Equilibrium Equivalent Concentration Research Articles

Comparative dosimetry of radon and thoron

There is a well-known discrepancy between dosimetrically derived dose conversion factor (DCF) and epidemiologically derived DCF for radon. As the latter DCFs, International Commission on Radiological Protection (ICRP) recommends a value of ∼6.4 nSv (Bq h m(-3))(-1) and 7.9 nSv (Bq h m(-3))(-1) for radon decay products (RnDP) in dwellings and workplaces, respectively. On the other hand, the dosimetric calculations based on the ICRP-66 respiratory tract model derived a DCF of 13 nSv (Bq h m(-3))(-1) and 17 nSv (Bq h m(-3))(-1) for RnDP in dwellings and workplaces, respectively, and 83 nSv (Bq h m(-3))(-1) for thoron decay products (TnDP) in dwellings. In addition, the DCFs derived from both approaches and UNSCEAR were applied to comparative dosimetry for two thoron-enhanced areas (cave dwellings in China and dwellings at a spa town in Japan), where the equilibrium equivalent concentration of radon and equilibrium equivalent concentration of thoron have been measured. In the case of the spa town dwellings, the dose from TnDP was larger than the dose from RnDP.

An instrument for measuring the unattached fraction of radon progeny with etched trackdetectors

To measure the unattached fraction of radon progeny, a new type of portable, low cost,reusable integrating monitor with etched track detector (CR-39) was developed. This monitorsimultaneously gives the average equilibrium-equivalent concentrations of unattached 222Rn progeny (EECRnu), attached 222Rn progeny (EECRna) andalso 220Rn progeny (EECTn). It was calculated, according to the detection efficiencies which werederived by the Monte Carlo method, that the lower detection limits forEECRnu,EECRna andEECTn are 0.03 Bq m−3, 0.12 Bq m−3 and0.07 Bq m−3, respectively for 24 h integrating sampling at a flow rate of 2.92 l min−1. The validity of the new monitor was confirmed through a series of intercomparisonexperiments.

Factors influencing antioxidant activities and total phenolic content of guava leaf extract

The aim of this study is to investigate the influence of certain factors on the yield, antioxidant activity (AA) and total phenolic content (TPC) of guava leaf extract. The effects of pretreatment of leaf sample prior to extract, extraction method, and the leaf age were investigated. Folin–Ciocalteau was used to determine the TPC. Trolox equivalent antioxidant capacity (TEAC) and equilibrium concentration (EC) were used for evaluation of AA. Results indicated that ultrasonication is the most suitable method for guava leaf extraction as it yielded the extract with the significantly highest TPC and AA. Blanching followed by ice water cooling (BCD) was suggested for the pretreatment process of guava leaves. The study of leaf maturity demonstrated that the highest activity was from the young leaves. Hot water was the best solvent to extract the active principles. The extract of BCD pretreated young leaves, extracted by hot water exhibited the highest TPC and AA with the TEAC and EC values of 24.30 ± 0.50 and 20.41 ± 0.67 mM/mg, respectively. These values are 1.88 and 8.72 times higher than the synthetic antioxidant butylated hydroxy toluene (BHT) and 1.75 and 1.21 times higher than vitamin E, respectively. It was concluded that pretreatment and drying process, method of extraction and leaf maturity played important roles on the bioactive compounds and their antioxidant power of guava leaf extract.

5039 3D-CT lymphography guides the sentinel node biopsy after preoperative systemic chemotherapy

This article reports results of the first investigations on indoor radon, thoron and their decay products concentration in 25 primary schools of Banja Luka, capital city of Republic Srpska. The measurements have been carried out in the period from May 2011 to April 2012 using 3 types of commercially available nuclear track detectors, named: long-term radon monitor (GAMMA 1)- for radon concentration measurements (CRn); radon-thoron discriminative monitor (RADUET) for thoron concentration measurements (CTn); while equilibrium equivalent radon concentration (EERC) and equilibrium equivalent thoron concentrations (EETC) measured by Direct Radon Progeny Sensors/Direct Thoron Progeny Sensors (DRPS/DTPS) were exposed in the period November 2011 to April 2012. In each school the detectors were deployed at 10 cm distance from the wall. The obtained geometric mean concentrations were CRn = 99 Bq m−3 and CTn = 51 Bq m−3 for radon and thoron gases respectively. Those for equilibrium equivalent radon concentration (EERC) and equilibrium equivalent thoron concentrations (EETC) were 11.2 Bq m−3 and 0.4 Bq m−3, respectively. The correlation analyses showed weak relation only between CRn and CTn as well as between CTn and EETC. The influence of the school geographical locations and factors linked to buildings characteristic in relation to measured concentrations were tested. The geographical location and floor level significantly influence CRn while CTn depend only from building materials (ANOVA, p ≤ 0.05). The obtained geometric mean values of the equilibrium factors were 0.123 for radon and 0.008 for thoron.

