Integrated environmental and health assessment from hydrogeochemistry and radiogeology parameters of hydrothermal spring attractions in Southern Thailand.

The present study aimed to investigate the hydrogeochemical patterns and contamination of the radiogeology, especially radon activity, related to geothermal aquifer properties and to perform a risk assessment of annual effective doses covering all hydrothermal spring attractions in Southern Thailand. Radon is an established lung carcinogen; especially longer term exposure to radioactive radon through inhalation could be a cause of lung cancer risk. Altogether 22 hydrothermal spring samples were collected from the six hydrothermal provinces in Southern Thailand in early November of 2023. Geochemical data represented by calcium chloride and sodium chloride type, most of which were influenced by seawater intrusion. In addition, the hydrothermal springs that located along local fault zones were mainly controlled by water‒rock interactions, indicating that hydrothermal spring quality was influenced by weathering. Hydrothermal springs located along the coastlines of the Gulf of Thailand and Andaman Sea were dominated by evaporation. Radon activity concentrations show value levels from 9 Bq/L (PG1) to 7,070 Bq/L (SR3), with an average of 580 Bq/L. Radon levels of hydrothermal spring attractions can be divided into three categories: (a) low radon levels below 100 Bq/L, (b) moderate to high radon levels between 100 and 580 Bq/L, and (c) very high radon levels greater than 580 Bq/L. The total annual effective doses for adults due to ingestion and dominantly inhalation of radon at hydrothermal spring attractions varied from 0.01 to 19.30 mSv/year. These results highlight the usefulness of this method as an essential tool for delineating radon concentrations, which could be used to introduce guidelines for health risk assessment.