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PubMed2003

The local time dependence of the anisotropic solar cosmic ray flux.

The distribution of the solar cosmic radiation flux over the earth is not uniform, but the result of complex phenomena involving the interplanetary magnetic field, the geomagnetic field and latitude and longitude of locations on the earth. The latitude effect relates to the geomagnetic shield; the longitude effect relates to local time. For anisotropic solar cosmic ray events the maximum particle flux is always along the interplanetary magnetic field direction, sometimes called the Archimedean spiral path from the sun to the earth. During anisotropic solar cosmic ray event, the locations on the earth viewing "sunward" into the interplanetary magnetic field direction will observe the largest flux (when adjustments are made for the magnetic latitude effect). To relate this phenomena to aircraft routes, for anisotropic solar cosmic ray events that occur during "normal quiescent" conditions, the maximum solar cosmic ray flux (and corresponding solar particle radiation dose) will be observed in the dawn quadrant, ideally at about 06 hours local time.

Aircraft↗
PubMed2003

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.

Astronomy↗
PubMed2003

On the conversion coefficients for cosmic ray dosimetry.

Calculations of fluence-to-effective dose conversion coefficients have typically been limited to the standard irradiation geometries of the human body: anterior-to-posterior (AP), posterior-to-anterior (PA), lateral from the right side to the left side (RLAT), lateral from the left side to the right side (LLAT), rotational around the vertical axis (ROT), and isotropic incidence from all directions (ISO). In order to estimate the doses to air crew members exposed to cosmic radiation, the geometrical conditions of irradiation are usually assumed to be isotropic. However, the assumption of isotropic irradiation is in many cases invalid for the high energy component of the radiation field, which is often peaked in the forward direction. Therefore, it was considered useful to extend the calculations of conversion coefficients to other geometries. New sets of conversion coefficients fluence-to-effective dose are presented for the semi-isotropic irradiation of the human body and for the irradiation from the top. Their application to cosmic ray dosimetry is discussed.

Aircraft↗
PubMed1998

Updated measurements from CREAM & CREDO & implications for environment & shielding models.

Flight data obtained between 1995 and 1997 from the Cosmic Radiation Environment Monitors CREAM & CREDO carried on UoSat-3, Space Shuttle, STRV-1a (Space Technology Research Vehicle) and APEX (Advanced Photovoltaic and Electronics Experiment Spacecraft) have been added to the dataset affording coverage since 1990. The modulation of cosmic rays and evolution of the South Atlantic Anomaly are observed, the former comprising a factor three increase at high latitudes and the latter a general increase accompanied by a westward drift. Comparison of particle fluxes and linear energy transfer spectra is made with improved environment & radiation transport calculations which account for shield distributions and secondary particles. While there is an encouraging convergence between predictions and observations, significant improvements are still required, particularly in the treatrnent of locally produced secondary particles.

Atlantic Ocean↗
PubMed2000

Cancer incidence and mortality among flight personnel: a meta-analysis.

BACKGROUND: Increased cancer risk among flight personnel have previously been noted, including breast cancer among flight attendants and acute myeloid leukemia among pilots. HYPOTHESIS: Exposure to cosmic radiation and other physical or chemical agents may pose health risks for flight personnel. METHODS: We performed an exhaustive search for published and unpublished cohort studies of flight personnel from 1986-98. We combined relative risks (RR) for selected causes from four mortality and/or incidence studies of pilots and two incidence studies of flight attendants, using standard meta-analytic methods. Heterogeneity among the combined studies was explored and adjustments were made for possible confounding by socioeconomic status (SES), where indicated, using correction factors from published studies. RESULTS: SES-adjusted combined RRs were elevated (>1.2) among male pilots for mortality from melanoma 11.97 (95%, CI: 1.02-3.82)] and brain cancer [1.49 (0.89-2.20)], and for cancer incidence of the prostate [1.65 (1.19-2.29)] and the brain [1.74 (0.87-3.30)]. Among female flight attendants, increases were seen for incidence of all cancers [1.29 (0.98-1.70)], melanoma [11.54 (0.83-2.87)], and breast cancer [1.35 (1.00-1.83)]. CONCLUSIONS: Flight personnel appear to be at increased risk for several types of cancer. Both occupational exposures and well-established non-occupational risk factors may contribute to this increased risk. To better control for confounding factors and to identify exposures potentially amenable to preventive measures, future studies should compare risks within cohorts by flight routes, work history, and exposure to cosmic and UV radiation, electromagnetic fields, and chemical substances.

