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PubMed2002

Recent studies on the exposure of aircrew to cosmic and solar radiation.

Investigations of the impact of cosmic and solar radiation on aircrew involve many challenges. The great variety of primary and secondary ionising and non-ionising radiation, the wide range of energies involved and the role played by the Earth's atmosphere and magnetic field and the Sun combine to produce a very complicated scenario. These factors are reflected in conditions on aviation routes where exposure to radiation varies with altitude, latitude and stage of solar cycle. The great increase in air travel and consequent rise in numbers of aircrew whose occupation requires them to work in this environment has prompted new concern about exposure risks at aviation altitudes. The situation has also been highlighted by the tendency for aircraft to fly at higher altitudes in recent years and by the 1990 recommendations of the ICRP that exposure of civil aircrew be considered as being occupational. These have recently been translated into a legal requirement in the European Union. Several studies have been completed using a very wide range of detectors on subsonic and supersonic routes and new investigations are underway. With the completion of the DOSMAX project in another three years or so. world data for a whole solar cycle will be more complete than ever before. Results indicate that for most routes investigated during solar minimum, aircrew are unlikely to receive doses in excess of 6 mSv.y(-1).

Aerospace Medicine↗
PubMed1989

A parametric study of space radiation exposures to critical body organs for low earth orbit missions.

The geomagnetically-trapped and galactic cosmic radiation environments are two of the major sources of naturally-occurring space radiation exposure to astronauts in low earth orbit. The exposure is dependent primarily on altitude, spacecraft shielding, crew stay-times, and solar cycle effects for a 28.5 deg orbital inclination. Based on Space Shuttle experience, the calculated results of a parametric study are presented for several mission scenarios using a computerized anatomical man model and are compared with the NASA crew exposure limits for several critical body organs.

Altitude↗
PubMed2006

Aircraft crew radiation workplaces: comparison of measured and calculated ambient dose equivalent rate data using the EURADOS in-flight radiation data base.

In May 2000, the chairman of the European Radiation Dosimetry Group (EURADOS) invited a number of experts with experience of cosmic radiation dosimetry to form a working group (WG 5) on aircraft crew dosimetry. Three observers from the Article 31 Group of Experts as well as one observer from the Joint Aviation Authorities (JAA) were also appointed. The European Commission funded the meetings. Full meetings were organised in January 2001 and in November 2001. An editorial group, who are the authors of this publication, started late in 2002 to finalise a draft report, which was submitted to the Article 31 Group of Experts in June 2003. The methods and data reported are the product of the work of 26 research institutes from the EU, USA and Canada. Some of the work was supported by contracts with the European Commission, Directorate General XII, Science, Research and Development. A first overview of the EC report was published late in 2004. In this publication we focus on a comparison of measured and calculated ambient dose rate data using the EURADOS In-Flight Data Base. The evaluation of results obtained by different methods and groups, and comparison of measurement results and the results of calculations were performed in terms of the operational quantity ambient dose equivalent, H*(10). Aspects of measurement uncertainty are reported also. The paper discusses the estimation of annual doses for given flight hours and gives an outline of further research needed in the field of aircraft crew dosimetry, such as the influence of solar particle events.

Aerospace Medicine↗
PubMed1997

The radiation environment in low-Earth orbit.

The radiation environment in low-Earth orbit is a complex mixture of galactic cosmic radiation, particles of trapped belts and secondary particles generated in both the spacecraft and Earth's atmosphere. Infrequently, solar energetic particles are injected into the Earth's magnetosphere and can penetrate into low-Earth orbiting spacecraft. In this paper, the sources of charged-particle radiation that contribute significantly to radiation exposure on manned spacecraft are reviewed briefly, and estimates of expected dose rate for the upcoming International Space Station that are based on measurements made on the Russian Mir orbital station are provided.

Aerospace Medicine↗
PubMed1984

Unique radiobiological aspects of high-LET radiation.

Since the beg inning of manned space flight the potentially unique radiobiological properties of the heavy ions of the cosmic radiation had been, apart from possible interactions of radiation effects with biological effects of weightlessness, of major concern with respect to the assessment of radiation hazards in manned space flight. Radiobiological findings obtained from space flight experiments and ground based experiments with densely ionizing radiation are discussed, which suggest qualitative differences between the radiobiological mechanisms of sparsely ionizing and densely ionizing radiation. These findings comprise the observation of a long lateral range of radiobiological effectiveness around tracks of single heavy ions, the observation of micro lesions induced in biological targets by the penetration of heavy ions, the nonadditivity of radiobiological effects from sparsely and densely ionizing radiation, the different kinetics for the expression of late effects induced by sparsely or densely ionizing radiation, and the observation of a reversed dose rate effect for early and late effects induced by densely ionizing radiation. These findings bear on the radiation protection standards to be installed for a general public in manned space flight and on the design of experiments, which intend to contribute to their specification.

