与电离辐射的因果关系判定及相应的赔偿裁定提供科学依据。     

Multivariate multilevel spline models for parallel growth processes: application to weight and mean arterial pressure in pregnancy

Growth models are commonly used in life course epidemiology to describe growth trajectories and their determinants or to relate particular patterns of change to later health outcomes. However, methods to analyse relationships between two or more change processes occurring in parallel, in particular to assess evidence for causal influences of change in one variable on subsequent changes in another, are less developed. We discuss linear spline multilevel models with a multivariate response and show how these can be used to relate rates of change in a particular time period in one variable to later rates of change in another variable by using the variances and covariances of individual‐level random effects for each of the splines. We describe how regression coefficients can be calculated for these associations and how these can be adjusted for other parameters such as random effect variables relating to baseline values or rates of change in earlier time periods, and compare different methods for calculating the standard errors of these regression coefficients. We also show that these models can equivalently be fitted in the structural equation modelling framework and apply each method to weight and mean arterial pressure changes during pregnancy, obtaining similar results for multilevel and structural equation models. This method improves on the multivariate linear growth models, which have been used previously to model parallel processes because it enables nonlinear patterns of change to be modelled and the temporal sequence of multivariate changes to be determined, with adjustment for change in earlier time periods. Copyright © 2012 John Wiley & Sons, Ltd.     

Associations between longitudinal changes in serum estrogen, testosterone, and bioavailable testosterone and changes in benign urologic outcomes

Some men have rapid increases in benign prostatic enlargement and lower urinary tract symptoms (LUTS), and it is not clear how sex steroid hormones contribute to the rates of change in these urologic outcomes. Therefore, the authors conducted a population-based cohort study of 648 men residing in Olmsted County, Minnesota, from 1990 to 2007, to examine associations between baseline sex steroid hormones, the rate of change in these hormones, and the rates of change in LUTS, maximum urinary flow rate, and prostate volume. Annual changes in hormone levels and urologic outcomes were calculated using mixed-effects regression models. Associations between hormone variables and rates of change in urologic outcomes were assessed with linear regression models. Higher baseline estradiol levels and rapid declines in estradiol over time were associated with rapid increases in LUTS and rapid decreases in maximum flow rate. Lower baseline bioavailable testosterone levels and more rapid declines in bioavailable testosterone were associated with more rapid increases in prostate volume. These results suggest that both absolute sex steroid hormone levels and the rates at which the levels change may be important in the development of urologic conditions in aging men.     

Chernobyl fallout and outcome of pregnancy in Finland

Possible effects of Chernobyl fallout on outcome of pregnancy in Finland were evaluated in a nationwide follow-up study. The outcomes were the rate of live births and stillbirths, pregnancy loss, and induced abortions by municipality. Exposure was assessed based on nationwide surveys of radiation dose rate from the Chernobyl fallout, from both external and internal exposures. Using these measurements, we estimated the monthly dose rate for each of the 455 Finnish municipalities. On average, the dose rate from Chernobyl fallout reached 50 microSv per month in May 1986--a doubling of the natural background radiation. In the most heavily affected area, 4 times the normal background dose rates were recorded. Given the underlying regional differences in live birth, stillbirth, and abortion rates, we used longitudinal analysis comparing changes over time within municipalities. A temporary decline in the live birth rate had already begun before 1986, with no clear relationship to the level of fallout. A statistically significant increase in spontaneous abortions with dose of radiation was observed. No marked changes in induced abortions or stillbirths were observed. The decrease in the live birth rate is probably not a biological effect of radiation, but more likely related to public concerns of the fallout. The effect on spontaneous abortions should be interpreted with caution, because of potential bias or confounding. Further, there is little support in the epidemiologic literature on effects of very low doses of radiation on pregnancy outcome.     

Relations between age at occupational exposure to ionising radiation and cancer risk.

OBJECTIVES: To discover how the age when a given dose of ionising radiation is received (exposure age) affects the subsequent cancer risk, and whether the types of cancer caused by repeated exposure to small doses during adult life differ from naturally occurring cancers at that age. METHOD: A nested case-control design with all possible controls in a cohort of nuclear workers, and a Mantel-Haenszel test (requiring only one degree of freedom) to discover whether there was any level of exposure age where the null hypothesis of no effects of radiation was rejected. This analysis was followed by inspection of how different types of cancers were related to the cancer risk. RESULTS: For radiation received at least 15 years before a cancer death (to allow for cancer latency) evidence of a dose related risk was found which was largely the result of exposures during the last 10 years of working life (between 55 and 65 years of age). The relative frequency of site specific cancers showed no signs of being different for radiogenic and idiopathic cancers, and there was no evidence of the exceptionally strong association between radiation and leukaemia found in atomic bomb data and other high dose situations. CONCLUSIONS: Sensitivity to carcinogenic effects of radiation increases progressively with age during adult life and, provided the dose is too small to produce many cell deaths, the ratio of leukaemias to solid tumours is no different for radiogenic and idiopathic cancers.     