Adult↗
PubMed1998

Observations and predictions of secondary neutrons on Space Shuttle and aircraft.

The Cosmic Radiation Effects and Activation Monitor has flown on six Shuttle flights between September 1991 and February 1995 covering the full range of inclinations as well as altitudes between 220 and 570 km, while a version has flown at supersonic altitudes on Concorde between 1988 and 1992 and at subsonic altitudes on a SAS Boeing 767 between May and August 1993. The Shuttle flights have included passive packages in addition to the active cosmic ray monitor which comprises an array of pin diodes. These are positioned at a number of locations to investigate the influence of shielding and local materials. Use of both metal activation foils and scintillator crystals enables neutron fluences to be inferred from the induced radioactivity which is observed on return to Earth. Supporting radiation transport calculations are performed to predict secondary neutron spectra and the energy deposition due to nuclear reactions in silicon pin diodes and the induced radioactivity in the various scintillator crystals. The wide variety of orbital and atmospheric locations enables investigation of the influence of shielding on cosmic ray, trapped proton and solar flare proton spectra.

Aircraft↗
PubMed2001

Validation of the galactic cosmic ray and geomagnetic transmission models.

A very high-momentum resolution particle spectrometer called the Alpha Magnetic Spectrometer (AMS) was flown in the payload bay of the Space Shuttle in a 51.65 degrees x 380-km orbit during the last solar minimum. This spectrometer has provided the first high statistics data set for galactic cosmic radiation protons, and helium, as well as limited spectral data on carbon and oxygen nuclei in the International Space Station orbit. First measurements of the albedo protons at this inclination were also made. Because of the high-momentum resolution and high statistics, the data can be separated as a function of magnetic latitude. A related investigation, the balloon borne experiment with a superconducting solenoid spectrometer (BESS), has been flown from Lynn Lake, Canada and has also provided excellent high-resolution data on protons and helium. These two data sets have been used here to study the validity of two galactic cosmic ray models and the geomagnetic transmission function developed from the 1990 geomagnetic reference field model. The predictions of both the CREME96 and NASA/JSC models are in good agreement with the AMS data. The shape of the AMS measured albedo proton spectrum, up to 2 GeV, is in excellent agreement with the previous balloon and satellite observations. A new LIS spectrum was developed that is consistent with both previous and new BESS 3He observations. Because the astronaut radiation exposures onboard ISS will be highest around the time of the solar minimum, these AMS measurements and these models provide important benchmarks for future radiation studies. AMS-02 slated for launch in September 2003, will provide even better momentum resolution and higher statistics data.

Cosmic Radiation↗
PubMed2003

Variations of the ambient dose equivalent rate in the ground level air.

The ambient dose equivalent rate is caused by ionizing radiation of radionuclides in the atmosphere and on the ground surface as well as by cosmic radiation. Seasonal and diurnal variations of the ambient dose equivalent rate (ADER) in the ground level air are influenced by the concentration of 222Rn daughters. The 222Rn concentration in the ground level atmosphere, in turn, depends on the rate of the 222Rn exhalation from soil and turbulent air mixing. Its diurnal and seasonal variations depend on meteorological conditions. The aim of this study is to estimate the influence of variations of the rate of the 222Rn exhalation from soil and its concentrations in the ground level air on variations of ADER in the ground level air, as well as the dependence of these parameters on meteorological conditions. The 222Rn diffusion coefficient and its exhalation rate in undisturbed loamy soil have been determined. The 222Rn concentration in the soil air and its concentration in the ground level air correlate inversely (correlation coefficient is r = -0.62). The main factors determining the 222Rn exhalation from soil are: the soil temperature (r = 0.64), the difference in temperature of soil and air (r = 0.57), and the precipitation amount (r = 0.50). The intensity of gamma radiation in the ground level air is mostly related to the 222Rn concentration in the air (r = 0.62), while the effect of the exhalation rate from soil is relatively low (r = 0.36). It has been shown that ADER due to 222Rn progeny causes only 7-16% of the total ADER and influences its variation. The comparison of variations of ADER due to 222Rn progeny and the total ADER during several years shows that these parameters correlate positively.