Cosmic Radiation↗
PubMed2004

Assessment of aircrew radiation exposure by further measurements and model development.

A methodology is presented for collecting and analysing exposure measurements from galactic cosmic radiation using a portable equipment suite and encapsulating these data into a semi-empirical model/Predictive Code for Aircrew Radiation Exposure (PCAIRE) for the assessment of aircrew radiation exposure on any flight over the solar cycle. The PCAIRE code has been validated against integral route dose measurements at commercial aircraft altitudes during experimental flights made by various research groups over the past 5 y with code predictions typically within +/-20% of the measured data. An empirical correlation, based on ground-level neutron monitoring data, is detailed further for estimation of aircrew exposure from solar particle events. The semi-empirical models have been applied to predict the annual and career exposure of a flight crew member using actual flight roster data, accounting for contributions from galactic radiation and several solar energetic-particle events over the period 1973-2002.

Aerospace Medicine↗
PubMed2006

Radiation exposure during travelling in Malaysia.

Absorbed dose rates in vehicles during travelling by different modes of transport in Malaysia were measured. Radiation levels measured on roads in Peninsular Malaysia were within a broad range, i.e. between 36 and 1560 nGy h(-1). The highest reading, recorded while travelling near monazite and zircon mineral dumps, was 13 times the mean environmental radiation level of Malaysia. It is evident that radioactive material dumps on the roadsides can influence the radiation level on the road. The absorbed dose rates measured while travelling on an ordinary train were between 60 and 350 nGy h(-1). The highest reading was measured when the train passed a tunnel built through a granite rock hill. The measurement during sea travelling by ferries gave the lowest radiation level owing to merely cosmic radiation at the sea level.

Environmental Exposure↗
PubMed2007

Chlorine-39 in rainfall at a temperate latitude (40 degrees N).

Rainwater samples were collected and measured for the radioactivity to confirm the presence of Chlorine-39 (T1/2=56.2 min) formed by the interaction of cosmic-ray slow negative muons, mu- with Argon-40 in the lower atmosphere. The presence of 39Cl was confirmed by estimating the half-life of a radionuclide present in the rainwater ranging from 58 to 63 min and averaging 60.4 min. The disintegration rate of this radionuclide varied from 2.1 to 2.7 Bq L(-1) (125-160 dpm/L) of rainwater and averaged 2.3 Bq L(-1) (140 dpm/L) of rainwater in Thessaloniki (40 degrees 38'N, 22 degrees 58'E), Northern Greece. This concentration is indicative of mid or temperate latitudes. This is clearly less than that reported in the literature, 1.7 Bq L(-1) (100 dpm/L) of rainwater, for a southern latitude 31 degrees 54'N, 34 degrees 49'E (Rehovot, Israel), due to the latitudinal effect of cosmic radiation.

Air Pollutants, Radioactive↗
PubMed1994

Long-term survival of bacterial spores in space.

On board of the NASA Long Duration Exposure Facility (LDEF), spores of Bacillus subtilis in monolayers (10(6)/sample) or multilayers (10(8)/sample) were exposed to the space environment for nearly six years and their survival was analyzed after retrieval. The response to space parameters, such as vacuum (10(-6) Pa), solar electromagnetic radiation up to the highly energetic vacuum-ultraviolet range (10(9) J/m2) and/or cosmic radiation (4.8 Gy), was studied and compared to the results of a simultaneously running ground control experiment. If shielded against solar ultraviolet (UV)-radiation, up to 80 % of spores in multilayers survive in space. Solar UV-radiation, being the most deleterious parameter of space, reduces survival by 4 orders of magnitude or more. However, up to 10(4) viable spores were still recovered, even in completely unprotected samples. Substances, such as glucose or buffer salts serve as chemical protectants. With this 6 year study in space, experimental data are provided to the discussion on the likelihood of "Panspermia".

Bacillus subtilis↗
PubMed1996

Recovery of Deinococcus radiodurans from radiation damage was enhanced under microgravity.

