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At least 73 records · Page 4Linked to original sources
PubMed1993

Cytotoxic and mutagenic effects of radon and radon daughters on murine L5178Y lines differing in DNA repair.

The effects of 222Rn were measured in mouse L5178Y (LY) lymphoblasts that differ in repair capabilities. Line LY-S1 is deficient in the repair of X-radiation-induced DNA doublestrand breaks, while lines LY-R16 and LY-R83 are presumed to be deficient in the excision of UV-radiation-induced pyrimidine dimers. Line LY-R83 is hemizygous while the other two lines are heterozygous at the thymidine kinase (tk) locus. After exposure to radon the D0's were found to be very similar for the three lines (0.30-0.31 Gy), whereas for X radiation the D0 for line LY-S1 is lower (0.7 Gy) than that for the two LY-R lines (1.3 Gy). Mutant frequencies at the tk locus were higher per gray after treatment with radon than X radiation, but at equitoxic doses the mutant frequencies were similar for X and alpha-particle radiation. A low radon-induced mutant frequency was observed for the hemizygous line, in agreement with the hypothesis that multilocus lesions were induced by the alpha-particle radiation and that mutants bearing intergenic lesions were not recovered in the TK+/- line. The entire active tk allele was lost by 81% of the TK-/- mutants of line LY-R16. In lines LY-S1 and LY-R16, 39-43% of the TK-/- mutants exhibited loss of galactokinase activity, indicating that the mutational lesion inactivating the tk gene frequently extended to the neighboring galactokinase gene.

Animals↗
PubMed2001

Measurements of deposition velocity of radon decay products for examination of the correlation between air activity concentration of radon and the accumulated Po-210 surface activity.

The retrospective determination of radon exposure levels in dwellings by means of the measurement of the Po-210 surface activity is subject to various uncertainties. These result partly from the values assumed for the equilibrium factor F and for the unattached fraction f(p), and, more importantly, from differences in the deposition velocities of short-lived decay products of Rn-222, caused by varying conditions of turbulence. In order to evaluate the actual range of the variation which occurs under German living conditions, measurements for the deposition velocity parameter were carried out in several dwellings in which increased levels of radon were present. The statistical evaluation of the measurements produced a mean deposition velocity of 1.7 m/h for Po-218 and 0.4 m/h for Pb-214, and a relative standard deviation in the measured values of as low as approximately 50%. This lay significantly below the uncertainty value expected from the literature and would seem to justify the retrospective determination of the radon exposure from Po-210 surface activity measurement for use in, for example, epidemiological studies.

Air Pollutants, Radioactive↗
PubMed2002

Evaluation of the effect of a cover layer on radon exhalation from uranium mill tailings: transient radon flux analysis.

An experimental study concerning the transport of 222Rn in uranium mill tailings (UMTs) and in the cover layer was launched in 1997 with the participation of the French uranium mining company (COGEMA). Evaluation of the cover layer's effectiveness in reducing 222Rn flux emanating from UMTs was one of its objectives. In the first phase, the 222Rn flux densities were measured regularly on a UMT layer. In the second phase, the UMT was covered with a one-meter layer of compacted material consisting of crushed waste rock derived from mining activities. Radon-222 flux was then measured at the surface of this cover layer. Observations were compared with radon flux calculated using TRACI, a model for vertical water and gas flow and radon transport. The results show that the calculations bear a fair resemblance to the observations in both cases. They also show that the effectiveness of the cover layer calculated with TRACI, using the thickness and textural properties of the cover material, is very close to the measured effectiveness.

France↗
PubMed2001

Radon exposure in slovene kindergartens based on continuous radon measurements.

Contiunuous measurements of concentration of radon and radon decay products, and equilibrium factor were carried out in the indoor air of 13 kindergartens at the beginning of 2000. Average values of the parameters measured during working time only and during the whole period, were compared and applied to estimate effective doses to the personnel. Results of short-term continuous measurements were used to correct the exposure, based generally on the radon concentration.

Air Pollution, Indoor↗
PubMed1983

On the effect of a negative ion-generator and a mixing fan on the plate-out of radon decay products in a radon box.

