Radon Detection in Drinking Water: Instruments and Measurement Techniques—A Comprehensive Review

Radon (222Rn) is a naturally occurring radioactive noble gas and a leading cause of lung cancer after tobacco smoking. Elevated concentrations in groundwater, mainly from uranium-rich geological formations, pose significant health risks in regions reliant on groundwater. This review critically examines current tools and techniques for detecting radon in drinking water, focusing on how methodological choices affect reported levels and risk assessments. A structured literature review from major scientific databases covers established laboratory methods like liquid scintillation counting (LSC), alpha/gamma spectrometry, Lucas cells, and electret chambers, alongside field methods such as the RAD7, and new technologies including IoT sensors and AI analytics. The review finds that accurate radon measurement is limited more by sampling losses due to volatility, radioactive decay (half-life: 3.82 days), and the heterogeneity of fractured aquifers, than by instrument precision. While LSC remains the regulation standard for its traceability and low detection limits, portable methods are key for quick field screening, and automated systems are increasingly important for capturing transient changes in treatment settings and high-risk aquifers. A decision matrix is provided to help choose methods based on monitoring goals, infrastructure, and needed confidence levels. The study emphasizes that improving data quality and comparability requires not just technological progress but also harmonized sampling protocols, rigorous quality assurance, transparent uncertainty reporting, and the inclusion of hydrogeological context in monitoring design. This comprehensive approach is crucial for translating measurements into effective exposure assessments, regulatory decisions, and public health protections.