Effect of microgravity on recovery of bacterial cells from radiation damage was examined on the IML-2 mission in 1994 using extremely radioresistant bacterium Deinococcus radiodurans. The cells were lyophilized and exposed to 60Co gamma-rays with doses 2 to 12 kGy before the space flight. At the end of the mission, the cells were mixed on board with liquid nutrient medium to allow the cells to start recovery process from the radiation damage. Afterwards the cells were stored at 4 degrees C until landing. The influence of cosmic radiation was negligible, because total absorbed dose of space radiation measured during the mission was less than 2 mGy and this bacterium does not decrease its viability after both gamma-rays and high-LET heavy charged particles irradiation with doses up to 5 kGy. The survival of the cells incubated in space increased significantly compared with the ground controls, suggesting that the recovery of this bacterium from radiation damage was enhanced under microgravity.

Colony Count, Microbial↗
PubMed1984

The radiation situation in space and its modification by geomagnetic field and shielding.

The fluxes of the nuclear component of the galactic cosmic radiation are discussed in terms of energy spectra for the different elements. Influences of shielding by the earth's magnetic field on these spectra are described. Then energy spectra behind absorbing matter are calculated considering energy loss and fragmentation. Based on these energy spectra LET-spectra are calculated. The form of the LET-spectra and their dependence on the composition of the shielding material are discussed. For LET-spectra measured by different detectors the restricted energy losses are converted to LETinfinity. in water. After this it is possible to compare the results of different experiments with each other and with calculated LET-spectra.

Cosmic Radiation↗
PubMed1973

On the effect of ionizing radiation upon the retina in man and animals.

The phenomenon of light flashes observed by the American cosmonauts on exposure to primary cosmic radiation during translunar flights, and also perceived by other observers on exposure of the eye to neutrons from accelerators, is indeed one of the latest manifestations of the sensitivity of the retina to very high energy radiation. The usual interpretations of this phenomenon are based either on the hypothesis of Vavilov-Cherenkov radiation in the ocular media, or on the direct stimulation of photoreceptors in the retina itself. The data available are submitted to adequate analysis, the experimental materials concerning the radiobiology of the retina are generalized, and a conclusion is drawn as to the most probable mechanism of light flashes considered as signals damaging the outer segments of the rods by particles arising from nuclear reactions in the retina.

Animals↗
PubMed2002

Radiation dose estimation for epidemiologic studies of flight attendants.

BACKGROUND: NIOSH is conducting health studies of female flight attendants. Exposures of interest include cosmic radiation and circadian rhythm disruption, however, the data needed to estimate cumulative radiation dose are not found in work histories. METHODS: We developed an algorithm to generate from work histories the required input data for Federal Aviation Administration radiation estimation software and evaluated whether effects of cumulative radiation dose could be distinguished analytically from effects of circadian rhythm disruption. RESULTS: The algorithm has relatively low bias (< 6%) for longer flights, which contribute most to cumulative radiation dose. In one NIOSH study, 44 crew incurred an estimated average annual occupational dose of 1.5-1.7 mSv. Selection of a study population flying predominantly North-South flights can provide the necessary distinction between radiation and time zone crossing exposures. CONCLUSIONS: Methods developed will be useful for exposure assessment in cabin crew studies with relatively short study periods, (e.g., reproductive health studies) for which limited flight history details are generally available.

Aerospace Medicine↗
PubMed2001

HZETRN: neutron and proton production in quasi-elastic scattering of GCR heavy-ions.

The development of transport models for radiation shielding design and evaluation has provided a series of deterministic computer codes that describe galactic cosmic radiation (GCR), solar particle events, and experimental beams at particle accelerators. These codes continue to be modified to accommodate new theory and improvements to the particle interaction database (Cucinotta et al., 1994, NASA Technical Paper 3472, US Government Printing Office, Washington DC). The solution employed by the heavy-ion transport code HZETRN was derived with the assumption that nuclear fragments are emitted with the same velocity as the incident ion through velocity conserving nuclear interactions. This paper presents a version of the HZETRN transport code that provides a more realistic distribution of the energy of protons and neutrons emitted from GCR interactions in shields. This study shows that the expected GCR dose equivalent is lower than previously calculated for water shields that are less than 110 g cm-2 thick. Calculations of neutron energy spectra in low Earth orbit indicate substantial contributions from relativistic neutrons.