Did the distribution of health insurance in China continue to grow less equitable in the nineties? Results from a longitudinal survey

This paper examines changes in the distribution of health insurance across socioeconomic groups in China over the 1989-1997 period. The analysis is based on the China Health and Nutrition Survey (CHNS), a unique micro-level longitudinal survey of households in eight Chinese provinces. Findings indicate that while aggregate insurance coverage rates in the sample changed little over this period, certain previously noted differences in coverage rates across socioeconomic groups narrowed significantly. These findings bring into question the presumption that continued market-oriented reform would lead to increased differences in coverage across those groups. The results, in fact, suggest exactly the opposite, that as the market oriented changes have occurred important disparities in health insurance coverage have been reduced. If these reductions are occurring there are important implications for policy. The groups normally targeted for equity reasons seem to be making progress over time but continued improvements are needed for these groups to reach the levels of coverage enjoyed by more fortunate subgroups.     

Radiation hormesis: challenging LNT theory via ecological and evolutionary considerations

Ecological and evolutionary considerations suggest that radiation hormesis is made up of two underlying components. The first (a) is background radiation hormesis based upon the background exposure to which all organisms are subjected throughout evolutionary time. The second and much larger component (b) is stress-derived radiation hormesis arising as a protective mechanism derived from metabolic adaptation to environmental stresses throughout evolutionary time especially from climate-based extremes. Since (b) > > (a), hormesis for ionizing radiation becomes an evolutionary expectation at exposures substantially exceeding background. This biological model renders linear no-threshold theory invalid. Accumulating evidence from experimental organisms ranging from protozoa to rodents, and from demographic studies on humans, is consistent with this interpretation. Although hormesis is not universally accepted, the model presented can be subjected to hypothesis-based empirical investigations in a range of organisms. At this stage, however, two consequences follow from this evolutionary model: (1) hormesis does not connote a value judgement usually expressed as a benefit; and (2) there is an emerging and increasingly convincing case for reviewing and relaxing some recommended radiation protection exposure levels in the low range.     

A longitudinal study of risk factors in asthma and chronic bronchitis in childhood

The prevalence, persistence, incidence and remission rates of reported diagnosed asthma and chronic bronchitis has been studied longitudinally over ten years in a representative community sample of children and adolescents. The objectives are to evaluate the rates of change over time, the role of family history of disease, and the social risk factors in the longitudinal course of disease. The relationship between the two reported diagnoses is very high, about half of each group having the other diagnosis. Each diagnosis has specific symptoms with which it is associated. Remission of clinical disease is associated with continuing symptoms in about half of such cases. The incidence rates and remissions of cases as they have occurred over time were associated with different symptoms and risk factors. A family history of lung disease and family social characteristics are significant risk factors affecting the presence of these diseases, and how they change. Discussion suggests these factors may affect possible precursors, such as lower respiratory tract illnesses, as well as personal habits (such as smoking), which are related to both diagnoses. Further, the interactions of these risk factors appear to significantly influence impairments of lung function at the beginning of adult life, and potential subsequent disease.     

Cancer mortality patterns around the San Onofre nuclear power plant, 1960-1978.

Because of the recent concern over possible health effects associated with nuclear power plants, cancer mortality patterns in Southern California have been examined for time periods before the San Onofre nuclear power plant began commercial operation in 1968 and since then. This is one of America's older plants and is surrounded by major population centers in Orange, Riverside and San Diego Counties. Infant mortality rates and age-adjusted mortality rates for leukemia, lung cancer, all cancer, and all causes have been calculated and compared for Orange, Riverside, and San Diego Counties, for California, and for the United States during 1960-1978. In addition, childhood leukemia death rates and clusters have been examined in detail in the communities within 25 miles of San Onofre. The cancer and total mortality rates near San Onofre have remained essentially identical to the corresponding rates in California and United States from 1960 to 1978. There have been no significant radiation releases to the population surrounding the San Onofre plant and the cancer rates show no patterns which have been influenced by the presence of the plant. Although no radiogenic health effects would be expected, these results do provide a means of assessing overall mortality trends in the population.     

Medical constructions of long‐term exhaustion,past and present

Culture and history affect the ways in which medical knowledge is shaped, sustained and changed. The less knowledge we have, the larger the space for the cultural imprint becomes. Based on these assumptions, we ask: how have medical constructions of long‐term exhaustion changed over time, and how are changing constructions related to societal change? To discuss these questions we conducted a comparative study of medical texts from two historical periods: 1860–1930 and 1970–2013. Our data are limited to two diagnoses: neurasthenia and encephalomyelitis. After comparing the two periods by identifying diverging and converging aspects, we interpreted observed continuities and interruptions in relation to historical developments. We found that in the medical literature, long‐term exhaustion became transformed from a somatic ailment bred by modern civilisation to a self‐inflicted psychiatric ailment. At the same time, it changed from being a male‐connoted high‐status condition to a female‐connoted low‐status condition. We interpret these changes as contingent upon culturally available modes of interpretations. Medical knowledge thereby becomes infused with cultural norms and values which give them a distinct cultural bias. The historical controversies surrounding this medically contested condition neatly display the socially contingent factors that govern the social construction of medical knowledge.     

