A study on measuring the 222Rn in the Buriganga River and tap water of the megacity Dhaka

Radon (Rn-222), an inert gas, is considered a silent killer due to its carcinogenic characteristics. Dhaka city is situated on the banks of the Buriganga River, which is regarded as the lifeline of Dhaka city because it serves as a significant source of the city's water supply for domestic and industrial purposes. Thirty water samples (10 tap water from Dhaka city and 20 surface samples from the Buriganga River) were collected and analyzed using a RAD H2O accessory for Rn-222 concentration. The average Rn-222 concentration in tap and river water was 1.54 +/- 0.38 Bq/L and 0.68 +/- 0.29 Bq/L, respectively. All the values were found below the maximum contamination limit (MCL) of 11.1 Bq/L set by the USEPA, the WHO-recommended safe limit of 100 Bq/L, and the UNSCEAR suggested range of 4-40 Bq/L. The mean values of the total annual effective doses due to inhalation and ingestion were calculated to be 9.77 mu Sv/y and 4.29 mu Sv/y for tap water and river water, respectively. Although all these values were well below the permissible limit of 100 mu Sv/y proposed by WHO, they cannot be neglected because of the hazardous nature of Rn-222, especially considering their entry to the human body via inhalation and ingestion pathways. The obtained data may serve as a reference for future Rn-222-related works.