Air Pollutants, Radioactive↗
PubMed2001

Cell inactivation by beryllium, boron and carbon ions at the low-energy irradiation facility of the Naples University.

The 3MV HVEC TTT-3 Tandem accelerator at the University of Naples, already used for radiobiological studies with protons and alpha particles, was set up for irradiation of biological samples with low energy carbon, boron, and beryllium beams. Radiobiological characterisation and study of these ion beams is essential in hadrontherapy (correction of hadrotherapy) to understand, for example, the possible biological effect of the target fragmentation products. Furthermore in space radiation biology we need to know the biological effects of heavy ions, a component of cosmic radiation that can contribute to the radiobiological risk when long sojourns in space are concerned. V79 Chinese hamster cells were irradiated with the different ions and the resulting cell inactivation data are reported.

Animals↗
PubMed1996

[Basis of radiation protection].

After an introduction, three selected contributions to the 10th Course on Radiation Protection held at the University Hospital of Basel are presented. The principles of radiation protection and new Swiss legislation are discussed as the basis for radiological protection. Ways are proposed of reducing radiation exposure while optimizing the X-ray picture with a minimum dose to patient and personnel. Radiation effects from low doses. From the beginning, life on this planet has been exposed to ionizing radiation from natural sources. For about one century additional irradiation has reached us from man-made sources as well. In Switzerland the overall annual radiation exposure from ambient and man-made sources amounts to about 4 mSv. The terrestrial and cosmic radiation and natural radionuclids in the body cause about 1.17 mSv (29%). As much as 1.6 mSv (40%) results from exposure to radon and its progenies, primarily inside homes. Medical applications contribute approximately 1 mSv (26%) to the annual radiation exposure and releases from atomic weapons, nuclear facilities and miscellaneous industrial operations yield less than 0.12 mSv (< 5%) to the annual dose. Observations of detrimental radiation effects from intermediate to high doses are challenged by observations of biopositive adaptive responses and hormesis following low dose exposure. The important question, whether cellular adaptive response or hormesis could cause beneficial effects to the human organism that would outweigh the detrimental effects attributed to low radiation doses, remains to be resolved. Whether radiation exerts a detrimental, inhibitory, modifying or even beneficial effect is likely to result from identical molecular lesions but to depend upon their quantity, localization and time scale of initiation, as well as the specific responsiveness of the cellular systems involved. For matters of radiation protection the bionegative radiation effects are classified as deterministic effects or stochastic effects respectively. The various histopathological reactions of tissues and organs following localized tissue irradiation, and the radiation syndromes following total body irradiation, constitute the deterministic effects. There will be a threshold below which deterministic effects do not appear and spontaneous incidences are not known. For low dose risk considerations deterministic effects are of no significance. Genetic effects and carcinogenesis are said to be stochastic effects. Characteristically the probability of stochastic effects increases with dose but the severity of the effects is independent of the dose. The shape of the dose-response relationship at intermediate to high dose levels is linear-quadratic. For exposure to low doses the response becomes linear, as is to be expected for a linear-quadratic function at low dose. No threshold is assumed for stochastic effects. The estimate of probability of fatal cancer by the ICRP is 4 x 10(-2) per Sv for the working population and 5 x 10(-2) per Sv for the total population. Their estimate of probability of serious hereditary disorders within the first two generations is 1 x 10(-2) per Sv. The highest probability coefficient is attributed to mental retardation following exposure in utero. Within the sensitive period at 8-15 weeks of gestation, a risk probability of 40 x 10(-2) per Sv is assumed but a threshold at 0.1 Sv is not excluded. Conclusions drawn from experiments, clinical observations and epidemiological studies following intermediate to high radiation exposures attribute a mutagenic and carcinogenic competence to all radiation doses. Microdosimetric considerations support this assumption. This conclusion cannot be confirmed experimentally nor by epidemiological studies of populations living under different conditions from natural sources of radiation. Nevertheless, a change in the present restrictive radiation protection policy does not yet appear appropriate.

Diagnostic Imaging↗
PubMed1964

Interaction of cosmic and solar flare radiations with the Martian atmosphere and their biological implications.