Probability of causation for radiation-attributable cancer in the Indian population.

Once a cancer is diagnosed in an individual with a history of radiation exposure, it may be required to know the probability that radiation exposure was the cause of the disease. The National Institute of Health, U.S., has generated radio epidemiological tables giving probability of causation for various radiogenic cancers for the population of the U.S. In this paper, the probability of causation has been calculated for the Indian population using two models: (1) the original National Institute of Health model, and (2) direct use of Japanese constant relative risk coefficients for solid tumors. In both cases, new risk coefficients based on DS86 dosimetry and extended follow-up for 35 y have been used. Calculations with new coefficients, based on the National Institute of Health model have been extended to the American population and compared with the results for the Indian population. These values are generally higher for the Indian population than for Americans because of the lower baseline incidence rates in India. Probability of causation values based on the constant relative risk model are independent of population characteristics.     

Lack of demonstratable effects of pollutants on cyt b sequences in wood ducks from a contaminated nuclear reactor cooling pond.

The effects of low levels of radiation on DNA mutation rates are largely unknown for free-living vertebrates. In this study we investigated the effects of contamination from cooling ponds at a nuclear production facility in South Carolina on the mutation rates in mitochondrial DNA in wood ducks (Aix sponsa). Specifically, we sequenced a 433-bp portion of the cytochrome b gene from 18 female-offspring pairs of wood ducks from contaminated ponds and 2 female-offspring pairs from control ponds. Very low haplotype diversity was observed overall, and no case of mutation between female and offspring could be satisfactorily documented. This suggests that the levels of radioactive contamination in these cooling ponds have little effect on the mutation rate of mitochondrial DNA in these waterfowl and that mitochondrial DNA may not be as sensitive an indicator as previously anticipated.     

Rising premature mortality in the UK’s persistently deprived areas: Only a Scottish phenomenon?

In the international literature, many studies find strong relationships between area-based measures of deprivation and mortality. In the U.K., mortality rates have generally fallen in recent decades but the life expectancy gap between the most and least deprived areas has widened, with a number of Scottish studies highlighting increased mortality rates in deprived areas especially in Glasgow. However, these studies relate health outcomes at different time points against period-specific measures of deprivation which may not be comparable over time. Using longitudinal deprivation measures where levels of area deprivation are made comparable over time, a recent study demonstrated how levels of mortality change in relation to changing or persistent levels of (non-) deprivation over time. The results showed that areas which were persistently deprived in Scotland experienced a rise in premature mortality rates by 9.5% between 1981 and 2001. Here, focussing on persistently deprived areas we extended the coverage to the whole of the U.K. to assess whether, between 1991 and 2001, rising premature mortality rates in persistently deprived areas are a Scottish only phenomenon or whether similar patterns are evident elsewhere and for men and women separately. We found that male premature mortality rates rose by over 14% in Scotland over the 10-year period between the early 1990s and 2000s in persistently deprived areas. We found no significant rise in mortality elsewhere in the U.K. and that the rise among men in Scotland was driven by results for Glasgow where mortality rates rose by over 15% during the decade. Our analyses demonstrate the importance of identifying areas experiencing persistent poverty. These results justify even more of a public health focus on Glasgow and further work is needed to understand the demographic factors, such as health selective migration, immobility and population residualisation, which may contribute to these findings.     

A review of changing episode definitions and their effects on estimates of diarrhoeal morbidity

This paper describes how the methodology used for measuring diarrhoeal morbidity has changed over time and assesses how differences in episode definition have affected estimates of diarrhoeal morbidity among children aged less than five years. The episode definition used in 73 studies included in three previously-published literature reviews was identified. In earlier work, a method was developed that adjusts morbidity estimates to take account of differences in episode definition. This adjustment method was applied to the studies identified in these three literature reviews. Episode definitions were better documented and were more consistent in studies published after 1980. Adjusting morbidity estimates to account for definitional differences did not substantially alter the reviews' conclusions. Diarrhoeal surveillance has steadily improved since 1980, with methodology becoming more consistent between studies and better documented. Although episode definitions have changed over time, the morbidity estimates derived in the three reviews appear robust to these changes.     

Migration

Over the past 70 years, several million people have immigrated into Germany—from different countries of origin and for different reasons. The categories used by society to label immigrants (“guest workers”, “persons with a migration background”) have changed over time. This change has occurred in parallel with changes in the societal attitude towards immigrants and in their legal position. There is unequivocal evidence that the forms that migration takes, in addition to the societal responses towards immigrants, have an effect on their health. The spectrum of migration to Germany is likely to remain fluent because of the continuing process of globalization; also, societal responses to migration will change over time. Thus, migration will continue to pose challenges to society and to health. Only through continuous attentiveness will it be possible to identify, and then avoid or reduce, health disadvantages faced by persons with a migration background.