Mitigation of the effective dose of radon decay products through the use of an air cleaner in a dwelling in Okinawa, Japan

Field measurements were conducted to assess the effects of an air cleaner on radon mitigation in a dwelling with a high radon concentration in Okinawa, Japan. The measurements included indoor radon concentration, individual radon progeny concentration, equilibrium equivalent concentration of radon (EECRn), unattached fraction, and size distribution of aerosol-attached radon progeny. These measurements were conducted in a 74 m 3 room with/without the use of an air cleaner. The results showed that the mean radon concentration during the measurement was quite high (301 Bq m −3). The operation of air cleaner decreased the radon progeny activity concentration, EECRn and equilibrium factor by 33%, 57% and 71%, respectively, whereas the unattached fraction increased by 174%. In addition, the activity concentration of attached radon progeny in the accumulation mode (50–2000 nm) was obviously deceased by 42%, when the air cleaner was operated. According to dosimetric calculations, the operation of air cleaner reduced the effective dose due to radon progeny by about 50%.

Radon mitigation using an air cleaner

Room experiments were conducted to investigate the effects of an air cleaner on radon mitigation. Radon concentration, equilibrium equivalent radon concentration and unattached fraction were measured during the experiments. Two types of filtration were tested using the air cleaner which has a high efficiency particulate air filter (HEPA-filter) and a deodorizing activated carbon (carbon-filter). One is the filtration with the HEPA-filter plus carbon-filter and the other is the filtration with only the HEPA-filter. The effective doses from radon progeny were significantly decreased. Both filtration methods were effective for the mitigation of effective dose due to radon progeny.

Monitoring radon and its progeny in the environment of the vertical 15 UD Pelletron accelerator facility

Environmental radioactivity due to radon and its progenies in the ambient air at the vertical 15 UD Pelletron accelerator facility of the Inter University Accelerator Centre, New Delhi, India was evaluated to calculate the annual effective dose to the workers and users. The radon activity was measured with an active monitor. The activity concentrations of the radon progenies were measured simultaneously using grab aerosol sampling and absolute beta counting. The effect of in situ meteorological parameters such as the temperature and relative humidity along the height of the Pelletron tower on the activity of radon and its progenies was studied. The measurements were carried out in the winter and rainy seasons. The values for the temperature, relative humidity (in percentage), radon activity concentration, radon Equilibrium Equivalent Concentration (EEC), annual exposure, annual inhalation and annual effective dose were recorded/calculated for locations with air conditioning and without air conditioning. Elements such as 218Po, 214Pb, 214Bi, radon and EEC activity concentrations were found to decrease with the height and relative humidity and increase with increasing temperatures. The dose levels observed in the facility were below the International Commission on Radiological Protection (ICRP) and United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) recommendations, even for the general public (1.2 mSv).

A simple technique for determining the equilibrium equivalent Thoron concentration using a CR-39 detector: Application in mineral treatment industry

The paper presents a simple technique for determination of the Equilibrium Equivalent Thoron Concentration (EETC). A solid-state nuclear alpha track detector (SSNATD) named CR-39 manufactured by BARYOTRAK is used as the detector. This technique can be utilized anywhere, provided that air sampling is carried out with a DC driving pump. Although the measurement of Thoron concentrations is useful enough for screening high Thoron exposure, it is still necessary to determine Thoron progeny concentrations in order to complete dose assessment. After applying this technique for determining the EETC in some selected areas in southern Thailand, it has been found that the obtained EETC values are consistent with the values presented in the report compiled by UNSCEAR in 2000.

