RADON CONCENTRATION IN SOIL AND GROUNDWATER OF WEST COASTAL AREA, BANGLADESH

Overview of radon gas in groundwater around the world: Health effects and treatment technologies

The natural radioactive decay of uranium in rocks and soils gives rise to the presence of radon in groundwater. The existence of radon in groundwater at activity levels way higher than the reference limits set by US-EPA and WHO was widely covered in literature. The exposure to elevated levels of radon in ground and drinking water have been reported in literature to cause adverse health impacts. The aim of the present paper is to give an overview of radon gas in groundwater followed by the safe limits suggested by international organizations and agencies such as US-EPA and WHO. The paper also discusses the health effects associated with the exposure to radon levels and the estimation of the annual effective dose through ingestion and inhalation. This is followed by the radon levels around the world as well as the corresponding annual effective doses reported in literature. The determination techniques of radon levels in water covered in literature such as liquid scintillation counting, gamma-ray spectrometry and emanometry were also discussed and reviewed in the present work. Next, the paper sheds light on the most frequently used treatment techniques such as aeration, adsorption, filtration as well as biological techniques and evaluates their efficiency in mitigating radon levels in water. The paper also highlights the main precautions and future mitigation plans for radon in groundwater as well as delved onto future research perspectives of radon. It was found out that the type of rock played a key role in determining the radon levels. For instance, granitic rock types were reported to contribute to the elevation in the groundwater radon levels due to their characteristic permeability as a result of the formed fractures as well as their natural incorporation of high levels of uranium. Some of the reported radon levels in groundwater in literature were way higher than the guidelines set by the World Health Organization (WHO) for drinking water and US-EPA alternative higher maximum contaminant level. This review paper could be of importance to researchers working on the evaluation as well as the treatment of radon gas in water as it will provide a critical and state of the art review on radon gas in groundwater.

A systematic review on groundwater radon distribution with human health consequences and probable mitigation strategy

Groundwater radon contamination is a serious global concern for its eco-toxicological effects. The major health hazard occurs due to toxic indoor air inhalation and consumption of contaminated drinking water supplied from different distribution systems, especially groundwater. There are fragmented reports on the measurement of radon contamination and their health consequences with physical radon removal strategies as well as characterization of inhabitant microbial communities. As it concerned with human health, collective information is much essential on their groundwater distribution, their physicochemical properties and possible mitigation strategies, not done so far. In such prospect, this review summarizes the physicochemical properties of radon, their sources, global as well as Indian groundwater radon contamination scenario, health effects and inhabitant microbes along with their survival strategies. It also summarizes the physical radon removal techniques and especially emphasizes the microbes based bioremediation process as well as a combination of both as a future effective radon remediation process.

Analysis of exposure to radon in Bulgarian rehabilitation hospitals

Mineral springs are used in spa resorts throughout the world. Radon is a natural radioactive source, which can dissolve, accumulate, and be transported by water. This study investigates the radon concentration in air and water in 12 Bulgarian rehabilitation hospitals and presents the assessment of the exposure to radon in them. The measurements were performed at 401 premises within 21 buildings, using two types of passive detectors for a dry and wet environment that were exposed from February, 2019 to June, 2019. The radon concentration varied from 19 to 2550 Bq/m³ with an arithmetic mean and a standard deviation of 102 Bq/m³ and 191 Bq/m³, respectively. The hypothesis that in hospitals the source of radon, besides soil under the buildings, is also the mineral water that is used for treatment was tested. Thermal water samples were procured sequentially from a spring and baths to analyse the reduction of radon concentration in them till reaching the premises. The results show that the concentration of radon decreased by approximately 50%. Further, the correlation analysis applied to the data proved the relation of the levels of indoor radon in the treatment rooms with those in the water. Mineral water used in rehabilitation hospitals have radon transfer coefficients ranging from 4.5·10^-4 to 8.4·10^-3. In addition, an analysis of the exposure of patients and workers to radon in rehabilitation hospitals based on the indoor radon levels and period of exposure was performed. The doses of workers do not exceed the limit of the annual effective dose for the population from all sources (1 mSv/year).

ASSESSMENT OF ANNUAL EFFECTIVE DOSE DUE TO INHALATION AND INGESTION OF RADON FROM GROUNDWATER AT THE SOUTHEAST COASTAL AREA, BANGLADESH

Naturally occurring radon-222 was evaluated for its use in estimating annual effective dose exposure in groundwater samples of the southeast coastal area of Bangladesh. On-site radon concentration was measured in groundwater using AlphaGUARD PQ2000 PRO (Saphymo, Germany) radon monitor. The measured values range 0.36-15.70 Bq per l, which lies within the safe limit of 4-40 Bq per l recommended by UNSCEAR. On the contrary, few samples show radon concentration above the safe limit of 11.1 Bq per l recommended by USEPA. The mean annual effective doses due to ingestion and inhalation resulting from radon in groundwater vary from 0.99 to 42.87 μSv per y with an average value of 12.45 μSv per y, which is far below the safe limit 100 μSv per y recommended by WHO and EU. Results reveal that there is no significant public health hazard due to radon ingestion and inhalation from groundwater in the study area.