Studies have been conducted on the effect of a negative ion-generator and a mixing fan on the radon daughter Working Level produced in an environmental radon "box". A dramatic decrease in the Working Level has been observed when either the ion-generator or the mixing fan is operating. The combined effect of the ion-generator and the mixing fan was substantially larger than that from either one of them alone. Experiments have been carried out over a wide range of relative humidity (45-95%) and at a temperature of 20 +/- 3 degrees C. The effects observed were nearly independent of relative humidity in the box. Preliminary experiments seem to indicate that the decrease in the Working Level is somewhat related to the possible build-up of electrostatic charge on the inner walls of the radon box. However, there is some difficulty in accepting charge build-up at high levels of relative humidity. To better understand the phenomena observed, a number of measurements are planned on the inner walls of the box. These include electrostatic charge, electric field, and measurement of alpha- and beta-activity.

Environmental Exposure↗
PubMed1993

Relationship among short- and long-term radon measurements within dwellings: influence of radon concentrations.

As part of a retrospective epidemiologic study of lung cancer in women, alpha-track and charcoal canister radon measurements were made in a sample of New Jersey residences. The alpha-track measurements were designed to yield estimates of annual average exposures of dwelling occupants, while charcoal canister measurements were designed to yield "worst case" concentrations for screening purposes. The year-long living area and basement screening measurements had geometric means of 19 Bq m-3 (0.52 pCi L-1) and 56 Bq m-3 (1.5 pCi L-1), respectively. Measurements of radon gas with different detectors and on different floors were compared to each other within residences. Ratios of screening to annual average results became more extreme as the measured concentrations increased; the mean ratio of basement canisters to year-long living area alpha-track detectors was 5.6 vs. 2.7 for houses that screened above and below 150 Bq m-3 (4 pCi L-1), respectively. Although the residence sample from which these data were drawn is not necessarily representative of either state or national housing stock, these observations, if verified, may have important implications for procedures and decision strategies designed to reduce individual and population exposures to radon.

Air Pollutants, Radioactive↗
PubMed1996

An in-situ method to measure a soil's undisturbed pore gas radon concentration, diffusion length for radon and air filled porosity.

Previous work has shown that work has shown that for soils of insignificant permeability (soils with permeability less than about 10(-12) m2) the important soil parameters for characterizing radon mobility in the soil are the soil's steady-state pore gas random concentration at depth (Cs), the soil's bulk diffusion length for radon (L) and the soil's air filled porosity (pa). Existing methods to measure these parameters have been based wholly or in part on measurements of soil samples taken to a laboratory for analysis. The drawbacks of this approach are twofold: (1) since soil structure can be quite heterogeneous, the sample may not have characteristics indicative of the site as a whole, and (2) since the parameters are dependent on soil structure and the soil structure of the sample may be changed in th e process of acquiring the sample, one may be changing the parameters that one is trying to measure. These problems can be avoided by using a totally in-situ method to measure Cs, L, and pa. This paper describes a totally in-situ method for simultaneously measuring the important soil parameters, based on measurements of the radon concentration as a function of time for the gas in a cavity in the soil.

Diffusion↗
PubMed1998

An international intercomparison of soil gas radon and radon exhalation measurements.

The Environmental Measurements Laboratory hosted the Sixth International Radon Metrology Programme Intercomparison Test and Workshop (IRMP6) from 12-15 June 1995. Thirty participants representing 24 different institutions from 11 countries attended. Laboratory exercises consisted of 220Rn and 222Rn concentration measurements from a source container, and exhalation measurements from a 226Ra-spiked concrete slab and a "normal" concrete slab. Field exercises included soil gas radon measurements and radon exhalation measurements. In this report, we pooled the participants' data and used the ratio of the standard deviation (SD) to the arithmetic mean, expressed as a percentage, to assess participant agreement for each exercise. For the exhalation measurements from the 226Ra-spiked slab, this value is 37%; for soil gas 222Rn, this value is 120%, 36% and 27% for each depth range, 0.4-0.5, 0.6-0.75 and 0.9-1.0 m, respectively; for the surface exhalation measurements, this value is 34%. For the drum 222Rn measurements, the percent SD after removing a linear trend was 13%. These results indicate that sampling errors are greater than instrument errors.

Air Pollutants, Radioactive↗
PubMed1995

Design issues in studies of radon and lung cancer: implications of the joint effect of smoking and radon.

Many case-control studies have been undertaken to assess whether and to what extent residential radon exposure is a risk factor for lung cancer. Nearly all these studies have been conducted in populations including smokers and nonsmokers. In this paper, we show that, depending on the nature of the joint effect of radon and tobacco on lung cancer risk, it may be very difficult to detect a main effect due to radon in mixed smoking and nonsmoking populations. If the joint effect is closer to additive than multiplicative, the most cost-effective way to achieve adequate statistical power may be to conduct a study among never-smokers. Because the underlying joint effect is unknown, and because many studies have been carried out among mixed smoker and nonsmoker populations, it would be desirable to conduct some studies with adequate power among never-smokers only.

