Health risk and dominant factors of indoor radon concentrations in Souq Al-Khamees and Ka'am, Libya

This study assessed indoor 222Rn concentrations and their determinants in Souq Al-Khamees and Ka’am, Libya, to quantify public health risks and identify mitigation strategies. Passive dosimeters were deployed in 55 dwellings for 90 days. Multiple Linear Regression (MLR) with advanced feature engineering analyzed 17 variables, including functional transformations. Arithmetic Mean (AM) concentrations were 77 Bq/m³ in Souq Al-Khamees and 116 Bq/m³ in Ka’am. While geometric means (39 and 44 Bq/m³) reflect a stable regional background, WHO reference level exceedance rates reached 18.4% and 21.3%, respectively. The MLR model (R² = 0.692) identified the reciprocals of modified ventilation (1/(V+2)) and storey level (1/(S+2)) as the primary significant predictors. To address single-season sampling bias (March–June), a regional Mediterranean seasonal correction factor of 1.29 was integrated, showing that true annual exposures, Annual Effective Dose Equivalents (AEDE), and lifetime health risks exceed measured seasonal parameters. Consequently, 222Rn exposure increases estimated lifetime lung cancer risk for never-smokers to 16 and 20 per 1,000, respectively, escalating synergistically to 276 and 352 per 1,000 for current smokers. Increasing daily ventilation past 2–4 hours provides a critical, cost-effective regional mitigation strategy.