A.J. Khan

Measurement of radon exhalation rate from some building materials

Passive integrating CR-39 plastic track detectors were used to measure the radon exhalation rate from building materials used in our region. It was found that the radon exhalation rate varies from 12.6 to 169 mBq m-2 h-1 in 10 different building materials.

Calibration of a CR-39 plastic track detector for the measurement of radon and its daughters in dwellings

Abstract Solid state nuclear track detectors have been widely used for the measurement of time-integrated radon levels in dwelling under different conditions. The track detector used for this purpose must be calibrated for concentrations of radon and its daughters likely to be found in dwellings. In the present investigations, a CR-39 plastic detector was calibrated bare and in a cup-with-membrane mode, along with a monodispersal aerosol 0.2 μm in size in an exposure chamber, to find the relationship between track density and the radon concentration, as well as potential alpha energy concentration (WL) of radon. The calibration factors of 0.18 tracks cm-2d-1 per (Bq m-3) for radon and 1628 tracks cm-2d-1 per (WL) were obtained. Some preliminary measurements for the concentration of radon and its daughters in different types of rooms in Indian dwellings were also made.

Interlaboratory calibration of track-etch detectors for the measurement of radon and radon daughter levels

Abstract This paper reports the results of the second interlaboratory calibration experiments, which were carried out in two parts. In the first, five types of commercially available and economically cheap membranes were tested as the barrier against thoron for “radon-only” measurements. It was found that all the membranes tested are good barriers against thoron and can be used in the “radon-only” device. In the second, actual calibration experiments were performed with LR-115 type-II and CR-39 track-etch detectors for different radon measuring configurations in a radon exposure chamber.

Study of airborne radon levels inside buildings

Abstract Radon and its daughter concentrations have been measured in 64 living rooms of six residential and 31 rooms of three non-residential buildings. CR-39 solid state nuclear track detectors were used to measure the radon concentrations inside the rooms. It was found that the radon concentration in winter was 1.5± 0.5 times higher than in summer. Radon concentration was higher at the ground storey rooms than the first and second storey rooms. The average dose equivalent rate due to radon daughters for a person is found to be 0.37 WLM yr -1 , using an equilibrium factor of 0.5 and an occupancy factor of 0.8.

Radon exhalation rate in building materials

Radon is present in trace amounts almost everywhere on the earth, being distributed in the soil, the ground water and in the lower atmosphere. Radon can originate from a deeply burried deposit and can migrate to the surface of earth by diffusion and transport process. The increased interest in indoor radon concentration is due to its health hazard and environmental pollution. For the measurements of radon activity and exhalation rate from commonly used building materials alpha sensitive CR-39 plastic track detectors were exposed. Effect of points and wall papers was also studied. The average dose equivalent rate due to radon daughters for a person living in different rooms was found to vary from 2.02 to 11.04 mSvY-1.

The indoor concentration of radon and its daughters in a multistorey building

Abstract Long-term measurements of radon and its daughters in nineteen different rooms of a multistorey building in Aligarh having different types of environmental conditions have been performed. CR-39 solid state nuclear track detectors were used to measure the radon concentration. Variations of radon concentration due to height from ground level, ventilation conditions, convection air currents and materials placed inside were investigated. The highest value of radon has been found in the basement and the ground floor rooms which indicates the influence of subsoil emanation. No appreciable effect was observed with height above ground. Our study also reveals that ventilation conditions, convection air currents, housed materials such as books, papers, etc., affect the radon concentration.

Estimation of dose rate for indoor radon from building materials.

The internal dose rate due to indoor radon (Rn) emissions from building materials is estimated. It is observed that the contribution from building materials to the dose rate is very small. The average indoor radon concentration in 75 different rooms is found to be 55 ± 12 Bq. m−3. Assuming an occupancy factor of 0.8, the annual average effective dose equivalent is 1.7 mSv. It seems that soil gas is mainly responsible for the internal exposure from indoor Rn.

Study of radon concentrations in oil refinery premises and city dwellings.

Radon and its progeny concentrations were measured in several dwellings at an oil refinery premises and these concentrations were compared with those found in dwellings in Mathura and Agra cities. Radon progeny concentrations were measured using LR-115 type II nuclear track etch detectors. The radon concentrations were estimated by using a value of 0.42 for the equilibrium factor. The geometric means (GM) of radon concentrations in the refinery dwellings, Mathura city and Agra city dwellings were 97, 91 and 75 Bq m(-3) with geometric standard deviations of 1.7, 1.8 and 1.8 respectively. The average lifetime risk of lung cancer for an adjusted annual average chronic radon exposure of 69 Bq m(-3) (7.8 mWL; WL = working level) with an occupancy factor of 0.7 comes out to be 5.4 x 10(-3).

Study of 222Rn concentrations in some dwellings of Rajasthan.

Total potential alpha energy concentrations due to radon progeny were measured in 143 dwellings of Udaipur, Bikaner, and Banswara towns of Rajasthan province of India with LR-115 type II detectors. The geometric mean values of total potential alpha energy concentrations in these three towns were found to be 1.9 x 10(-7) J m(-3), 1.2 x 10(-7) J m(-3) and 1.7 x 10(-7) J m(-3) with a geometric standard deviation of 2.2, 2.2, and 2.5, respectively. The estimated lifetime risk of lung cancer due to indoor radon exposure for a total population of study area was estimated to be 6.7 x 10(-3) or 0.67%. The mean relative loss of life expectancies were 0.20%, 0.12%, and 0.18%, respectively.

Radon estimation in some Indian tobacco, tea and tooth powder using CR-39 nuclear track detector

SummaryRadon contents in some samples of tobacco, tea and tooth powder have been estimated using CR-39 solid state nuclear track detectors. The Radon content in tobacco has been found to vary from 14.06 ± 1.4 to 89.91 ± 3.3 mBq/l. The Radon content in tea and tooth powder has been found to vary from 27.38 ± 1.8 to 41.81 ± 2.2 mBq/l and 26.27 ± 1.4 to 413 ± 6.0 mBq/l respectively. The present investigations are useful from the health hazards point of view.