Case-Control Studies↗
PubMed1991

[Protection from radon emissions from a radon laboratory].

An absorbing chuck with activated coal has been suggested for absorbing radon and its daughter products' wastes from the air which are formed in the device YPP-1 in the process of preparation of radon water concentrate. Testing of such a device has shown that it is simple, reliable and efficient in functioning, thus it can be recommended to be used in radon laboratories.

Air Pollutants, Radioactive↗
PubMed1996

The biological effectiveness of radon-progeny alpha particles. V. Comparison of oncogenic transformation by accelerator-produced monoenergetic alpha particles and by polyenergetic alpha particles from radon progeny.

Generation of estimates of risk caused by exposure to radon in the home, either from miner data or from A-bomb data, requires several scaling factors such as for dose, dose rate and radiation quality, and possible synergisms. Such scaling factors are best developed from laboratory-based studies. Two possible sources of alpha particles for such studies are (1) a polyenergetic spectrum, generated directly by radon and its progeny, or (2) a series of monoenergetic alpha particles. We compare here the results of oncogenic transformation from studies using both systems. At the Columbia University Radiological Research Accelerator Facility (RARAF), C3H 10T1/2 cells were irradiated with alpha particles of various energies, with defined LETs from 70 to 200 keV/mum. At Pacific Northwest Laboratory, cells from the same stock were exposed to alpha particles from radon gas and its progeny, which were in equilibrium with the culture medium. There was good agreement between the results of oncogenic transformation experiments using the two different exposure systems. Apart from the experimental transformation frequencies themselves, such a comparison requires (1) reliable dosimetry at both facilities and (2) estimated LET distributions for the polyenergetic alpha-particle irradiator. Thus this good agreement gives some confirmation to the technique which is used to fold together oncogenic transformation rates from monoenergetic alpha particles to yield a predicted rate for a spectrum of alpha particles.

Alpha Particles↗
PubMed1997

A new mechanism for DNA alterations induced by alpha particles such as those emitted by radon and radon progeny.

The mechanism(s) by which alpha (alpha) particles like those emitted from inhaled radon and radon progeny cause their carcinogenic effects in the lung remains unclear. Although direct nuclear traversals by alpha-particles may be involved in mediating these outcomes, increasing evidence indicates that a particles can cause alterations in DNA in the absence of direct hits to cell nuclei. Using the occurrence of excessive sister chromatid exchanges (SCE) as an index of DNA damage in human lung fibroblasts, we investigated the hypothesis that alpha-particles may induce DNA damage through the generation of extracellular factors. We have found that a relatively low dose of alpha-particles can result in the generation of extracellular factors, which, upon transfer to unexposed normal human cells, can cause excessive SCE to an extent equivalent to that observed when the cells are directly irradiated with the same irradiation dose. A short-lived, SCE-inducing factor(s) is generated in alpha-irradiated culture medium containing serum in the absence of cells. A more persistent SCE-inducing factor(s), which can survive freeze-thaw and is heat labile is produced by fibroblasts after exposure to the alpha-particles. These results indicate that the initiating target for alpha-particle-induced genetic changes can be larger than a cell's nucleus or even a whole cell. How transmissible factors like those observed here in vitro may extend to the in vivo condition in the context of a-particle-induced carcinogenesis in the respiratory tract remains to be determined.

Air Pollutants, Radioactive↗
PubMed1993

Interlaboratory comparison of the effects of radon on L5178Y cells: dose contribution of radon daughter association with cells.

The cytotoxic and mutagenic effects of radon and its progeny were compared in murine lymphoblast L5178Y-R16 cells after exposure at three institutions. The cells were exposed to 222Rn at Case Western Reserve University (CWRU) and Pacific Northwest Laboratories (PNL) and to 212Bi, a decay product of 220Rn, at the University of Chicago (UC). The dose to the cell nucleus was calculated using a dosimetric model which addressed both the contribution of the dose from the radioactivity in the medium and that associated with the cells. The dose-response curves for cell survival showed D0's of 0.30 Gy at CWRU, 0.20 Gy at PNL, 0.37 Gy for chelated 212Bi, and 0.13 Gy for unchelated 212Bi. Induced mutant frequencies at the thymidine kinase locus at the 37% survival level were 1470 x 10(-6) at CWRU, 1518 at PNL, and 2414 x 10(-6) at UC using combined results for chelated and unchelated 212Bi. The variation between institutions was greater than obtained in a previous interlaboratory comparison of the effects of radon on CHO cells. Since less radioactivity was associated with CHO cells than L5178Y cells, we have concluded that the variation between institutions in the case of L5178Y cells is caused by the differences in cell-associated radioactivity and errors related to the measurement of this parameter.