Assuming a constant interplanetary flux of galactic cosmic radiation and a model planetary atmosphere, it is possible to evaluate the magnitude of secondary ionization phenomena therein from parameters measured on Earth. The Martian atmosphere is of particular interest as its total air mass, estimated between 354 and 109 g cm-2, is in the vicinity of the Pfotzer cosmic ray maximum. Assuming the absence of a magnetic field on Mars the maximum neutron production would occur at an atmospheric depth of 75 +/- 5 g cm-2. With the lower air mass limit the surface flux of neutrons reaching the Martian surface could be about 240 times greater than observed at Earth's sea level. Surface minerals containing nuclei with large capture cross sections for slow neutrons, such as Li6, B10 and U235, could thus serve as valuable indicators for the age of the Martian crust. In general, the tenuous Martian atmosphere would result in greater surface radiation dose rates, particularly during times of relativistic solar flares. If the surface air mass is as low as 109 g cm-2 then the rate of nuclear disintegrations due to galactic cosmic radiation would exceed that on Earth's sea level approximately 1000-fold. The tenuous Martian atmosphere would not be a complete shield for heavy primary nuclei and about 1 percent of the incident flux could reach the surface.

Atmosphere↗
PubMed1996

In-flight radiation measurements on STS-60.

A joint investigation between the United States and Russia to study the radiation environment inside the Space Shuttle flight STS-60 was carried out as part of the Shuttle-Mir Science Program (Phase 1). This is the first direct comparison of a number of different dosimetric measurement techniques between the two countries. STS-60 was launched on 3 February 1994 in a nearly circular 57 degrees x 353 km orbit with five U.S. astronauts and one Russian cosmonaut for 8.3 days. A variety of instruments provided crew radiation exposure, absorbed doses at fixed locations, neutron fluence and dose equivalent, linear energy transfer (LET) spectra of trapped and galactic cosmic radiation, and energy spectra and angular distribution of trapped protons. In general, there is good agreement between the U.S. and Russian measurements. The AP8 Min trapped proton model predicts an average of 1.8 times the measured absorbed dose. The average quality factor determined from measured lineal energy, y, spectra using a tissue equivalent proportional counter (TEPC), is in good agreement with that derived from the high temperature peak in the 6LiF thermoluminescent detectors (TLDs). The radiation exposure in the mid-deck locker from neutrons below 1 MeV was 2.53 +/- 1.33 microSv/day. The absorbed dose rates measured using a tissue equivalent proportional counter, were 171.1 +/- 0.4 and 127.4 +/- 0.4 microGy/day for trapped particles and galactic cosmic rays, respectively. The combined dose rate of 298.5 +/- 0.82 microGy/day is about a factor of 1.4 higher than that measured using TLDs. The westward longitude drift of the South Atlantic Anomaly (SAA) is estimated to be 0.22 +/- 0.02 degrees/y. We evaluated the effects of spacecraft attitudes on TEPC dose rates due to the highly anisotropic low-earth orbit proton environment. Changes in spacecraft attitude resulted in dose-rate variations by factors of up to 2 at the location of the TEPC.

Atlantic Ocean↗
PubMed2002

Survival of microorganisms in space protected by meteorite material: results of the experiment 'EXOBIOLOGIE' of the PERSEUS mission.

During the early evolution of life on Earth, before the formation of a protective ozone layer in the atmosphere, high intensities of solar UV radiation of short wavelengths could reach the surface of the Earth. Today the full spectrum of solar UV radiation is only experienced in space, where other important space parameters influence survival and genetic stability additionally, like vacuum, cosmic radiation, temperature extremes, microgravity. To reach a better understanding of the processes leading to the origin, evolution and distribution of life we have performed space experiments with microorganisms. The ability of resistant life forms like bacterial spores to survive high doses of extraterrestrial solar UV alone or in combination with other space parameters, e.g. vacuum, was investigated. Extraterrestrial solar UV was found to have a thousand times higher biological effectiveness than UV radiation filtered by stratospheric ozone concentrations found today on Earth. The protective effects of anorganic substances like artificial or real meteorites were determined on the MIR station. In the experiment EXOBIOLOGIE of the French PERSEUS mission (1999) it was found that very thin layers of anorganic material did not protect spores against the deleterious effects of energy-rich UV radiation in space to the expected amount, but that layers of UV radiation inactivated spores serve as a UV-shield by themselves, so that a hypothetical interplanetary transfer of life by the transport of microorganisms inside rocks through the solar system cannot be excluded, but requires the shielding of a substantial mass of anorganic substances.

