Journal of Applied and Fundamental Sciences JAFS|ISSN 2395-5554 (Print)|ISSN 2395-5562 (Online)|Vol 1(1)|May 2015 93 A STUDY ON THE INDOOR RADON CONCENTRATION IN HOSPITALS IN THE SHILLONG REGION, MEGHALAYA Yubaraj Sharma 1 , Deveshwori Maibam 1 , Priya P. Ram 2 , Atul Saxena* 1 and Devesh Walia 2 1 Department of Physics, North-Eastern Hill University, Shillong-793022 2 Department of Environmental Studies, North-Eastern Hill University, Shillong-793022 *For correspondence. (atulnehu@yahoo.co.in) Abstract: In this paper, we report our findings on indoor radon survey at 8 major hospitals in the Shillong region and also present estimates on the associated annual effective doses and life-time fatality risks. The survey was undertaken using LR-115 Type2 detectors. The measured radon activity concentration values were found to range from 65.66 Bq.m -3 to 783.77 Bq.m -3 with an arithmetic mean value of 260.4 ± 138.3 Bq.m -3 and a geometric mean value of 228.4 ± 1.67 Bq.m -3 . Of the total rooms surveyed, 60% have radon concentration more than the ICRP prescribed lower limit of 200 Bq.m -3 ; about 4% of the rooms had values higher than the upper limit of 600 Bq.m -3 . Distribution analysis of the radon activity concentration measured at the hospital rooms is carried out. Floor-wise variation was studied and a decrease in radon concentration with increase in floor- number has been observed. Keywords: SSNTD; radon; annual effective dose; life time fatality risk; statistical distribution PACS: 87.55N- and 02.50.-r 1. Introduction: Radon has become a topic of considerable attention and concern in recent years as the single most significant source of natural radiation exposure to humans. It is present ubiquitously in varying amounts in our living environment, which necessitates its accurate and reliable monitoring for the assessment of radiological health risk arising from it [1]. The association of lung cancer to radon has been known since decades, and although the initial study focused on underground miners exposed to high radon levels, several studies conducted since the early 1980's in homes and buildings have concluded that sufficient indirect evidence exists which link significant lung cancer risk in the general population to the radon levels found commonly in buildings [2]. Radon concentration was measured in 105 rooms of 8 major hospitals located in the Shillong region of East- Khasi Hills District, Meghalaya viz. Supercare, Robert, Ganesh Das, Nazareth, Woodland, Bethany, Civil and NEIGRIHMS. About 10 to 16 rooms located at different floors were chosen from hospital building which consists of OPD (Out Patient Department), Emergency, Pharmacies, X-ray rooms, CT-scan rooms, Medicine ward - both male and female, OT (Operation Theatres), General Surgical Wards, Baby rooms, Post Operative wards, Pediatrics Department, Nurse rooms, Plaster rooms etc. The location of the study sites are given in table 1. 2. Materials and Methods: Solid State Nuclear Track Detectors, namely LR-115 Type2 films are used for our study. The films are cut into small sizes of about 2.5x2.5 cm 2 , pasted onto a cardboard of dimension 6x9 cm 2 , and hung in the selected rooms such that the detectors are at a distance of at least 10 cm away from the nearest wall and about 2 meters from the ground. The detectors are retrieved after an exposure period of about 60 days; these exposed films are then chemically etched in 2.5N NaOH solution at 60ºC for 90 minutes. The perforated holes or etched tracks formed by the alpha particles (mostly from radioactive decay of radon) appear as bright spot in reddish background; these tracks are counted manually using an optical microscope at 150x magnification. The track density obtained are then converted into radon activity concentration using the following equation: C RN =   (1)