Spatial distribution of radon contamination in hot springs water and its cancer and non-cancer risks in the Hunza-Nagar valley, Pakistan

Abstract

Radon (222Rn) is a ubiquitous radioactive gas and could threaten human life due to its potential for cancer and non-cancer risks. This study examined 222Rn concentration in the Hunza-Nagar valley along the Main Karakoram Thrust (MKT) fault. For this purpose, hot springs water of Hunza and Nagar districts and that background sites were analyzed using the RAD7 detector (Durridge Company, USA). Results showed that 222Rn concentration of hot spring water was found multifold higher than the background sites. 222Rn concentrations for hot springs water in Hunza-Nagar valley had surpassed the maximum contamination level (MCL) set by the USA environmental protection agency (USEPA). The concentration of 222Rn showed a strong positive correlation (> 0.68) with hot springs' water temperature and pH. The annual mean exposure dose rates of humans for various age groups were calculated for the estimated lifetime cancer risk (ELCR) and non-cancer risks. Among the age groups of humans, infants showed higher risk compared to others. Results showed that hot spring water consumption surpassed the world health organization (WHO) threshold limit of 100 µSv/y for chronic or non-cancer and USEPA 0.1x10− 3 for ELCR risks.