Animals↗
PubMed2001

Diurnal and seasonal variation of the equilibrium state between short-lived radon decay products and radon gas in ground-level air.

To study seasonal and diurnal variations and the effect of meteorological parameters, the equilibrium factor F (i.e. the ratio of equilibrium equivalent radon daughter concentration and radon gas concentration) was determined as a result of measurements on a test field at Munich-Neuherberg, Germany, continuously from October 1995 through March 1997. On average, F was found to be 0.62+/-0.09 (95% confidence level). The time series of F showed no distinct seasonal variations. Nevertheless, typical diurnal variations as well as seasonal variations of the diurnal behaviour were observed. Generally, F was found to be increased in the early afternoon, i.e. under conditions of enhanced vertical mixing in the atmosphere. The daily differences between high and low values of F depended on the season. On average, low F values were characteristic for days with precipitation and high wind speed, i.e. under turbulent atmospheric conditions. Therefore, taking daily mean values into account, F was found to be positively correlated with the aerosol concentration, although a relationship between the diurnal behaviour of the aerosol concentration and that of F was not detectable.

Air Pollutants, Radioactive↗
PubMed1985

Radon and radon daughter evaluation in a natural radioactivity survey indoors.

An indoor survey in order to estimate the population exposure in five towns of an Italian Region is presented. A particular methodology for the campaign was planned and is being applied. Gamma spectrometry of building materials, exposure rate measurements indoors and outdoors and radon concentration measurements indoors were taken with different techniques. A correlation was found between mean gamma exposure rate and mean radon concentration in the houses investigated. An evaluation of mean effective dose equivalents for the inhabitants of the five towns is reported.

Construction Materials↗
PubMed1985

The first long time comparison of techniques for passive integrated measurement of radon and radon daughter concentration performed in an occupied dwelling.

The accuracy and variance of passive integrating detectors for radon and radon daughters presently in use in Sweden have been studied. Sets of 10 of each participating detector were exposed in an occupied dwelling. The results were compared with accurate measurements made with instruments from the National Swedish Institute of Radiation Protection. The results from the first test, in the summer of 1983, became an incitement to improved calibration procedures for some of the participating detectors. The test was repeated in February - April 1984. The results showed that all detectors participating in the test and presently in general use in Sweden are reasonably accurate.

Environmental Exposure↗
PubMed1994

A new coccidian (Apicomplexa: eimeriidae) in the northern pocket gopher (Thomomys talpoides) and a comparison of oocyst survival in hosts from radon-rich and radon-poor soils.

Forty (93%) of 43 northern pocket gophers (Thomomys talpoides) from the Jemez Mountains, Sandoval County, New Mexico (USA), had coccidian oocysts in their feces when examined. We describe this parasite, Eimeria jemezi, n. sp. Sporulated oocysts were subspheroidal, 13.3 by 12.2 (10 to 17 by 9 to 15) microns, with sporocysts ellipsoidal, 7.1 by 4.4 (5 to 9 by 4 to 5) microns; micropyle and oocyst residuum were absent, but polar bodies, Stieda bodies and sporocyst residua were present. All gophers were collected from two sites of similar habitat 7 km apart. One site (R+) had a high soil radon content (> or = 50 to 70 picocuries (pCi) per liter of air) whereas the other site (R-) had soils that were near average natural levels (1.2 to 1.6 pCi/g uranium nucleotides per gram of soil; < 1.9 pCi/g thorium nucleotides). Twenty-one (88%) of 24 gophers from the R+ site had coccidian oocysts in their intestines when examined, but none of these oocysts ever sporulated, whereas all 19 (100%) gophers from the R- site had coccidian oocysts in their intestines and 16 (84%) of these samples sporulated normally under laboratory conditions. The elevated radon content of the soil may have had an adverse effect on the sporulation of this coccidian while it still was intracellular within its host.

Animals↗