Measurements of thoron and radon progeny concentrations in Beijing, China

It has been reported that thoron levels in China are above the world average and maytherefore make a significant contribution to the natural background radiation dose. Wetherefore conducted a pilot study of concentrations of both thoron and radon progeny duringthe spring of 2006 in the Beijing area, China. A new type of portable 24 h integratingmonitor with a CR-39 detector was used during the survey. Seventy dwellings and eightoutdoor sites were measured during the survey. For country houses built of red bricks andslurry, the average equilibrium equivalent concentrations (EEC) of thoron and radon were1.02 ± 0.48 and 16.41 ± 9.02 Bq m−3, respectively, whereas for city dwellings built of cement blocks and floor slabs, the results were0.48 ± 0.47 and 11.50 ± 6.99 Bq m−3 for thoron and radon, respectively. For outdoor air, concentrations of thoron and radon progeny were0.29 ± 0.28 and 7.05 ± 2.68 Bq m−3, respectively. Radiation exposures from thoron and radon progeny were alsoevaluated; the ratio of dose contribution from thoron progeny to that of radonprogeny was evaluated to be 28% and 17% in country houses and city dwellings,respectively.

QA programme for radon and its short-lived progeny measuring instruments in NRPI Prague

To subserve the institutional research and tasks coming out from the Czech National Radon Programme, a new QA programme to calibrate all the known types of devices that measure radon and its short-lived progeny was developed at the Department of Radon mobile group of the National Radiation Protection Institute (NRPI) at Prague. The programme also included calibration of instruments measuring a unique quantity of unattached and attached fractions of short- lived radon progeny Generally, NRPI declares estimation of radon concentration during all routine calibration measurements with an overall uncertainty <5% (one sigma) and of equilibrium-equivalent radon concentration with an overall uncertainty <10% (one sigma). The results of the comparative measurements of the unattached and attached fractions of each short-lived radon progeny carried out with a comparing continuous monitor Fritra 4 in the German reference radon chamber at PTB Braunschweig indicated an acceptable level of agreement, up to 10%.

Study of a deposition-based direct thoron progeny sensor (DTPS) technique for estimating equilibrium equivalent thoron concentration (EETC) in indoor environment

A study has been carried out to examine the suitability of a passive, deposition-based technique for estimating the time-integrated equilibrium equivalent thoron concentration (EETC) in indoor environment using a direct thoron progeny sensor (DTPS). DTPS is an absorber-mounted LR-115-type nuclear track detector tuned to respond only to the 8.78 MeV alpha particles emitted from the deposited activity of 212Po on the absorber surface. The study has been carried out in two steps, the first step comprising the estimation of track registration efficiency ( η ) and the second step comprising the estimation of effective deposition velocity of thoron progeny aerosols on the detector surface in natural and laboratory environments. The track registration efficiency is found to be 8.3% for 212Po and less than 0.02% for all other alpha emitters including 222Rn (radon) progeny, thereby enabling a precise discrimination of thoron progeny. The deposition velocity of thoron progeny aerosols on DTPS surface has been measured in conjunction with active air sampling techniques for different orientations of the deposition surface. The geometric mean deposition velocity was found to be 0.077 m h - 1 having a narrow spread (geometric standard deviation of 1.35). Upon combining these factors, the overall sensitivity factor is estimated to be 0.94 Tr cm - 2 d - 1 / EETC ( Bq m - 3 ) , which indicates ∼ 45 times higher sensitivity as compared with conventional bare detector techniques (which register alpha particles emitted directly from air). The results obtained have been compared with currently used aerosol deposition models and progeny equilibrium models by using the aerosol number size and progeny activity distributions measured with scanning mobility particle sizer (SMPS) and low-pressure cascade impactor, respectively. The results are in good agreement with each other. A sensitivity analysis of the response characteristics of DTPS with respect to room ventilation rate and aerosol concentrations has been carried out to assess the variability of the sensitivity factor in the context of indoor dosimetry. The results are further discussed.

Variation of indoor radon progeny concentration and its role in dose assessment

Instantaneous measurements of equilibrium equivalent concentration of radon (EEC Rn) were taken over a period of 1 year in 2004 in a typical house at Amritsar city, located in the northwest part of India. A method based on absolute beta counting subsequent to grab aerosol sampling was used. During that year, EEC Rn varied between 1.56 Bq m −3 and 22.77 Bq m −3 with average value of 8.76 Bq m −3. EEC Rn decreased with the transition from winter to summer and vice versa, having a negative correlation with outdoor temperature. The use of mechanical ventilation, under normal living conditions during summer, caused an extra decrease in the concentrations. The variations with temperature and mechanical ventilation are discussed. Some major issues related to the uncertainties in dose calculations caused by the lack of knowledge of equilibrium factor and ignoring the effect of life style on the radon and its progeny concentrations are discussed.