Aluminum Silicates↗
PubMedDate not supplied

[Thoughts on carcinogenic pollution caused by ionizing radiation].

The pollution phenomenon groups the effects of small doses of radiation on large populations. These effects on Man are not directly accessible. One must: a) consider some epidemiological statistics (cosmic radiation at high altitudes; radioactivity from granitic surroundings); b) extrapolate from datas obtained with high doses; c) extrapolate from datas obtained with low doses in micro-organisms or mammalian cells in vitro. The interpolation scheme of Abrahamson et al. is so available for mutagenicity. The question of a threshold remains theoretical, although radiation-induced carcinogenesis often displays a dose-effects curve with a well market threshold. A new concept, that of a "practical threshold" is developped, which may be of great usefulness. The main genetic considerations are listed upon which the present international admissible doses are based. Finally, in order to establish quantitative comparisons between chemical and radiation carcinogenic pollution, the concept of "rad equivalents" for the main chemical mutagens is stressed.

Animals↗
PubMed2004

Heavy ion radiobiology for hadrontherapy and space radiation protection.

Research in the field of biological effects of heavy charged particles is needed for both heavy-ion therapy (hadrontherapy) and protection from the exposure to galactic cosmic radiation in long-term manned space missions. Although the exposure conditions (e.g. high- vs. low-dose rate) and relevant endpoints (e.g. cell killing vs. neoplastic transformation) are different in the two fields, it is clear that a substantial overlap exists in several research topics. Three such topics are discussed in this short review: individual radiosensitivity, mixed radiation fields, and late stochastic effects of heavy ions. In addition, researchers involved either in experimental studies on space radiation protection or heavy-ion therapy will basically use the same accelerator facilities. It seems to be important that novel accelerator facilities planned (or under construction) for heavy-ion therapy reserve a substantial amount of beamtime to basic studies of heavy-ion radiobiology and its applications in space radiation research.

Heavy Ion Radiotherapy↗
PubMed1984

[Biological effects of weightlessness at the cellular level. Comparative study of cultures of Paramecia aboard the orbital station Salyut-6 and a stratospheric balloon].

In order to distinguish the effects of cosmic rays from those of weightlessness at the cellular level, we performed experiments aboard stratospheric balloon, where gravity is equal to 1 g and cosmic radiation roughly equal to that aboard Salyut-6. The results suggest that the stimulation of cell proliferation is probably due to cosmic rays, metabolic changes being related to microgravity.

Calcium↗
PubMedDate not supplied

The cosmic microwave background radiation temperature at a redshift of 2.34.

The existence of the cosmic microwave background radiation is a fundamental prediction of hot Big Bang cosmology, and its temperature should increase with increasing redshift. At the present time (redshift z = 0), the temperature has been determined with high precision to be T(CMBR)(0) = 2.726 +/- 0.010 K. In principle, the background temperature can be determined using measurements of the relative populations of atomic fine-structure levels, which are excited by the background radiation. But all previous measurements have achieved only upper limits, thus still formally permitting the radiation temperature to be constant with increasing redshift. Here we report the detection of absorption lines from the first and second fine-structure levels of neutral carbon atoms in an isolated cloud of gas at z = 2.3371. We also detected absorption due to several rotational transitions of molecular hydrogen, and fine-structure lines of singly ionized carbon. These constraints enable us to determine that the background radiation was indeed warmer in the past: we find that T(CMBR)(z = 2.3371) is between 6.0 and 14 K. This is in accord with the temperature of 9.1 K predicted by hot Big Bang cosmology.

Journal Article↗
PubMed1989

Changes in per capita and collective dose equivalent due to natural radiation in Taiwan (1950-1983).

This paper deals with the changes in per capita and collective dose equivalent in Taiwan in the past three decades based on the measured terrestrial and cosmic radiation levels and the population distribution as well. Over 70% of the population is concentrated in three population centers which have been naturally formed in the north, middle and south of Taiwan along the west coast as a result of industrialization and population growth. The population has increased 2.5 times in the past 33 y and reached to 1.9 X 10(7) persons, yet the migration of population was from the rural areas where the natural radiation is usually high to the urban areas where the natural radiation is usually low. The resulting collective dose equivalent has been increasing, yet the per capita dose equivalent, on the contrary, has been decreasing.

Background Radiation↗