Computer Simulation↗
PubMed1999

Radiation-induced acute myeloid leukaemia and other cancers in commercial jet cockpit crew: a population-based cohort study.

BACKGROUND: Cockpit crews receive cosmic radiation during flight operations. The increasing total accumulated dose over the years might be expected to cause increased frequency of radiation-induced cancer. The rate should increase with number of flight hours per year, number of years of flying, and higher flight altitude. If the cumulative radiation exposure during flights is of concern, we would expect an increased cancer risk to be present among those crew members flying jets. METHODS: Cockpit-crew medical records (pilots and flight engineers) from 1946 onwards, holding information on the individual, flight hours, aircraft type, and date of commercial certification and decertification, were linked to the population-based Danish Cancer Registry, the central population registry, and the National Death Index. FINDINGS: Altogether 3877 cockpit crew members could be traced for follow-up, accruing 61095 person-years at risk in 3790 men and 661 in 87 women. The total number of cancers observed was 169 whereas 153.1 were expected (standardised incidence ratio 1.1 [95% CI 0.94-1.28]). Significantly increased risks of acute myeloid leukaemia (5.1 [1.03-14.91]), skin cancer, excluding melanoma (3.0 [2.12-4.23]), and total cancer (1.2 [1.00-1.53]) were observed among Danish male jet cockpit crew members flying more than 5000 h. Increased risk of malignant melanoma irrespective of aircraft type was also found among those flying more than 5000 h. INTERPRETATION: Both malignant melanoma and skin cancer were found in excess in cockpit crew members with a long flying history, probably attributable to sun exposure during leisure time at holiday destinations. We cannot confirm previously reported increased risk of brain and rectal cancers in pilots. The study shows that male cockpit crew members in jets flying more than 5000 h have significantly increased frequency of acute myeloid leukaemia.

Adolescent↗
PubMed2002

Lunar lava tube radiation safety analysis.

For many years it has been suggested that lava tubes on the Moon could provide an ideal location for a manned lunar base, by providing shelter from various natural hazards, such as cosmic radiation, meteorites, micrometeoroids, and impact crater ejecta, and also providing a natural environmental control, with a nearly constant temperature, unlike that of the lunar surface showing extreme variation in its diurnal cycle. An analysis of radiation safety issues on lunar lava tubes has been performed by considering radiation from galactic cosmic rays (GCR) and Solar Particle Events (SPE) interacting with the lunar surface, modeled as a regolith layer and rock. The chemical composition has been chosen as typical of the lunar regions where the largest number of lava tube candidates are found. Particles have been transported all through the regolith and the rock, and received particles flux and doses have been calculated. The radiation safety of lunar lava tubes environments has been demonstrated.

Cosmic Radiation↗
PubMed1997

Cell growth and morphology of Dictyostelium discoideum in space environment.

Two strains of cellular slime mold Dictyostelium discoideum, a radiation-sensitive mutant and the parental wild-type strain, were used to investigate the effects of microgravity and/or cosmic radiation on their morphology through the whole life span from spores to fruiting bodies for about 7 days in space shuttle of NASA. We found almost no effect of space environment on amoeba cell growth in both strains. It was also observed that almost the same number and shape of fruiting bodies in space compared to the control experiments on earth. These results suggest that there is little effect of microgravity and space radiation on germination, cell aggregation, cell differentiation and cell morphology in the cellular slime mold.

Animals↗
PubMed2000

Epidemiologic studies of pilots and aircrew.

During flight, pilots and cabin crew are exposed to increased levels of cosmic radiation which consists primarily of neutrons and gamma rays. Neutron dosimetry is not straightforward, but typical annual effective doses are estimated to range between two and five mSv. Higher dose rates are experienced at the highest altitudes and in the polar regions. Mean doses have been increasing over time as longer flights at higher altitudes have become more frequent. Because there are so few populations exposed to neutrons, studies of airline personnel are of particular interest. However, because the cumulative radiation exposure is so low, statistical power is a major concern. Further, finding an appropriate comparison group is problematic due to selection into these occupations and a number of biases are possible. For example, increased rates of breast cancer among flight attendants have been attributed to reproductive factors such as nulliparity and increased rates of melanoma among pilots have been attributed to excessive sun exposure during leisure time activities. Epidemiologic studies conducted over the last 20 y provide little consistent evidence linking cancer with radiation exposures from air travel.

Aircraft↗