Radon–Thoron Discriminative Measurements in Gansu Province, China, and Their Implication for Dose Estimates

Indoor radon measurements were carried out in cave dwellings of the Chinese loess plateau in Gansu province, where previously the Laboratory of Industrial Hygiene (LIH), China, and the U.S. National Cancer Institute (NCI) had conducted an international collaborative epidemiological study. The LIH–NCI study showed an increased lung cancer risk due to high residential radon levels, and estimated the excess odds ratio at 100 Bq/m3 to be 0.19 (Wang et al., 2002). The present study used two types of newly developed passive monitors: One is a discriminative monitor for radon and thoron; the other is a selective monitor for thoron decay products. The arithmetic mean concentrations of indoor radon and thoron were 91 and 351 Bq/m3, respectively. As reported by our previous study in Shanxi and Shaanxi provinces (Tokonami et al., 2004), the presence of high thoron concentration was confirmed and thoron was predominant over radon in the cave dwellings. However, the mean equilibrium equivalent thoron concentration (EETC) was found to be much lower than expected when assuming the equilibrium factor of 0.1 provided by the UNSCEAR (2000) report. The effective dose by radon and thoron decay products was estimated to be 3.08 mSv/yr. It was significantly lower than the dose of 8.22 mSv/yr estimated from the measurements that did not take into consideration any discrimination between radon and thoron. Excess relative risk of lung cancer per sievert may be much higher than the risk estimated from the LIH–NCI study, considering that discriminative measurements were not used in their study.

Simultaneous measurements of indoor radon, radon–thoron progeny and high-resolution gamma spectrometry in Greek dwellings

Simultaneous indoor radon, radon-thoron progeny and high-resolution in situ gamma spectrometry measurements, with portable high-purity Ge detector were performed in 26 dwellings of Thessaloniki, the second largest town of Greece, during March 2003-January 2005. The radon gas was measured with an AlphaGUARD ionisation chamber (in each of the 26 dwellings) every 10 min, for a time period between 7 and 10 d. Most of the values of radon gas concentration are between 20 and 30 Bq m(-3), with an arithmetic mean of 34 Bq m(-3). The maximum measured value of radon gas concentration is 516 Bq m(-3). The comparison between the radon gas measurements, performed with AlphaGUARD and short-term electret ionisation chamber, shows very good agreement, taking into account the relative short time period of the measurement and the relative low radon gas concentration. Radon and thoron progeny were measured with a SILENA (model 4s) instrument. From the radon and radon progeny measurements, the equilibrium factor F could be deduced. Most of the measurements of the equilibrium factor are within the range 0.4-0.5. The mean value of the equilibrium factor F is 0.49 +/- 0.10, i.e. close to the typical value of 0.4 adopted by UNSCEAR. The mean equilibrium equivalent thoron concentration measured in the 26 dwellings is EEC(thoron) = 1.38 +/- 0.79 Bq m(-3). The mean equilibrium equivalent thoron to radon ratio concentration, measured in the 26 dwellings, is 0.1 +/- 0.06. The mean total absorbed dose rate in air, owing to gamma radiation, is 58 +/- 12 nGy h(-1). The contribution of the different radionuclides to the total indoor gamma dose rate in air is 38% due to 40K, 36% due to thorium series and 26% due to uranium series. The annual effective dose, due to the different source terms (radon, thoron and external gamma radiation), is 1.05, 0.39 and 0.28 mSv, respectively.

Thoron levels in traditional Chinese residential dwellings

A survey on radon (222Rn), thoron (220Rn) and its decay products (220RnD) was conducted in Chinese traditional residential dwellings constructed with loam bricks or soil wall. The activity concentrations in 164 dwellings under investigation were 72.4+/-59.2 (arithmetic mean, AM) and 57.5+/-2.0 Bq m-3 (geometric mean, GM) for 222Rn, and 318+/-368 and 162+/-3.7 Bq m-3 for 220Rn, respectively. For 220RnD, 67 dwellings were studied. The AM of the 220RnD equilibrium equivalent concentration was 3.8+/-3.3 Bq m-3 with a maximum value of 15.8 Bq m-3. On the basis of these results, the average annual effective doses to the local residents due to radon and thoron exposure were 1.44-4.62 mSv. Thoron contributes 12.9-56.6% to the total doses. Preliminary results show that there is a relation between 220RnD in air and 232Th in soil. The correlation factors of outdoor and indoor were 0.88 and 0.40. The 232Th activity content of Chinese soil is estimated to be about two times the world average. The traditional residential dwellings with soil construction are still common in China. Further investigations on the 220Rn level in these dwelling with the aim of dose reduction are proposed.

