Guwahati, Oct 7: A first-of-its-kind scientific investigation has revealed the presence of elevated radon concentrations in groundwater from Baridua in Ri-Bhoi district, Meghalaya — raising potential public health concerns for communities relying on wells for drinking water.
The study, titled “Assessments of Radon Concentrations and Radiological Risks in Ground Water from Baridua, Meghalaya,” was conducted by researchers Hari Prasad Jaishi and Devashree Borgohain of USTM and published in the Water Conservation Science and Engineering journal. It marks the first documented attempt to monitor radon in groundwater in Meghalaya, a state known for its uranium-rich geological formations.
Uranium-238 ( 238 U) is a naturally occurring radioactive isotope of uranium, commonly found in various types of soil and rocks. One of its decay products is radon, which has three isotopes: radon (²²²Rn), thoron (²²⁰Rn) and actinon (²¹⁹Rn). Due to its longer half-life, (²²²Rn), is the most abundant isotope, allowing it to easily transfer from the pore spaces of soil and rocks into the air, surface water, and groundwater, depending upon the air–water partition coefficient. A large percentage of the global population relies on groundwater for drinking, irrigation, industrial processes, and other essential uses. The presence of elevated 222Rn levels in water can pose serious health risks.
Using advanced emanometry techniques involving radon bubblers and Lucas Cells, the scientists analysed groundwater samples collected from 15 wells across Baridua. Their results showed radon levels ranging from 15.44 to 224.41 becquerels per litre (Bq/L), with an average concentration of 50.31 Bq/L. While the average values were below the World Health Organisation (WHO) recommended limit of 100 Bq/L, all samples exceeded the U.S. Environmental Protection Agency (USEPA) guidelines of 11.1 Bq/L,q/L — and one sample surpassed even the WHO limit.
According to the researchers, radon exposure occurs through two main pathways — ingestion of contaminated water and inhalation of radon released during household activities such as showering and cooking. When consumed or inhaled, radon and its decay products can increase the risk of lung and stomach cancers over prolonged periods of exposure.
The study also revealed that the combined annual effective dose from both ingestion and inhalation exceeded the WHO’s safe limit of 100 microsieverts per year (µSv/y) in several samples, particularly posing a greater threat to children. The higher doses for children were attributed to their increased respiratory rates, smaller lung volumes, and greater tissue sensitivity to radiation.
“Although the mean radon concentration remains within the WHO limit, the exceedance of USEPA standards in all samples is a matter of concern. Prolonged exposure can pose health risks, especially for children,” the authors cautioned in their report.
The researchers linked the elevated radon concentrations to the unique geology of Meghalaya, including the presence of uranium-bearing granite, quartzite, and gneiss formations, as well as active tectonic features such as the Dauki Fault and Barapani–Tyrsad shear zone. These formations are known to release radon gas, a decay product of uranium-into the surrounding soil and water.
Baridua, located in the mineral-rich Ri-Bhoi district, is also an active boulder-mining zone, where continuous rock extraction may enhance the release of naturally occurring radioactive gases into groundwater sources.
The emphasis sizes the urgent need for regular monitoring of groundwater quality, especially in regions with uranium deposits, and calls for public awareness initiatives to mitigate radon-related health risks. It also recommends technological interventions such as improved ventilation systems in homes and radon mitigation in water storage to reduce exposure.
“This baseline study opens the door for broader radon mapping and radiological risk assessment in Meghalaya and across Northeast India,” the authors added, urging authorities to adopt in-situ and continuous monitoring tools for more efficient detection.
EOM