Measurement of radon and thoron progeny outdoors in Malout, India, using grab aerosol sampling and beta counting

Defined solid angle absolute beta counting (DSAABC) technique was used to measure the equilibrium equivalent concentration of radon (EEC Rn) and thoron (EEC Th) from the filtered aerosol samples collected at Malout, India, in the months of May–June 2003. Air was sampled thrice a day and relative humidity and temperature were noted to find the dependence of radon progeny on these variables in air. EEC Rn and EEC Th were computed from concentrations of their respective progeny. In general, both EEC Rn and EEC Th were higher during the morning and evening and were minimum in the afternoon. The value of EEC Rn ranged from 2.29 to 12.96 Bq m - 3 , being minimum in the evening and maximum in the morning. Simultaneously measured values of EEC Th varied from 0.058 to 1.799 Bq m - 3 , having minimum and maximum values during the morning.

Temperature variation of indoor and outdoor radon progeny

Abstract The indoor and outdoor radon progeny concentrations were investigated at a semi-hilly area of Pathankot in Punjab using the method of beta particle counting of aerosol samples collected on a glass micro-fiber filter. A linear relation was found between indoor and outdoor equilibrium equivalent concentrations of radon-222 (EECRn) with correlation coefficient of R = 0.9 . The indoor and outdoor EECRn levels were also studied as a function of outdoor temperature. The variations with temperature in both cases showed negative correlation with correlation coefficient of R = - 0.66 and R = - 0.73 , respectively. The ratio of outdoor to indoor EECRn investigated as a function of absolute difference of indoor and outdoor temperatures (|Tin–Tout|) resulted in a correlation coefficient of R = 0.52 , which is positive. The indoor EECRn was also estimated from an empirical relation based on transport of inside and outside radon progeny through ventilation. The measured inside EECRn agrees well with the computed value.

A pilot survey on indoor radon and thoron progeny in Yangjiang, China

A pilot survey on indoor radon and thoron progeny concentration was carried out in five villages in HBRA of Yangjiang and one village in the controlled area(CA) in March 2004. Totally 26 adobe houses and 29 brick houses in HBRA were investigated. A portable 24-h integrating monitor with CR-39 detectors was adopted for progeny measurements, and the average equilibrium equivalent 222Rn and 220Rn concentrations (EEC Rn and EEC Tn) were obtained. Rather high levels of EEC Rn and EEC Tn with an average of 57.1±33.3 and 12.6±9.5 Bq·m −3, respectively, were observed in adobe houses. In addition, 222Rn/ 220Rn concentrations and exhalation rate were also measured by an Electrostatic-Radon-Sampler (ERS-2) monitor.

Thoron in the living environments of Japan

High thoron concentrations have been investigated in various living environments with radon–thoron discriminative measurements; however, behavior of the thoron and its decay products and their effects on human health have not been clearly elucidated yet. In Japan, some kinds of building materials rich in natural radionuclides of thorium series, such as clay and soil plaster, are commonly used for construction and/or surface finishing of wall in traditional Japanese style houses. Measurements with different types of monitor for thoron and its decay products were carried out to investigate general characteristics of thoron in Japanese living environments. From the result of the measurements, thoron concentrations ranged from almost 0 to more than thousands Bq m −3. Extremely high concentrations can be found in the places near wall surface, and it decreases drastically as distance from the surface of the wall increases. Thoron concentration was found to be changed drastically with time. The equilibrium equivalent thoron concentrations (EETC) ranged from nearly 0 to about 6 Bq m −3. Correlation between the thoron concentration and EETC was not good. This report summarized the results of an investigation of thoron in living environments of Japan.

Variation of radon ( [formula omitted]Rn) progeny concentrations in outdoor air as a function of time, temperature and relative humidity

A sensitive grab sampling technique was used to measure the equilibrium equivalent concentration of radon ( 222 Rn) progeny, EEC Rn , outdoors at Bathinda, Punjab (India), over a period of 6 months. The method was based on the beta counting of aerosol samples collected on glass micro-fiber filters by drawing the air through the filters. Measurements, covering two of the three sessions of the day (morning, afternoon, evening), were performed two times per day at a fixed place at a height of 1.8 m above the ground surface. The total average value of EEC Rn was 5.62 Bq m - 3 , while the morning, afternoon and evening averages were 9.15, 2.85 and 5.33 Bq m - 3 , respectively. Negative correlation was observed for air temperature and EEC Rn , while positive correlation was found for relative humidity and EEC Rn , EEC Rn was higher in winter than in summer.